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Sample records for accurate reverse phase

  1. Accurate phase-shift velocimetry in rock.

    PubMed

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models. PMID:27111139

  2. Accurate phase-shift velocimetry in rock

    NASA Astrophysics Data System (ADS)

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R.; Holmes, William M.

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.

  3. Accurate phase-shift velocimetry in rock.

    PubMed

    Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R; Holmes, William M

    2016-06-01

    Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.

  4. Accurate whole human genome sequencing using reversible terminator chemistry.

    PubMed

    Bentley, David R; Balasubramanian, Shankar; Swerdlow, Harold P; Smith, Geoffrey P; Milton, John; Brown, Clive G; Hall, Kevin P; Evers, Dirk J; Barnes, Colin L; Bignell, Helen R; Boutell, Jonathan M; Bryant, Jason; Carter, Richard J; Keira Cheetham, R; Cox, Anthony J; Ellis, Darren J; Flatbush, Michael R; Gormley, Niall A; Humphray, Sean J; Irving, Leslie J; Karbelashvili, Mirian S; Kirk, Scott M; Li, Heng; Liu, Xiaohai; Maisinger, Klaus S; Murray, Lisa J; Obradovic, Bojan; Ost, Tobias; Parkinson, Michael L; Pratt, Mark R; Rasolonjatovo, Isabelle M J; Reed, Mark T; Rigatti, Roberto; Rodighiero, Chiara; Ross, Mark T; Sabot, Andrea; Sankar, Subramanian V; Scally, Aylwyn; Schroth, Gary P; Smith, Mark E; Smith, Vincent P; Spiridou, Anastassia; Torrance, Peta E; Tzonev, Svilen S; Vermaas, Eric H; Walter, Klaudia; Wu, Xiaolin; Zhang, Lu; Alam, Mohammed D; Anastasi, Carole; Aniebo, Ify C; Bailey, David M D; Bancarz, Iain R; Banerjee, Saibal; Barbour, Selena G; Baybayan, Primo A; Benoit, Vincent A; Benson, Kevin F; Bevis, Claire; Black, Phillip J; Boodhun, Asha; Brennan, Joe S; Bridgham, John A; Brown, Rob C; Brown, Andrew A; Buermann, Dale H; Bundu, Abass A; Burrows, James C; Carter, Nigel P; Castillo, Nestor; Chiara E Catenazzi, Maria; Chang, Simon; Neil Cooley, R; Crake, Natasha R; Dada, Olubunmi O; Diakoumakos, Konstantinos D; Dominguez-Fernandez, Belen; Earnshaw, David J; Egbujor, Ugonna C; Elmore, David W; Etchin, Sergey S; Ewan, Mark R; Fedurco, Milan; Fraser, Louise J; Fuentes Fajardo, Karin V; Scott Furey, W; George, David; Gietzen, Kimberley J; Goddard, Colin P; Golda, George S; Granieri, Philip A; Green, David E; Gustafson, David L; Hansen, Nancy F; Harnish, Kevin; Haudenschild, Christian D; Heyer, Narinder I; Hims, Matthew M; Ho, Johnny T; Horgan, Adrian M; Hoschler, Katya; Hurwitz, Steve; Ivanov, Denis V; Johnson, Maria Q; James, Terena; Huw Jones, T A; Kang, Gyoung-Dong; Kerelska, Tzvetana H; Kersey, Alan D; Khrebtukova, Irina; Kindwall, Alex P; Kingsbury, Zoya; Kokko-Gonzales, Paula I; Kumar, Anil; Laurent, Marc A; Lawley, Cynthia T; Lee, Sarah E; Lee, Xavier; Liao, Arnold K; Loch, Jennifer A; Lok, Mitch; Luo, Shujun; Mammen, Radhika M; Martin, John W; McCauley, Patrick G; McNitt, Paul; Mehta, Parul; Moon, Keith W; Mullens, Joe W; Newington, Taksina; Ning, Zemin; Ling Ng, Bee; Novo, Sonia M; O'Neill, Michael J; Osborne, Mark A; Osnowski, Andrew; Ostadan, Omead; Paraschos, Lambros L; Pickering, Lea; Pike, Andrew C; Pike, Alger C; Chris Pinkard, D; Pliskin, Daniel P; Podhasky, Joe; Quijano, Victor J; Raczy, Come; Rae, Vicki H; Rawlings, Stephen R; Chiva Rodriguez, Ana; Roe, Phyllida M; Rogers, John; Rogert Bacigalupo, Maria C; Romanov, Nikolai; Romieu, Anthony; Roth, Rithy K; Rourke, Natalie J; Ruediger, Silke T; Rusman, Eli; Sanches-Kuiper, Raquel M; Schenker, Martin R; Seoane, Josefina M; Shaw, Richard J; Shiver, Mitch K; Short, Steven W; Sizto, Ning L; Sluis, Johannes P; Smith, Melanie A; Ernest Sohna Sohna, Jean; Spence, Eric J; Stevens, Kim; Sutton, Neil; Szajkowski, Lukasz; Tregidgo, Carolyn L; Turcatti, Gerardo; Vandevondele, Stephanie; Verhovsky, Yuli; Virk, Selene M; Wakelin, Suzanne; Walcott, Gregory C; Wang, Jingwen; Worsley, Graham J; Yan, Juying; Yau, Ling; Zuerlein, Mike; Rogers, Jane; Mullikin, James C; Hurles, Matthew E; McCooke, Nick J; West, John S; Oaks, Frank L; Lundberg, Peter L; Klenerman, David; Durbin, Richard; Smith, Anthony J

    2008-11-01

    DNA sequence information underpins genetic research, enabling discoveries of important biological or medical benefit. Sequencing projects have traditionally used long (400-800 base pair) reads, but the existence of reference sequences for the human and many other genomes makes it possible to develop new, fast approaches to re-sequencing, whereby shorter reads are compared to a reference to identify intraspecies genetic variation. Here we report an approach that generates several billion bases of accurate nucleotide sequence per experiment at low cost. Single molecules of DNA are attached to a flat surface, amplified in situ and used as templates for synthetic sequencing with fluorescent reversible terminator deoxyribonucleotides. Images of the surface are analysed to generate high-quality sequence. We demonstrate application of this approach to human genome sequencing on flow-sorted X chromosomes and then scale the approach to determine the genome sequence of a male Yoruba from Ibadan, Nigeria. We build an accurate consensus sequence from >30x average depth of paired 35-base reads. We characterize four million single-nucleotide polymorphisms and four hundred thousand structural variants, many of which were previously unknown. Our approach is effective for accurate, rapid and economical whole-genome re-sequencing and many other biomedical applications.

  5. Benchmarking accurate spectral phase retrieval of single attosecond pulses

    NASA Astrophysics Data System (ADS)

    Wei, Hui; Le, Anh-Thu; Morishita, Toru; Yu, Chao; Lin, C. D.

    2015-02-01

    A single extreme-ultraviolet (XUV) attosecond pulse or pulse train in the time domain is fully characterized if its spectral amplitude and phase are both determined. The spectral amplitude can be easily obtained from photoionization of simple atoms where accurate photoionization cross sections have been measured from, e.g., synchrotron radiations. To determine the spectral phase, at present the standard method is to carry out XUV photoionization in the presence of a dressing infrared (IR) laser. In this work, we examine the accuracy of current phase retrieval methods (PROOF and iPROOF) where the dressing IR is relatively weak such that photoelectron spectra can be accurately calculated by second-order perturbation theory. We suggest a modified method named swPROOF (scattering wave phase retrieval by omega oscillation filtering) which utilizes accurate one-photon and two-photon dipole transition matrix elements and removes the approximations made in PROOF and iPROOF. We show that the swPROOF method can in general retrieve accurate spectral phase compared to other simpler models that have been suggested. We benchmark the accuracy of these phase retrieval methods through simulating the spectrogram by solving the time-dependent Schrödinger equation numerically using several known single attosecond pulses with a fixed spectral amplitude but different spectral phases.

  6. Reverse Phase Protein Arrays for Compound Profiling.

    PubMed

    Moerke, Nathan; Fallahi-Sichani, Mohammad

    2016-01-01

    Reverse phase protein arrays (RPPAs), also called reverse phase lysate arrays (RPLAs), involve immobilizing cell or tissue lysates, in small spots, onto solid supports which are then probed with primary antibodies specific for proteins or post-translational modifications of interest. RPPA assays are well suited for large-scale, high-throughput measurement of protein and PTM levels in cells and tissues. RPPAs are affordable and highly multiplexable, as a large number of arrays can readily be produced in parallel and then probed separately with distinct primary antibodies. This article describes a procedure for treating cells and preparing cell lysates, as well as a procedure for generating RPPAs using these lysates. A method for probing, imaging, and analyzing RPPAs is also described. These procedures are readily adaptable to a wide range of studies of cell signaling in response to drugs and other perturbations. © 2016 by John Wiley & Sons, Inc. PMID:27622568

  7. Accurate Parameter Estimation for Unbalanced Three-Phase System

    PubMed Central

    Chen, Yuan

    2014-01-01

    Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS. PMID:25162056

  8. Accurate parameter estimation for unbalanced three-phase system.

    PubMed

    Chen, Yuan; So, Hing Cheung

    2014-01-01

    Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS.

  9. Highly Accurate Calculations of the Phase Diagram of Cold Lithium

    NASA Astrophysics Data System (ADS)

    Shulenburger, Luke; Baczewski, Andrew

    The phase diagram of lithium is particularly complicated, exhibiting many different solid phases under the modest application of pressure. Experimental efforts to identify these phases using diamond anvil cells have been complemented by ab initio theory, primarily using density functional theory (DFT). Due to the multiplicity of crystal structures whose enthalpy is nearly degenerate and the uncertainty introduced by density functional approximations, we apply the highly accurate many-body diffusion Monte Carlo (DMC) method to the study of the solid phases at low temperature. These calculations span many different phases, including several with low symmetry, demonstrating the viability of DMC as a method for calculating phase diagrams for complex solids. Our results can be used as a benchmark to test the accuracy of various density functionals. This can strengthen confidence in DFT based predictions of more complex phenomena such as the anomalous melting behavior predicted for lithium at high pressures. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  10. Accurate analytical approximation of the OTFTs surface potential by means of the Lagrange Reversion Theorem

    NASA Astrophysics Data System (ADS)

    Colalongo, Luigi; Ghittorelli, Matteo; Torricelli, Fabrizio; Kovács-Vajna, Zsolt Miklos

    2015-12-01

    Surface-potential-based mathematical models are among the most accurate and physically based compact models of Thin-Film Transistors (TFTs) and, in turn, of Organic Thin-Film Transistors (OTFTs), available today. However, the need for iterative computations of the surface potential limits their computational efficiency and diffusion in CAD applications. The existing closed-form approximations of the surface potential are based on regional approximations and empirical smoothing functions that could result not enough accurate to model OTFTs and, in particular, transconductances and transcapacitances. In this paper we present an accurate and computationally efficient closed-form approximation of the surface potential, based on the Lagrange Reversion Theorem, that can be exploited in advanced surface-potential-based OTFTs and TFTs device models.

  11. Accurate Inference of Local Phased Ancestry of Modern Admixed Populations

    PubMed Central

    Ma, Yamin; Zhao, Jian; Wong, Jian-Syuan; Ma, Li; Li, Wenzhi; Fu, Guoxing; Xu, Wei; Zhang, Kui; Kittles, Rick A.; Li, Yun; Song, Qing

    2014-01-01

    Population stratification is a growing concern in genetic-association studies. Averaged ancestry at the genome level (global ancestry) is insufficient for detecting the population substructures and correcting population stratifications in association studies. Local and phase stratification are needed for human genetic studies, but current technologies cannot be applied on the entire genome data due to various technical caveats. Here we developed a novel approach (aMAP, ancestry of Modern Admixed Populations) for inferring local phased ancestry. It took about 3 seconds on a desktop computer to finish a local ancestry analysis for each human genome with 1.4-million SNPs. This method also exhibits the scalability to larger datasets with respect to the number of SNPs, the number of samples, and the size of reference panels. It can detect the lack of the proxy of reference panels. The accuracy was 99.4%. The aMAP software has a capacity for analyzing 6-way admixed individuals. As the biomedical community continues to expand its efforts to increase the representation of diverse populations, and as the number of large whole-genome sequence datasets continues to grow rapidly, there is an increasing demand on rapid and accurate local ancestry analysis in genetics, pharmacogenomics, population genetics, and clinical diagnosis. PMID:25052506

  12. Accurate inference of local phased ancestry of modern admixed populations.

    PubMed

    Ma, Yamin; Zhao, Jian; Wong, Jian-Syuan; Ma, Li; Li, Wenzhi; Fu, Guoxing; Xu, Wei; Zhang, Kui; Kittles, Rick A; Li, Yun; Song, Qing

    2014-01-01

    Population stratification is a growing concern in genetic-association studies. Averaged ancestry at the genome level (global ancestry) is insufficient for detecting the population substructures and correcting population stratifications in association studies. Local and phase stratification are needed for human genetic studies, but current technologies cannot be applied on the entire genome data due to various technical caveats. Here we developed a novel approach (aMAP, ancestry of Modern Admixed Populations) for inferring local phased ancestry. It took about 3 seconds on a desktop computer to finish a local ancestry analysis for each human genome with 1.4-million SNPs. This method also exhibits the scalability to larger datasets with respect to the number of SNPs, the number of samples, and the size of reference panels. It can detect the lack of the proxy of reference panels. The accuracy was 99.4%. The aMAP software has a capacity for analyzing 6-way admixed individuals. As the biomedical community continues to expand its efforts to increase the representation of diverse populations, and as the number of large whole-genome sequence datasets continues to grow rapidly, there is an increasing demand on rapid and accurate local ancestry analysis in genetics, pharmacogenomics, population genetics, and clinical diagnosis. PMID:25052506

  13. MONA: An accurate two-phase well flow model based on phase slippage

    SciTech Connect

    Asheim, H.

    1984-10-01

    In two phase flow, holdup and pressure loss are related to interfacial slippage. A model based on the slippage concept has been developed and tested using production well data from Forties, the Ekofisk area, and flowline data from Prudhoe Bay. The model developed turned out considerably more accurate than the standard models used for comparison.

  14. Phase reversal technique decreases cortical stimulation time during motor mapping.

    PubMed

    Simon, Mirela V; Sheth, Sameer A; Eckhardt, Christine A; Kilbride, Ronan D; Braver, Diana; Williams, Ziv; Curry, William; Cahill, Dan; Eskandar, Emad N

    2014-06-01

    Neurophysiologic mapping of the primary motor cortex (PMC) is commonly used in supratentorial surgery. Electrical cortical stimulation is guided by anatomic landmarks towards the precentral gyrus, with recording of the triggered primary motor responses (TPMR) in the contralateral hemibody. Thus, factors such as distortion of the pericentral anatomy, small surgical fields, brain shifts and miscalibrated neuronavigational systems may lengthen the process and result in unnecessary stimulations, increasing the probability of triggering seizures. We hypothesized that central sulcus localization via the median somatosensory evoked potentials phase reversal technique (MSSEP PRT) accurately guides the surgeon, resulting in prompt identification of the PMC with minimal electrical stimulation. Multivariate Cox regression was used to study the impact of MSSEP PRT on time spent performing electrical cortical stimulation to TPMR. The analysis was adjusted for presence of increased cortical excitability, high motor thresholds, lesions close to PMC and fMRI data, in 100 consecutive standardized motor mapping procedures for brain tumor resection and epilepsy surgery. Phase reversal and change morphology of the recorded somatosensory evoked potentials quadrupled (hazard ratio [HR] 4.13, p<0.0001) and doubled (HR 2.14, p=0.02) the rate of obtaining TPMR, respectively. A 1mA increase in motor threshold decreased the rate by 9% (HR 0.91, p=0.0002). Afterdischarges triggered before TPMR and lesions in close proximity to PMC decreased the rate of TPMR by 76% (HR 0.23, p<0.0001) and 48% (HR 0.52, p=0.04), respectively. Informative PRT decreases stimulation time. Afterdischarges triggered before TPMR, high motor thresholds and lesions close to the PMC increase it. PMID:24679940

  15. Separation of Chloroplast Pigments Using Reverse Phase Chromatography.

    ERIC Educational Resources Information Center

    Reese, R. Neil

    1997-01-01

    Presents a protocol that uses reverse phase chromatography for the separation of chloroplast pigments. Provides a simple and relatively safe procedure for use in teaching laboratories. Discusses pigment extraction, chromatography, results, and advantages of the process. (JRH)

  16. Phase Change of Gallium Enables Highly Reversible and Switchable Adhesion.

    PubMed

    Ye, Zhou; Lum, Guo Zhan; Song, Sukho; Rich, Steven; Sitti, Metin

    2016-07-01

    Gallium exhibits highly reversible and switchable adhesion when it undergoes a solid-liquid phase transition. The robustness of gallium is notable as it exhibits strong performance on a wide range of smooth and rough surfaces, under both dry and wet conditions. Gallium may therefore find numerous applications in transfer printing, robotics, electronic packaging, and biomedicine. PMID:27146217

  17. Phase behaviors of supramolecular graft copolymers with reversible bonding

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Wang, Liquan; Jiang, Tao; Lin, Jiaping

    2013-11-01

    Phase behaviors of supramolecular graft copolymers with reversible bonding interactions were examined by the random-phase approximation and real-space implemented self-consistent field theory. The studied supramolecular graft copolymers consist of two different types of mutually incompatible yet reactive homopolymers, where one homopolymer (backbone) possesses multifunctional groups that allow second homopolymers (grafts) to be placed on. The calculations carried out show that the bonding strength exerts a pronounced effect on the phase behaviors of supramolecular graft copolymers. The length ratio of backbone to graft and the positions of functional groups along the backbone are also of importance to determine the phase behaviors. Phase diagrams were constructed at high bonding strength to illustrate this architectural dependence. It was found that the excess unbounded homopolymers swell the phase domains and shift the phase boundaries. The results were finally compared with the available experimental observations, and a well agreement is shown. The present work could, in principle, provide a general understanding of the phase behaviors of supramolecular graft copolymers with reversible bonding.

  18. The use of Fourier reverse transforms in crystallographic phase refinement

    SciTech Connect

    Ringrose, S.

    1997-10-08

    Often a crystallographer obtains an electron density map which shows only part of the structure. In such cases, the phasing of the trial model is poor enough that the electron density map may show peaks in some of the atomic positions, but other atomic positions are not visible. There may also be extraneous peaks present which are not due to atomic positions. A method for determination of crystal structures that have resisted solution through normal crystallographic methods has been developed. PHASER is a series of FORTRAN programs which aids in the structure solution of poorly phased electron density maps by refining the crystallographic phases. It facilitates the refinement of such poorly phased electron density maps for difficult structures which might otherwise not be solvable. The trial model, which serves as the starting point for the phase refinement, may be acquired by several routes such as direct methods or Patterson methods. Modifications are made to the reverse transform process based on several assumptions. First, the starting electron density map is modified based on the fact that physically the electron density map must be non-negative at all points. In practice a small positive cutoff is used. A reverse Fourier transform is computed based on the modified electron density map. Secondly, the authors assume that a better electron density map will result by using the observed magnitudes of the structure factors combined with the phases calculated in the reverse transform. After convergence has been reached, more atomic positions and less extraneous peaks are observed in the refined electron density map. The starting model need not be very large to achieve success with PHASER; successful phase refinement has been achieved with a starting model that consists of only 5% of the total scattering power of the full molecule. The second part of the thesis discusses three crystal structure determinations.

  19. Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.

    PubMed

    Gharbi, Mohamed Amine; Manet, Sabine; Lhermitte, Julien; Brown, Sarah; Milette, Jonathan; Toader, Violeta; Sutton, Mark; Reven, Linda

    2016-03-22

    Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials.

  20. Reversed-phase High Performance Liquid Chromatography of proteins.

    PubMed

    Josic, Djuro; Kovac, Spomenka

    2010-08-01

    Reversed-phase HPLC (RP-HPLC) is one of most important techniques for protein separations and the method of choice for peptide separation. RP-HPLC has been applied on the nano, micro, and analytical scale, and has also been scaled up for preparative purifications, to large industrial scale. Because of its compatibility with mass spectrometry, RP-HPLC is an indispensable tool in proteomic research. With modern instrumentation and columns, complex mixtures of peptides and proteins can be separated at attomolar levels for further analysis. In addition, preparative RP-HPLC is often used for large-scale purification of proteins. This unit provides protocols for packing and testing a column, protein separation by use of gradient or step elution, desalting of protein solutions, and separation of enzymatic digests before mass spectrometric analyses. A protocol is also provided for cleaning, regenerating, and storing reversed-phase chromatography columns.

  1. Gradient Scouting in Reversed-Phase HPLC Revisited

    ERIC Educational Resources Information Center

    Alcazar, A.; Jurado, J. M.; Gonzalez, A. G.

    2011-01-01

    Gradient scouting is the best way to decide the most suitable elution mode in reversed-phase high-performance liquid chromatography (RP-HPLC). A simple rule for this decision involves the evaluation of the ratio [delta]t/t[subscript G] (where [delta]t is the difference in the retention time between the last and the first peak and t[subscript G] is…

  2. On-demand generation of aqueous two-phase microdroplets with reversible phase transitions

    SciTech Connect

    Boreyko, Jonathan B; Mruetusatorn, Prachya; Retterer, Scott T; Collier, Pat

    2013-01-01

    Aqueous two-phase systems contained entirely within microdroplets enable a bottom-up approach to mimicking the dynamic microcompartmentation of biomaterial that naturally occurs within the cytoplasm of cells. Here, we demonstrate the on-demand generation of femtolitre aqueous two-phase droplets within a microfluidic oil channel. Gated pressure pulses were used to generate individual, stationary two-phase microdroplets with a well-defined time zero for carrying out controlled and sequential phase transformations over time. Reversible phase transitions between single-phase, two-phase, and core-shell microgel states were obtained via evaporation-induced dehydration and on-demand water rehydration. In contrast to other microfluidic aqueous two-phase droplets, which require continuous flows and high-frequency droplet formation, our system enables the controlled isolation and reversible transformation of a single microdroplet and is expected to be useful for future studies in dynamic microcompartmentation and affinity partitioning.

  3. On-demand generation of aqueous two-phase microdroplets with reversible phase transitions

    NASA Astrophysics Data System (ADS)

    Collier, Charles

    2013-03-01

    Aqueous two-phase systems contained within microdroplets enable a bottom-up approach to mimicking the dynamic microcompartmentation of biomaterial that naturally occurs within the cytoplasm of cells. Here, we demonstrate the on-demand generation of femtolitre aqueous two-phase droplets within a microfluidic oil channel. Gated pressure pulses were used to generate individual, stationary two-phase microdroplets with a well-defined time zero for carrying out controlled and sequential phase transformations over time. Reversible phase transitions between single-phase, two-phase, and core-shell microbead states were obtained via evaporation-induced dehydration and on-demand water rehydration. In contrast to other microfluidic aqueous two-phase droplets, which require continuous flows and high-frequency droplet formation, our system enables the controlled isolation and reversible transformation of a single microdroplet and is expected to be useful for future studies in dynamic microcompartmentation and affinity partitioning.

  4. Pressure-induced reversible phase transition in thiourea dioxide crystal

    SciTech Connect

    Wang, Qinglei; Yan, Tingting; Zhu, Hongyang; Cui, Qiliang; Zou, Bo E-mail: zoubo@jlu.edu.cn; Wang, Kai E-mail: zoubo@jlu.edu.cn

    2015-06-28

    The effect of high pressure on the crystal structure of thiourea dioxide has been investigated by Raman spectroscopy and angle-dispersive X-ray diffraction (ADXRD) in a diamond anvil cell up to 10.3 GPa. The marked changes in the Raman spectra at 3.7 GPa strongly indicated a structural phase transition associated with the distortions of hydrogen bonding. There were no further changes up to the maximum pressure of 10.3 GPa and the observed transition was completely reversible when the system was brought back to ambient pressure. This transition was further confirmed by the changes of ADXRD spectra. The high-pressure phase was indexed and refined to an orthorhombic structure with a possible space group Pbam. The results from the first-principles calculations suggested that this phase transition was mainly related to the changes of hydrogen-bonded networks in thiourea dioxide.

  5. An Effective Method to Accurately Calculate the Phase Space Factors for β - β - Decay

    DOE PAGES

    Neacsu, Andrei; Horoi, Mihai

    2016-01-01

    Accurate calculations of the electron phase space factors are necessary for reliable predictions of double-beta decay rates and for the analysis of the associated electron angular and energy distributions. We present an effective method to calculate these phase space factors that takes into account the distorted Coulomb field of the daughter nucleus, yet it allows one to easily calculate the phase space factors with good accuracy relative to the most exact methods available in the recent literature.

  6. A float mechanism of retention in reversed-phase chromatography

    NASA Astrophysics Data System (ADS)

    Deineka, V. I.; Deineka, L. A.; Saenko, I. I.; Chulkov, A. N.

    2015-07-01

    A float mechanism of retention in reversed-phase HPLC is proposed as an alternative to the known mechanisms of the distribution and hydrophobic expulsion of sorbate to the surface of a sorbent. Experimental data that the sorption of a flavylium structure is poorly sensitive to the position of OH groups, and that the retention of anthocyanins depends on the length of bonded alkyl radicals of reversed phase, form the basis of the proposed hypothesis. It is noted that the retention of anthocyanins depends on the orientation of hydroxyl groups in carbohydrate radicals, due to which the chromatographic behavior of anthocyanins is different for glucosides and galactosides, for arabinosides and xylosides, and so on. In other words, retention is a reliable indicator of the composition of a carbohydrate fragment. It is concluded that carbohydrate radicals serve as unique floats, while flat flavilic ions penetrate into the bonded phase. The existence of floats is the main reason for the lower efficiency (of the number of theoretical plates) of the peaks of anthocyanins. It is shown that if two carbohydrate radicals are present at different sites of aglycone (a two-float sorbate), the peaks of the substance are characterized by substantial additional broadening.

  7. Producing reverse phase protein microarrays from formalin-fixed tissues.

    PubMed

    Wolff, Claudia; Schott, Christina; Malinowsky, Katharina; Berg, Daniela; Becker, Karl-Friedrich

    2011-01-01

    In most hospitals around the world FFPE (formalin fixed, paraffin embedded) tissues have been used for diagnosis and have subsequently been archived since decades. This has lead to a sizeable pool of this kind of tissues. Till quite recently it was not possible to use this congeries of samples for protein analysis, but now several groups described successful protein extraction from FFPE tissues. In this chapter, we describe a protein extraction protocol established in our laboratory combined with the use of reverse phase protein microarray.

  8. Demonstration of a reversible phase-insensitive optical amplifier

    SciTech Connect

    Yoshikawa, Jun-ichi; Miwa, Yoshichika; Furusawa, Akira; Filip, Radim

    2011-05-15

    We experimentally demonstrate phase-insensitive linear amplification of a continuous variable system in the optical regime, preserving the ancilla system at the output. Since our amplification operation is unitary up to small excess noise, it is reversible beyond the classical limit. Here, entanglement between the amplified output system and the ancilla system is the resource for the reversibility, and the amplification gain is G=2.0. In addition, combining this amplifier with a beamsplitter, we also demonstrate approximate cloning of coherent states where an anticlone is present. We investigate the reversibility by reconstructing the initial state from the output correlations, and the results are slightly beyond the cloning limit. Furthermore, full characterization of the amplifier and cloner is given by using coherent states with several different mean values as inputs. Our amplifier is based on linear optics, offline-prepared additional ancillas in nonclassical states, and homodyne measurements followed by feedforward. Squeezed states are used as the additional ancillas, and nonlinear optical effects are exploited only for their generation. They introduce nonclassicality into the amplifying operation, making entanglement at the output.

  9. RNA footprinting analysis using ion pair reverse phase liquid chromatography.

    PubMed Central

    Dickman, Mark J; Conroy, Matthew J; Grasby, Jane A; Hornby, David P

    2002-01-01

    Hydroxyl radical footprinting is a powerful technique often employed in characterization of the tertiary interactions between proteins and nucleic acids. Following the generation of a nucleic acid "ladder" either by chemical or enzymatic reactions, the radiolabeled products are traditionally separated by denaturing gel electrophoresis and further quantified by phosphorimaging techniques. Here we report the use of ion pair reverse phase liquid chromatography to analyze the products of an RNA footprinting reaction using fluorescently labeled RNA molecules. This technique offers several advantages over existing procedures, including rapid analysis, automation, and direct quantification of the cleavage products without the need to employ radiolabeling. To illustrate the resolving power of this technique, we have analyzed the products of base hydrolysis, generated from a fluorescently labeled RNA molecule and have subsequently used this method to define the solvent accessibility of the substrate strand as it docks with the hairpin ribozyme. PMID:11911369

  10. Reverse phase protein microarrays advance to use in clinical trials

    PubMed Central

    Mueller, Claudius; Liotta, Lance A.; Espina, Virginia

    2010-01-01

    Individualizing cancer therapy for molecular targeted inhibitors requires a new class of molecular profiling technology that can map the functional state of the cancer cell signal pathways containing the drug targets. Reverse phase protein microarrays (RPMA) are a technology platform designed for quantitative, multiplexed analysis of specific phosphorylated, cleaved, or total (phosphorylated and non-phosphorylated) forms of cellular proteins from a limited amount of sample. This class of microarray can be used to interrogate tissue samples, cells, serum, or body fluids. RPMA were previously a research tool; now this technology has graduated to use in research clinical trials with clinical grade sensitivity and precision. In this review we describe the application of RPMA for multiplexed signal pathway analysis in therapeutic monitoring, biomarker discovery, and evaluation of pharmaceutical targets, and conclude with a summary of the technical aspects of RPMA construction and analysis. PMID:20974554

  11. Mass transfer mechanism in chiral reversed phase liquid chromatography.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2014-03-01

    The mechanism of mass transfer in chiral chromatography was investigated using an experimental protocol already applied in RPLC and HILIC chromatography. The different contributions to the reduced height equivalent to a theoretical plate (HETP) include the longitudinal diffusion HETP term, the solid-liquid mass transfer resistance HETP term, the short-range eddy dispersion HETP term, and the long-range eddy dispersion HETP term. Their accurate measurement permits the determination of the adsorption rate constant kads of trans-stilbene enantiomers on a column packed with Lux 5 μm Cellulose-1 particles. The experimental results demonstrate that the number of adsorption-desorption steps per unit time of chiral compounds on polysaccharide-based chiral stationary phases is four orders of magnitude smaller than that of achiral compounds.

  12. Predictability of enantiomeric chromatographic behavior on various chiral stationary phases using typical reversed phase modeling software.

    PubMed

    Wagdy, Hebatallah A; Hanafi, Rasha S; El-Nashar, Rasha M; Aboul-Enein, Hassan Y

    2013-09-01

    Pharmaceutical companies worldwide tend to apply chiral chromatographic separation techniques in their mass production strategy rather than asymmetric synthesis. The present work aims to investigate the predictability of chromatographic behavior of enantiomers using DryLab HPLC method development software, which is typically used to predict the effect of changing various chromatographic parameters on resolution in the reversed phase mode. Three different types of chiral stationary phases were tested for predictability: macrocyclic antibiotics-based columns (Chirobiotic V and T), polysaccharide-based chiral column (Chiralpak AD-RH), and protein-based chiral column (Ultron ES-OVM). Preliminary basic runs were implemented, then exported to DryLab after peak tracking was accomplished. Prediction of the effect of % organic mobile phase on separation was possible for separations on Chirobiotic V for several probes: racemic propranolol with 97.80% accuracy; mixture of racemates of propranolol and terbutaline sulphate, as well as, racemates of propranolol and salbutamol sulphate with average 90.46% accuracy for the effect of percent organic mobile phase and average 98.39% for the effect of pH; and racemic warfarin with 93.45% accuracy for the effect of percent organic mobile phase and average 99.64% for the effect of pH. It can be concluded that Chirobiotic V reversed phase retention mechanism follows the solvophobic theory. PMID:23775938

  13. Accurate and fast fiber transfer delay measurement based on phase discrimination and frequency measurement

    NASA Astrophysics Data System (ADS)

    Dong, J. W.; Wang, B.; Gao, C.; Wang, L. J.

    2016-09-01

    An accurate and fast fiber transfer delay measurement method is demonstrated. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency measurement is used to overcome the contradiction between measurement accuracy and system complexity. The system achieves a high measurement accuracy of 0.2 ps with a 0.1 ps measurement resolution and a large dynamic range up to 50 km as well as no dead zone.

  14. Accurate phase measurements for thick spherical objects using optical quadrature microscopy

    NASA Astrophysics Data System (ADS)

    Warger, William C., II; DiMarzio, Charles A.

    2009-02-01

    In vitro fertilization (IVF) procedures have resulted in the birth of over three million babies since 1978. Yet the live birth rate in the United States was only 34% in 2005, with 32% of the successful pregnancies resulting in multiple births. These multiple pregnancies were directly attributed to the transfer of multiple embryos to increase the probability that a single, healthy embryo was included. Current viability markers used for IVF, such as the cell number, symmetry, size, and fragmentation, are analyzed qualitatively with differential interference contrast (DIC) microscopy. However, this method is not ideal for quantitative measures beyond the 8-cell stage of development because the cells overlap and obstruct the view within and below the cluster of cells. We have developed the phase-subtraction cell-counting method that uses the combination of DIC and optical quadrature microscopy (OQM) to count the number of cells accurately in live mouse embryos beyond the 8-cell stage. We have also created a preliminary analysis to measure the cell symmetry, size, and fragmentation quantitatively by analyzing the relative dry mass from the OQM image in conjunction with the phase-subtraction count. In this paper, we will discuss the characterization of OQM with respect to measuring the phase accurately for spherical samples that are much larger than the depth of field. Once fully characterized and verified with human embryos, this methodology could provide the means for a more accurate method to score embryo viability.

  15. Characterization of signalling pathways by reverse phase protein arrays.

    PubMed

    Malinowsky, Katharina; Wolff, Claudia; Schott, Christina; Becker, Karl-Friedrich

    2013-01-01

    Reverse phase protein array (RPPA) is a very suitable technique to analyze large numbers of proteins in small samples like for example tumor biopsies. Beside their small size another major hindrance for the analysis of proteins from biopsies is the extraction of proteins from formalin-fixed and paraffin-embedded (FFPE) tissues. Here we describe a protocol, allowing quantitative extraction of large numbers of proteins from FFPE tissues and their subsequent analysis by RPPA. To elucidate the role of epidermal growth factor receptor (EGFR) signalling in ovarian cancer, we analyzed 23 primary tumors and corresponding metastases for the expression of 25 proteins involved in EGFR signalling with special emphasis on epithelial-mesenchymal transition (EMT). We found a significant correlation of Snail with EGFR((Tyr1086)) and p38 MAPK((Thr180/Tyr182)) in primary ovarian carcinoma and with EGFR((Tyr1086)) in their corresponding metastases. Additionally, we showed that high expression levels of the E-cadherin repressor Snail in primary tumors combined with high expression levels of the pp38 MAPK((Thr180/Tyr182)) in metastasis lead to an increased risk for death in ovarian carcinoma patients.

  16. Spatial Normalization of Reverse Phase Protein Array Data

    PubMed Central

    Kaushik, Poorvi; Molinelli, Evan J.; Miller, Martin L.; Wang, Weiqing; Korkut, Anil; Liu, Wenbin; Ju, Zhenlin; Lu, Yiling; Mills, Gordon; Sander, Chris

    2014-01-01

    Reverse phase protein arrays (RPPA) are an efficient, high-throughput, cost-effective method for the quantification of specific proteins in complex biological samples. The quality of RPPA data may be affected by various sources of error. One of these, spatial variation, is caused by uneven exposure of different parts of an RPPA slide to the reagents used in protein detection. We present a method for the determination and correction of systematic spatial variation in RPPA slides using positive control spots printed on each slide. The method uses a simple bi-linear interpolation technique to obtain a surface representing the spatial variation occurring across the dimensions of a slide. This surface is used to calculate correction factors that can normalize the relative protein concentrations of the samples on each slide. The adoption of the method results in increased agreement between technical and biological replicates of various tumor and cell-line derived samples. Further, in data from a study of the melanoma cell-line SKMEL-133, several slides that had previously been rejected because they had a coefficient of variation (CV) greater than 15%, are rescued by reduction of CV below this threshold in each case. The method is implemented in the R statistical programing language. It is compatible with MicroVigene and SuperCurve, packages commonly used in RPPA data analysis. The method is made available, along with suggestions for implementation, at http://bitbucket.org/rppa_preprocess/rppa_preprocess/src. PMID:25501559

  17. Magnetic-field-induced shape recovery by reverse phase transformation.

    PubMed

    Kainuma, R; Imano, Y; Ito, W; Sutou, Y; Morito, H; Okamoto, S; Kitakami, O; Oikawa, K; Fujita, A; Kanomata, T; Ishida, K

    2006-02-23

    Large magnetic-field-induced strains have been observed in Heusler alloys with a body-centred cubic ordered structure and have been explained by the rearrangement of martensite structural variants due to an external magnetic field. These materials have attracted considerable attention as potential magnetic actuator materials. Here we report the magnetic-field-induced shape recovery of a compressively deformed NiCoMnIn alloy. Stresses of over 100 MPa are generated in the material on the application of a magnetic field of 70 kOe; such stress levels are approximately 50 times larger than that generated in a previous ferromagnetic shape-memory alloy. We observed 3 per cent deformation and almost full recovery of the original shape of the alloy. We attribute this deformation behaviour to a reverse transformation from the antiferromagnetic (or paramagnetic) martensitic to the ferromagnetic parent phase at 298 K in the Ni45Co5Mn36.7In13.3 single crystal.

  18. Design and rationale for RE-VERSE AD: A phase 3 study of idarucizumab, a specific reversal agent for dabigatran.

    PubMed

    Pollack, Charles V; Reilly, Paul A; Bernstein, Richard; Dubiel, Robert; Eikelboom, John; Glund, Stephan; Huisman, Menno V; Hylek, Elaine; Kam, Chak-Wah; Kamphuisen, Pieter W; Kreuzer, Joerg; Levy, Jerrold H; Sellke, Frank; Stangier, Joachim; Steiner, Thorsten; Wang, Bushi; Weitz, Jeffrey I

    2015-07-01

    Idarucizumab, a Fab fragment directed against dabigatran, produced rapid and complete reversal of the anticoagulation effect of dabigatran in animals and in healthy volunteers. The Study of the REVERSal Effects of Idarucizumab in Patients on Active Dabigatran (RE-VERSE AD™) is a global phase 3 prospective cohort study aimed at investigating idarucizumab in dabigatran-treated patients who present with uncontrollable or life-threatening bleeding, and in those requiring urgent surgery or intervention. We describe the rationale for, and design of the trial (clinicaltrials.gov NCT02104947).

  19. Homogeneous edge-plane carbon as stationary phase for reversed-phase liquid chromatography.

    PubMed

    Lu, Tian; Olesik, Susan V

    2015-04-01

    Carbon stationary phases have been widely used in HPLC due to their unique selectivity and high stability. Amorphous carbon as a stationary phase has at least two sites of interaction with analytes: basal-plane and edge-plane carbon sites. The polarity and adsorptivity of the two sites are different. In this work, the edge-plane carbon stationary phase is prepared by surface-directed liquid crystal assembly. Specific precursor polymers form discotic liquid crystal phases during the pyrolysis process. By using silica as the substrate to align the discotic liquid crystal, edge-plane carbon surfaces were formed. Similar efficiencies as observed for Hypercarb were observed in chromatograms. The column efficiency was studied as a function of linear flow rate. A minimum reduced plate height of 6 was observed in these studies. To evaluate the performance of the homogeneous edge-plane carbon stationary phase, linear solvation energy relationships were used to compare these ordered carbon surfaces to commercially available carbon stationary phases, including Hypercarb. Reversed-phase separations of nucleosides, nucleotides, and amino acids and derivatives were demonstrated using the ordered carbon surfaces, respectively. The column batch-to-batch reproducibility was also evaluated. The retention times for the analytes were reproducible within 1-6% depending on the analyte.

  20. Retention mechanism for polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography with monomeric stationary phases.

    PubMed

    Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

    2011-12-23

    Reversed-phase liquid chromatography (RPLC) is the foremost technique for the separation of analytes that have very similar chemical functionalities, but differ only in their molecular shape. This ability is crucial in the analysis of various mixtures with environmental and biological importance including polycyclic aromatic hydrocarbons (PAHs) and steroids. A large amount of effort has been devoted to studying this phenomenon experimentally, but a detailed molecular-level description remains lacking. To provide some insight on the mechanism of shape selectivity in RPLC, particle-based simulations were carried out for stationary phases and chromatographic parameters that closely mimic those in an experimental study by Sentell and Dorsey [J. Chromatogr. 461 (1989) 193]. The retention of aromatic hydrocarbons ranging in size from benzene to the isomeric PAHs of the formula C(18)H(12) was examined for model RPLC systems consisting of monomeric dimethyl octadecylsilane (ODS) stationary phases with surface coverages ranging from 1.6 to 4.2 μmol/m(2) (i.e., stationary phases yielding low to intermediate shape selectivity) in contact with a 67/33 mol% acetonitrile/water mobile phase. The simulations show that the stationary phase acts as a very heterogeneous environment where analytes with different shapes prefer different spatial regions with specific local bonding environments of the ODS chains. However, these favorable retentive regions cannot be described as pre-existing cavities because the chain conformation in these local stationary phase regions adapts to accommodate the analytes.

  1. Impact of blocking and detection chemistries on antibody performance for reverse phase protein arrays.

    PubMed

    Ambroz, Kristi

    2011-01-01

    Careful selection of well-qualified antibodies is critical for accurate data collection from reverse phase protein arrays (RPPA). The most common way to qualify antibodies for RPPA analysis is by Western blotting because the detection mechanism is based on the same immunodetection principles. Western blots of tissue or cell lysates that result in single bands and low cross-reactivity indicate appropriate antibodies for RPPA detection. Western blot conditions used to validate antibodies for RPPA experiments, including blocking and detection reagents, have significant effects on aspects of antibody performance such as cross-reactivity against other proteins in the sample. We have found that there can be a dramatic impact on antibody behavior with changes in blocking reagent and detection method, and offer an alternative method that allows detection reagents and conditions to be held constant in both antibody validation and RPPA experiments. PMID:21901590

  2. Accurate means of detecting and characterizing abnormal patterns of ventricular activation by phase image analysis

    SciTech Connect

    Botvinick, E.H.; Frais, M.A.; Shosa, D.W.; O'Connell, J.W.; Pacheco-Alvarez, J.A.; Scheinman, M.; Hattner, R.S.; Morady, F.; Faulkner, D.B.

    1982-08-01

    The ability of scintigraphic phase image analysis to characterize patterns of abnormal ventricular activation was investigated. The pattern of phase distribution and sequential phase changes over both right and left ventricular regions of interest were evaluated in 16 patients with normal electrical activation and wall motion and compared with those in 8 patients with an artificial pacemaker and 4 patients with sinus rhythm with the Wolff-Parkinson-White syndrome and delta waves. Normally, the site of earliest phase angle was seen at the base of the interventricular septum, with sequential change affecting the body of the septum and the cardiac apex and then spreading laterally to involve the body of both ventricles. The site of earliest phase angle was located at the apex of the right ventricle in seven patients with a right ventricular endocardial pacemaker and on the lateral left ventricular wall in one patient with a left ventricular epicardial pacemaker. In each case the site corresponded exactly to the position of the pacing electrode as seen on posteroanterior and left lateral chest X-ray films, and sequential phase changes spread from the initial focus to affect both ventricles. In each of the patients with the Wolff-Parkinson-White syndrome, the site of earliest ventricular phase angle was located, and it corresponded exactly to the site of the bypass tract as determined by endocardial mapping. In this way, four bypass pathways, two posterior left paraseptal, one left lateral and one right lateral, were correctly localized scintigraphically. On the basis of the sequence of mechanical contraction, phase image analysis provides an accurate noninvasive method of detecting abnormal foci of ventricular activation.

  3. Home Circadian Phase Assessments with Measures of Compliance Yield Accurate Dim Light Melatonin Onsets

    PubMed Central

    Burgess, Helen J.; Wyatt, James K.; Park, Margaret; Fogg, Louis F.

    2015-01-01

    Study Objectives: There is a need for the accurate assessment of circadian phase outside of the clinic/laboratory, particularly with the gold standard dim light melatonin onset (DLMO). We tested a novel kit designed to assist in saliva sampling at home for later determination of the DLMO. The home kit includes objective measures of compliance to the requirements for dim light and half-hourly saliva sampling. Design: Participants were randomized to one of two 10-day protocols. Each protocol consisted of two back-to-back home and laboratory phase assessments in counterbalanced order, separated by a 5-day break. Setting: Laboratory or participants' homes. Participants: Thirty-five healthy adults, age 21–62 y. Interventions: N/A. Measurements and Results: Most participants received at least one 30-sec epoch of light > 50 lux during the home phase assessments (average light intensity 4.5 lux), but on average for < 9 min of the required 8.5 h. Most participants collected every saliva sample within 5 min of the scheduled time. Ninety-two percent of home DLMOs were not affected by light > 50 lux or sampling errors. There was no significant difference between the home and laboratory DLMOs (P > 0.05); on average the home DLMOs occurred 9.6 min before the laboratory DLMOs. The home DLMOs were highly correlated with the laboratory DLMOs (r = 0.91, P < 0.001). Conclusions: Participants were reasonably compliant to the home phase assessment procedures. The good agreement between the home and laboratory dim light melatonin onsets (DLMOs) demonstrates that including objective measures of light exposure and sample timing during home saliva sampling can lead to accurate home DLMOs. Clinical Trial Registration: Circadian Phase Assessments at Home, http://clinicaltrials.gov/show/NCT01487252, NCT01487252. Citation: Burgess HJ, Wyatt JK, Park M, Fogg LF. Home circadian phase assessments with measures of compliance yield accurate dim light melatonin onsets. SLEEP 2015;38(6):889–897

  4. Accurate determination of absolute carrier-envelope phase dependence using photo-ionization.

    PubMed

    Sayler, A M; Arbeiter, M; Fasold, S; Adolph, D; Möller, M; Hoff, D; Rathje, T; Fetić, B; Milošević, D B; Fennel, T; Paulus, G G

    2015-07-01

    The carrier-envelope phase (CEP) dependence of few-cycle above-threshold ionization (ATI) of Xe is calibrated for use as a reference measurement for determining and controlling the absolute CEP in other interactions. This is achieved by referencing the CEP-dependent ATI measurements of Xe to measurements of atomic H, which are in turn referenced to ab initio calculations for atomic H. This allows for the accurate determination of the absolute CEP dependence of Xe ATI, which enables relatively easy determination of the offset between the relative CEP measured and/or controlled by typical devices and the absolute CEP in the interaction. PMID:26125386

  5. Microwave-immobilized polybutadiene stationary phase for reversed-phase high-performance liquid chromatography.

    PubMed

    Lopes, Nilva P; Collins, Kenneth E; Jardim, Isabel C S F

    2004-03-19

    Polybutadiene (PBD) has been immobilized on high-performance liquid chromatography (HPLC) silica by microwave radiation at various power levels (52-663 W) and actuation times (3-60 min). Columns prepared from these reversed-phase HPLC materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (%C) and infrared spectroscopy. A microwave irradiation of 20 min at 663 W gives a layer of immobilized PBD that presented good performance. Longer irradiation times give thicker immobilized layers having less favorable chromatographic properties.

  6. Accurate characterization of mask defects by combination of phase retrieval and deterministic approach

    NASA Astrophysics Data System (ADS)

    Park, Min-Chul; Leportier, Thibault; Kim, Wooshik; Song, Jindong

    2016-06-01

    In this paper, we present a method to characterize not only shape but also depth of defects in line and space mask patterns. Features in a mask are too fine for conventional imaging system to resolve them and coherent imaging system providing only the pattern diffracted by the mask are used. Then, phase retrieval methods may be applied, but the accuracy it too low to determine the exact shape of the defect. Deterministic methods have been proposed to characterize accurately the defect, but it requires a reference pattern. We propose to use successively phase retrieval algorithm to retrieve the general shape of the mask and then deterministic approach to characterize precisely the defects detected.

  7. In-band asymmetry compensation for accurate time/phase transport over optical transport network.

    PubMed

    Siu, Sammy; Tseng, Wen-Hung; Hu, Hsiu-fang; Lin, Shinn-Yan; Liao, Chia-Shu; Lai, Yi-Liang

    2014-01-01

    The demands of precise time/phase synchronization have been increasing recently due to the next generation of telecommunication synchronization. This paper studies the issues that are relevant to distributing accurate time/phase over optical transport network (OTN). Each node and link can introduce asymmetry, which affects the adequate time/phase accuracy over the networks. In order to achieve better accuracy, protocol level full timing support is used (e.g., Telecom-Boundary clock). Due to chromatic dispersion, the use of different wavelengths consequently causes fiber link delay asymmetry. The analytical result indicates that it introduces significant time error (i.e., phase offset) within 0.3397 ns/km in C-band or 0.3943 ns/km in L-band depending on the wavelength spacing. With the proposed scheme in this paper, the fiber link delay asymmetry can be compensated relying on the estimated mean fiber link delay by the Telecom-Boundary clock, while the OTN control plane is responsible for processing the fiber link delay asymmetry to determine the asymmetry compensation in the timing chain.

  8. Development and Validation of Reversed-Phase High Performance Liquid Chromatographic Method for Hydroxychloroquine Sulphate

    PubMed Central

    Singh, A.; Roopkishora; Singh, C. L.; Gupta, R.; Kumar, S.; Kumar, M.

    2015-01-01

    In the present work new, simple reversed-phase high performance liquid chromatographic method was developed and validated for the determination of hydroxychloroquine sulphate in blood plasma. Chloroquine sulphate was used as an internal standard. The chromatographic separation was achieved with octadecyl silane Hypersil C18 column (250×6 mm, 5 μm) using water and organic (acetonitrile:methanol: 50:50, v/v) mobile phase in 75:25 v/v ratio, with sodium 1-pentanesulfonate and phosphoric acid. This organic phase was maintained at pH 3.0 by orthophosphoric acid. The flow rate of 2.0 ml/min. with detection at 343 nm was used in the analysis. The calibration curve of standard hydroxychloroquine sulphate was linear in range 0.1-20.0 μg/ml. The method was validated with respected to linearity, range, precision, accuracy, specificity and robustness studies according to ICH guidelines. The method was found to be accurate and robust to analyze the hydroxychloroquine sulphate in plasma samples. PMID:26798174

  9. Development and Validation of Reversed-Phase High Performance Liquid Chromatographic Method for Hydroxychloroquine Sulphate.

    PubMed

    Singh, A; Roopkishora; Singh, C L; Gupta, R; Kumar, S; Kumar, M

    2015-01-01

    In the present work new, simple reversed-phase high performance liquid chromatographic method was developed and validated for the determination of hydroxychloroquine sulphate in blood plasma. Chloroquine sulphate was used as an internal standard. The chromatographic separation was achieved with octadecyl silane Hypersil C18 column (250×6 mm, 5 μm) using water and organic (acetonitrile:methanol: 50:50, v/v) mobile phase in 75:25 v/v ratio, with sodium 1-pentanesulfonate and phosphoric acid. This organic phase was maintained at pH 3.0 by orthophosphoric acid. The flow rate of 2.0 ml/min(.) with detection at 343 nm was used in the analysis. The calibration curve of standard hydroxychloroquine sulphate was linear in range 0.1-20.0 μg/ml. The method was validated with respected to linearity, range, precision, accuracy, specificity and robustness studies according to ICH guidelines. The method was found to be accurate and robust to analyze the hydroxychloroquine sulphate in plasma samples. PMID:26798174

  10. Synthesis and characterization of silica-based hyper-crosslinked sulfonate-modified reversed stationary phases

    PubMed Central

    Luo, Hao; Ma, Lianjia; Zhang, Yu; Carr, Peter W.

    2011-01-01

    A novel type of silica-based sulfonate-modified reversed phase (−SO3-HC-C8 ) has been synthesized; it is based on a newly developed acid stable “hyper-crosslinked” C8 derivatized reversed phase, denoted HC-C8. The −SO3-HC-C8 phases containing controlled amounts of sulfonyl groups were made by sulfonating the aromatic hyper-crosslinked network of the HC-C8 phase at different temperatures. The −SO3-HC-C8 phases are only slightly less hydrophobic than the parent HC-C8 phase. The added sulfonyl groups provide a unique strong cation-exchange selectivity to the hydrophobic hyper-crosslinked substrate as indicated by the very large C coefficient as shown by Snyder’s hydrophobic subtraction reversed-phase characterization method. This cation-exchange activity clearly distinguishes the sulfonated phase from all other reversed phases as confirmed by the extraordinary high values of Snyder’s column comparison function Fs. In addition, as was found in previous studies of silica-based and zirconia-based reversed phases, a strong correlation between the cation-exchange interaction and hydrophobic interaction was observed for these sulfonated phases in studies of the retention of cationic solutes. The overall chromatographic selectivity of these −SO3-HC-C8 phases is greatly enhanced by its high hydrophobicity through a “hydrophobically assisted” ion-exchange retention process. PMID:18207150

  11. A validated stability indicating high performance reverse phase liquid chromatographic method for the determination of cilostazol in bulk drug substance.

    PubMed

    Jadhav, A S; Pathare, D B; Shingare, M S

    2007-02-01

    A simple, rapid and accurate reverse phase high-performance liquid chromatographic (RP-HPLC) method was developed for the quantitative determination of cilostazol. The developed method is also applicable for the related substance determination in bulk drugs. The chromatographic separation was achieved on reversed-phase C-18 column. Eluents were monitored on photo-diode array detector at a wavelength of 210 nm using a mixture (50:50) of water and acetonitrile. Solution concentrations were quantified by external calibration. In the developed HPLC method, resolution between cilostazol and its potential impurities, namely Imp-A, Imp-B, and Imp-C were found greater than two. The drug was subjected to stress condition of hydrolysis, oxidation, photolysis and thermal degradation. Considerable degradation was found to occur in alkaline medium stress condition. The developed RP-HPLC method was validated with respect to linearity, accuracy, precision, stability of analytical solutions, and robustness.

  12. Methylammonium formate as a mobile phase modifier for reversed-phase liquid chromatography

    PubMed Central

    Grossman, Shau; Danielson, Neil D.

    2009-01-01

    Although alkylammonium ionic liquids such as ethylammonium nitrate and ethylammonium formate have been used as mobile phase “solvents” for liquid chromatography (LC), we have shown that methylammonium formate (MAF), in part because of its lower viscosity, can be an effective replacement for methanol (MeOH) in reversed-phase LC. Plots of log retention factor versus the fraction of MeOH and MAF in the mobile phase indicate quite comparable solvent strength slope values of 2.50 and 2.05, respectively. Using a polar endcapped C18 column, furazolidone and nitrofurantoin using 20% MAF-80% water could be separated in 22 min but no baseline separation was possible using MeOH as the modifier, even down to 10%. Suppression of silanol peak broadening effects by MAF is important permitting a baseline separation of pyridoxine, thiamine, and nicotinamide using 5% MAF-95% water at 0.7 mL/min. Using 5% MeOH-95% water, severe peak broadening for thiamine is evident. The compatibility of MAF as a mobile phase modifer for LC with mass spectrometry detection of water soluble vitamins is also shown. PMID:18849044

  13. Phase Modulation of Wave Radiated from Time Reversal Array

    NASA Astrophysics Data System (ADS)

    Kikuchi, Toshiaki; Saito, Hideaki; Tsuchiya, Toshio; Hiyoshi, Yoshihisa

    2005-06-01

    In shallow water, since the propagation path of an acoustic wave exists in multiplex, the transfer of information is usually difficult. On the other hand, phase conjugate wave has the property converged on a sound source location even in shallow water and an inhomogeneous medium. A communication simulation of the information that utilized the phase conjugate wave was then performed. Phase modulation was added to the probe wave sent from the sound source, and the signal was reradiated from the array. This not only converged the emitted acoustic wave on the sound source location, but the phase of the converging wave changed in proportion to the modulation phase.

  14. Application of statistical design for the optimization of amino acid separation by reverse-phase HPLC.

    PubMed

    Gheshlaghi, R; Scharer, J M; Moo-Young, M; Douglas, P L

    2008-12-01

    Modified resolution and overall separation factors used to quantify the separation of complex chromatography systems are described. These factors were proven to be applicable to the optimization of amino acid resolution in reverse-phase (RP) HPLC chromatograms. To optimize precolumn derivatization with phenylisothiocyanate, a 2(5-1) fractional factorial design in triplicate was employed. The five independent variables for optimizing the overall separation factor were triethylamine content of the aqueous buffer, pH of the aqueous buffer, separation temperature, methanol/acetonitrile concentration ratio in the organic eluant, and mobile phase flow rate. Of these, triethylamine concentration and methanol/acetonitrile concentration ratio were the most important. The methodology captured the interaction between variables. Temperature appeared in the interaction terms; consequently, it was included in the hierarchic model. The preliminary model based on the factorial experiments was not able to explain the response curvature in the design space; therefore, a central composite design was used to provide a quadratic model. Constrained nonlinear programming was used for optimization purposes. The quadratic model predicted the optimal levels of the variables. In this study, the best levels of the five independent variables that provide the maximum modified resolution for each pair of consecutive amino acids appearing in the chromatograph were determined. These results are of utmost importance for accurate analysis of a subset of amino acids.

  15. [Determination of corosolic acid in Eriobotrya japonica leaves by reversed-phase high performance liquid chromatography].

    PubMed

    Hu, Changping; Chen, Longsheng; Xin, Yang; Cai, Qunxing

    2006-09-01

    Corosolic acid is clinically proven to activate cell glucose-transporter "shuttles" and thus helps balance blood glucose levels. A method was developed for the determination of corosolic acid in Eriobotrya japonica leaves by reversed-phase high performance liquid chromatography (RP-HPLC). The peak of corosolic acid in Eriobotrya japonica leaves was qualitatively analyzed by comparing the retention times and mass spectra of corosolic acid standard and the extract on HPLC-mass spectrometry (MS). Eriobotrya japonica leaves were extracted thrice for 3.0 h at 90 degrees C with 90% ethanol. The extract was concentrated and deposited by water to remove the impurity which interfered the determination. The deposit was dissolved by methanol and separated on an ODS column (250 mm x 4.6 mm i.d., 5 microm). Methanol-1.0% acetic acid (88:12, v/v) was used as the mobile phase with a flow rate of 0.8 mL/min. The detection wavelength was 215 nm. The linearity was good within the range of 1.0-6.0 microg (r = 0.9999). The corosolic acid content of Eriobotrya japonica leaves from Huangshan was 0.36%. The average recovery of corosolic acid was 99%. The method is simple, rapid, accurate and reliable for the determination of corosolic acid in Eriobotrya japonica leaves.

  16. Realizing the promise of reverse phase protein arrays for clinical, translational, and basic research: a workshop report: the RPPA (Reverse Phase Protein Array) society.

    PubMed

    Akbani, Rehan; Becker, Karl-Friedrich; Carragher, Neil; Goldstein, Ted; de Koning, Leanne; Korf, Ulrike; Liotta, Lance; Mills, Gordon B; Nishizuka, Satoshi S; Pawlak, Michael; Petricoin, Emanuel F; Pollard, Harvey B; Serrels, Bryan; Zhu, Jingchun

    2014-07-01

    Reverse phase protein array (RPPA) technology introduced a miniaturized "antigen-down" or "dot-blot" immunoassay suitable for quantifying the relative, semi-quantitative or quantitative (if a well-accepted reference standard exists) abundance of total protein levels and post-translational modifications across a variety of biological samples including cultured cells, tissues, and body fluids. The recent evolution of RPPA combined with more sophisticated sample handling, optical detection, quality control, and better quality affinity reagents provides exquisite sensitivity and high sample throughput at a reasonable cost per sample. This facilitates large-scale multiplex analysis of multiple post-translational markers across samples from in vitro, preclinical, or clinical samples. The technical power of RPPA is stimulating the application and widespread adoption of RPPA methods within academic, clinical, and industrial research laboratories. Advances in RPPA technology now offer scientists the opportunity to quantify protein analytes with high precision, sensitivity, throughput, and robustness. As a result, adopters of RPPA technology have recognized critical success factors for useful and maximum exploitation of RPPA technologies, including the following: preservation and optimization of pre-analytical sample quality, application of validated high-affinity and specific antibody (or other protein affinity) detection reagents, dedicated informatics solutions to ensure accurate and robust quantification of protein analytes, and quality-assured procedures and data analysis workflows compatible with application within regulated clinical environments. In 2011, 2012, and 2013, the first three Global RPPA workshops were held in the United States, Europe, and Japan, respectively. These workshops provided an opportunity for RPPA laboratories, vendors, and users to share and discuss results, the latest technology platforms, best practices, and future challenges and

  17. A reversed-phase compatible thin-layer chromatography autography for the detection of acetylcholinesterase inhibitors.

    PubMed

    Ramallo, I Ayelen; García, Paula; Furlan, Ricardo L E

    2015-11-01

    A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed-phase or normal-phase thin-layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed-phase thin-layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed-phase thin-layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10(-4) μg. The results can be read by a change in color and/or a change in fluorescence. PMID:26489065

  18. A reversed-phase compatible thin-layer chromatography autography for the detection of acetylcholinesterase inhibitors.

    PubMed

    Ramallo, I Ayelen; García, Paula; Furlan, Ricardo L E

    2015-11-01

    A dual readout autographic assay to detect acetylcholinesterase inhibitors present in complex matrices adsorbed on reversed-phase or normal-phase thin-layer chromatography plates is described. Enzyme gel entrapment with an amphiphilic copolymer was used for assay development. The effects of substrate and enzyme concentrations, pH, incubation time, and incubation temperature on the sensitivity and the detection limit of the assay were evaluated. Experimental design and response surface methodology were used to optimize conditions with a minimum number of experiments. The assay allowed the detection of 0.01% w/w of physostigmine in both a spiked Sonchus oleraceus L. extract chromatographed on normal phase and a spiked Pimenta racemosa (Mill.) J.W. Moore leaf essential oil chromatographed on reversed phase. Finally, the reversed-phase thin-layer chromatography assay was applied to reveal the presence of an inhibitor in the Cymbopogon citratus (DC.) Stapf essential oil. The developed assay is able to detect acetylcholinesterase inhibitors present in complex matrixes that were chromatographed in normal phase or reversed-phase thin-layer chromatography. The detection limit for physostigmine on both normal and reversed phase was of 1×10(-4) μg. The results can be read by a change in color and/or a change in fluorescence.

  19. Reversible phase-structure modification of photostructurable glass ceramic by CO2 laser irradiation

    NASA Astrophysics Data System (ADS)

    Sergeev, Maksim M.; Veiko, Vadim P.; Savochkin, Denis A.; Zakoldaev, Roman A.

    2016-10-01

    Structural changes and phase transformations of the photostructurable glass (PhG) surfaces under the impact of 10.6-μm wavelength laser radiation are examined. The regimes initiating the formation and development of crystalline phase and its reversible (secondary) amorphization are determined. In addition, the kinetic of crystalline phase formation and its melting on the surface of PhG are investigated. The characteristics of multiple reversible phase-structure transformations in the temperature range of 470-800 °C are investigated.

  20. Effect of temperature in reversed phase liquid chromatography.

    PubMed

    Guillarme, D; Heinisch, S; Rocca, J L

    2004-10-15

    The high temperature liquid chromatography (HTLC) reveals interesting chromatographic properties but even now, it misses some theoretical aspects concerning the influence of high temperature on thermodynamic and kinetic aspects of chromatography: such a knowledge is very essential for method development. In this work, the effect of temperature on solute behavior has been studied using various stationary phases which are representative of the available thermally stable materials present on the market. The thermodynamic properties were evaluated by using different mobile phases: acetonitrile-water, methanol-water and pure water. The obtained results were discussed on the basis of both type of mobile phases and type of stationary phases. Type of mobile phase was found to play an important role on the retention of solutes. The kinetic aspect was studied at various temperatures ranging from ambient temperature to high temperature (typically from about 30 to 200 degrees C) by fitting the experimental data with the Knox equation and it was shown that the efficiency is improved significantly when the temperature is increased. In this paper, we also discussed the problem of temperature control for thermostating columns which may represent a significant source of peak broadening: by taking into account the three main parameters such as heat transfer, pressure drop and band broadening resulting from the preheating tube, suitable rules are set up for a judicious choice of the column internal diameter. PMID:15527119

  1. Accurate Iris Recognition at a Distance Using Stabilized Iris Encoding and Zernike Moments Phase Features.

    PubMed

    Tan, Chun-Wei; Kumar, Ajay

    2014-07-10

    Accurate iris recognition from the distantly acquired face or eye images requires development of effective strategies which can account for significant variations in the segmented iris image quality. Such variations can be highly correlated with the consistency of encoded iris features and the knowledge that such fragile bits can be exploited to improve matching accuracy. A non-linear approach to simultaneously account for both local consistency of iris bit and also the overall quality of the weight map is proposed. Our approach therefore more effectively penalizes the fragile bits while simultaneously rewarding more consistent bits. In order to achieve more stable characterization of local iris features, a Zernike moment-based phase encoding of iris features is proposed. Such Zernike moments-based phase features are computed from the partially overlapping regions to more effectively accommodate local pixel region variations in the normalized iris images. A joint strategy is adopted to simultaneously extract and combine both the global and localized iris features. The superiority of the proposed iris matching strategy is ascertained by providing comparison with several state-of-the-art iris matching algorithms on three publicly available databases: UBIRIS.v2, FRGC, CASIA.v4-distance. Our experimental results suggest that proposed strategy can achieve significant improvement in iris matching accuracy over those competing approaches in the literature, i.e., average improvement of 54.3%, 32.7% and 42.6% in equal error rates, respectively for UBIRIS.v2, FRGC, CASIA.v4-distance. PMID:25029459

  2. Reversals.

    ERIC Educational Resources Information Center

    National Center on Educational Media and Materials for the Handicapped, Columbus, OH.

    Selected from the National Instructional Materials Information System (NIMIS)--a computer based on-line interactive retrieval system on special education materials--the bibliography covers nine materials for remediating reversals in handicapped students at the early childhood and elementary levels. Entries are presented in order of NIMIS accession…

  3. The development of a growth regime map for a novel reverse-phase wet granulation process.

    PubMed

    Wade, Jonathan B; Martin, Gary P; Long, David F

    2016-10-15

    The feasibility of a novel reverse-phase wet granulation process has been established and potential advantages identified. Granule growth in the reverse-phase process proceeds via a steady state growth mechanism controlled by capillary forces, whereas granule growth in the conventional process proceeds via an induction growth regime controlled by viscous forces. The resultant reverse-phase granules generally have greater mass mean diameter and lower intragranular porosity when compared to conventional granules prepared under the same liquid saturation and impeller speed conditions indicating the two processes may be operating under different growth regimes. Given the observed differences in growth mechanism and consolidation behaviour of the reverse-phase and conventional granules the applicability of the current conventional granulation regime map is unclear. The aim of the present study was therefore to construct and evaluate a growth regime map, which depicts the regime as a function of liquid saturation and Stokes deformation number, for the reverse-phase granulation process. Stokes deformation number was shown to be a good predictor of both granule mass mean diameter and intragranular porosity over a wide range of process conditions. The data presented support the hypothesis that reverse-phase granules have a greater amount of surface liquid present which can dissipate collision energy and resist granule rebound resulting in the greater granule growth observed. As a result the reverse-phase granulation process results in a greater degree of granule consolidation than that produced using the conventional granulation process. Stokes deformation number was capable of differentiating these differences in the granulation process.

  4. Stochastic and reversible assembly of a multiprotein DNA repair complex ensures accurate target site recognition and efficient repair

    PubMed Central

    Luijsterburg, Martijn S.; von Bornstaedt, Gesa; Gourdin, Audrey M.; Politi, Antonio Z.; Moné, Martijn J.; Warmerdam, Daniël O.; Goedhart, Joachim; Vermeulen, Wim

    2010-01-01

    To understand how multiprotein complexes assemble and function on chromatin, we combined quantitative analysis of the mammalian nucleotide excision DNA repair (NER) machinery in living cells with computational modeling. We found that individual NER components exchange within tens of seconds between the bound state in repair complexes and the diffusive state in the nucleoplasm, whereas their net accumulation at repair sites evolves over several hours. Based on these in vivo data, we developed a predictive kinetic model for the assembly and function of repair complexes. DNA repair is orchestrated by the interplay of reversible protein-binding events and progressive enzymatic modifications of the chromatin substrate. We demonstrate that faithful recognition of DNA lesions is time consuming, whereas subsequently, repair complexes form rapidly through random and reversible assembly of NER proteins. Our kinetic analysis of the NER system reveals a fundamental conflict between specificity and efficiency of chromatin-associated protein machineries and shows how a trade off is negotiated through reversibility of protein binding. PMID:20439997

  5. Stochastic and reversible assembly of a multiprotein DNA repair complex ensures accurate target site recognition and efficient repair.

    PubMed

    Luijsterburg, Martijn S; von Bornstaedt, Gesa; Gourdin, Audrey M; Politi, Antonio Z; Moné, Martijn J; Warmerdam, Daniël O; Goedhart, Joachim; Vermeulen, Wim; van Driel, Roel; Höfer, Thomas

    2010-05-01

    To understand how multiprotein complexes assemble and function on chromatin, we combined quantitative analysis of the mammalian nucleotide excision DNA repair (NER) machinery in living cells with computational modeling. We found that individual NER components exchange within tens of seconds between the bound state in repair complexes and the diffusive state in the nucleoplasm, whereas their net accumulation at repair sites evolves over several hours. Based on these in vivo data, we developed a predictive kinetic model for the assembly and function of repair complexes. DNA repair is orchestrated by the interplay of reversible protein-binding events and progressive enzymatic modifications of the chromatin substrate. We demonstrate that faithful recognition of DNA lesions is time consuming, whereas subsequently, repair complexes form rapidly through random and reversible assembly of NER proteins. Our kinetic analysis of the NER system reveals a fundamental conflict between specificity and efficiency of chromatin-associated protein machineries and shows how a trade off is negotiated through reversibility of protein binding. PMID:20439997

  6. SEPARATION OF T-MAZ ETHOXYLATED SORBITAN FATTY ACID ESTERS BY REVERSE PHASE CHROMATOGRAPHY

    EPA Science Inventory

    The method for determination of T-MAZ ethoxylated sorbitan fatty acid esters is described. This work demonstrates that with a less retentive C8 alkyl bonded phase packing, reverse phase chromatography can be used to analyze nonionic polymer mixtures with a molecular weight range ...

  7. Separation of bacteriochlorophyll homologues from green photosynthetic sulfur bacteria by reversed-phase HPLC.

    PubMed

    Borrego, C M; Garcia-Gil, L J

    1994-07-01

    A reversed-phase High Performance Liquid Cromatography (HPLC) method has been developed to accurately separate bacteriochlorophyllsc, d ande homologues in a reasonably short run time of 60 minutes. By using this method, two well-defined groups of bacteriochlorophyll homologue peaks can be discriminated. The first one consists of 4 peaks (min 24 to 30), which corresponds to the four main farnesyl homologues. The second peak subset is formed by a cluster of up to 10 minor peaks (min 33 to 40). These peaks can be related with series of several alcohol esters of the different chlorosome chlorophylls. The number of homologues was, however, quite variable depending on both, the bacteriochlorophyll and the bacterial species. The method hereby described, also provides a good separation of other photosynthetic pigments, either bacterial (Bacteriochlorophylla, chlorobactene, isorenieratene and okenone) or algal ones (Chlorophylla, Pheophytina and β-carotene). A preliminary screening of the homologue composition of several green photosynthetic bacterial species and isolates, has revealed different relative quantitative patterns. These differences seem to be related to physiological aspects rather than to taxonomic ones. The application of the method to the study of natural populations avoids the typical drawbacks on the pigment identification of overlapping eukaryotic and prokaryotic phototrophic microorganisms, giving further information about their physiological status.

  8. Concentration-Controlled Reversible Phase Transitions in Self-Assembled Monolayers on HOPG Surfaces.

    PubMed

    Shen, Xueli; Wei, Xiaodong; Tan, Pengli; Yu, Yingguo; Yang, Biao; Gong, Zhongmiao; Zhang, Haiming; Lin, Haiping; Li, Youyong; Li, Qing; Xie, Yongshu; Chi, Lifeng

    2015-05-20

    Rational control of molecular ordering on surfaces and interfaces is vital in supramolecular chemistry and nanoscience. Here, a systematic scanning tunneling microscopy (STM) study for controlling the self-assembly behavior of alkoxylated benzene (B-OC(n)) molecules on a HOPG surface is presented. Three different phases have been observed and, of great importance, they can transform to each other by modifying the solute concentration. Further studies, particularly in situ diluting and concentrating experiments, demonstrate that the transitions among the three phases are highly controllable and reversible, and are driven thermodynamically. In addition, it is found that concentration-controlled reversible phase transitions are general for different chain lengths of B-OC(n) molecules. Such controllable and reversible phase transitions may have potential applications in the building of desirable functional organic thin films and provide a new understanding in thermodynamically driven self-assembly of organic molecules on surfaces and interfaces.

  9. Reverse phase liquid chromatographic determination of some food additives.

    PubMed

    Veerabhadrarao, M; Narayan, M S; Kapur, O

    1987-01-01

    Liquid chromatographic methods are described for the separation and determination of non-nutritive sweeteners, namely, acesulfame, aspartame, saccharin, and dulcin; preservatives such as benzoic acid and p-hydroxybenzoic acid; and caffeine and vanillin in ready-to-serve beverages, ice candy, ice cream, squash beverage, tomato sauce, and dry beverage mix samples. These additives are separated on a muBondapak C18 column using methanol-acetic acid-water (20 + 5 + 75) as mobile phase and detected by UV absorption at 254 nm. Caffeine, vanillin, dulcin, and benzoic acid can be analyzed quickly by using a mobile phase of methanol-acetic acid-water (35 + 5 + 60). Aspartame can be separated in the presence of caffeine and vanillin by using the mobile phase pH 3 acetate buffer-methanol (95 + 5). Retention factors and minimum detectable limits are described. The percentage error and the percent relative standard deviation for 6 replicate samples ranged from 0.3 to 2.8 and from 1.64 to 3.60, respectively. Recovery of additives added to the foods named and analyzed by the direct method and by extraction ranged from 98.0 to 100.6% and from 91.6 to 101.8%, respectively. The proposed LC techniques are simple, rapid, and advantageous because all the additives can be detected in a single step, which makes it useful for the routine analysis of various food products.

  10. I/Q reversal phenomena in 4-phase modified Costas Loops. [in-phase and quadrature outputs of unbalanced QPSK

    NASA Technical Reports Server (NTRS)

    Weinberg, A.

    1985-01-01

    A method for predicting the occurrence of I/Q reversals in unbalanced QPSK 4-phase modified Costas Loops is discussed. Potential causes for the reversal of in-phase and quadrature outputs of the unbalanced QPSK demodulator during acquisition and tracking are studied. The design of the unbalance QPSK demodulator and loop characteristics are described. The effect of an anomalous condition during a transient interval or demod/remod operation on data source output is examined. Filtering and hard-limiting effects, and the demodulator loop S-curve stability during tracking are evaluated.

  11. Dopaminergic modulation of phase reversal in desert locusts

    PubMed Central

    Alessi, Ahmad M.; O'Connor, Vincent; Aonuma, Hitoshi; Newland, Philip L.

    2014-01-01

    Phenotypic plasticity allows animals to modify their behavior, physiology, and morphology to adapt to environmental change. The global pest, the desert locust, shows two extreme phenotypes; a solitarious phase that is relatively harmless and a gregarious phase that forms swarms and causes extensive agricultural and economic damage. In the field, environmental conditions can drive isolated animals into crowded populations and previous studies have identified the biogenic amine serotonin as a key determinant of this transition. Here we take an integrated approach to investigate the neurochemical, physiological, and behavioral correlates defined by a laboratory based paradigm that mimics facets of swarm break down as gregarious locusts become isolated. Following isolation there was an increased propensity of locusts to avoid conspecifics, and show a reduced locomotion. Changes in choice behavior occurred within 1 h of isolation although isolation-related changes progressed with increased isolation time. Isolation was accompanied by changes in the levels of the biogenic amines dopamine, octopamine, and serotonin within the CNS within 1 h. Dopamine levels were higher in isolated animals and we focused on the role played by this transmitter in synaptic changes that may underpin solitarization. Dopamine reduced synaptic efficacy at a key central synapse between campaniform sensilla (CS) and a fast extensor tibiae motor neuron that is involved in limb movement. We also show that dopamine injection into the haemocoel was sufficient to induce solitarious-like behavior in otherwise gregarious locusts. Further, injection of a dopamine antagonist, fluphenazine, into isolated locusts induced gregarious-like behavior. This highlights that dopaminergic modulation plays an important role in the plasticity underpinning phase transition and sets a context to deepen the understanding of the complementary role that distinct neuromodulators play in polyphenism in locusts. PMID:25426037

  12. Dopaminergic modulation of phase reversal in desert locusts.

    PubMed

    Alessi, Ahmad M; O'Connor, Vincent; Aonuma, Hitoshi; Newland, Philip L

    2014-01-01

    Phenotypic plasticity allows animals to modify their behavior, physiology, and morphology to adapt to environmental change. The global pest, the desert locust, shows two extreme phenotypes; a solitarious phase that is relatively harmless and a gregarious phase that forms swarms and causes extensive agricultural and economic damage. In the field, environmental conditions can drive isolated animals into crowded populations and previous studies have identified the biogenic amine serotonin as a key determinant of this transition. Here we take an integrated approach to investigate the neurochemical, physiological, and behavioral correlates defined by a laboratory based paradigm that mimics facets of swarm break down as gregarious locusts become isolated. Following isolation there was an increased propensity of locusts to avoid conspecifics, and show a reduced locomotion. Changes in choice behavior occurred within 1 h of isolation although isolation-related changes progressed with increased isolation time. Isolation was accompanied by changes in the levels of the biogenic amines dopamine, octopamine, and serotonin within the CNS within 1 h. Dopamine levels were higher in isolated animals and we focused on the role played by this transmitter in synaptic changes that may underpin solitarization. Dopamine reduced synaptic efficacy at a key central synapse between campaniform sensilla (CS) and a fast extensor tibiae motor neuron that is involved in limb movement. We also show that dopamine injection into the haemocoel was sufficient to induce solitarious-like behavior in otherwise gregarious locusts. Further, injection of a dopamine antagonist, fluphenazine, into isolated locusts induced gregarious-like behavior. This highlights that dopaminergic modulation plays an important role in the plasticity underpinning phase transition and sets a context to deepen the understanding of the complementary role that distinct neuromodulators play in polyphenism in locusts. PMID:25426037

  13. Multimodal Quantitative Phase Imaging with Digital Holographic Microscopy Accurately Assesses Intestinal Inflammation and Epithelial Wound Healing.

    PubMed

    Lenz, Philipp; Brückner, Markus; Ketelhut, Steffi; Heidemann, Jan; Kemper, Björn; Bettenworth, Dominik

    2016-01-01

    The incidence of inflammatory bowel disease, i.e., Crohn's disease and Ulcerative colitis, has significantly increased over the last decade. The etiology of IBD remains unknown and current therapeutic strategies are based on the unspecific suppression of the immune system. The development of treatments that specifically target intestinal inflammation and epithelial wound healing could significantly improve management of IBD, however this requires accurate detection of inflammatory changes. Currently, potential drug candidates are usually evaluated using animal models in vivo or with cell culture based techniques in vitro. Histological examination usually requires the cells or tissues of interest to be stained, which may alter the sample characteristics and furthermore, the interpretation of findings can vary by investigator expertise. Digital holographic microscopy (DHM), based on the detection of optical path length delay, allows stain-free quantitative phase contrast imaging. This allows the results to be directly correlated with absolute biophysical parameters. We demonstrate how measurement of changes in tissue density with DHM, based on refractive index measurement, can quantify inflammatory alterations, without staining, in different layers of colonic tissue specimens from mice and humans with colitis. Additionally, we demonstrate continuous multimodal label-free monitoring of epithelial wound healing in vitro, possible using DHM through the simple automated determination of the wounded area and simultaneous determination of morphological parameters such as dry mass and layer thickness of migrating cells. In conclusion, DHM represents a valuable, novel and quantitative tool for the assessment of intestinal inflammation with absolute values for parameters possible, simplified quantification of epithelial wound healing in vitro and therefore has high potential for translational diagnostic use. PMID:27685659

  14. Quantum Dots-based Reverse Phase Protein Microarray

    SciTech Connect

    Shingyoji, Masato; Gerion, Daniele; Pinkel, Dan; Gray, Joe W.; Chen, Fanqing

    2005-07-15

    CdSe nanocrystals, also called quantum dots (Qdots) are a novel class of fluorophores, which have a diameter of a few nanometers and possess high quantum yield, tunable emission wavelength and photostability. They are an attractive alternative to conventional fluorescent dyes. Quantum dots can be silanized to be soluble in aqueous solution under biological conditions, and thus be used in bio-detection. In this study, we established a novel Qdot-based technology platform that can perform accurate and reproducible quantification of protein concentration in a crude cell lysate background. Protein lysates have been spiked with a target protein, and a dilution series of the cell lysate with a dynamic range of three orders of magnitude has been used for this proof-of-concept study. The dilution series has been spotted in microarray format, and protein detection has been achieved with a sensitivity that is at least comparable to standard commercial assays, which are based on horseradish peroxidase (HRP) catalyzed diaminobenzidine (DAB) chromogenesis. The data obtained through the Qdot method has shown a close linear correlation between relative fluorescence unit and relative protein concentration. The Qdot results are in almost complete agreement with data we obtained with the well-established HRP-DAB colorimetric array (R{sup 2} = 0.986). This suggests that Qdots can be used for protein quantification in microarray format, using the platform presented here.

  15. Impact of reversed phase column pairs in comprehensive two-dimensional liquid chromatography.

    PubMed

    Allen, Robert C; Barnes, Brian B; Haidar Ahmad, Imad A; Filgueira, Marcelo R; Carr, Peter W

    2014-09-26

    A major issue in optimizing the resolving power of two-dimensional chromatographic separations is the choice of the two phases so as to maximize the distribution of the analytes over the separation space. In this work, we studied the choice of appropriate reversed phases to use in on-line comprehensive two-dimensional liquid chromatography (LC×LC). A set of four chemically different conventional bonded reversed phases was used in the first dimension. The second dimension column was either a conventional bonded C18 phase or a carbon-clad phase (CCP). The LC×LC chromatograms and contour plots were all rather similar indicating that the selectivities of the two phases were also similar regardless of the reverse phase column used in the first dimension. Further, the spatial coverage seen with all four first dimension stationary phases when paired with a second dimension C18 phase were low and the retention times were strongly correlated. However, when the C18 column was replaced with the CCP column much improved separations were observed with higher spatial coverages, greater orthogonalities and significant increases in the number of observed peaks.

  16. Molecular Simulation of the Free Energy for the Accurate Determination of Phase Transition Properties of Molecular Solids

    NASA Astrophysics Data System (ADS)

    Sellers, Michael; Lisal, Martin; Brennan, John

    2015-06-01

    Investigating the ability of a molecular model to accurately represent a real material is crucial to model development and use. When the model simulates materials in extreme conditions, one such property worth evaluating is the phase transition point. However, phase transitions are often overlooked or approximated because of difficulty or inaccuracy when simulating them. Techniques such as super-heating or super-squeezing a material to induce a phase change suffer from inherent timescale limitations leading to ``over-driving,'' and dual-phase simulations require many long-time runs to seek out what frequently results in an inexact location of phase-coexistence. We present a compilation of methods for the determination of solid-solid and solid-liquid phase transition points through the accurate calculation of the chemical potential. The methods are applied to the Smith-Bharadwaj atomistic potential's representation of cyclotrimethylene trinitramine (RDX) to accurately determine its melting point (Tm) and the alpha to gamma solid phase transition pressure. We also determine Tm for a coarse-grain model of RDX, and compare its value to experiment and atomistic counterpart. All methods are employed via the LAMMPS simulator, resulting in 60-70 simulations that total 30-50 ns. Approved for public release. Distribution is unlimited.

  17. Metal-organic framework MIL-100(Fe) as the stationary phase for both normal-phase and reverse-phase high performance liquid chromatography.

    PubMed

    Fu, Yan-Yan; Yang, Cheng-Xiong; Yan, Xiu-Ping

    2013-01-25

    Metal-organic framework MIL-100(Fe) was explored as a novel stationary phase for both normal-phase and reverse-phase high performance liquid chromatography. Two groups of analytes (benzene, toluene, ethylbenzene, naphthalene and 1-chloronaphthalene; aniline, acetanilide, 2-nitroaniline and 1-naphthylamine) were used to test the separation performance of MIL-100(Fe) in the reverse-phase mode, while the isomers of chloroaniline or toluidine were employed to evaluate its performance in the normal-phase mode. The MIL-100(Fe) packed column gave a baseline separation of all the tested analytes with good precision. The separation was controlled by negative enthalpy change and entropy change in the reverse-phase mode, but positive enthalpy change and entropy change in the normal-phase mode. The relative standard deviations of retention time, peak area, peak height, and half peak width for eleven replicate separations of the tested analytes were 0.2-0.7%, 0.5-3.6%, 0.6-2.3% and 0.8-1.7%, respectively. The mesoporous cages, accessible windows, excellent chemical and solvent stability, metal active sites and aromatic pore walls make MIL-100(Fe) a good candidate as a novel stationary phase for both normal-phase and reverse-phase high performance liquid chromatography. PMID:23290359

  18. Surface diffusion in reversed-phase liquid chromatography

    SciTech Connect

    Miyabe, Kanji; Guiochon, Georges A

    2010-01-01

    More than 40 years ago, Giddings pointed out in 'Dynamics of Chromatography' that surface diffusion should become an important research topic in the kinetics of chromatographic phenomena. However, few studies on surface diffusion in adsorbents used in chromatography were published since then. Most scientists use ordinary rate equations to study mass transfer kinetics in chromatography. They take no account of surface diffusion and overlook the significant contributions of this mass transfer process to chromatographic behavior and to column efficiency at high mobile phase flow rate. Only recently did the significance of surface diffusion in separation processes begin to be recognized in connection with the development of new techniques of fast flow, high efficiency chromatography. In this review, we revisit the reports on experimental data on surface diffusion and introduce a surface-restricted molecular diffusion model, derived as a first approximation for the mechanism of surface diffusion, on the basis of the absolute rate theory. We also explain how this model accounts for many intrinsic characteristics of surface diffusion that cannot properly be explained by the conventional models of surface diffusion.

  19. I/Q reversal phenomena in 4-phase modified Costas Loops

    NASA Astrophysics Data System (ADS)

    Weinberg, A.

    A method for predicting the occurrence of I/Q reversals in unbalanced QPSK 4-phase modified Costas Loops is discussed. Potential causes for the reversal of in-phase and quadrature outputs of the unbalanced QPSK demodulator during acquisition and tracking are studied. The design of the unbalance QPSK demodulator and loop characteristics are described. The effect of an anomalous condition during a transient interval or demod/remod operation on data source output is examined. Filtering and hard-limiting effects, and the demodulator loop S-curve stability during tracking are evaluated.

  20. [Research on the separation of limonoid glucosides by reversed-phase preparative high performance liquid chromatography].

    PubMed

    Tian, Q G; Dai, J; Ding, X L

    2000-03-01

    Obacunone-17-beta-D-glucopyranoside (OG) was isolated from the seeds of Citrus Sinensis Osbeck by using solvent extraction, classical polymer adsorption column separation and weak base anion ion-exchange separation, OG was finally purified by C18 reversed-phase preparative high performance liquid chromatography and was identified by thin-layer chromatography. The purity of OG was analyzed by analytical reversed-phase HPLC. At last the structure of OG was determined by 1H and 13C nuclear magnetic resonance spectrometry (NMR). In this work, the conditions of the reversed-phase preparative HPLC technique to purify limonoid glucosides was optimized. The reversed-phase preparative HPLC on a C18 column with a mobile phase of acidic acetonitrile-water (about 0.2% TFA, V/V) at pH 3 enabled the baseline separation of limonoid glucosides in the extract. The results show that OG is the predominant limonoid glucoside in the seeds of Citrus Sinensis Osbeck and nomilin glucoside is the second one. The results also show that the classical polymer adsorption column separation and weak base anion ion-exchange separation are effective for purifying limonoid glucosides.

  1. Phase stability of a reversible supramolecular polymer solution mixed with nanospheres

    NASA Astrophysics Data System (ADS)

    Tuinier, Remco

    2011-05-01

    Theory is presented for the phase stability of mixtures containing nanospheres and non-adsorbing reversible supramolecular polymers. This was made possible by incorporating the depletion thickness and osmotic pressure of reversible supramolecular polymer chains into generalized free-volume theory, recently developed for investigating the phase behaviour of colloidal spheres mixed with interacting polymers (Fleer and Tuinier 2008 Adv. Colloid Interface Sci. 143 1-47). It follows that the fluid-fluid phase stability region where reversible supramolecular polymer chains can be mixed with nanospheres is sensitive to the energy of scission between the monomers and to the nanoparticle radius. One can then expect the fluid-fluid coexistence curves to have a strong dependence on temperature and that shifting of phase boundaries within a single experimental system should be possible by varying the temperature. The calculations reveal the width of the stability region to be rather small. This implies that phase homogeneity of product formulations containing reversible supramolecular polymers is only possible at low nanoparticle concentrations.

  2. Reversible work of formation of an embryo of a new phase within a uniform macroscopic mother phase

    SciTech Connect

    Debenedetti, P.G.; Reiss, H. |

    1998-04-01

    A thermodynamically consistent formalism is derived for calculating the reversible work needed to form a small amount of a new phase (embryo) within a uniform macroscopic mother phase. The treatment goes beyond the classic work of Gibbs, who solved the problem for the particular case in which the embryo is in equilibrium with the mother phase, constituting a so-called critical nucleus. The formalism results in a new expression for the reversible work of embryo formation, the extrema conditions for which yield the correct conditions of equilibrium between the critical nucleus and the mother phase, as well as Gibbs{close_quote} result for the reversible work needed to form the critical nucleus. The new expression for the work of embryo formation differs from the one commonly used in the nucleation literature. In order to extend the Gibbsian formalism to noncritical nuclei, it is necessary to introduce a constraint that prevents the free transfer of matter between the embryo and the mother phase. The present approach is valid in the limit in which curvature contributions to the interfacial energy can be neglected. {copyright} {ital 1998 American Institute of Physics.}

  3. Reversible Phase Transfer of Nanoparticles Based on Photoswitchable Host–Guest Chemistry

    PubMed Central

    2015-01-01

    An azobenzene-containing surfactant was synthesized for the phase transfer of α-cyclodextrin (α-CD)-capped gold nanoparticles between water and toluene phases by host–guest chemistry. With the use of the photoisomerization of azobenzene, the reversible phase transfer of gold nanoparticles was realized by irradiation with UV and visible light. Furthermore, the phase transfer scheme was applied for the quenching of a reaction catalyzed by gold nanoparticles, as well as the recovery and recycling of the gold nanoparticles from aqueous solutions. This work will have significant impact on materials transfer and recovery in catalysis and biotechnological applications. PMID:24524295

  4. Direct observation of the recovery of an antiferroelectric phase during polarization reversal of an induced ferroelectric phase

    NASA Astrophysics Data System (ADS)

    Guo, Hanzheng; Tan, Xiaoli

    2015-04-01

    Electric fields are generally known to favor the ferroelectric polar state over the antiferroelectric nonpolar state for their Coulomb interactions with dipoles in the crystal. In this paper, we directly image an electric-field-assisted ferroelectric-to-antiferroelectric phase transition during polarization reversal of the ferroelectric phase in polycrystalline P b0.99{N b0.02[(Zr0.57Sn0.43) 0.92T i0.08] 0.98}O3 . With the electric-field in situ transmission electron microscopy technique, such an unlikely phenomenon is verified to occur by both domain morphology change and electron-diffraction analysis. The slower kinetics of the phase transition, compared with ferroelectric polarization reversal, is suggested to contribute to this unusual behavior.

  5. Accurate Predictions of Mean Geomagnetic Dipole Excursion and Reversal Frequencies, Mean Paleomagnetic Field Intensity, and the Radius of Earth's Core Using McLeod's Rule

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.; Conrad, Joy

    1996-01-01

    The geomagnetic spatial power spectrum R(sub n)(r) is the mean square magnetic induction represented by degree n spherical harmonic coefficients of the internal scalar potential averaged over the geocentric sphere of radius r. McLeod's Rule for the magnetic field generated by Earth's core geodynamo says that the expected core surface power spectrum (R(sub nc)(c)) is inversely proportional to (2n + 1) for 1 less than n less than or equal to N(sub E). McLeod's Rule is verified by locating Earth's core with main field models of Magsat data; the estimated core radius of 3485 kn is close to the seismologic value for c of 3480 km. McLeod's Rule and similar forms are then calibrated with the model values of R(sub n) for 3 less than or = n less than or = 12. Extrapolation to the degree 1 dipole predicts the expectation value of Earth's dipole moment to be about 5.89 x 10(exp 22) Am(exp 2)rms (74.5% of the 1980 value) and the expected geomagnetic intensity to be about 35.6 (mu)T rms at Earth's surface. Archeo- and paleomagnetic field intensity data show these and related predictions to be reasonably accurate. The probability distribution chi(exp 2) with 2n+1 degrees of freedom is assigned to (2n + 1)R(sub nc)/(R(sub nc). Extending this to the dipole implies that an exceptionally weak absolute dipole moment (less than or = 20% of the 1980 value) will exist during 2.5% of geologic time. The mean duration for such major geomagnetic dipole power excursions, one quarter of which feature durable axial dipole reversal, is estimated from the modern dipole power time-scale and the statistical model of excursions. The resulting mean excursion duration of 2767 years forces us to predict an average of 9.04 excursions per million years, 2.26 axial dipole reversals per million years, and a mean reversal duration of 5533 years. Paleomagnetic data show these predictions to be quite accurate. McLeod's Rule led to accurate predictions of Earth's core radius, mean paleomagnetic field

  6. (PRESENT AT NCCU) ANALYSIS OF SELECTED PYRETHROID PESTICIDES USING REVERSE PHASE HIGH LIQUID CHROMATOGRAPHY

    EPA Science Inventory

    This research was conducted in cooperation with EPA Region 4 in Athens, GA to develop a method to analyze selected pyrethroid pesticides using Reverse Phase-High Pressure Liquid Chromatography (HPLC). This HPLC method will aid researchers in separating and identifying these pyre...

  7. ANALYSIS OF SELECTED PYRETHROID PESTICIDES USING REVERSE PHASE HIGH PRESSURE LIQUID CHROMATOGRAPHY/UV

    EPA Science Inventory

    This research was conducted in cooperation with EPA Region 4 in Athens, GA to develop a method to analyze selected pyrethroid pesticides using Reverse Phase-High Pressure Liquid Chromatography (HPLC). This HPLC method will aid researchers in separating and identifying these py...

  8. Selective distributions of functionalized single-walled carbon nanotubes in a polymeric reverse hexagonal phase.

    PubMed

    Ha, Jae-Min; Jang, Hyung-Sik; Lim, Sung-Hwan; Choi, Sung-Min

    2015-08-01

    We have investigated the distributions of individually isolated and hydrophilically functionalized single-walled carbon nanotubes (p-SWNTs) in the Pluronic L121-water system at the reverse hexagonal phase using small-angle X-ray scattering (SAXS) and contrast-matched small-angle neutron scattering (SANS) measurements. As the p-SWNT-L121-water system is transitioned from the lamellar phase to the reverse hexagonal phase with temperature, p-SWNTs which were selectively distributed in the polar layers of the lamellar structure become selectively distributed in the cylindrical polar cores of the reverse hexagonal structure, forming a hexagonal array of p-SWNTs. This was clearly confirmed by the contrast-matched SANS measurements. The selective distribution of p-SWNTs in the reverse hexagonal phase is driven by the selective affinity of p-SWNTs to the polar domains of the block copolymer system. The method demonstrated in this study provides a new route for fabricating ordered SWNT superstructures and may be applicable for inorganic 1D nanoparticles such as semiconducting, metallic and magnetic nanorods which are of great interest.

  9. 40Ar/39Ar dating of Pleistocene tuffs: an accurate age for the Matuyama-Brunhes geomagnetic reversal (MBGR)

    NASA Astrophysics Data System (ADS)

    Mark, D. F.; Renne, P. R.; Morgan, L. E.; Deino, A.; Smith, V. C.; Ellis, B. S.; Pearce, N. J.

    2012-12-01

    Recent recalibrations of the 40Ar/39Ar system [1,2] reveal inconsistencies with some previous ages inferred for the MBGR. An Ar/Ar age [3] for the Bishop Tuff (BT) (which post-dates the MBGR by at least 15.3 ± 2.2 ka [3]) recalculated [2] yields an age of 778.0 ± 3.8 ka (1σ, full systematic uncertainty). The age is c. 10 ka older than the BT zircon ID-TIMS U-Pb age [4] and places the MBGR at c. 793 ka, c. 13 and 20 ka older than astronomical ages for the MBGR of 780 ka [5] and 773 ka [6], respectively. To determine an accurate age for the MBGR, we have made a series of 40Ar/39Ar age determinations for Pleistocene tuffs from both Indonesia and North America that have direct relationships to the MBGR. Blind analyses were conducted at SUERC and BGC. We observed excellent inter-laboratory agreement and no systematic offset in data. Ar/Ar ages are reported relative to [2] (1σ, full systematic uncertainty). Drill cores from ODP Site 758 show the precise location of the MBGR. Below the MBGR are two distal tephra horizons that we have identified as products of two temporally distinct Old Toba Tuff (OTT) eruptions (layer d OTT1 and layer D OTT2). Continuous sedimentation between OTT1 (802.8 ± 0.7 ka, n = 100, MSWD 1.2) and OTT2 (796.2 ± 0.8 ka, n = 62, MSWD 1.3) allows for calculation of an accurate sedimentation rate and for extrapolation of an age from OTT2 to the MBGR. Data define an age for the MBGR of 795.2 ± 0.9 ka. Using tephra above the MBGR boundary, the Middle Toba Tuff (layer C) and Young Toba Tuff (layer A), extrapolation down core supports a MBGR age of c. 795 ka. Recent age data for BT sanidine reported relative to FCs at 28.172 Ma (767.4 ± 1.1 Ma) [7] oddly yielded an Ar/Ar age that was indistinguishable from the BT zircon U-Pb age [4], which is consistent with previous 40Ar/39Ar age measurements made relative to FCs at 28.02 Ma [3]. Thus we made a series of 40Ar/39Ar measurements on the exact same sample as used by Rivera et al. [7] and observed

  10. Reversed-phase thin-layer chromatography of homologs of Antimycin-A and related derivatives

    USGS Publications Warehouse

    Abidi, Sharon L.

    1989-01-01

    Using a reversed-phase high-performance liquid chromatographic (HPLC) technique, a mixture of antimycins A was separated into eight hitherto unreported subcomponents, Ala, Alb, A2a, A2b, A3a, A3b, A4a, and A4b. Although a base-line resolution of the known four major antimycins Al, A2, A3, and A4 was readily achieved with mobile phases containing acetate buffers, the separation of the new antibiotic subcomponents was highly sensitive to variation in mobile phase conditions. The type and composition of organic modifiers, the nature of buffer salts, and the concentration of added electrolytes had profound effects on capacity factors, separation factors, and peak resolution values. Of the numerous chromatographic systems examined, a mobile phase consisting of methanol-water (70:30) and 0.005 M tetrabutylammonium phosphate at pH 3.0 yielded the most satisfactory results for the separation of the subcomponents. Reversed-phase gradient HPLC separation of the dansylated or methylated antibiotic compounds produced superior chromatographic characteristics and the presence of added electrolytes was not a critical factor for achieving separation. Differences in the chromatographic outcome between homologous and structural isomers were interpretated based on a differential solvophobic interaction rationale. Preparative reversed-phase HPLC under optimal conditions enabled isolation of pure samples of the methylated antimycin subcomponents for use in structural studies.

  11. Simultaneous determinations by theophylline and its major metabolites in urine by reversed-phase ion-pair high-performance liquid chromatography.

    PubMed

    Muir, K T; Jonkman, J H; Tang, D S; Kunitani, M; Riegelman, S

    1980-11-14

    A new, highly slective high-performance liquid-chromatographic (HPLC) assay for theophylline and its major metabolites in urine is described. The method utilizes an ion-pair extraction followed by separation and quantitation by reversed-phase ion-pair gradient-elution HPLC. Comparison with several other methods showed that interferences were present in too many blank urine samples to allow for the accurate quantitation of the metabolites of theophylline by direct injection--isocratic HPLC assays. Sample processing involving ion-pair complexing and extraction together with gradient-elution systems is recommended for accurate pharmacokinetic studies.

  12. Reversible phase modulation and hydrogen storage in multivalent VO2 epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Yoon, Hyojin; Choi, Minseok; Lim, Tae-Won; Kwon, Hyunah; Ihm, Kyuwook; Kim, Jong Kyu; Choi, Si-Young; Son, Junwoo

    2016-10-01

    Hydrogen, the smallest and the lightest atomic element, is reversibly incorporated into interstitial sites in vanadium dioxide (VO2), a correlated oxide with a 3d1 electronic configuration, and induces electronic phase modulation. It is widely reported that low hydrogen concentrations stabilize the metallic phase, but the understanding of hydrogen in the high doping regime is limited. Here, we demonstrate that as many as two hydrogen atoms can be incorporated into each VO2 unit cell, and that hydrogen is reversibly absorbed into, and released from, VO2 without destroying its lattice framework. This hydrogenation process allows us to elucidate electronic phase modulation of vanadium oxyhydride, demonstrating two-step insulator (VO2)-metal (HxVO2)-insulator (HVO2) phase modulation during inter-integer d-band filling. Our finding suggests the possibility of reversible and dynamic control of topotactic phase modulation in VO2 and opens up the potential application in proton-based Mottronics and novel hydrogen storage.

  13. Reversible phase modulation and hydrogen storage in multivalent VO2 epitaxial thin films.

    PubMed

    Yoon, Hyojin; Choi, Minseok; Lim, Tae-Won; Kwon, Hyunah; Ihm, Kyuwook; Kim, Jong Kyu; Choi, Si-Young; Son, Junwoo

    2016-10-01

    Hydrogen, the smallest and the lightest atomic element, is reversibly incorporated into interstitial sites in vanadium dioxide (VO2), a correlated oxide with a 3d(1) electronic configuration, and induces electronic phase modulation. It is widely reported that low hydrogen concentrations stabilize the metallic phase, but the understanding of hydrogen in the high doping regime is limited. Here, we demonstrate that as many as two hydrogen atoms can be incorporated into each VO2 unit cell, and that hydrogen is reversibly absorbed into, and released from, VO2 without destroying its lattice framework. This hydrogenation process allows us to elucidate electronic phase modulation of vanadium oxyhydride, demonstrating two-step insulator (VO2)-metal (HxVO2)-insulator (HVO2) phase modulation during inter-integer d-band filling. Our finding suggests the possibility of reversible and dynamic control of topotactic phase modulation in VO2 and opens up the potential application in proton-based Mottronics and novel hydrogen storage.

  14. Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors

    PubMed Central

    Yu, Zhenhai; Wang, Lin; Wang, Luhong; Liu, Haozhe; Zhao, Jinggeng; Li, Chunyu; Sinogeikin, Stanislav; Wu, Wei; Luo, Jianlin; Wang, Nanlin; Yang, Ke; Zhao, Yusheng; Mao, Ho-kwang

    2014-01-01

    Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram of the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). The cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure. PMID:25417655

  15. Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors.

    PubMed

    Yu, Zhenhai; Wang, Lin; Wang, Luhong; Liu, Haozhe; Zhao, Jinggeng; Li, Chunyu; Sinogeikin, Stanislav; Wu, Wei; Luo, Jianlin; Wang, Nanlin; Yang, Ke; Zhao, Yusheng; Mao, Ho-kwang

    2014-01-01

    Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram of the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). The cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure. PMID:25417655

  16. Determination of pantothenic acid in multivitamin pharmaceutical preparations by reverse-phase high-performance liquid chromatography.

    PubMed

    Hudson, T J; Allen, R J

    1984-01-01

    A high-performance liquid chromatographic procedure was developed for the analysis of calcium pantothenate in nutritional supplements. The method involves a simple extraction using phosphate buffer and sonication. Chromatographic separation is obtained using an aminopropyl-loaded silica gel column in the reverse-phase mode. A UV detector set at 210 nm was used to monitor the effluent. Quantitative recoveries were obtained, and precision of the method is discussed. The method is applicable to multivitamin tablets, calcium pantothenate raw material, and yeast grown in the presence of high levels of calcium pantothenate. The results of the method are compared with results obtained from the USP microbiological method of analysis. It was concluded that the procedure is rapid, accurate, easily automated, and practical for routine quality control use. PMID:6694064

  17. Preparation of a polybutadiene stationary phase immobilized by gamma radiation for reversed-phase high-performance liquid chromatography.

    PubMed

    Lopes, Nilva P; Collins, Kenneth E; Jardim, Isabel C S F

    2003-02-14

    Polybutadiene (PBD) has been immobilized on HPLC silica by gamma radiation doses in the range from 5 to 180 kGy. Columns prepared from these reversed-phase materials, as well as from similar non-irradiated materials, were tested with standard sample mixtures and characterized by elemental analysis (% C) and infrared spectroscopy. A low dose of 5 kGy is sufficient to produce a layer of immobilized PBD which functions as an efficient and stable stationary phase. Higher doses give thicker immobilized layers having less favorable chromatographic properties.

  18. Phase Space Tomography: A Simple, Portable and Accurate Technique to Map Phase Spaces of Beams with Space Charge

    SciTech Connect

    Stratakis, D.; Kishek, R. A.; Bernal, S.; Walter, M.; Haber, I.; Fiorito, R.; Thangaraj, J. C. T.; Quinn, B.; Reiser, M.; O'Shea, P. G.; Li, H.

    2006-11-27

    In order to understand the charged particle dynamics, e.g. the halo formation, emittance growth, x-y energy transfer and coupling, knowledge of the actual phase space is needed. Other the past decade there is an increasing number of articles who use tomography to map the beam phase space and measure the beam emittance. These studies where performed at high energy facilities where the effect of space charge was neglible and therefore not considered in the analysis. This work extends the tomography technique to beams with space charge. In order to simplify the analysis linear forces where assumed. By carefully modeling the tomography process using the particle-in-cell code WARP we test the validity of our assumptions and the accuracy of the reconstructed phase space. Finally, we report experimental results of phase space mapping at the University of Maryland Electron Ring (UMER) using tomography.

  19. Preparation of stationary phases for reversed-phase high-performance liquid chromatography using thermal treatments at high temperature.

    PubMed

    Vigna, Camila R M; Bottoli, Carla B G; Collins, Kenneth E; Collins, Carol H

    2007-07-13

    Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 degrees C for 24h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4h at higher temperatures (150-400 degrees C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, (29)Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 degrees C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 degrees C and an increase in the resolution of the components, mainly for the phase heated at 300 degrees C. Such results demonstrate that a two-step thermal treatment (100 degrees C then 150-300 degrees C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography.

  20. An accurate two-phase approximate solution to the acute viral infection model

    SciTech Connect

    Perelson, Alan S

    2009-01-01

    During an acute viral infection, virus levels rise, reach a peak and then decline. Data and numerical solutions suggest the growth and decay phases are linear on a log scale. While viral dynamic models are typically nonlinear with analytical solutions difficult to obtain, the exponential nature of the solutions suggests approximations can be found. We derive a two-phase approximate solution to the target cell limited influenza model and illustrate the accuracy using data and previously established parameter values of six patients infected with influenza A. For one patient, the subsequent fall in virus concentration was not consistent with our predictions during the decay phase and an alternate approximation is derived. We find expressions for the rate and length of initial viral growth in terms of the parameters, the extent each parameter is involved in viral peaks, and the single parameter responsible for virus decay. We discuss applications of this analysis in antiviral treatments and investigating host and virus heterogeneities.

  1. Estimation of the phase ratio in reversed-phase high-performance liquid chromatography.

    PubMed

    Moldoveanu, Serban; David, Victor

    2015-02-13

    Phase ratio Φ for an HPLC column is a common parameter being defined as the ratio between the volume of the stationary phase V(st) and the void volume of the column V0. Although apparently simple, the evaluation of phase ratio presents difficulties because there is no sharp boundary between the mobile phase and the stationary phase, and different mobile phases lead to different "effective" phase ratios. A considerable number of studies have been dedicated to the evaluation of V(st) and V0 with the goal of obtaining the value for Φ. However, the parameter is seldom reported for common commercially available columns and key information for its calculation (e.g. the weight of column packing) is not typically reported by the vendors. Present study describes a novel procedure for the evaluation of phase ratio for a chromatographic column when used with a given mobile phase. The procedure allows the calculation of Φ only from the measurements of retention factors k' for two hydrocarbons i and j, for which the octanol/water partition coefficients log K(ow) are known. A theoretical support for this procedure based on solvophobic theory of interactions in solution is presented, and several experimental results reported in the literature are used to demonstrate the validity of the procedure. PMID:25618362

  2. Effect of pressure on the chromatographic separation of enantiomers under reversed-phase conditions.

    PubMed

    Makarov, Alexey A; Regalado, Erik L; Welch, Christopher J; Schafer, Wes A

    2014-07-25

    Commercially available ultra high pressure liquid chromatography (UHPLC) equipment offers the ability to explore the influence of backpressure on chromatographic separations. However, the influence of pressure on the chromatographic separation of enantiomers on chiral stationary phases remains largely unexplored. In this investigation we surveyed the effects of pressure on the separation of enantiomers using several reversed-phase chiral stationary phases. The experiments were conducted at constant flow rate and column temperature, using isocratic conditions. The only variable parameter was pressure, which was adjusted using a post-column backpressure regulator. For the separation of enantiomers on chiral stationary phases, an increase in pressure from approximately 2,000 psi (138 bar) to approximately 8,000 psi (552 bar) at constant flow rate and temperature led to an increase of retention factors for some analytes and a decrease for others. Achiral separations on a C-18 stationary phase always led only to an increase of retention factor. Interestingly, changes in pressure led to small changes in enantioselectivity during reversed-phase chiral separation of enantiomers, suggesting that such studies may be of value for better understanding the mechanisms underlying chromatographic enantioseparation.

  3. Analysis of short range entangled topological phases protected by time-reversal symmetry

    NASA Astrophysics Data System (ADS)

    Dick, Sebastian

    We discuss a short-range entangled topological phase in 3+1 dimensions that is protected by time-reversal symmetry. Two models are compared that realize this phase: The first is a construction developed by Chen, Gu, Liu and Wen, which encodes the system's topological properties in the representation of the symmetry group. The second theory uses a non-linear sigma model in which the distinct topological phases differ by the way the symmetry acts on the order parameter. Both theories have in common that the modeled phases are in one to one correspondence with the elements of the co-homology group Hd+1(Z2 T, UT(1)). In this work, we extend the Chen-Gu construction to 3+1 dimensional systems. Furthermore, we show that both models coincide with respect to their topological properties. This is proved by comparing spin-flip processes and their associated topological phase factors. We derive spin-flip operators on the surface of the (3+1)-dimensional Chen-Gu construction that commute with time-reversal symmetry. To implement spin-flip processes in the non-linear sigma model, we interpolate spin-configurations from a discrete, triangular lattice into the continuum. We proceed by analyzing the phases, generated by the theta-term, for spacetime configurations of the O(4) order parameter that correspond to these spin-flip processes.

  4. A Quadratic Spline based Interface (QUASI) reconstruction algorithm for accurate tracking of two-phase flows

    NASA Astrophysics Data System (ADS)

    Diwakar, S. V.; Das, Sarit K.; Sundararajan, T.

    2009-12-01

    A new Quadratic Spline based Interface (QUASI) reconstruction algorithm is presented which provides an accurate and continuous representation of the interface in a multiphase domain and facilitates the direct estimation of local interfacial curvature. The fluid interface in each of the mixed cells is represented by piecewise parabolic curves and an initial discontinuous PLIC approximation of the interface is progressively converted into a smooth quadratic spline made of these parabolic curves. The conversion is achieved by a sequence of predictor-corrector operations enforcing function ( C0) and derivative ( C1) continuity at the cell boundaries using simple analytical expressions for the continuity requirements. The efficacy and accuracy of the current algorithm has been demonstrated using standard test cases involving reconstruction of known static interface shapes and dynamically evolving interfaces in prescribed flow situations. These benchmark studies illustrate that the present algorithm performs excellently as compared to the other interface reconstruction methods available in literature. Quadratic rate of error reduction with respect to grid size has been observed in all the cases with curved interface shapes; only in situations where the interface geometry is primarily flat, the rate of convergence becomes linear with the mesh size. The flow algorithm implemented in the current work is designed to accurately balance the pressure gradients with the surface tension force at any location. As a consequence, it is able to minimize spurious flow currents arising from imperfect normal stress balance at the interface. This has been demonstrated through the standard test problem of an inviscid droplet placed in a quiescent medium. Finally, the direct curvature estimation ability of the current algorithm is illustrated through the coupled multiphase flow problem of a deformable air bubble rising through a column of water.

  5. High pH reversed-phase chromatography with fraction concatenation for 2D proteomic analysis

    SciTech Connect

    Yang, Feng; Shen, Yufeng; Camp, David G.; Smith, Richard D.

    2012-04-01

    Orthogonal high-resolution separations are critical for attaining improved analytical dynamic ranges of proteome measurements. Concatenated high pH reversed phase liquid chromatography affords better separations than the strong cation exchange conventionally applied for two-dimensional shotgun proteomic analysis. For example, concatenated high pH reversed phase liquid chromatography increased identification coverage for peptides (e.g., by 1.8-fold) and proteins (e.g., by 1.6-fold) in shotgun proteomics analyses of a digested human protein sample. Additional advantages of concatenated high pH RPLC include improved protein sequence coverage, simplified sample processing, and reduced sample losses, making this an attractive first dimension separation strategy for two-dimensional proteomics analyses.

  6. Features of separation on polymeric reversed phase for two classes of higher saturated fatty acids esters

    NASA Astrophysics Data System (ADS)

    Deineka, V. I.; Lapshova, M. S.; Zakharenko, E. V.; Deineka, L. A.

    2013-11-01

    The principles of sorption on polymeric reversed phase (PRP) YMS C30 for members of the two classes of esters formed by higher saturated fatty acids, i.e., lutein diesters ( I) and triacylglycerols ( II), are investigated. It is shown that the logarithm of the retention factor increases nonlinearly with an increase of the length of the acid radical, although the retention on PRP is higher in the case of I and lower in the case of II, compared to their retention on traditional monomeric reversed phase (MRP) Kromasil-100 5C18; however, the equivalence of the contributions to the retention of I that correspond to an identical change in acids, does not depend on the length of the hydrocarbon radical of the second acid. It is noted that the Van't Hoff plot for PRP contains a curve break, indicating a change in the retention mechanism upon a rise in temperature.

  7. Separation of Quadruplex Polymorphism in DNA Sequences by Reversed-Phase Chromatography.

    PubMed

    Miller, M Clarke; Ohrenberg, Carl J; Kuttan, Ashani; Trent, John O

    2015-01-01

    This unit describes a method for the separation of a mixture of quadruplex conformations formed from the same parent sequence via reversed-phase chromatography (RPC). Polymorphism is inherent to quadruplex formation and even relatively simple quadruplex-forming sequences can fold into a cornucopia of possible conformations and topologies. Isolation of a specific conformation for study can be problematic. This is especially true for conformations of the human telomere sequence d(GGG(TTAGGG)3). High performance liquid chromatography (HPLC), especially reversed-phase chromatography, has been a mainstay of nucleic acid research and purification for many decades. We have successfully applied this method to the problem of separating individual quadruplex species in the ensemble from the same parent sequence. PMID:26344226

  8. Aniline-modified porous graphitic carbon for hydrophilic interaction and attenuated reverse phase liquid chromatography.

    PubMed

    Iverson, Chad D; Lucy, Charles A

    2014-12-19

    Most stationary phases for hydrophilic interaction liquid chromatography (HILIC) and reversed phase liquid chromatography (RPLC) are based on silica. Porous graphitic carbon (PGC) is an attractive alternative to silica-based phases due to its chemical and thermal stability, and unique selectivity. However, native PGC is strongly hydrophobic and in some instances excessively retentive. PGC particles with covalently attached aniline groups (Dimethylaniline-PGC and Aniline-PGC) were synthesized to alter the surface polarity of PGC. First, the diazonium salt of N,N-dimethyl-p-phenylenediamine or 4-nitroaniline was adsorbed onto the PGC surface. The adsorbed salt was reduced with sodium borohydride and (Aniline-PGC only) the nitro group was further reduced with iron powder to the aniline. X-ray photoelectron spectroscopy confirmed the surface functionalities and that these moieties were introduced to the surface at concentrations of 0.9 and 2.1molecules/nm(2), respectively. These modified PGC phases (especially Aniline-PGC) were evaluated as HILIC and reversed phases. The Dimethylaniline-PGC phase displayed only weak HILIC retention of phenolic solutes. In contrast, the Aniline-PGC phase displayed up to nearly a 7-fold increase in HILIC retention vs. an aniline-silica phase and selectivity that differed from 10 other HILIC phases. Introduction of aniline groups to the PGC surface reduced the RPLC retentivity of PGC up to more than 5-fold and improved the separation efficiency up to 6-fold. The chromatographic performance of Aniline-PGC is demonstrated by separations of nucleotides, nucleosides, carboxylic acids, basic pharmaceuticals, and other compounds.

  9. Unconditionally stable, second-order accurate schemes for solid state phase transformations driven by mechano-chemical spinodal decomposition

    DOE PAGES

    Sagiyama, Koki; Rudraraju, Shiva; Garikipati, Krishna

    2016-09-13

    Here, we consider solid state phase transformations that are caused by free energy densities with domains of non-convexity in strain-composition space; we refer to the non-convex domains as mechano-chemical spinodals. The non-convexity with respect to composition and strain causes segregation into phases with different crystal structures. We work on an existing model that couples the classical Cahn-Hilliard model with Toupin’s theory of gradient elasticity at finite strains. Both systems are represented by fourth-order, nonlinear, partial differential equations. The goal of this work is to develop unconditionally stable, second-order accurate time-integration schemes, motivated by the need to carry out large scalemore » computations of dynamically evolving microstructures in three dimensions. We also introduce reduced formulations naturally derived from these proposed schemes for faster computations that are still second-order accurate. Although our method is developed and analyzed here for a specific class of mechano-chemical problems, one can readily apply the same method to develop unconditionally stable, second-order accurate schemes for any problems for which free energy density functions are multivariate polynomials of solution components and component gradients. Apart from an analysis and construction of methods, we present a suite of numerical results that demonstrate the schemes in action.« less

  10. Unconditionally stable, second-order accurate schemes for solid state phase transformations driven by mechano-chemical spinodal decomposition

    NASA Astrophysics Data System (ADS)

    Sagiyama, K.; Rudraraju, S.; Garikipati, K.

    2016-11-01

    We consider solid state phase transformations that are caused by free energy densities with domains of non-convexity in strain-composition space; we refer to the non-convex domains as mechano-chemical spinodals. The non-convexity with respect to composition and strain causes segregation into phases with different crystal structures. We work on an existing model that couples the classical Cahn-Hilliard model with Toupin's theory of gradient elasticity at finite strains. Both systems are represented by fourth-order, nonlinear, partial differential equations. The goal of this work is to develop unconditionally stable, second-order accurate time-integration schemes, motivated by the need to carry out large scale computations of dynamically evolving microstructures in three dimensions. We also introduce reduced formulations naturally derived from these proposed schemes for faster computations that are still second-order accurate. Although our method is developed and analyzed here for a specific class of mechano-chemical problems, one can readily apply the same method to develop unconditionally stable, second-order accurate schemes for any problems for which free energy density functions are multivariate polynomials of solution components and component gradients. Apart from an analysis and construction of methods, we present a suite of numerical results that demonstrate the schemes in action.

  11. Reversed phase HPLC-FTIR by on-line extraction and solvent elimination

    NASA Astrophysics Data System (ADS)

    Somsen, G. W.; Gooijer, Cees; Brinkman, Udo A. T.; Velthorst, Nel H.; Visser, T.

    1994-01-01

    A reversed phase LC-FTIR interface is described using on-line extraction of the aqueous effluent with a volatile organic solvent in conjunction with a solvent eliminating spray-jet device. Results are shown of the analysis of a 2. 10-4 M solution of acenaphthenequinone, phenanthrenequinone and two polar pesticides linuron and diuron. The mixture was separated with a mobile phase of acetonitrile-phosphate buffer and post-column extracted with dichloro-methane. Detection was carried out by FTIR transmission microscopy. The characteristics of the on-line extraction system are discussed in relation to results obtained from a direct deposition method.

  12. Phase twisted modes and current reversals in a lattice model of waveguide arrays with nonlinear coupling

    SciTech Connect

    Oester, Michael; Johansson, Magnus

    2005-02-01

    We consider a lattice model for waveguide arrays embedded in nonlinear Kerr media. Inclusion of nonlinear coupling results in many phenomena involving complex, phase-twisted, stationary modes. The norm (Poynting power) current of stable plane-wave solutions can be controlled in magnitude and direction, and may be reversed without symmetry-breaking perturbations. Also stable localized phase-twisted modes with zero current exist, which for particular parameter values may be compact and expressed analytically. The model also describes coupled Bose-Einstein condensates.

  13. Determination of the pH of binary mobile phases for reversed-phase liquid chromatography.

    PubMed

    Rosés, Martí

    2004-05-28

    The measurement of pH in chromatographic mobile phases has been a constant subject of discussion during many years. The pH of the mobile phase is an important parameter that determines the chromatographic retention of many analytes with acid-base properties. In many instances a proper pH measurement is needed to assure the accuracy of retention-pH relationships or the reproducibility of chromatographic procedures. Three different methods are common in pH measurement of mobile phases: measurement of pH in the aqueous buffer before addition of the organic modifier, measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with standard solutions prepared in the same mobile phase solvent, and measurement of pH in the mobile phase prepared by mixing aqueous buffer and organic modifier after pH calibration with aqueous standard solutions. This review discusses the different pH measurement and calibration procedures in terms of the theoretical and operational definitions of the different pH scales that can be applied to water-organic solvent mixtures. The advantages and disadvantages of each procedure are also presented through chromatographic examples. Finally, practical recommendations to select the most appropriate pH measurement procedure for particular chromatographic problems are given.

  14. Gas-phase purification enables accurate, large-scale, multiplexed proteome quantification with isobaric tagging

    PubMed Central

    Wenger, Craig D; Lee, M Violet; Hebert, Alexander S; McAlister, Graeme C; Phanstiel, Douglas H; Westphall, Michael S; Coon, Joshua J

    2011-01-01

    We describe a mass spectrometry method, QuantMode, which improves the accuracy of isobaric tag–based quantification by alleviating the pervasive problem of precursor interference—co-isolation of impurities—through gas-phase purification. QuantMode analysis of a yeast sample ‘contaminated’ with interfering human peptides showed substantially improved quantitative accuracy compared to a standard scan, with a small loss of spectral identifications. This technique will allow large-scale, multiplexed quantitative proteomics analyses using isobaric tagging. PMID:21963608

  15. Enhanced reversibility and unusual microstructure of a phase-transforming material.

    PubMed

    Song, Yintao; Chen, Xian; Dabade, Vivekanand; Shield, Thomas W; James, Richard D

    2013-10-01

    Materials undergoing reversible solid-to-solid martensitic phase transformations are desirable for applications in medical sensors and actuators, eco-friendly refrigerators and energy conversion devices. The ability to pass back and forth through the phase transformation many times without degradation of properties (termed 'reversibility') is critical for these applications. Materials tuned to satisfy a certain geometric compatibility condition have been shown to exhibit high reversibility, measured by low hysteresis and small migration of transformation temperature under cycling. Recently, stronger compatibility conditions called the 'cofactor conditions' have been proposed theoretically to achieve even better reversibility. Here we report the enhanced reversibility and unusual microstructure of the first martensitic material, Zn45Au30Cu25, that closely satisfies the cofactor conditions. We observe four striking properties of this material. (1) Despite a transformation strain of 8%, the transformation temperature shifts less than 0.5 °C after more than 16,000 thermal cycles. For comparison, the transformation temperature of the ubiquitous NiTi alloy shifts up to 20 °C in the first 20 cycles. (2) The hysteresis remains approximately 2 °C during this cycling. For comparison, the hysteresis of the NiTi alloy is up to 70 °C (refs 9, 12). (3) The alloy exhibits an unusual riverine microstructure of martensite not seen in other martensites. (4) Unlike that of typical polycrystal martensites, its microstructure changes drastically in consecutive transformation cycles, whereas macroscopic properties such as transformation temperature and latent heat are nearly reproducible. These results promise a concrete strategy for seeking ultra-reliable martensitic materials.

  16. Electric-field-induced switchable dark conglomerate phases in a bent-core liquid crystal exhibiting reverse columnar phases.

    PubMed

    Deepa, G B; Radhika, S; Sadashiva, B K; Pratibha, R

    2013-06-01

    Electric-field-induced transitions into switchable dark conglomerate (DC) phases from two types of reverse columnar mesophases have been observed in the bent-core (BC) compound 2,7-naphthylene bis[4-(3-methyl-4-n-tetradecyloxybenzoyloxy)] benzoate. Optical and x-ray studies show that the higher temperature columnar phase corresponds to the orthogonal B(1rev) phase, whereas the lower temperature columnar phase is a variant of the B(1revtilt) phase. As the layer fragments in this phase are modulated in order to relieve the steric hindrance caused by an anticlinic tilting in adjacent blocks, it has been named B(1revtiltM). The shape of the chiral domains are different in the DC phases viz. DC-B(1rev) and DC-B(1revtiltM) obtained by applying the electric field in the B(1rev) and B(1revtiltM) phases, respectively. While the chiral domains in the DC-B(1rev) phase appear similar to those observed in other DC phases, the shape of the domains in the DC-B(1revtiltM) phase appear to have some similarity to the domains in the banana leaf texture in the B(1revtiltM) phase implying that the detailed structure in this DC phase may be different. Optical observations, electro-optics, and dielectric studies show that the DC-B(1rev) and DC-B(1revtiltM) phases are both switchable and possess a local SmC(S)P(F) type of structure. As the temperature is decreased the switching behavior changes from ferroelectric to antiferroelectric. The temperature at which this changeover starts occurring coincides with the temperature at which the layer modulation occurs to overcome anticlinic tilt and the B(1rev) to B(1revtiltM) phase transition takes place without the application of the electric field. The change in switching behavior is attributed to a transformation into flat layers with the SmC(A)P(A) type of structure as also evidenced by the nucleation of bright regions alongside the chiral domains.

  17. Performance of amines as silanol suppressors in reversed-phase liquid chromatography.

    PubMed

    Calabuig-Hernández, S; García-Alvarez-Coque, M C; Ruiz-Angel, M J

    2016-09-23

    In reversed-phase liquid chromatography, cationic basic compounds yield broad and asymmetrical peaks, as a result of their ionic interaction with the anionic free silanol groups present in the silica-based stationary phases (commonly derivatised with C18 groups). A simple way to improve the peak shape is the addition to the hydro-organic mobile phase of a reagent (usually called additive) with cationic character. This associates with the stationary phase to prevent the access of analytes to the free silanol groups. Cationic additives may interact electrostatically with the anionic silanols. The hydrophobic region of the additive may also associate with the alkyl chains bound to the stationary phase, with the positive charge oriented towards the mobile phase. The access to the silanol groups is thus blocked, but in turn, the stationary phase is positively charged and will repel the protonated basic compounds, which unless their polarity is sufficiently low, will elute at very short times. In this work, a comparative study of the performance of a group of amines (butylamine, pentylamine, hexylamine, cyclopentylamine, cycloheptylamine, N,N-dimethyloctylamine and tributylmethylammonium chloride), as modifiers of the chromatographic behaviour of basic compounds, is carried out. The behaviour is compared with that obtained with the ionic liquids 1-butyl-3-methylimidazolium chloride and 1-hexyl-3-methylimidazolium chloride, used as additives. The study revealed that the performance of the cationic additives to block the silanol activity is mainly explained by the additive size and its ability to be adsorbed onto the stationary phase.

  18. Feasibility assessment for a novel reverse-phase wet granulation process: the effect of liquid saturation and binder liquid viscosity.

    PubMed

    Wade, J B; Martin, G P; Long, D F

    2014-11-20

    A novel reverse-phase wet granulation process was developed and the feasibility of the process compared to a conventional wet granulation process. The reverse-phase granulation approach involves the immersion of the dry powder formulation into the binder liquid followed by controlled breakage to form granules. Conventional wisdom would warn against this approach due to the initial formation of a slurry or over-wetted powder formulation. However, a feasibility assessment of the novel approach was motivated by the potential advantages of eliminating traditional granule nucleation variables and reducing risk of uncontrolled granule growth. The effects of liquid saturation and binder liquid viscosity on the physical properties of granules formed using both the reverse-phase and conventional granulation processes were compared. Liquid saturation significantly affected the physical properties of granules prepared using both processes. At liquid saturation up to ∼1 the reverse-phase process typically resulted in larger, less porous granules than the conventional process. However, at a liquid saturation >1.1 the conventional process exhibited uncontrolled growth and significantly larger granule size as a result of decreased intragranular porosity. The response to liquid saturation was seen as a steady growth mechanism for the reverse-phase process compared to an induction growth mechanism for the conventional process, indicating potential robustness advantages of the reverse-phase approach. Despite institutional perceptions to the contrary, the reverse-phase process was shown to be feasible and merits further detailed investigation. PMID:25218187

  19. Phase diagram for the onset of rolling waves and flow reversal in inclined falling films

    NASA Astrophysics Data System (ADS)

    Rohlfs, Wilko; Scheid, Benoit; Kneer, Reinhold

    2014-11-01

    The onset of rolling waves and the onset of flow reversal in inclined falling films is investigated in dependence of the Reynolds and the inclination number. For this, the weighted integral boundary layer model (WIBL) and direct numerical simulations (DNS) are used. Analytical criteria for the onset of rolling waves and flow reversal based on the wave celerity, the average film thickness and the maxi-mum/minimum film thickness have been approximated using self-similar parabolic velocity profiles. This approximation has been validated by second-order WIBL and DNS simulations. It is shown that the various transitions in the phase diagram for homoclinic solutions (waves of infinite wave length) are strongly dependent on the inclination, but independent on the streamwise viscous dissipation effect. Compared to the onset of flow reversal, the onset of rolling waves occurs for higher Reynolds numbers, resulting in a regime in which flow reversal and non-rolling waves coexist. Furthermore, simulation results for limit cycles (finite wave length) reveal a strong increase of the critical Reynolds number with the excitation frequency. Institute of Heat and Mass Transfer, Augustinerbach 6, 52056 Aachen, Germany.

  20. In-situ characterization of highly reversible phase transformation by synchrotron X-ray Laue microdiffraction

    NASA Astrophysics Data System (ADS)

    Chen, Xian; Tamura, Nobumichi; MacDowell, Alastair; James, Richard D.

    2016-05-01

    The alloy Cu25Au30Zn45 undergoes a huge first-order phase transformation (6% strain) and shows a high reversibility under thermal cycling and an unusual martensitc microstructure in sharp contrast to its nearby compositions. This alloy was discovered by systematically tuning the composition so that its lattice parameters satisfy the cofactor conditions (i.e., the kinematic conditions of compatibility between phases). It was conjectured that satisfaction of these conditions is responsible for the enhanced reversibility as well as the observed unusual fluid-like microstructure during transformation, but so far, there has been no direct evidence confirming that these observed microstructures are those predicted by the cofactor conditions. To verify this hypothesis, we use synchrotron X-ray Laue microdiffraction to measure the orientations and structural parameters of variants and phases near the austenite/martensite interface. The areas consisting of both austenite and multi-variants of martensite are scanned by microLaue diffraction. The cofactor conditions have been examined from the kinematic relation of lattice vectors across the interface. The continuity condition of the interface is precisely verified from the correspondent lattice vectors between two phases.

  1. Reverse projection retrieval in edge illumination x-ray phase contrast computed tomography

    NASA Astrophysics Data System (ADS)

    Hagen, Charlotte K.; Endrizzi, Marco; Diemoz, Paul C.; Olivo, Alessandro

    2016-06-01

    Edge illumination (EI) x-ray phase contrast computed tomography (CT) can provide three-dimensional distributions of the real and imaginary parts of the complex refractive index (n=1-δ +\\text{i}β ) of the sample. Phase retrieval, i.e. the separation of attenuation and refraction data from projections that contain a combination of both, is a key step in the image reconstruction process. In EI-based x-ray phase contrast CT, this is conventionally performed on the basis of two projections acquired in opposite illumination configurations (i.e. with different positions of the pre-sample mask) at each CT angle. Displacing the pre-sample mask at each projection makes the scan susceptible to motor-induced misalignment and prevents a continuous sample rotation. We present an alternative method for the retrieval of attenuation and refraction data that does not require repositioning the pre-sample mask. The method is based on the reverse projection relation published by Zhu et al (2010 Proc. Natl Acad. Sci. USA 107 13576–81) for grating interferometry-based x-ray phase contrast CT. We use this relation to derive a simplified acquisition strategy that allows acquiring data with a continuous sample rotation, which can reduce scan time when combined with a fast read-out detector. Besides discussing the theory and the necessary alignment of the experimental setup, we present tomograms obtained with reverse projection retrieval and demonstrate their agreement with those obtained with the conventional EI retrieval.

  2. Reverse projection retrieval in edge illumination x-ray phase contrast computed tomography

    NASA Astrophysics Data System (ADS)

    Hagen, Charlotte K.; Endrizzi, Marco; Diemoz, Paul C.; Olivo, Alessandro

    2016-06-01

    Edge illumination (EI) x-ray phase contrast computed tomography (CT) can provide three-dimensional distributions of the real and imaginary parts of the complex refractive index (n=1-δ +\\text{i}β ) of the sample. Phase retrieval, i.e. the separation of attenuation and refraction data from projections that contain a combination of both, is a key step in the image reconstruction process. In EI-based x-ray phase contrast CT, this is conventionally performed on the basis of two projections acquired in opposite illumination configurations (i.e. with different positions of the pre-sample mask) at each CT angle. Displacing the pre-sample mask at each projection makes the scan susceptible to motor-induced misalignment and prevents a continuous sample rotation. We present an alternative method for the retrieval of attenuation and refraction data that does not require repositioning the pre-sample mask. The method is based on the reverse projection relation published by Zhu et al (2010 Proc. Natl Acad. Sci. USA 107 13576-81) for grating interferometry-based x-ray phase contrast CT. We use this relation to derive a simplified acquisition strategy that allows acquiring data with a continuous sample rotation, which can reduce scan time when combined with a fast read-out detector. Besides discussing the theory and the necessary alignment of the experimental setup, we present tomograms obtained with reverse projection retrieval and demonstrate their agreement with those obtained with the conventional EI retrieval.

  3. Rapid reversible formation of a metastable subgel phase in saturated diacylphosphatidylcholines.

    PubMed Central

    Koynova, R; Tenchov, B G; Todinova, S; Quinn, P J

    1995-01-01

    Formation of well ordered lamellar subgel (SGII) phase in aqueous dispersions of L-dipalmitoylphosphatidylcholine upon cooling from the lamellar gel phase, without low-temperature equilibration, is observed in real time using synchrotron x-ray diffraction. It has the same lamellar repeat period as the gel phase from which it was formed but differs in its wide-angle diffraction pattern. The SGII phase forms at about 7 degrees C upon cooling at 2 degrees C/min. In temperature jump experiments at 1 degree C/s from 50 to -5 degrees C, the relaxation time of the lamellar gel-SGII transition is found to be approximately 15 s. The conversion between the lamellar gel and SGII phase is cooperative and rapidly reversible. Upon heating, it coincides in temperature with an endothermic event with a calorimetric enthalpy of 0.35 kcal/mol, the so-called sub-subtransition. Similar sub-subtransitions are also observed calorimetrically at temperatures approximately 10 degrees C below the subtransition, without low-temperature storage, in aqueous dispersions of L-dimyristoylphosphatidylcholine and L-distearoylphosphatidylcholine, but not in racemic DL-dipalmitoylphosphatidylcholine. The formation of the equilibrium lamellar crystalline Lc phase appears to take place only from within the SGII phase. PMID:7647241

  4. Properties of subcritical water as an eluent for reversed-phase liquid chromatography--disruption of the hydrogen-bond network at elevated temperature and its consequences.

    PubMed

    Allmon, Steven D; Dorsey, John G

    2010-09-10

    The use of subcritical water as an eluent for reversed-phase liquid chromatography is further explored. Shape selectivity as well as thermodynamic values for solute transfer were measured and compared to those seen with traditional ambient methanol/water and acetonitrile/water mobile phases. Linear solvation energy analysis was also used to analyze extrapolated values of the retention factor in pure water at ambient temperatures (k'w) for subcritical water and ambient hydroorganic mobile phases. Results indicate that it is likely that a large disruption in the hydrogen-bonding network of water at high temperatures causes unique chromatographic selectivity, as well as prohibits accurate extrapolation from high temperature to ambient conditions using pure water. Additionally, subcritical water was not found to be a suitable mobile phase for determining k'w for use in estimating octanol/water partition coefficients.

  5. Reversible temperature regulation of electrical and thermal conductivity using liquid-solid phase transitions.

    PubMed

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions.

  6. Reversible temperature regulation of electrical and thermal conductivity using liquid–solid phase transitions

    PubMed Central

    Zheng, Ruiting; Gao, Jinwei; Wang, Jianjian; Chen, Gang

    2011-01-01

    Reversible temperature tuning of electrical and thermal conductivities of materials is of interest for many applications, including seasonal regulation of building temperature, thermal storage and sensors. Here we introduce a general strategy to achieve large contrasts in electrical and thermal conductivities using first-order phase transitions in percolated composite materials. Internal stress generated during a phase transition modulates the electrical and thermal contact resistances, leading to large contrasts in the electrical and thermal conductivities at the phase transition temperature. With graphite/hexadecane suspensions, the electrical conductivity changes 2 orders of magnitude and the thermal conductivity varies up to 3.2 times near 18 °C. The generality of the approach is also demonstrated in other materials such as graphite/water and carbon nanotube/hexadecane suspensions. PMID:21505445

  7. Time-reversal symmetry breaking superconductivity in the coexistence phase with magnetism in Fe pnictides.

    PubMed

    Hinojosa, Alberto; Fernandes, Rafael M; Chubukov, Andrey V

    2014-10-17

    We argue that superconductivity in the coexistence region with spin-density-wave (SDW) order in weakly doped Fe pnictides erdiffers qualitatively from the ordinary s(+-) state outside the coexistence region as it develops an additional gap component which is a mixture of intrapocket singlet (s(++)) and interpocket spin-triplet pairings (the t state). The coupling constant for the t channel is proportional to the SDW order and involves interactions that do not contribute to superconductivity outside of the SDW region. We argue that the s(+-)- and t-type superconducting orders coexist at low temperatures, and the relative phase between the two is, in general, different from 0 or π, manifesting explicitly the breaking of the time-reversal symmetry promoted by long-range SDW order. We argue that time reversal may get broken even before true superconductivity develops.

  8. Evaluation of perphenylcarbamated cyclodextrin clicked chiral stationary phase for enantioseparations in reversed phase high performance liquid chromatography.

    PubMed

    Pang, Limin; Zhou, Jie; Tang, Jian; Ng, Siu-Choon; Tang, Weihua

    2014-10-10

    In this study, perphenylcarbamated cyclodextrin clicked chiral stationary phase (CSP) was developed with high column efficiency. The characteristics of the column were evaluated in terms of linearity, limit of detection and limit of quantification. The enantioselectivity of the as-prepared clicked CSP was explored with 26 recemates including aryl alcohols, flavanoids and adrenergic drugs in reversed phase high-performance liquid chromatography. The effect of separation parameters including flow rate, column temperature, organic modifier and buffer on the enantioselectivity of the clicked CSP was investigated in detail. The correlation study of the analytes structure and their chiral resolution revealed the great influence of analytes' structure on the enantioseparations with cyclodextrin CSP. Methanol with 1% of triethylammonium acetate buffer (pH 4) was proved to be the best choice for the chiral separation of basic enantiomers.

  9. Quantification of reverse transcriptase activity by real-time PCR as a fast and accurate method for titration of HIV, lenti- and retroviral vectors.

    PubMed

    Vermeire, Jolien; Naessens, Evelien; Vanderstraeten, Hanne; Landi, Alessia; Iannucci, Veronica; Van Nuffel, Anouk; Taghon, Tom; Pizzato, Massimo; Verhasselt, Bruno

    2012-01-01

    Quantification of retroviruses in cell culture supernatants and other biological preparations is required in a diverse spectrum of laboratories and applications. Methods based on antigen detection, such as p24 for HIV, or on genome detection are virus specific and sometimes suffer from a limited dynamic range of detection. In contrast, measurement of reverse transcriptase (RT) activity is a generic method which can be adapted for higher sensitivity using real-time PCR quantification (qPCR-based product-enhanced RT (PERT) assay). We present an evaluation of a modified SYBR Green I-based PERT assay (SG-PERT), using commercially available reagents such as MS2 RNA and ready-to-use qPCR mixes. This assay has a dynamic range of 7 logs, a sensitivity of 10 nU HIV-1 RT and outperforms p24 ELISA for HIV titer determination by lower inter-run variation, lower cost and higher linear range. The SG-PERT values correlate with transducing and infectious units in HIV-based viral vector and replication-competent HIV-1 preparations respectively. This assay can furthermore quantify Moloney Murine Leukemia Virus-derived vectors and can be performed on different instruments, such as Roche Lightcycler® 480 and Applied Biosystems ABI 7300. We consider this test to be an accurate, fast and relatively cheap method for retroviral quantification that is easily implemented for use in routine and research laboratories.

  10. Quantification of Reverse Transcriptase Activity by Real-Time PCR as a Fast and Accurate Method for Titration of HIV, Lenti- and Retroviral Vectors

    PubMed Central

    Vermeire, Jolien; Naessens, Evelien; Vanderstraeten, Hanne; Landi, Alessia; Iannucci, Veronica; Van Nuffel, Anouk; Taghon, Tom; Pizzato, Massimo; Verhasselt, Bruno

    2012-01-01

    Quantification of retroviruses in cell culture supernatants and other biological preparations is required in a diverse spectrum of laboratories and applications. Methods based on antigen detection, such as p24 for HIV, or on genome detection are virus specific and sometimes suffer from a limited dynamic range of detection. In contrast, measurement of reverse transcriptase (RT) activity is a generic method which can be adapted for higher sensitivity using real-time PCR quantification (qPCR-based product-enhanced RT (PERT) assay). We present an evaluation of a modified SYBR Green I-based PERT assay (SG-PERT), using commercially available reagents such as MS2 RNA and ready-to-use qPCR mixes. This assay has a dynamic range of 7 logs, a sensitivity of 10 nU HIV-1 RT and outperforms p24 ELISA for HIV titer determination by lower inter-run variation, lower cost and higher linear range. The SG-PERT values correlate with transducing and infectious units in HIV-based viral vector and replication-competent HIV-1 preparations respectively. This assay can furthermore quantify Moloney Murine Leukemia Virus-derived vectors and can be performed on different instruments, such as Roche Lightcycler® 480 and Applied Biosystems ABI 7300. We consider this test to be an accurate, fast and relatively cheap method for retroviral quantification that is easily implemented for use in routine and research laboratories. PMID:23227216

  11. Cause of Delayed First Peak and Reversed Initial Phase of Distant Tsunami

    NASA Astrophysics Data System (ADS)

    Watada, S.; Kusumoto, S.; Fujii, Y.; Satake, K.

    2012-12-01

    Distant tsunami waveforms recorded at deep open oceans from the 2010 Chile and 2011 Tohoku-Oki earthquakes show delayed arrival of the first tsunami peak relative to expected tsunami arrival times based on the long-wave theory and a reversed small initial phase relative to the main peak. The small reversed polarity before the main peak is visible in the original bottom pressure gauge data and not introduced during the de-tide process. Thanks to the low-noise DART data from large earthquakes, the arrival of the small initial phases at distant buoys is identified as early as a half hour before the arrival of large amplitude tsunami. Amplitude of the small initial phase is as large as 10 % of the main phase at largest distances. Such an initial phase is not observed at buoys near the tsunami sources. The synthetic tsunami waveforms are computed for a 1D earth model, referred from the Preliminary Reference Earth Model (PREM), including the effects of the elastic crust, mantle, and core of the earth, the effect of compressibility of the ocean water, and the effect of the gravity potential change caused by the motions of water mass and the solid earth during the tsunami propagation. Comparison of synthetic tsunami waveforms based on the conventional non-dispersive long-wave theory and from the 1D earth model shows that the observed two features, delayed arrival of the first peak and the small initial phase with a reversed polarity, are successfully reproduced by the 1D tsunami computation for the PREM. The small initial tsunami with a reversed polarity observed at a distant location is caused by the dispersion of the long-wavelength tsunami, and should not be misinterpreted as an evidence of a precursory crustal movement prior to the large earthquakes. The contributions of the elasticity of the solid earth, compressibility of water, and the gravity potential change due to the mass-motion to the tsunami phase and group velocities are period or wavelength dependent. For a

  12. Chromatographic evaluation of self-immobilized stationary phases for reversed-phase liquid chromatography.

    PubMed

    Bottoli, Carla B G; Collins, Kenneth E; Collins, Carol H

    2003-02-14

    The preparation of stationary phases for HPLC using polymers deposited on silica usually includes an immobilization step involving cross-linking by free radicals induced by ionizing radiation or by other radical initiators. The present paper reports changes which occur at ambient temperature in the character of poly(methyloctylsiloxane) deposited on porous silica particles as a function of the time interval between particle loading and column packing. Column performance and retention factors increase with time and these changes are attributed to rearrangement (self-assembly) which result in "self-immobilization" of the polymer molecules on the silica surface.

  13. Determination of Cefadroxil in Tablet/Capsule formulations by a validated Reverse Phase High Performance Liquid Chromatographic method.

    PubMed

    Rahim, Najia; Naqvi, Syed Baqir-Shyum; Shakeel, Sadia; Iffat, Wajiha; Muhammad, Iyad Naeem

    2015-07-01

    An innovative, selective and rapid reversed phase High Performance Liquid Chromatographic (RP-HPLC) method for the analysis of cefadroxil in bulk material and oral solid dosage forms has been developed and validated. The chromatographic system consisted of Sil-20A auto sampler, LC-20A pump and SPD-20A UV/visible detector. The separation was achieved by C18 column at ambient temperature with a mobile phase consisting of methanol: Phosphate buffer (10: 90) at a flow rate of 1.5 ml/min. The method is reproducible, repeatable (%RSD for intra-day and inter-day ranged between 1.75-5.33% and 0.58-2.69%) and linear (R2=0.9935). The LOD and LOQ of the method were 0.5 and 1.0 μg/ml, respectively. The present RP-HPLC method was found to be sensitive, accurate, precise, rapid and cost effective that can be efficiently used in QC/QA laboratories for routine analysis of the raw materials as well as oral dosage formulations of cefadroxil. PMID:26142506

  14. Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors

    SciTech Connect

    Yu, Zhenhai; Wang, Lin; Wang, Luhong; Liu, Haozhe; Zhao, Jinggeng; Li, Chunyu; Sinogeikin, Stanislav; Wu, Wei; Luo, Jianlin; Wang, Nanlin; Yang, Ke; Zhao, Yusheng; Mao, Ho -kwang

    2014-11-24

    Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram of the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). As a result, the cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure.

  15. Development of porous polymer monoliths for reverse-phase chromatography of proteins.

    SciTech Connect

    Shepodd, Timothy J.; Stephens, Christopher P.

    2003-09-01

    The polymers developed in this project are intended for use as a stationary phase in reverse-phase chromatography of proteins, where the mobile phase is a solution of acetonitrile and a phosphate buffer, 6.6 pH. A full library of pore sizes have been developed ranging from 0.41{micro}m to 4.09 {micro}m; these pore sizes can be determined by the solvent ratio of tetrahydrofuran:methoxyethanol during polymerization. A column that can separate proteins in an isocratic mode would be a vast improvement from the common method of separating proteins through gradient chromatography using multiple solvents. In the stationary phase, the main monomers have hydrophobic tails, lauryl acrylate and steryl acrylate. Separations of small hydrophobic molecules and peptides (trial molecules) have efficiencies of 24,000-33,000 theoretical plates m{sup -1}. The combination of a highly non-polar stationary phase and a mobile phase where the polarity can be controlled provide for excellent separation.

  16. Conventional empirical law reverses in the phase transitions of 122-type iron-based superconductors

    DOE PAGES

    Yu, Zhenhai; Wang, Lin; Wang, Luhong; Liu, Haozhe; Zhao, Jinggeng; Li, Chunyu; Sinogeikin, Stanislav; Wu, Wei; Luo, Jianlin; Wang, Nanlin; et al

    2014-11-24

    Phase transition of solid-state materials is a fundamental research topic in condensed matter physics, materials science and geophysics. It has been well accepted and widely proven that isostructural compounds containing different cations undergo same pressure-induced phase transitions but at progressively lower pressures as the cation radii increases. However, we discovered that this conventional law reverses in the structural transitions in 122-type iron-based superconductors. In this report, a combined low temperature and high pressure X-ray diffraction (XRD) measurement has identified the phase transition curves among the tetragonal (T), orthorhombic (O) and the collapsed-tetragonal (cT) phases in the structural phase diagram ofmore » the iron-based superconductor AFe2As2 (A = Ca, Sr, Eu, and Ba). As a result, the cation radii dependence of the phase transition pressure (T → cT) shows an opposite trend in which the compounds with larger ambient radii cations have a higher transition pressure.« less

  17. A selective determination of azide by ion-interaction reversed-phase HPLC

    SciTech Connect

    Gennaro, M.C.; Abrigo, C.; Marengo, E.; Liberatori, A.

    1993-01-01

    A method is presented for the analysis of sodium azide, based on the use of ion-interaction reversed-phase HPLC chromatography. A C-18 reversed-phase is the stationary phase and octylammonium ortho-phosphate at different pH values is the interaction reagent. Spectrophotometric detection at 230 nm is employed. The analysis is free from interference by acetate, carbonate, chloride, fluoride, sulfite, hydrazine, hydroxylamine, nitrate, bromide, iodide, sulfide, thiocyanate and nitrite. A good correlation (r[sup 2] = 0.9782) is obtained between peak area and concentration in the range between 1 and 250 ppb. Samples of tap water spiked with sodium azide (in the range within 25 and 250 ppb) gave per cent average recovery of 98%. The method sensitivity, expressed as signal-to-noise ratio equal to 3, is 50 ppb when the pH of the interaction reagent is equal to 3.0, 30 ppb for pH 6.4 and 10 ppb at pH 8.0.

  18. High-contrast, reversible thermal conductivity regulation utilizing the phase transition of polyethylene nanofibers.

    PubMed

    Zhang, Teng; Luo, Tengfei

    2013-09-24

    Reversible thermal conductivity regulation at the nanoscale is of great interest to a wide range of applications such as thermal management, phononics, sensors, and energy devices. Through a series of large-scale molecular dynamics simulations, we demonstrate a thermal conductivity regulation utilizing the phase transition of polyethylene nanofibers, enabling a thermal conductivity tuning factor of as high as 12, exceeding all previously reported values. The thermal conductivity change roots from the segmental rotations along the polymer chains, which introduce along-chain morphology disorder that significantly interrupts phonon transport along the molecular chains. This phase transition, which can be regulated by temperature, strain, or their combinations, is found to be fully reversible in the polyethylene nanofibers and can happen at a narrow temperature window. The phase change temperature can be further tuned by engineering the diameters of the nanofibers, making such a thermal conductivity regulation scheme adaptable to different application needs. The findings can stimulate significant research interest in nanoscale heat transfer control.

  19. Liquid-solid phase transition alloy as reversible and rapid molding bone cement.

    PubMed

    Yi, Liting; Jin, Chao; Wang, Lei; Liu, Jing

    2014-12-01

    Acrylic bone cement has been an essential non-metallic implant used as fixing agent in the cemented total joint arthroplasty (THA). However, the currently available materials based mainly on polymethylmethacrylate (PMMA) still encounter certain limitations, such as time-consuming polymerization, thermal and chemical necrosis and troublesome revision procedure. Here from an alternative way, we proposed for the first time to adopt the injectable alloy cement to address such tough issues through introducing its unique liquid-solid phase transition mechanism. A typical cement along this way is thus made of an alloy Bi/In/Sn/Zn with a specifically designed low melting point 57.5 °C, which enables its rapid molding into various desired shapes with high plasticity and ultimate metallic behaviors. The fundamental characteristics including the mechanical strength, biocompatibility and phase transition-induced thermal effects have been clarified to demonstrate the importance of such alloy as unconventional cement with favorable merits. In addition, we also disclosed its advantage as an excellent contrast agent for radiation imaging on the bone interior structure which is highly beneficial for guiding the surgery and monitoring the therapeutic effects. Particularly, the proposed alloy cement with reversible phase transition feature significantly simplifies the revision of the cement and prosthesis. This study opens the way for employing the injectable alloy materials as reversible bone cement to fulfill diverse clinical needs in the coming time. PMID:25239039

  20. Imaging non-classical elastic nonlinearities using reciprocal time reversal and phase symmetry analysis

    NASA Astrophysics Data System (ADS)

    Ciampa, Francesco; Meo, Michele

    2012-04-01

    In this research work, an imaging method of the nonlinear signature in a reverberant complex anisotropic structure with hysteretic behaviour is reported. The proposed technique relies on a combination of phase symmetry analysis with frequency modulation excitation and nonlinear time reversal, and it is applied to a number of waveforms containing the nonlinear impulse responses of the medium. Phase symmetry analysis was used to characterize the third order nonlinearity of the structure due to delamination and cracks, by exploiting its invariant properties with the phase angle of the input waveforms. Then, a "virtual" reciprocal time reversal imaging process, using only two sensors in pitch-catch mode, was used to "illuminate" the damage. Taking advantage of multiple linear scattering, this methodology allows achieving the optimal focalization at the nonlinear source by a compensation of the distortion effects in a dissipative medium. The robustness of this technique was experimentally demonstrated on a damaged sandwich panel undergone to low-velocity impact loading. The nonlinear source was retrieved with a high level of accuracy with little computational time (less than 1 sec). Its minimal processing requirements make this method a valid alternative to the traditional nonlinear elastic wave spectroscopy techniques for materials showing either classical or non-classical nonlinear behaviour.

  1. Characterization of protein expression levels with label-free detected reverse phase protein arrays.

    PubMed

    Guo, Xuexue; Deng, Yihong; Zhu, Chenggang; Cai, Junlong; Zhu, Xiangdong; Landry, James P; Zheng, Fengyun; Cheng, Xunjia; Fei, Yiyan

    2016-09-15

    In reverse-phase protein arrays (RPPA), one immobilizes complex samples (e.g., cellular lysate, tissue lysate or serum etc.) on solid supports and performs parallel reactions of antibodies with immobilized protein targets from the complex samples. In this work, we describe a label-free detection of RPPA that enables quantification of RPPA data and thus facilitates comparison of studies performed on different samples and on different solid supports. We applied this detection platform to characterization of phosphoserine aminotransferase (PSAT) expression levels in Acanthamoeba lysates treated with artemether and the results were confirmed by Western blot studies. PMID:27372609

  2. Optical spectroscopic and reverse-phase HPLC analyses of Hg(II) binding to phytochelatins.

    PubMed

    Mehra, R K; Miclat, J; Kodati, V R; Abdullah, R; Hunter, T C; Mulchandani, P

    1996-02-15

    Optical spectroscopy and reverse-phase HPLC were used to investigate the binding of Hg(II) to plant metal-binding peptides (phytochelatins) with the structure (gammaGlu-Cys)2Gly, (gammaGlu-Cys)3Gly and (gammaGlu-Cys)4Gly. Glutathione-mediated transfer of Hg(II) into phytochelatins and the transfer of the metal ion from one phytochelatin to another was also studied using reverse-phase HPLC. The saturation of Hg(II)-induced bands in the UV/visible and CD spectra of (gammaGlu-Cys)2Gly suggested the formation of a single Hg(II)-binding species of this peptide with a stoichiometry of one metal ion per peptide molecule. The separation of apo-(gammaGlu-Cys)2Gly from its Hg(II) derivative on a C18 reverse-phase column also indicated the same metal-binding stoichiometry. The UV/visible spectra of both (gammaGlu-Cys)3Gly and (gammaGlu-Cys)4Gly at pH 7.4 showed distinct shoulders in the ligand-to-metal charge-transfer region at 280-290 mm. Two distinct Hg(II)-binding species, occurring at metal-binding stoichiometries of around 1.25 and 2.0 Hg(II) ions per peptide molecule, were observed for (gammaGlu-Cys)3Gly. These species exhibited specific spectral features in the charge-transfer region and were separable by HPLC. Similarly, two main Hg(II)-binding species of (gammaGlu-Cys)4Gly were observed by UV/visible and CD spectroscopy at metal-binding stoichiometries of around 1.25 and 2.5 respectively. Only a single peak of Hg(II)-(gammaGlu-Cys)4Gly complexes was resolved under the conditions used for HPLC. The overall Hg(II)-binding stoichiometries of phytochelatins were similar at pH 2.0 and at pH 7.4, indicating that pH did not influence the final Hg(II)-binding capacity of these peptides. The reverse-phase HPLC assays indicated a rapid transfer of Hg(II) from glutathione to phytochelatins. These assays also demonstrated a facile transfer of the metal ion from shorter- to longer-chain phytochelatins. The strength of Hg(II) binding to glutathione and phytochelatins followed the

  3. Study of polyphenols in grape berries by reversed-phase high-performance liquid chromatography.

    PubMed

    Palomino, O; Gómez-Serranillos, M P; Slowing, K; Carretero, E; Villar, A

    2000-02-18

    Several polyphenols have been tested in grape berries from Spain. The flavonoid content is important because of the pharmacological properties of these compounds, whereas resveratrol has been proved to be an antifungal, antiinflammatory and an anticarcinogenic compound. A reversed-phase HPLC method has been developed and applied to determine resveratrol, quercetine, quercitrine and rutine content in several grape berries samples in a single analysis. Covering the grapes with a preservative paper yields a healthier product, but one which has a lower polyphenol content than unprotected grapes.

  4. Microchip free flow planar reversed phase electrochromatography with monolithic stationary phase.

    PubMed

    Wang, Pingli; Tao, Dingyin; Zhang, Lihua; Liang, Zhen; Zhang, Yukui

    2009-08-01

    In this study, microchip free flow planar RP electrochromatography (microFF-PRPEC) was developed by in situ polymerization of monolithic materials in microchamber, and successfully applied for the separation of dyes and proteins. Poly(butyle methyacrylate-co-ethylene dimethacrylate) was prepared by UV-initiated polymerization in a glass microchamber (42 mm long, 23 mm wide, and 28 microm deep). A mixture of 1-propanol, 1,4-butanediol, and water was chosen as porogens, and 1.2% (wt%) 2-acrylamide-2-methyl-propanesulfonic acid (AMPS) was added into the polymerization solution to generate EOF. With 30% v/v ACN-15 mM Tris-HCl as the mobile phase, rhodamine B and methyl green were separated from each other with 400 V transverse voltage applied, and resolution as high as 4.6 was obtained, much higher than that obtained by microFFE under optimal conditions. Furthermore, microFF-PRPEC was also successfully applied into the separation of lysozyme and ribonuclease B, and resolution as high as 9.4 was obtained. All these results demonstrate that microFF-RPPEC might have great potential in the microscale continuous preparation of samples with improved resolution compared to microFFE.

  5. Synthesis and evaluation of an aromatic polymer-coated zirconia for reversed-phase liquid chromatography.

    PubMed

    Zhao, J; Carr, P W

    1999-11-15

    We synthesized a novel aromatic polymer-coated zirconia-based RPLC stationary phase by chemical adsorption of a copolymer of chloromethylstyrene and diethoxymethylvinylsilane onto zirconia (CMS/VMS-ZrO2). Characterization of the pore structure of the support by nitrogen porosimetry and inverse size-exclusion chromatography indicates that CMS/VMS-ZrO2 maintains the well-defined pore structure of the base material. Flow studies show that CMS/VMS-ZrO2 has good mass transfer characteristics. The reversed-phase retention characteristics of the new support are comparable to those of conventional silica-bonded phases. We have also evaluated the mechanical, thermal, and pH stability of CMS/VMS-ZrO2. The results show that CMS/VMS-ZrO2 is stable over a very wide range of pH (pH = 1-13) and at temperatures as high as 160 degrees C. Chromatographic separations of some low molecular weight aromatic analytes on CMS/VMS-ZrO2 and octadecyl-bonded silica phases indicate that there are some subtle but significant differences in the chromatographic selectivity of these two types of phases. PMID:10575967

  6. β-Cyclodextrin at the Water/1-Bromobutane Interface: Molecular Insight into Reverse Phase Transfer Catalysis.

    PubMed

    Elk, Jackson Chief; Benjamin, Ilan

    2015-05-12

    Molecular insight into the role of β-cyclodextrin (βCD) as a phase transfer catalyst at the liquid/liquid interface is obtained by molecular dynamics simulations of the structure and dynamics of βCD adsorbed at the interface between water and 1-bromobutane. In particular, we consider the structure and dynamics of the water and bromobutane molecules inside the βCD cavity and compare them with the behavior when βCD is dissolved in bulk water. βCD is preferentially oriented at the interface, with the cavity opening along the interface normal. While in bulk water the cavity includes 6-8 water molecules that are relatively mobile with short residence time, at the interface the cavity is mostly dehydrated and includes a single bromobutane molecule. This inclusion complex is stable in bulk water. The implication of this behavior for reverse phase transfer catalysis is discussed. PMID:25909764

  7. Determination of oxfendazole in cow milk by reversed-phase high-performance liquid chromatography.

    PubMed

    Tsina, I W; Matin, S B

    1981-08-01

    A specific and sensitive high-performance liquid chromatographic method for the analysis of oxfendazole in cow milk is described. Oxfendazole was extracted from milk using a mixture of acetone and chloroform under alkaline conditions. The solvents were evaporated, and the oily residue was purified by hexane-acetonitrile partition and acid-base extraction. The residue obtained after cleanup was redissolved in methanol for chromatographic analysis. Chromatography was performed on a reversed-phase column with acetonitrile-water as the mobile phase. As low as 0.005 microgram of oxfendazole/g can be measured by this method using 50 g of milk. The method was applied to measure oxfendazole in the milk of a cow given an oral 5-mg/kg dose.

  8. Macroscopic and microscopic analysis of mass transfer in reversed phase liquid chromatography.

    PubMed

    Bacskay, Ivett; Felinger, Attila

    2009-02-20

    For the correct description of a chromatographic process, the determination of mass-transfer kinetics in the column is required because the influence of the mass-transfer kinetics on the shape of chromatographic band profiles is crucial. Several sources of mass transfer in a chromatographic bed have been identified and studied: the axial dispersion in the stream of mobile phase, the external mass-transfer resistance, intraparticle diffusion, and the kinetics of adsorption-desorption In this study we compare mass-transfer coefficients obtained in a reversed phase chromatographic column using macroscopic and microscopic approaches. The general rate model, the plate height equation, moment analysis, and stochastic analysis were used to assess chromatographic process during the separation of alkylbenzenes.

  9. Quantification of phytochelatins in plants by reversed-phase HPLC-ESI-MS-MS.

    PubMed

    El-Zohri, M H A; Cabala, R; Frank, H

    2005-08-01

    An on-line HPLC-ESI-MS-MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS-MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 micromol kg(-1) plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions. PMID:16001238

  10. Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface

    DOE PAGES

    Banerjee, R.; Sanyal, M. K.; Bera, M. K.; Gibaud, A.; Lin, B.; Meron, M.

    2015-02-17

    We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initialmore » monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.« less

  11. Reversible monolayer-to-crystalline phase transition in amphiphilic silsesquioxane at the air-water interface

    SciTech Connect

    Banerjee, R.; Sanyal, M. K.; Bera, M. K.; Gibaud, A.; Lin, B.; Meron, M.

    2015-02-17

    We report on the counter intuitive reversible crystallisation of two-dimensional monolayer of Trisilanolisobutyl Polyhedral Oligomeric SilSesquioxane (TBPOSS) on water surface using synchrotron x-ray scattering measurements. Amphiphilic TBPOSS form rugged monolayers and Grazing Incidence X-ray Scattering (GIXS) measurements reveal that the in-plane inter-particle correlation peaks, characteristic of two-dimensional system, observed before transition is replaced by intense localized spots after transition. The measured x-ray scattering data of the non-equilibrium crystalline phase on the air-water interface could be explained with a model that assumes periodic stacking of the TBPOSS dimers. These crystalline stacking relaxes upon decompression and the TBPOSS layer retains its initial monolayer state. The existence of these crystals in compressed phase is confirmed by atomic force microscopy measurements by lifting the materials on a solid substrate.

  12. Identification of cosmetic dyes by ion-pair reversed-phase high-performance liquid chromatography.

    PubMed

    Gagliardi, L; Cavazzutti, G; Amato, A; Basili, A; Tonelli, D

    1987-05-22

    A method based on ion-pair reversed-phase high-performance liquid chromatography with detection at four wavelengths between 400 and 600 nm is reported for the separation and identification of the most common synthetic colour additives in cosmetic products. All the dyes generally employed in the U.S.A. and almost all those in current use in cosmetics in the European Community have been taken into account. The chromatography was performed on a C8 bonded silica packed column, with a 60-min gradient changing from 10 to 95% acetonitrile in water containing 10(-2) M sodium perchlorate (pH 3.0) as mobile phase (flow-rate 2.5 ml/min). Detection limits are in the range 20-100 ng for all dyes investigated. The method has been applied to the analysis of commercial lipsticks.

  13. Reversed-phase HPLC determination of eight anticoagulant rodenticides in animal liver.

    PubMed

    Fauconnet, V; Pouliquen, H; Pinault, L

    1997-01-01

    A reversed-phase high-performance liquid chromatographic method was developed for the analysis of eight anticoagulant rodenticides in animal liver. Coumarinic anticoagulant rodenticides (brodifacoum, bromadiolone, coumachlor, coumatetralyl, difenacoum, and warfarin) were detected by using a gradient elution and a fluorimetric detection. Indanedione anticoagulant rodenticides (chlorophacinone and diphacinone) were detected by using an isocratic elution and an UV detection. Anticoagulants were extracted from liver with mixtures of acetone/diethylether and acetone/chloroform. Extracts were applied to solid-phase extraction cartridges. Linearity was checked over the concentration range 0.1-0.6 microgram/g. Relative standard deviations of within-run and between-run variability were all between 5.7 and 10.3%. Recoveries from spiked liver samples were between 51.7 (difenacoum) and 78.2% (warfarin). Limits of detection were between 0.01 (difenacoum and warfarin) and 0.11 microgram/g (chlorophacinone). PMID:9399124

  14. Quantification of phytochelatins in plants by reversed-phase HPLC-ESI-MS-MS.

    PubMed

    El-Zohri, M H A; Cabala, R; Frank, H

    2005-08-01

    An on-line HPLC-ESI-MS-MS method has been developed for determination of glutathione and phytochelatins (PC) in plant tissues. For sample pretreatment, dithiothreitol (DTT) must be added at the very beginning, as an anti-oxidant. Optimization of instrumental conditions i.e. composition of HPLC mobile phase, ionization efficiency of the electrospray interface, and MS-MS detection in the multiple ion-monitoring mode, are the central aspects of this work. A polystyrene-packed column was found to be superior to a standard silica-packed reversed-phase column. A concave quadratic gradient of ammonium formate buffer and acetonitrile was found to be optimum. The limits of quantitation were 0.2 micromol kg(-1) plant tissue for glutathione and PC. The method has been applied to analysis of tissue samples from Vicia faba grown in Cd-containing nutrient solutions.

  15. Determination of paraquat in marijuana by reversed-phase paired-ion high performance liquid chromatography.

    PubMed

    Needham, L; Paschal, D; Rollen, Z J; Liddle, J; Bayse, D

    1979-02-01

    A sensitive and selective method is described for the quantitative determination of paraquat in marijuana. Paraquat is extracted from finely ground plant material with hydrochloric acid with sonification, and the resulting acidic solution is extracted with chloroform:isopropanol (9:1) and evaporated to dryness. The residue is reconstituted with aqueous phosphate buffer pH 7.0; the solution is passed through a C-18 SEP-PAK TM and is analyzed with high performance liquid chromatography, using a reversed-phase column and an "ion pairing" reagent in the mobile phase. The recovery of paraquat in laboratory-spiked material varied from 90-97%. Results obtained with confiscated, field-sprayed marijuana by the procedure described were in excellent agreement with those obtained with a well-established ultraviolet procedure. The calculated limit of detection with this method is 2 ng of paraquat.

  16. Reversed-phase liquid chromatography analysis of imatinib mesylate and impurity product in Glivec capsules.

    PubMed

    Ivanovic, D; Medenica, M; Jancic, B; Malenovic, A

    2004-02-01

    The reversed-phase high-performance liquid chromatographic (RP-HPLC) method has been developed and validated for the simultaneous determination of imatinib mesylate and of the impurity product in Glivec capsules (Novartis, Switzerland). Separations were performed on a X Terra 150 mm x 4.6 mm, 5 microm particle size column at 25 degrees C. The mobile phase was a mixture of methanol-water-triethylamine (25:74:1, v/v/v) with flow rate of 1.0 ml min(-1). pH value of water-triethylamine (TEA) was adjusted to 2.4 with orthophosphoric acid before adding of methanol. UV detection was performed at 267 nm. Acetaminophen was used as an internal standard. The method was validated statistically for its selectivity, linearity, precision, accuracy and robustness. Due to its speed and accuracy, the method may be used for quality control analyses.

  17. Reverse-phase liquid chromatographic determination of clioquinol in cream and ointment preparations: collaborative study.

    PubMed

    Wojtowicz, E J

    1989-01-01

    Seven laboratories participated in a collaborative study to analyze, in duplicate, 2 synthetic formulations and 2 commercial preparations, labeled to contain 3% clioquinol. Clioquinol is determined as its nickel (II) complex by reverse-phase liquid chromatography on a phenyl-bonded column with a mobile phase of acetonitrile-methanol-water, containing ammonium acetate and nickel chloride. Detection is at 273 nm and diphenylamine is added as an internal standard. Mean recoveries were 99.1 and 101.1%, respectively, for the ointment and cream synthetic preparations and 96.7 and 99.7%, respectively, for the commercial ointment and cream. All results are consistent with the variability of other methods at this concentration range. The method has been approved interim official first action.

  18. [Determination of main degradation products of lignin using reversed-phase high performance liquid chromatography].

    PubMed

    Jiang, Zhijing; Zhu, Junjun; Li, Xin; Lian, Zhina; Yu, Shiyuan; Yong, Qiang

    2011-01-01

    An analytical method using reversed-phase high performance liquid chromatography (RP-HPLC) was developed for the separation and quantitative determination of main degradation products of lignin (4-hydroxybenzoic acid, vanillic acid, syringic acid, 4-hydroxybenzaldehyde, vanillin and syringaldehyde) during the steam exploded pretreatment for corn stovers. The separation was carried out on a C18 column with the mobile phase of acetonitrile-water (containing 1.5% acetic acid) at 30 degrees C at a flow rate of 0.8 mL/min and the detection wavelengths of 254 and 280 nm. Under the optimized conditions, the correlation coefficients of the 6 compounds were between 0.999 9 and 1.000 0. The recoveries of the 6 compounds were all above 96% and the relative standard deviations (n = 6) were less than 2.5%. This method is suitable for the determination of the main degradation products of lignin during the steam exploded pretreatment of lignocellulosics.

  19. Fatigue properties of a metastable beta-type titanium alloy with reversible phase transformation.

    PubMed

    Li, S J; Cui, T C; Hao, Y L; Yang, R

    2008-03-01

    Due to recent concern about allergic and toxic effects of Ni ions released from TiNi alloy into human body, much attention has been focused on the development of new Ni-free, metastable beta-type biomedical titanium alloys with a reversible phase transformation between the beta phase and the alpha'' martensite. This study investigates the effect of the stress-induced alpha'' martensite on the mechanical and fatigue properties of Ti-24Nb-4Zr-7.6Sn (wt.%) alloy. The results show that the as-forged alloy has a low dynamic Young's modulus of 55GPa and a recoverable tensile strain of approximately 3%. Compared with Ti-6Al-4V ELI, the studied alloy has quite a high low-cycle fatigue strength because of the effective suppression of microplastic deformation by the reversible martensitic transformation. Due to the low critical stress required to induce the martensitic transformation, it has low fatigue endurance comparable to that of Ti-6Al-4V ELI. Cold rolling produces a beta+alpha'' two-phase microstructure that is characterized by regions of nano-size beta grains interspersed with coarse grains containing alpha'' martensite plates. Cold rolling increases fatigue endurance by approximately 50% while decreasing the Young's modulus to 49GPa along the rolling direction but increasing it to 68GPa along the transverse direction. Due to the effective suppression of the brittle isothermal omega phase, balanced properties of high strength, low Young's modulus and good ductility can be achieved through ageing treatment at intermediate temperature.

  20. Separation and characterization of phenolic compounds and triterpenoid saponins in licorice (Glycyrrhiza uralensis) using mobile phase-dependent reversed-phase×reversed-phase comprehensive two-dimensional liquid chromatography coupled with mass spectrometry.

    PubMed

    Qiao, Xue; Song, Wei; Ji, Shuai; Wang, Qi; Guo, De-an; Ye, Min

    2015-07-10

    Licorice is one of the most popular herbal medicines worldwide. It contains a big array of phenolic compounds (flavonoids, coumarins, and diphenylethanones). Due to high structural diversity, low abundance, and co-elution with licorice saponins, these phenolic compounds are difficult to be separated by conventional chromatography. In this study, a mobile phase-dependent reversed-phase×reversed phase comprehensive two-dimensional liquid chromatography (RP×RP 2DLC) method was established to separate phenolic compounds in licorice (the roots of Glycyrrhiza uralensis). Organic solvents in the mobile phase were optimized to improve orthogonality of the first and second dimensions, and a synchronized gradient mode was used to improve chromatographic resolution. Finally, licorice extracts were eluted with methanol/water/formic acid in the first dimension (Acquity CSH C18 column), and acetonitrile/water/formic acid in the second dimension (Poroshell Phenyl-Hexyl column). By using this 2DLC system, a total of 311 compounds were detected within 40min. The practical and effective peak capacity was 1329 and 524, respectively, and the orthogonality was 79.8%. The structures of 21 selected unknown compounds were tentatively characterized by mass spectrometry, and 8 of them were discovered from G. uralensis for the first time. The mobile phase-dependent 2DLC/MS system could benefit the separation and characterization of natural products in complicated herbal extracts.

  1. Application of Statistical Thermodynamics To Predict the Adsorption Properties of Polypeptides in Reversed-Phase HPLC.

    PubMed

    Tarasova, Irina A; Goloborodko, Anton A; Perlova, Tatyana Y; Pridatchenko, Marina L; Gorshkov, Alexander V; Evreinov, Victor V; Ivanov, Alexander R; Gorshkov, Mikhail V

    2015-07-01

    The theory of critical chromatography for biomacromolecules (BioLCCC) describes polypeptide retention in reversed-phase HPLC using the basic principles of statistical thermodynamics. However, whether this theory correctly depicts a variety of empirical observations and laws introduced for peptide chromatography over the last decades remains to be determined. In this study, by comparing theoretical results with experimental data, we demonstrate that the BioLCCC: (1) fits the empirical dependence of the polypeptide retention on the amino acid sequence length with R(2) > 0.99 and allows in silico determination of the linear regression coefficients of the log-length correction in the additive model for arbitrary sequences and lengths and (2) predicts the distribution coefficients of polypeptides with an accuracy from 0.98 to 0.99 R(2). The latter enables direct calculation of the retention factors for given solvent compositions and modeling of the migration dynamics of polypeptides separated under isocratic or gradient conditions. The obtained results demonstrate that the suggested theory correctly relates the main aspects of polypeptide separation in reversed-phase HPLC. PMID:26023813

  2. Phosphoprotein Stability in Clinical Tissue and Its Relevance for Reverse Phase Protein Microarray Technology

    PubMed Central

    Espina, Virginia; Mueller, Claudius; Liotta, Lance A.

    2013-01-01

    Phosphorylated proteins reflect the activity of specific cell signaling nodes in biological kinase protein networks. Cell signaling pathways can be either activated or deactivated depending on the phosphorylation state of the constituent proteins. The state of these kinase pathways reflects the in vivo activity of the cells and tissue at any given point in time. As such, cell signaling pathway information can be extrapolated to infer which phosphorylated proteins/pathways are driving an individual tumor’s growth. Reverse Phase Protein Microarrays (RPMA) are a sensitive and precise platform that can be applied to the quantitative measurement of hundreds of phosphorylated signal proteins from a small sample of tissue. Pre-analytical variability originating from tissue procurement and preservation may cause significant variability and bias in downstream molecular analysis. Depending on the ex vivo delay time in tissue processing, and the manner of tissue handling, protein biomarkers such as signal pathway phosphoproteins will be elevated or suppressed in a manner that does not represent the biomarker levels at the time of excision. Consequently, assessment of the state of these kinase networks requires stabilization, or preservation, of the phosphoproteins immediately post tissue procurement. We have employed reverse phase protein microarray analysis of phosphoproteins to study the factors influencing stability of phosphoproteins in tissue following procurement. Based on this analysis we have established tissue procurement guidelines for clinical research with an emphasis on quantifying phosphoproteins by RPMA. PMID:21901591

  3. Application of Statistical Thermodynamics To Predict the Adsorption Properties of Polypeptides in Reversed-Phase HPLC.

    PubMed

    Tarasova, Irina A; Goloborodko, Anton A; Perlova, Tatyana Y; Pridatchenko, Marina L; Gorshkov, Alexander V; Evreinov, Victor V; Ivanov, Alexander R; Gorshkov, Mikhail V

    2015-07-01

    The theory of critical chromatography for biomacromolecules (BioLCCC) describes polypeptide retention in reversed-phase HPLC using the basic principles of statistical thermodynamics. However, whether this theory correctly depicts a variety of empirical observations and laws introduced for peptide chromatography over the last decades remains to be determined. In this study, by comparing theoretical results with experimental data, we demonstrate that the BioLCCC: (1) fits the empirical dependence of the polypeptide retention on the amino acid sequence length with R(2) > 0.99 and allows in silico determination of the linear regression coefficients of the log-length correction in the additive model for arbitrary sequences and lengths and (2) predicts the distribution coefficients of polypeptides with an accuracy from 0.98 to 0.99 R(2). The latter enables direct calculation of the retention factors for given solvent compositions and modeling of the migration dynamics of polypeptides separated under isocratic or gradient conditions. The obtained results demonstrate that the suggested theory correctly relates the main aspects of polypeptide separation in reversed-phase HPLC.

  4. A Two-Phase Space Resection Model for Accurate Topographic Reconstruction from Lunar Imagery with PushbroomScanners

    PubMed Central

    Xu, Xuemiao; Zhang, Huaidong; Han, Guoqiang; Kwan, Kin Chung; Pang, Wai-Man; Fang, Jiaming; Zhao, Gansen

    2016-01-01

    Exterior orientation parameters’ (EOP) estimation using space resection plays an important role in topographic reconstruction for push broom scanners. However, existing models of space resection are highly sensitive to errors in data. Unfortunately, for lunar imagery, the altitude data at the ground control points (GCPs) for space resection are error-prone. Thus, existing models fail to produce reliable EOPs. Motivated by a finding that for push broom scanners, angular rotations of EOPs can be estimated independent of the altitude data and only involving the geographic data at the GCPs, which are already provided, hence, we divide the modeling of space resection into two phases. Firstly, we estimate the angular rotations based on the reliable geographic data using our proposed mathematical model. Then, with the accurate angular rotations, the collinear equations for space resection are simplified into a linear problem, and the global optimal solution for the spatial position of EOPs can always be achieved. Moreover, a certainty term is integrated to penalize the unreliable altitude data for increasing the error tolerance. Experimental results evidence that our model can obtain more accurate EOPs and topographic maps not only for the simulated data, but also for the real data from Chang’E-1, compared to the existing space resection model. PMID:27077855

  5. A Two-Phase Space Resection Model for Accurate Topographic Reconstruction from Lunar Imagery with PushbroomScanners.

    PubMed

    Xu, Xuemiao; Zhang, Huaidong; Han, Guoqiang; Kwan, Kin Chung; Pang, Wai-Man; Fang, Jiaming; Zhao, Gansen

    2016-04-11

    Exterior orientation parameters' (EOP) estimation using space resection plays an important role in topographic reconstruction for push broom scanners. However, existing models of space resection are highly sensitive to errors in data. Unfortunately, for lunar imagery, the altitude data at the ground control points (GCPs) for space resection are error-prone. Thus, existing models fail to produce reliable EOPs. Motivated by a finding that for push broom scanners, angular rotations of EOPs can be estimated independent of the altitude data and only involving the geographic data at the GCPs, which are already provided, hence, we divide the modeling of space resection into two phases. Firstly, we estimate the angular rotations based on the reliable geographic data using our proposed mathematical model. Then, with the accurate angular rotations, the collinear equations for space resection are simplified into a linear problem, and the global optimal solution for the spatial position of EOPs can always be achieved. Moreover, a certainty term is integrated to penalize the unreliable altitude data for increasing the error tolerance. Experimental results evidence that our model can obtain more accurate EOPs and topographic maps not only for the simulated data, but also for the real data from Chang'E-1, compared to the existing space resection model.

  6. A reversed-phase/hydrophilic interaction mixed-mode C18-Diol stationary phase for multiple applications.

    PubMed

    Wang, Qing; Ye, Mao; Xu, Li; Shi, Zhi-guo

    2015-08-12

    A mixed-mode chromatographic packing material, C18 and diol groups modified silica (C18-Diol), was prepared with controllable hydrophobicity and hydrophilicity. It demonstrated excellent aqueous compatibility and stability in aqueous mobile phase; compared to the traditional C18 column, improved peak shape of basic analytes was also obtained. Additionally, it exhibited both reversed-phase liquid chromatographic (RPLC) and hydrophilic interaction chromatographic (HILIC) performance; the analyte separation scope was thus enlarged, demonstrated by simultaneous separation of twenty acids, bases and neutrals. More interestingly, a novel on-line two-dimensional liquid chromatography on the single column (2D-LC-1C) was established by modifying the high performance liquid chromatographic instrument only with the addition of an extra six-port two-position valve. The early co-eluted components of the extract of Lonicera japonica on the 1st-dimension (RPLC) were collected for the online re-injection to the 2nd-dimension (HILIC) by conveniently varying the mobile phase components. Six more peaks were obtained. The established system was simple, easy operation and low cost, which had advantages in analyzing complicated samples. PMID:26320974

  7. [Determination of glucosinolates in rapeseed by reversed-phase ion-pair liquid chromatography].

    PubMed

    Peng, A J; Tang, G F; Lan, Z H; Dong, W B; Wu, M C

    2000-01-01

    This paper presents a method for the direct determination of intact glucosinolates in rapeseed by reversed-phase ion-pair liquid chromatography (RILC). The catechin, mercaptoethanol and phytic acid was adopted respectively in sample pretreatment to prevent indole glucosinolates being oxidized. Among them, the effect of mercaptoethanol was the most obvious. The effects of composition and concentration of the mobile phase, the pH of the mobile phase and the column temperature on the retention and the capacity factor of the glucosinolates were studied. The condition of this method by RILC has been set up: column, YWG-C18 H37(10 microns, 250 mm x 4 mm i.d.); mobile phase, 0.02 mol/L KH2PO4 buffer(pH 6) containing 4.5 mmol/L (C4H8)4NBr and CH3CN(90/10, V/V); flow rate, 1 mL/min; detector, UV-226 nm; column temperation, 30 degrees C. In this condition, six glucosinolates were separated completely. The relative correction factors were determined by using sinigrin or benzoic acid as the internal standard. The characteristics of glucosinolates in different kinds of Chinese rapeseed can be determined by this RILC method.

  8. Retention behavior of alkyl-substituted polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography.

    PubMed

    Wilson, Walter B; Sander, Lane C; de Alda, Miren Lopez; Lee, Milton L; Wise, Stephen A

    2016-08-26

    Retention indices for 79 alkyl-substituted polycyclic aromatic sulfur heterocycles (PASHs) were determined by using reversed-phase liquid chromatography (LC) on a monomeric and polymeric octadecylsilane (C18) stationary phase. Molecular shape parameters [length, breadth, thickness (T), and length-to-breadth ratio (L/B)] were calculated for all the compounds studied. Based on separations of isomeric methylated polycyclic aromatic hydrocarbons on polymeric C18 phases, alkyl-substituted PASHs are expected to elute based on increasing L/B ratios. However, the correlation coefficients had a wide range of values from r=0.43 to r=0.93. Several structural features besides L/B ratios were identified to play an important role in the separation mechanism of PASHs on polymeric C18 phases. First, the location of the sulfur atom in a bay-like-region results in alkylated-PASHs being more retentive than non-bay-like-region alkylated-PASHs, and they elute later than expected based on L/B value. Second, the placement of the alkyl group in the k region of the structure resulted in a later elution than predicted by L/B. Third, highly nonplanar methyl-PASHs (i.e., 1-Me and 11-MeBbN12T) elute prior to the parent PASH (BbN12T).

  9. Linking phase behavior and reversible colloidal aggregation at low concentrations: simulations and stochastic mean field theory.

    PubMed

    Puertas, Antonio M; Odriozola, Gerardo

    2007-05-24

    We have studied the link between the kinetics of clustering and the phase behavior of dilute colloids with short range attractions of moderate strength. This was done by means of computer simulations and a theoretical kinetic model originally developed to deal with reversible colloidal aggregation. Three different regions of the phase diagram were accessed. For weak attractions, a gas phase of small clusters in equilibrium forms in the system. For intermediate attractions, the system undergoes liquid-gas separation, which is signatured by the formation of a few large droplike aggregates, a gas phase of small clusters, and an overall kinetics where a few seeds succeed in explosively growing at long times, after a lag time. Finally, for very strong attractions, fractal unbreakable clusters form and grow following DLCA-like (diffusion limited cluster aggregation) kinetics; liquid-gas separation is prevented by the strength of the bonds, which do not allow restructuration. Good qualitative and quantitative agreement is found between the dynamic simulations and the kinetic model in all the three regions.

  10. Retention behavior of isomeric polycyclic aromatic sulfur heterocycles in reversed-phase liquid chromatography.

    PubMed

    Wilson, Walter B; Sander, Lane C; de Alda, Miren Lopez; Lee, Milton L; Wise, Stephen A

    2016-08-26

    Retention indices for 70 polycyclic aromatic sulfur heterocycles (PASHs) were determined using reversed-phase liquid chromatography (LC) on a monomeric and a polymeric C18 stationary phase. Molecular shape parameters [length, breadth, thickness (T), and length-to-breadth ratio (L/B)] were calculated for all the compounds studied. Correlations between the retention on the polymeric C18 phase and PASH geometry (L/B and T) were investigated for six specific PASH isomer groups with molecular mass (MM) 184Da, 234Da, 258Da, 284Da, 334Da, and 384Da. Similar to previous studies for polycyclic aromatic hydrocarbons (PAHs), PASH elution order on the polymeric C18 phase was generally found to follow increasing L/B values. Correlation coefficients for retention vs L/B ranged from r=0.45 (MM 184Da) to r=0.89 (MM 284Da). In the case of smaller PASHs (MM≤258Da), the location of the sulfur atom in the bay-region of the structure resulted in later than expected elution of these isomers based on L/B. In the case of the larger PASHs (MM≥284Da), nonplanarity had a significant influence on earlier than predicted elution based on L/B values. PMID:27481401

  11. Novel ultra stable silica-based stationary phases for reversed phase liquid chromatography--study of a hydrophobically assisted weak acid cation exchange phase.

    PubMed

    Zhang, Yu; Carr, Peter W

    2011-02-11

    A mixed-mode reversed-phase/weak cation exchange (RP/WCX) phase has been developed by introducing a small amount of carboxylate functionality into a hydrophobic hyper-crosslinked (HC) platform. This silica-based HC platform was designed to form an extensive polystyrene network completely confined to the particle's surface. The fully connected polymer network prevents the loss of bonded phase, which leads to superior hydrolytic stability of the new phase when compared to conventional silica-based phases. Compared to previously introduced HC phases the added carboxylic groups impart a new weak cation exchange selectivity to the base hydrophobic HC platform. The phase thus prepared shows a mixed-mode retention mechanism, allowing for both neutral organic compounds and bases of a wide polarity range to be simultaneously separated on the same phase under the same conditions. In addition, the new phase offers the flexibility that gradients in organic modifier, pH or ionic competitors can be used to affect the separation of a wide range of solutes. Moreover, the inherent weak acid cation exchange groups allow formic and acetic acid buffers to be used as eluents thereby avoiding the mass spectrometric ionization suppression problems concomitant to the use of non-volatile additives such as strong amine modifiers (e.g. triethylamine) or salts (e.g. NaCl) to elute basic solutes from the strong cation exchange phase which was previously developed in this lab. The use of the new phase for achieving strong retention of rather hydrophilic neurotransmitters and drugs of abuse without the need for ion pairing agents is demonstrated.

  12. The TITAN Reversed-Field Pinch fusion reactor study: Scoping phase report

    SciTech Connect

    Not Available

    1987-01-01

    The TITAN research program is a multi-institutional effort to determine the potential of the Reversed-Field Pinch (RFP) magnetic fusion concept as a compact, high-power-density, and ''attractive'' fusion energy system from economic (cost of electricity, COE), environmental, and operational viewpoints. In particular, a high neutron wall loading design (18 MW/m/sup 2/) has been chosen as the reference case in order to quantify the issue of engineering practicality, to determine the physics requirements and plasma operating mode, to assess significant benefits of compact systems, and to illuminate the main drawbacks. The program has been divided into two phases, each roughly one year in length: the Scoping Phase and the Design Phase. During the scoping phase, the TITAN design team has defined the parameter space for a high mass power density (MPD) RFP reactor, and explored a variety of approaches to the design of major subsystems. Two major design approaches consistent with high MPD and low COE, the lithium-vanadium blanket design and aqueous loop-in-pool design, have been selected for more detailed engineering evaluation in the design phase. The program has retained a balance in its approach to investigating high MPD systems. On the one hand, parametric investigations of both subsystems and overall system performance are carried out. On the other hand, more detailed analysis and engineering design and integration are performed, appropriate to determining the technical feasibility of the high MPD approach to RFP fusion reactors. This report describes the work of the scoping phase activities of the TITAN program. A synopsis of the principal technical findings and a brief description of the TITAN multiple-design approach is given. The individual chapters on Plasma Physics and Engineering, Parameter Systems Studies, Divertor, Reactor Engineering, and Fusion Power Core Engineering have been cataloged separately.

  13. Accurate and agile digital control of optical phase, amplitude and frequency for coherent atomic manipulation of atomic systems.

    PubMed

    Thom, Joseph; Wilpers, Guido; Riis, Erling; Sinclair, Alastair G

    2013-08-12

    We demonstrate a system for fast and agile digital control of laser phase, amplitude and frequency for applications in coherent atomic systems. The full versatility of a direct digital synthesis radiofrequency source is faithfully transferred to laser radiation via acousto-optic modulation. Optical beatnotes are used to measure phase steps up to 2π, which are accurately implemented with a resolution of ≤ 10 mrad. By linearizing the optical modulation process, amplitude-shaped pulses of durations ranging from 500 ns to 500 ms, in excellent agreement with the programmed functional form, are demonstrated. Pulse durations are limited only by the 30 ns rise time of the modulation process, and a measured extinction ratio of > 5 × 10(11) is achieved. The system presented here was developed specifically for controlling the quantum state of trapped ions with sequences of multiple laser pulses, including composite and bichromatic pulses. The demonstrated techniques are widely applicable to other atomic systems ranging across quantum information processing, frequency metrology, atom interferometry, and single-photon generation.

  14. Using reversed phase high performance liquid chromatography to study the complexation of anthocyanins with β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Deineka, V. I.; Lapshova, M. S.; Deineka, L. A.

    2014-06-01

    It is shown by means of reversed phase high performance liquid chromatography (RP HPLC) with mobile phases containing additions of β-cyclodextrin that 5-glucosides of cyanidin and pelargonidin form stronger inclusion complexes than 3-glucosides; this is explained by the steric interference of the glucoside radical.

  15. Phosphopeptide Enrichment by Covalent Chromatography after Derivatization of Protein Digests Immobilized on Reversed-Phase Supports

    PubMed Central

    Nika, Heinz; Nieves, Edward; Hawke, David H.; Angeletti, Ruth Hogue

    2013-01-01

    A rugged sample-preparation method for comprehensive affinity enrichment of phosphopeptides from protein digests has been developed. The method uses a series of chemical reactions to incorporate efficiently and specifically a thiol-functionalized affinity tag into the analyte by barium hydroxide catalyzed β-elimination with Michael addition using 2-aminoethanethiol as nucleophile and subsequent thiolation of the resulting amino group with sulfosuccinimidyl-2-(biotinamido) ethyl-1,3-dithiopropionate. Gentle oxidation of cysteine residues, followed by acetylation of α- and ε-amino groups before these reactions, ensured selectivity of reversible capture of the modified phosphopeptides by covalent chromatography on activated thiol sepharose. The use of C18 reversed-phase supports as a miniaturized reaction bed facilitated optimization of the individual modification steps for throughput and completeness of derivatization. Reagents were exchanged directly on the supports, eliminating sample transfer between the reaction steps and thus, allowing the immobilized analyte to be carried through the multistep reaction scheme with minimal sample loss. The use of this sample-preparation method for phosphopeptide enrichment was demonstrated with low-level amounts of in-gel-digested protein. As applied to tryptic digests of α-S1- and β-casein, the method enabled the enrichment and detection of the phosphorylated peptides contained in the mixture, including the tetraphosphorylated species of β-casein, which has escaped chemical procedures reported previously. The isolates proved highly suitable for mapping the sites of phosphorylation by collisionally induced dissociation. β-Elimination, with consecutive Michael addition, expanded the use of the solid-phase-based enrichment strategy to phosphothreonyl peptides and to phosphoseryl/phosphothreonyl peptides derived from proline-directed kinase substrates and to their O-sulfono- and O-linked β-N-acetylglucosamine (O

  16. Effect of microwave dielectric heating on intraparticle diffusion in reversed-phase liquid chromatography

    SciTech Connect

    Galinada, Wilmer; Guiochon, Georges A

    2005-08-01

    The influence of microwave (MW) irradiation on the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) was studied by placing a column in a microwave oven and measuring the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase compositions. The microwave energy dissipated in the column was set between 15 and 200 W and the mobile phase composition used varied from 100 to 70, 50, and 10% methanol in water at 1.2 mL/min. At all the mobile phase compositions considered, the effluent temperature increased with increasing microwave energy. At 70% methanol, the mobile phase flow rate was set at 1.2, 2.0, and 2.8 mL/min. At 1.2 mL/min, the effluent temperatures at the lowest (15 W) and highest (200 W) microwave energy inputs were 25 {+-} 1 C and 41 {+-} 1 C for pure methanol, 25 {+-} 1 C and 48 {+-} 1 C for 70% methanol, 25 {+-} 1 C and 50 {+-} 1 C for 50% methanol, and, 25 {+-} 1 C and 52 {+-} 1 C for 10% methanol, respectively. With 70% methanol and microwave energy inputs of 15, 30, and 50 W, the effluent temperature did not change with increasing flow rate; a considerable change was observed at 100, 150, and 200 W between 1.2 and 2.0 mL/min and none between 2.0 and 2.8 mL/min. Chromatographic elution band profiles of propylbenzene were recorded under linear conditions, in 70% methanol solutions, for microwave energy inputs of 0, 15 and 30 W, at constant temperature. The intraparticle diffusion coefficient, D{sub e}, under microwave irradiation was ca. 20% higher than without irradiation. These preliminary results suggest that microwave irradiation may have a considerable influence on intraparticle diffusion in RPLC.

  17. Effect of microwave dielectric heating on intraparticle diffusion in reversed-phase liquid chromatography.

    PubMed

    Galinada, Wilmer A; Guiochon, Georges

    2005-09-30

    The influence of microwave (MW) irradiation on the mass transfer kinetics in reversed-phase liquid chromatography (RPLC) was studied by placing a column in a microwave oven and measuring the incremental change in the temperature of the column effluent stream at various microwave energies and mobile phase compositions. The microwave energy dissipated in the column was set between 15 and 200 W and the mobile phase composition used varied from 100 to 70, 50, and 10% methanol in water at 1.2 mL/min. At all the mobile phase compositions considered, the effluent temperature increased with increasing microwave energy. At 70% methanol, the mobile phase flow rate was set at 1.2, 2.0, and 2.8 mL/min. At 1.2 mL/min, the effluent temperatures at the lowest (15 W) and highest (200 W) microwave energy inputs were 25 +/- 1 degrees C and 41 +/- 1 degrees C for pure methanol, 25 +/- 1 degrees C and 48 +/- 1 degrees C for 70% methanol, 25 +/- 1 degrees C and 50 +/- 1 degrees C for 50% methanol, and, 25 +/- 1 degrees C and 52 +/- 1 degrees C for 10% methanol, respectively. With 70% methanol and microwave energy inputs of 15, 30, and 50 W, the effluent temperature did not change with increasing flow rate; a considerable change was observed at 100, 150, and 200 W between 1.2 and 2.0 mL/min and none between 2.0 and 2.8 mL/min. Chromatographic elution band profiles of propylbenzene were recorded under linear conditions, in 70% methanol solutions, for microwave energy inputs of 0, 15 and 30 W, at constant temperature. The intraparticle diffusion coefficient, De, under microwave irradiation was ca. 20% higher than without irradiation. These preliminary results suggest that microwave irradiation may have a considerable influence on intraparticle diffusion in RPLC.

  18. Ion-pair reversed phase liquid chromatography with ultraviolet detection for analysis of ultraviolet transparent cations.

    PubMed

    He, Yan; Cook, Kenneth S; Littlepage, Eric; Cundy, John; Mangalathillam, Ratish; Jones, Michael T

    2015-08-21

    This paper describes the use of an anionic ion-pair reagent (IPR) to impove the ultraviolet (UV) detection and hydrophobic retention of polar and UV transparent cations. Anionic IPR added to the mobile phase forms an ion-pair with cations. Formation of the ion-pair causes a redshift in the absorption wavength, making it possible for direct UV detection of UV-inactive cations. The ion-pairs with increased hydrophobicity were separated by reversed phase liquid chromatography (RPLC). Different perfluorinated caboxylic acids (trifluoroacetic acid, heptafluorobutyric acid, nonafluoropentanoic acid) were evaluted as IPR in the separation and detection of the common cations sodium, ammonium and Tris(hydroxymethyl)aminomethane (Tris). The effects of the IPR type and concentration on separation and detection have been investigated to understand the separation and detection mechanisms. The optimal separation and detection condtions were attained with mobile phase containing 0.1% nonafluoropentanoic acid and with the UV detection at 210nm. UV detection and charged aerosol detection (CAD) were compared in the quantitation of the cations. The limit of quantitation (LOQ) of sodium and Tris with UV detection is comparable to that by CAD. The LOQ of ammonium with UV detection (1ppm or 3ng) is about 20-fold lower than that (20ppm or 60ng) by CAD. The RPLC-UV method was used to monitor ammonium clearance during ultrafiltration and diafiltration in the manfucaturing of biopharmceutical drug substance.

  19. [Preparation of soybean isoflavone glucosides by reversed-phase high performance liquid chromatography].

    PubMed

    Yang, Xuedong; Deng, Zhicheng; Wang, Jing; Ding, Mingyu

    2006-07-01

    A method was established for the isolation of soybean isoflavone glucosides from the total isoflavone extracts of soybean using preparative reversed-phase high performance liquid chromatography (RP-HPLC). The total isoflavone extracts were separated into four parts by solvent extraction, those are the ethyl acetate extract, butanol extract, precipitate (D4), and the remaining aqueous phase. The part D4 containing soybean isoflavone glucosides was acquired and subjected to preparative HPLC for the isolation of target components. A preparative Nova-Pak HR C18 column (100 mm x 25 mm i. d. , 6 microm) was used in the preparation process. By isocratic elution with methanol-0.1% aqueous acetic acid (23:77, v/v) as the mobile phase at a flow rate of 20 mL/min, followed by concentration and desalination, three soybean isoflavone glucosides were obtained and subsequently identified by mass spectrometry as daidzin, glycitin, and genistin. HPLC analysis showed that the purities of the three soybean isoflavone glucosides were all higher than 99%.

  20. The intra-S phase checkpoint targets Dna2 to prevent stalled replication forks from reversing.

    PubMed

    Hu, Jiazhi; Sun, Lei; Shen, Fenfen; Chen, Yufei; Hua, Yu; Liu, Yang; Zhang, Mian; Hu, Yiren; Wang, Qingsong; Xu, Wei; Sun, Fei; Ji, Jianguo; Murray, Johanne M; Carr, Antony M; Kong, Daochun

    2012-06-01

    When replication forks stall at damaged bases or upon nucleotide depletion, the intra-S phase checkpoint ensures they are stabilized and can restart. In intra-S checkpoint-deficient budding yeast, stalling forks collapse, and ∼10% form pathogenic chicken foot structures, contributing to incomplete replication and cell death (Lopes et al., 2001; Sogo et al., 2002; Tercero and Diffley, 2001). Using fission yeast, we report that the Cds1(Chk2) effector kinase targets Dna2 on S220 to regulate, both in vivo and in vitro, Dna2 association with stalled replication forks in chromatin. We demonstrate that Dna2-S220 phosphorylation and the nuclease activity of Dna2 are required to prevent fork reversal. Consistent with this, Dna2 can efficiently cleave obligate precursors of fork regression-regressed leading or lagging strands-on model replication forks. We propose that Dna2 cleavage of regressed nascent strands prevents fork reversal and thus stabilizes stalled forks to maintain genome stability during replication stress.

  1. Steganographic optical image encryption system based on reversible data hiding and double random phase encoding

    NASA Astrophysics Data System (ADS)

    Chuang, Cheng-Hung; Chen, Yen-Lin

    2013-02-01

    This study presents a steganographic optical image encryption system based on reversible data hiding and double random phase encoding (DRPE) techniques. Conventional optical image encryption systems can securely transmit valuable images using an encryption method for possible application in optical transmission systems. The steganographic optical image encryption system based on the DRPE technique has been investigated to hide secret data in encrypted images. However, the DRPE techniques vulnerable to attacks and many of the data hiding methods in the DRPE system can distort the decrypted images. The proposed system, based on reversible data hiding, uses a JBIG2 compression scheme to achieve lossless decrypted image quality and perform a prior encryption process. Thus, the DRPE technique enables a more secured optical encryption process. The proposed method extracts and compresses the bit planes of the original image using the lossless JBIG2 technique. The secret data are embedded in the remaining storage space. The RSA algorithm can cipher the compressed binary bits and secret data for advanced security. Experimental results show that the proposed system achieves a high data embedding capacity and lossless reconstruction of the original images.

  2. Rapid reverse phase-HPLC assay of HMG-CoA reductase activity

    PubMed Central

    Mozzicafreddo, Matteo; Cuccioloni, Massimiliano; Eleuteri, Anna Maria; Angeletti, Mauro

    2010-01-01

    Radioisotope-based and mass spectrometry coupled to chromatographic techniques are the conventional methods for monitoring HMG-CoA reductase (HMGR) activity. Irrespective of offering adequate sensitivity, these methods are often cumbersome and time-consuming, requiring the handling of radiolabeled chemicals or elaborate ad-hoc derivatizing procedures. We propose a rapid and versatile reverse phase-HPLC method for assaying HMGR activity capable of monitoring the levels of both substrates (HMG-CoA and NADPH) and products (CoA, mevalonate, and NADP+) in a single 20 min run with no pretreatment required. The linear dynamic range was 10–26 pmol for HMG-CoA, 7–27 nmol for NADPH, 0.5–40 pmol for CoA and mevalonate, and 2–27 nmol for NADP+, and limit of detection values were 2.67 pmol, 2.77 nmol, 0.27 pmol, and 1.3 nmol, respectively. PMID:20418539

  3. Analysis of antimycin A by reversed-phase liquid chromatography/nuclear magnetic-resonance spectrometry

    USGS Publications Warehouse

    Ha, Steven T.K.; Wilkins, Charles L.; Abidi, Sharon L.

    1989-01-01

    A mixture of closely related streptomyces fermentation products, antimycin A, Is separated, and the components are identified by using reversed-phase high-performance liquid chromatography with directly linked 400-MHz proton nuclear magnetic resonance detection. Analyses of mixtures of three amino acids, alanine, glycine, and valine, are used to determine optimal measurement conditions. Sensitivity increases of as much as a factor of 3 are achieved, at the expense of some loss in chromatographic resolution, by use of an 80-μL NMR cell, Instead of a smaller 14-μL cell. Analysis of the antimycin A mixture, using the optimal analytical high performance liquid chromatography/nuclear magnetic resonance conditions, reveals it to consist of at least 10 closely related components.

  4. Reverse Phase Protein Arrays—Quantitative Assessment of Multiple Biomarkers in Biopsies for Clinical Use

    PubMed Central

    Boellner, Stefanie; Becker, Karl-Friedrich

    2015-01-01

    Reverse Phase Protein Arrays (RPPA) represent a very promising sensitive and precise high-throughput technology for the quantitative measurement of hundreds of signaling proteins in biological and clinical samples. This array format allows quantification of one protein or phosphoprotein in multiple samples under the same experimental conditions at the same time. Moreover, it is suited for signal transduction profiling of small numbers of cultured cells or cells isolated from human biopsies, including formalin fixed and paraffin embedded (FFPE) tissues. Owing to the much easier sample preparation, as compared to mass spectrometry based technologies, and the extraordinary sensitivity for the detection of low-abundance signaling proteins over a large linear range, RPPA have the potential for characterization of deregulated interconnecting protein pathways and networks in limited amounts of sample material in clinical routine settings. Current aspects of RPPA technology, including dilution curves, spotting, controls, signal detection, antibody validation, and calculation of protein levels are addressed. PMID:27600215

  5. Reverse Phase Protein Arrays—Quantitative Assessment of Multiple Biomarkers in Biopsies for Clinical Use

    PubMed Central

    Boellner, Stefanie; Becker, Karl-Friedrich

    2015-01-01

    Reverse Phase Protein Arrays (RPPA) represent a very promising sensitive and precise high-throughput technology for the quantitative measurement of hundreds of signaling proteins in biological and clinical samples. This array format allows quantification of one protein or phosphoprotein in multiple samples under the same experimental conditions at the same time. Moreover, it is suited for signal transduction profiling of small numbers of cultured cells or cells isolated from human biopsies, including formalin fixed and paraffin embedded (FFPE) tissues. Owing to the much easier sample preparation, as compared to mass spectrometry based technologies, and the extraordinary sensitivity for the detection of low-abundance signaling proteins over a large linear range, RPPA have the potential for characterization of deregulated interconnecting protein pathways and networks in limited amounts of sample material in clinical routine settings. Current aspects of RPPA technology, including dilution curves, spotting, controls, signal detection, antibody validation, and calculation of protein levels are addressed.

  6. RPPAML/RIMS: A metadata format and an information management system for reverse phase protein arrays

    PubMed Central

    Stanislaus, Romesh; Carey, Mark; Deus, Helena F; Coombes, Kevin; Hennessy, Bryan T; Mills, Gordon B; Almeida, Jonas S

    2008-01-01

    Background Reverse Phase Protein Arrays (RPPA) are convenient assay platforms to investigate the presence of biomarkers in tissue lysates. As with other high-throughput technologies, substantial amounts of analytical data are generated. Over 1000 samples may be printed on a single nitrocellulose slide. Up to 100 different proteins may be assessed using immunoperoxidase or immunoflorescence techniques in order to determine relative amounts of protein expression in the samples of interest. Results In this report an RPPA Information Management System (RIMS) is described and made available with open source software. In order to implement the proposed system, we propose a metadata format known as reverse phase protein array markup language (RPPAML). RPPAML would enable researchers to describe, document and disseminate RPPA data. The complexity of the data structure needed to describe the results and the graphic tools necessary to visualize them require a software deployment distributed between a client and a server application. This was achieved without sacrificing interoperability between individual deployments through the use of an open source semantic database, S3DB. This data service backbone is available to multiple client side applications that can also access other server side deployments. The RIMS platform was designed to interoperate with other data analysis and data visualization tools such as Cytoscape. Conclusion The proposed RPPAML data format hopes to standardize RPPA data. Standardization of data would result in diverse client applications being able to operate on the same set of data. Additionally, having data in a standard format would enable data dissemination and data analysis. PMID:19102773

  7. Validated Reverse-Phase High-Performance Liquid Chromatography for Quantification of Furosemide in Tablets and Nanoparticles

    PubMed Central

    Youm, Ibrahima; Youan, Bi-Botti Celestin

    2013-01-01

    A simple, sensitive, and specific method for furosemide (FUR) analysis by reverse-phase-HPLC was developed using a Spherisorb C18 ODS 2 column. A chromatographic analysis was carried out using a mobile phase consisting of acetonitrile and 10 mM potassium phosphate buffer solution: 70 : 30 (v/v) at pH 3.85, at a flow rate of 1 mL·min−1. The UV-detection method was carried out at 233 nm at room temperature. Validation parameters including limit of detection (LOD), limit of quantitation (LOQ), linearity range, precision, accuracy, robustness, and specificity were investigated. Results indicated that the calibration curve was linear (r2 = 0.9997) in the range of 5.2 to 25,000 ng·mL−1, with ε value equal to 3.74 × 104 L·M−1·cm−1. The LOD and LOQ were found to be 5.2 and 15.8 ng·mL−1, respectively. The developed method was found to be accurate (RSD less than 2%), precise, and specific with an intraday and interday RSD range of 1.233–1.509 and 1.615 to 1.963%. The stability of native FUR has also been performed in simulated perilymph and endolymph media (with respective potency in each medium of 99.8 ± 2.3% and 96.68 ± 0.7%, n = 3) after 6 hours. This method may be routinely used for the quantitative analysis of FUR from nanocarriers, USP tablets and release media related to hearing research PMID:24163777

  8. Simultaneous determination of gatifloxacin and ambroxol hydrochloride from tablet dosage form using reversed-phase high performance liquid chromatography.

    PubMed

    Shahed, Mirza; Nanda, Rabindra; Dehghan, Muhammad Hassan; Nasreen, Huda; Feroz, Shaikh

    2008-05-01

    A reversed-phase high performance liquid chromatography (HPLC) method was developed, validated, and used for the quantitative determination of gatifloxacin (GA) and ambroxol hydrochloride (AM), from its tablet dosage form. Chromatographic separation was performed on a HiQ Sil C18 column (250 mm x 4.6 mm, 5 microm), with a mobile phase comprising of a mixture of 0.01 mol/L potassium dihydrogen orthophosphate buffer and acetonitrile (70 : 30, v/v), and pH adjusted to 3 with orthophosphoric acid, at a flow rate of 1 mL/min, with detection at 247 nm. Separation was completed in less than 10 min. As per International Conference on Harmonisation (ICH) guidelines the method was validated for linearity, accuracy, precision, limit of quantitation, limit of detection, and robustness. Linearity of GA was found to be in the range of 10 -60 microg/mL and that for AM was found to be 5 - 30 microg/mL. The correlation coefficients were 0.999 6 and 0.999 3 for GA and AM respectively. The results of the tablet analysis (n = 5) were found to be 99.94% with +/- 0.25% standard deviation (SD) and 99.98% with +/- 0.36% SD for GA and AM respectively. Percent recovery of GA was found to be 99.92% - 100.02% and that of AM was 99.86% - 100.16%. The assay experiment shows that the method is free from interference of excipients. This demonstrates that the developed HPLC method is simple, linear, precise, and accurate, and can be conveniently adopted for the routine quality control analysis of the tablet.

  9. Gallium Adhesion: Phase Change of Gallium Enables Highly Reversible and Switchable Adhesion (Adv. Mater. 25/2016).

    PubMed

    Ye, Zhou; Lum, Guo Zhan; Song, Sukho; Rich, Steven; Sitti, Metin

    2016-07-01

    M. Sitti and co-workers find that gallium exhibits highly reversible and switchable adhesive characteristics during the liquid-solid phase change. As described on page 5088, this reversible adhesive allows miniature capsule-like robots, which are able to easily pick-and-place objects with irregular geometries and rough surfaces, and thus assemble such objects into a complex structure. The contact interface between gallium and the rough object is illustrated in the magnified image. PMID:27372722

  10. A versatile reversed phase-strong cation exchange-reversed phase (RP-SCX-RP) multidimensional liquid chromatography platform for qualitative and quantitative shotgun proteomics.

    PubMed

    Law, Henry C H; Kong, Ricky P W; Szeto, Samuel S W; Zhao, Yun; Zhang, Zaijun; Wang, Yuqiang; Li, Guohui; Quan, Quan; Lee, Simon M Y; Lam, Herman C; Chu, Ivan K

    2015-02-21

    An automatable, robust, high-performance online multidimensional liquid chromatography (MDLC) platform comprising of pH 10 reversed-phase (RP), strong cation exchange (SCX), and pH 2 RP separation stages has been integrated into a modified commercial off-the-shelf LC instrument with a simple rewiring, enabling accelerated routine qualitative and quantitative proteomics analyses. This system has been redesigned with a dual-trap column configuration to improve the throughput by greatly decreasing the system idle time. The performance of this new design has been benchmarked through analysis of the total lysate of S. cerevisiae, in comparison with that of the former tailor-made system featuring more complicated components; the total run time per "load-and-go" LC/MS analysis was approximately 24 h, with minimal idle time and no labor-intensive steps. This platform features high-resolution fractionations, ease of use and a high degree of user programmability in the first two chromatographic dimensions, allowing flexible and effective sampling with (RP-SCX-RP) or without (RP-RP) the inclusion of SCX sub-fractionation; good proteome coverage and reproducibility was demonstrated through the analyses of bacterial, cell culture, and monkey brain tissue proteomes. The viability of the 3D RP-SCX-RP has been proven in proteome-wide studies of STO fibroblasts and yeast tryptic digests, resulting in extended proteome and protein coverages with high reproducibility-in particular, discovering extra-hydrophilic peptides-at the expense of the acquisition time. The identified inventory of the rat pheochromocytoma PC12 cell proteome-a total of 6345 proteins and 97 309 unique peptides is the most comprehensive dataset to date-provides an example of the value of the 3D RP-SCX-RP. The use of orthogonal chromatographic dimensions in the 3D RP-SCX-RP also circumvents the issues of isobaric interference of mass-tagging background contaminations, while significantly improving the accuracy of

  11. Accurate recovery of 4D left ventricular deformations using volumetric B-splines incorporating phase based displacement estimates

    NASA Astrophysics Data System (ADS)

    Chen, Jian; Tustison, Nicholas J.; Amini, Amir A.

    2006-03-01

    In this paper, an improved framework for estimation of 3-D left-ventricular deformations from tagged MRI is presented. Contiguous short- and long-axis tagged MR images are collected and are used within a 4-D B-Spline based deformable model to determine 4-D displacements and strains. An initial 4-D B-spline model fitted to sparse tag line data is first constructed by minimizing a 4-D Chamfer distance potential-based energy function for aligning isoparametric planes of the model with tag line locations; subsequently, dense virtual tag lines based on 2-D phase-based displacement estimates and the initial model are created. A final 4-D B-spline model with increased knots is fitted to the virtual tag lines. From the final model, we can extract accurate 3-D myocardial deformation fields and corresponding strain maps which are local measures of non-rigid deformation. Lagrangian strains in simulated data are derived which show improvement over our previous work. The method is also applied to 3-D tagged MRI data collected in a canine.

  12. A quantitatively accurate theory of stable crack growth in single phase ductile metal alloys under the influence of cyclic loading

    NASA Astrophysics Data System (ADS)

    Huffman, Peter oel

    Although fatigue has been a well studied phenomenon over the past century and a half, there has yet to be found a quantitative link between fatigue crack growth rates and materials properties. This work serves to establish that link, in the case of well behaved, single phase, ductile metals. The primary mechanisms of fatigue crack growth are identified in general terms, followed by a description of the dependence of the stress intensity factor range on those mechanisms. A method is presented for calculating the crack growth rate for an ideal, linear elastic, non-brittle material, which is assumed to be similar to the crack growth rate for a real material at very small crack growth rate values. The threshold stress intensity factor is discussed as a consequence of "crack tip healing". Residual stresses are accounted for in the form of an approximated residual stress intensity factor. The results of these calculations are compared to data available in the literature. It is concluded that this work presents a new way to consider crack growth with respect to cyclic loading which is quantitatively accurate, and introduces a new way to consider fracture mechanics with respect to the relatively small, cyclic loads, normally associated with fatigue.

  13. Analysis and accurate reconstruction of incomplete data in X-ray differential phase-contrast computed tomography.

    PubMed

    Fu, Jian; Tan, Renbo; Chen, Liyuan

    2014-01-01

    X-ray differential phase-contrast computed tomography (DPC-CT) is a powerful physical and biochemical analysis tool. In practical applications, there are often challenges for DPC-CT due to insufficient data caused by few-view, bad or missing detector channels, or limited scanning angular range. They occur quite frequently because of experimental constraints from imaging hardware, scanning geometry, and the exposure dose delivered to living specimens. In this work, we analyze the influence of incomplete data on DPC-CT image reconstruction. Then, a reconstruction method is developed and investigated for incomplete data DPC-CT. It is based on an algebraic iteration reconstruction technique, which minimizes the image total variation and permits accurate tomographic imaging with less data. This work comprises a numerical study of the method and its experimental verification using a dataset measured at the W2 beamline of the storage ring DORIS III equipped with a Talbot-Lau interferometer. The numerical and experimental results demonstrate that the presented method can handle incomplete data. It will be of interest for a wide range of DPC-CT applications in medicine, biology, and nondestructive testing.

  14. Electric Field Induced Reversible Phase Transition in Li Doped Phosphorene: Shape Memory Effect and Superelasticity.

    PubMed

    Deng, Junkai; Chang, Zhenyue; Zhao, Tong; Ding, Xiangdong; Sun, Jun; Liu, Jefferson Zhe

    2016-04-13

    Phosphorene, the single-layer form of black phosphorus, as a new member of atomically thin material family, has unique puckered atomistic structure and remarkable physical and chemical properties. In this paper, we report a discovery of an unexpected electromechanical energy conversion phenomenon-shape memory effect-in Li doped phosphorene P4Li2, using ab initio density functional theory simulations. Two stable phases are found for the two-dimensional (2D) P4Li2 crystal. Applying an external electric field can turn on or off the unique adatom switches in P4Li2 crystals, leading to a reversible structural phase transition and thereby the shape memory effect with an tunable strain output as high as 2.06%. Our results demonstrate that multiple temporary shapes are attainable in one piece of P4Li2 material, offering programmability that is particularly useful for device designs. Additionally, the P4Li2 displays superelasticity that can generate a pseudoelastic tensile strain up to 6.2%. The atomic thickness, superior flexibility, excellent electromechanical strain output, the special shape memory phenomenon, and the programmability feature endow P4Li2 with great application potential in high-efficient energy conversion at nanoscale and flexible nanoelectromechanical systems. PMID:27043220

  15. Electric Field Induced Reversible Phase Transition in Li Doped Phosphorene: Shape Memory Effect and Superelasticity.

    PubMed

    Deng, Junkai; Chang, Zhenyue; Zhao, Tong; Ding, Xiangdong; Sun, Jun; Liu, Jefferson Zhe

    2016-04-13

    Phosphorene, the single-layer form of black phosphorus, as a new member of atomically thin material family, has unique puckered atomistic structure and remarkable physical and chemical properties. In this paper, we report a discovery of an unexpected electromechanical energy conversion phenomenon-shape memory effect-in Li doped phosphorene P4Li2, using ab initio density functional theory simulations. Two stable phases are found for the two-dimensional (2D) P4Li2 crystal. Applying an external electric field can turn on or off the unique adatom switches in P4Li2 crystals, leading to a reversible structural phase transition and thereby the shape memory effect with an tunable strain output as high as 2.06%. Our results demonstrate that multiple temporary shapes are attainable in one piece of P4Li2 material, offering programmability that is particularly useful for device designs. Additionally, the P4Li2 displays superelasticity that can generate a pseudoelastic tensile strain up to 6.2%. The atomic thickness, superior flexibility, excellent electromechanical strain output, the special shape memory phenomenon, and the programmability feature endow P4Li2 with great application potential in high-efficient energy conversion at nanoscale and flexible nanoelectromechanical systems.

  16. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material

    NASA Astrophysics Data System (ADS)

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W. W.; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U.; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors.

  17. Reverse phase liquid chromatographic assay for calcium pantothenate in multivitamin preparations and raw materials.

    PubMed

    Timmons, J A; Meyer, J C; Steible, D J; Assenza, S P

    1987-01-01

    A reverse phase liquid chromatographic (LC) method has been developed for the assay of calcium pantothenate in commercial multivitamin tablet formulations and raw materials. The assay was validated according to the Pharmaceutical Manufacturers Association Quality Control HPLC Committee guidelines. The chromatographic system includes a C-18 column and a mobile phase consisting of 0.25M sodium phosphate buffer, pH 2.5, and acetonitrile (97 + 3 v/v). The column effluent is monitored by UV detection at 205 nm. The sample preparation involves only extraction in water followed by filtration. The method is stability-indicating with a detection limit of approximately 50 ng/mL of the calcium pantothenate in the samples. The system is linear from at least 0.02 to 0.10 mg/mL. The mean recovery of spiked placebos ranged from 98.7 to 99.8%. The within-day precision of the assay on finished products (N = 6) ranged from 0.3 to 2.0% CV. A system suitability criterion for resolution is based on the separation between calcium pantothenate and 2 closely eluting compounds, saccharin and a saccharin degradation product, 2-sulfamoylbenzoic acid. PMID:3610964

  18. Single-molecule insights into retention at a reversed-phase chromatographic interface.

    PubMed

    Mabry, Joshua N; Skaug, Michael J; Schwartz, Daniel K

    2014-10-01

    The efficiency of chromatographic separations decreases markedly when peaks exhibit asymmetry (e.g., "peak tailing"). Theoretically, these effects can arise from heterogeneous adsorption kinetics. To investigate the nature and consequences of such heterogeneity, we used a combination of single-molecule imaging and reversed-phase liquid chromatography (RPLC). In both single-molecule and macroscopic RPLC experiments, the stationary phase was hydrophobic end-capped (trimethylsilyl-functionalized) silica, which we exposed to different methanol/water solutions (50%-62% methanol), containing a fluorescent fatty acid analyte. Super-resolution maps based on single-molecule observations revealed rare, strong adsorption sites with activity that varied significantly with methanol concentration. The adsorption and desorption kinetics on the strong sites were heterogeneous and positively correlated, suggesting a broad underlying distribution of site binding energies. Adsorption equilibrium on the strong sites was more sensitive to solution conditions than overall retention measured in RPLC experiments, suggesting that the effect of strong sites on the overall adsorption kinetics should change with solution conditions. Interestingly, in RPLC experiments, peak tailing had a nonmonotonic dependence on methanol concentration within the range studied. Using the stochastic model of chromatography, we showed quantitatively that our single-molecule kinetic results were consistent with this macroscopic trend. This approach to identifying and quantifying adsorption sites should be useful for designing better chromatographic separations and for identifying the role of heterogeneous surface chemistry in molecular dynamics. PMID:25188676

  19. [Preparation of senkyunolide I by reversed-phase high performance liquid chromatography].

    PubMed

    Zhang, Xiaozhe; Xu, Qing; Xiao, Hongbin; Liang, Xinmiao

    2004-01-01

    A method for the isolation of senkyunolide I from Chuanxiong with reversed-phase preparative high performance liquid chromatography (HPLC) is described. After 95% ethanol extract was obtained with solvent extraction and normal-phase silica column separation, a fraction containing senkyunolide I was acquired and subjected to preparative HPLC for the isolation of target component. In the experiment a solvent system consisting of methanol-0.05 mol/L NH4Ac aqueous solution was found effective to eliminate the interference of ferulic acid that was the major compound in the sample. Senkyunolide I and ferulic acid were separated completely by using a stepwise gradient solvent system of 10% methanol in 10 min, and 60% methanol in 10 - 40 min. The subfractions were collected and subjected to an open MCI gel CHP-20P column for desalination respectively. Senkyunolide I was obtained and the structure was identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). This method is effective and reliable for the preparation of senkyunolide I from Chuanxiong.

  20. [Preparation of senkyunolide I by reversed-phase high performance liquid chromatography].

    PubMed

    Zhang, Xiaozhe; Xu, Qing; Xiao, Hongbin; Liang, Xinmiao

    2004-01-01

    A method for the isolation of senkyunolide I from Chuanxiong with reversed-phase preparative high performance liquid chromatography (HPLC) is described. After 95% ethanol extract was obtained with solvent extraction and normal-phase silica column separation, a fraction containing senkyunolide I was acquired and subjected to preparative HPLC for the isolation of target component. In the experiment a solvent system consisting of methanol-0.05 mol/L NH4Ac aqueous solution was found effective to eliminate the interference of ferulic acid that was the major compound in the sample. Senkyunolide I and ferulic acid were separated completely by using a stepwise gradient solvent system of 10% methanol in 10 min, and 60% methanol in 10 - 40 min. The subfractions were collected and subjected to an open MCI gel CHP-20P column for desalination respectively. Senkyunolide I was obtained and the structure was identified by mass spectrometry (MS) and nuclear magnetic resonance (NMR). This method is effective and reliable for the preparation of senkyunolide I from Chuanxiong. PMID:15712944

  1. [Rapid determination of aspartame in compound sweetening by reversed-phase high performance liquid chromatography].

    PubMed

    Zhang, R; Jiang, M

    1997-11-01

    A method for rapid determination of Aspartame in compound sweetening by reversed-phase high performance liquid chromatography is presented. Aspartame in compound sweetening was separated in a short column (Ultrasphere XL-ODS, 3 microm, 4.6 mm x 70 mm) by using CH3OH-0.02 mol/L NH4Ac as mobile phase. The flow rate was 0.8 mL/min. Detection was performed with UV detector at 220 nm. The injection volume was 20 microL. It was qualitatively analysed by UV scanning at a wavelength range of 200-350 nm under no-stop flow according to their retention time. Quantitative analysis was carried out by measuring peak height and comparing it with external standard. The minimum detectable amount was 5 microg/L. The linear range of the calibration curve was 40-200 mg/L. The average recovery of Aspartame was 92%. The relative standard deviation was 2.9%. This method is simple, rapid and sensitive.

  2. The simultaneous determination of active ingredients in cough-cold mixtures by isocratic reversed-phase ion-pair high-performance liquid chromatography.

    PubMed

    Lau, O W; Chan, K; Lau, Y K; Wong, W C

    1989-01-01

    A simple, rapid and accurate method for the simultaneous determination of active ingredients in cough-cold mixtures using isocratic reversed-phase ion-pair high-performance liquid chromatography has been developed. It involves the use of an octadecylsilane column as the stationary phase with methanol, water, tetrahydrofuran, phosphoric acid mixtures as mobile phase including sodium dioctylsulphosuccinate as the ion-pair agent. The pH of the mobile phase was adjusted to 4.6 by means of phosphoric acid and ammonium hydroxide solutions. The proposed method involves the simple dilution of the samples with the mobile phase and the addition of metoclopramide hydrochloride as the internal standard. The active ingredients under investigation were chlorpheniramine, codeine, diphenhydramine, ephedrine, ethylmorphine, phenylephrine, phenylpropanolamine and pholcodine, which exist as various combinations in cough-cold mixtures. The optimum composition of the mobile phase and the optimum flow rate were determined and are reported. The method was applied to the determination of active ingredients in seven commercially available cough-cold mixtures. PMID:2577452

  3. The simultaneous determination of active ingredients in cough-cold mixtures by isocratic reversed-phase ion-pair high-performance liquid chromatography.

    PubMed

    Lau, O W; Chan, K; Lau, Y K; Wong, W C

    1989-01-01

    A simple, rapid and accurate method for the simultaneous determination of active ingredients in cough-cold mixtures using isocratic reversed-phase ion-pair high-performance liquid chromatography has been developed. It involves the use of an octadecylsilane column as the stationary phase with methanol, water, tetrahydrofuran, phosphoric acid mixtures as mobile phase including sodium dioctylsulphosuccinate as the ion-pair agent. The pH of the mobile phase was adjusted to 4.6 by means of phosphoric acid and ammonium hydroxide solutions. The proposed method involves the simple dilution of the samples with the mobile phase and the addition of metoclopramide hydrochloride as the internal standard. The active ingredients under investigation were chlorpheniramine, codeine, diphenhydramine, ephedrine, ethylmorphine, phenylephrine, phenylpropanolamine and pholcodine, which exist as various combinations in cough-cold mixtures. The optimum composition of the mobile phase and the optimum flow rate were determined and are reported. The method was applied to the determination of active ingredients in seven commercially available cough-cold mixtures.

  4. Protons accumulation during anodic phase turned to advantage for oxygen reduction during cathodic phase in reversible bioelectrodes.

    PubMed

    Blanchet, Elise; Pécastaings, Sophie; Erable, Benjamin; Roques, Christine; Bergel, Alain

    2014-12-01

    Reversible bioelectrodes were designed by alternating acetate and oxygen supply. It was demonstrated that the protons produced and accumulated inside the biofilm during the anodic phase greatly favored the oxygen reduction reaction when the electrode was switched to become the biocathode. Protons accumulation, which hindered the bioanode operation, thus became an advantage for the biocathode. The bioanodes, formed from garden compost leachate under constant polarization at -0.2 V vs. SCE, were able to support long exposure to forced aeration, with only a slight alteration of their anodic efficiency. They produced a current density of 16±1.7 A/m2 for acetate oxidation and up to -0.4 A/m2 for oxygen reduction. Analysis of the microbial communities by 16S rRNA pyrosequencing revealed strong selection of Chloroflexi (49±1%), which was not observed for conventional bioanodes not exposed to oxygen. Chloroflexi were found as the dominant phylum of electroactive biofilms for the first time.

  5. Multilayered vesicles prepared by reverse-phase evaporation: liposome structure and optimum solute entrapment

    SciTech Connect

    Pidgeon, C.; McNeely, S.; Schmidt, T.; Johnson, J.E.

    1987-01-13

    Liposome structure and solute entrapment in multilayered vesicles (MLVs) prepared by reverse-phase evaporation (REV) were studied. MLV-REV vesicles prepared from ether/water emulsions have high entrapment. Entrapment depends on drug, drug concentration, lipid, lipid concentration, and the container used to prepare the vesicles. By use of 300 /sup +/L of aqueous phase and 100 mg of phosphatidylcholine (PC), vesicles prepared in a test tube 25 mm x 175 mm have higher entrapment than vesicles prepared in a 100-mL round-bottom or pear-shaped flask. By use of a test tube, 100 mg of PC, and 300 ..mu..L of aqueous phase containing sucrose (1-50 mg/mL), >90% sucrose entrapment was obtained. Increasing lipid content to 150 mg of PC decreased entrapment to approx.80%. Neutral PC MLV-REV vesicles have optimum entrapment. Mixing negatively charged lipids or cholesterol (CH) with PC to make MLV-REV vesicles results in decreased entrapment compared to using only PC. Preparing vesicles with the solid lipid dipalmitoylphosphatidylcholine (DPPC) or DPPC/CH mixtures results in 30-40% entrapment when diethyl ether is used to make the MLV-REV emulsion. The high entrapment found for MLV vesicles prepared from water/organic solvent emulsions depends on maintaining a core during the process of liposome formation. A method to calculate the fraction of water residing in the liposomes' core is presented and used to compare multilayered vesicles prepared by different processes. X-ray diffraction data demonstrate that a heterogeneous distribution of lipid may exist in multilayered vesicles prepared by the REV process.

  6. Multivariate assessment of lipophilicity scales-computational and reversed phase thin-layer chromatographic indices.

    PubMed

    Andrić, Filip; Bajusz, Dávid; Rácz, Anita; Šegan, Sandra; Héberger, Károly

    2016-08-01

    Needs for fast, yet reliable means of assessing the lipophilicities of diverse compounds resulted in the development of various in silico and chromatographic approaches that are faster, cheaper, and greener compared to the traditional shake-flask method. However, at present no accepted "standard" approach exists for their comparison and selection of the most appropriate one(s). This is of utmost importance when it comes to the development of new lipophilicity indices, or the assessment of the lipophilicity of newly synthesized compounds. In this study, 50 well-known, diverse compounds of significant pharmaceutical and environmental importance have been selected and examined. Octanol-water partition coefficients have been measured with the shake-flask method for most of them. Their retentions have been studied in typical reversed thin-layer chromatographic systems, involving the most frequently employed stationary phases (octadecyl- and cyano-modified silica), and acetonitrile and methanol as mobile phase constituents. Twelve computationally estimated logP-s and twenty chromatographic indices together with the shake-flask octanol-water partition coefficient have been investigated with classical chemometric approaches-such as principal component analysis (PCA), hierarchical cluster analysis (HCA), Pearson's and Spearman's correlation matrices, as well as novel non-parametric methods: sum of ranking differences (SRD) and generalized pairwise correlation method (GPCM). Novel SRD and GPCM methods have been introduced based on the Comparisons with One VAriable (lipophilicity metric) at a Time (COVAT). For the visualization of COVAT results, a heatmap format was introduced. Analysis of variance (ANOVA) was applied to reveal the dominant factors between computational logPs and various chromatographic measures. In consensus-based comparisons, the shake-flask method performed the best, closely followed by computational estimates, while the chromatographic estimates often

  7. Multivariate assessment of lipophilicity scales-computational and reversed phase thin-layer chromatographic indices.

    PubMed

    Andrić, Filip; Bajusz, Dávid; Rácz, Anita; Šegan, Sandra; Héberger, Károly

    2016-08-01

    Needs for fast, yet reliable means of assessing the lipophilicities of diverse compounds resulted in the development of various in silico and chromatographic approaches that are faster, cheaper, and greener compared to the traditional shake-flask method. However, at present no accepted "standard" approach exists for their comparison and selection of the most appropriate one(s). This is of utmost importance when it comes to the development of new lipophilicity indices, or the assessment of the lipophilicity of newly synthesized compounds. In this study, 50 well-known, diverse compounds of significant pharmaceutical and environmental importance have been selected and examined. Octanol-water partition coefficients have been measured with the shake-flask method for most of them. Their retentions have been studied in typical reversed thin-layer chromatographic systems, involving the most frequently employed stationary phases (octadecyl- and cyano-modified silica), and acetonitrile and methanol as mobile phase constituents. Twelve computationally estimated logP-s and twenty chromatographic indices together with the shake-flask octanol-water partition coefficient have been investigated with classical chemometric approaches-such as principal component analysis (PCA), hierarchical cluster analysis (HCA), Pearson's and Spearman's correlation matrices, as well as novel non-parametric methods: sum of ranking differences (SRD) and generalized pairwise correlation method (GPCM). Novel SRD and GPCM methods have been introduced based on the Comparisons with One VAriable (lipophilicity metric) at a Time (COVAT). For the visualization of COVAT results, a heatmap format was introduced. Analysis of variance (ANOVA) was applied to reveal the dominant factors between computational logPs and various chromatographic measures. In consensus-based comparisons, the shake-flask method performed the best, closely followed by computational estimates, while the chromatographic estimates often

  8. Retention of [(18)F]fluoride on reversed phase HPLC columns.

    PubMed

    Ory, Dieter; Van den Brande, Jeroen; de Groot, Tjibbe; Serdons, Kim; Bex, Marva; Declercq, Lieven; Cleeren, Frederik; Ooms, Maarten; Van Laere, Koen; Verbruggen, Alfons; Bormans, Guy

    2015-01-01

    As [(18)F]fluoride is a starting reagent in the radiosynthesis of most fluorine-18 labeled positron emission tomography (PET) tracers, its chromatographic behavior on reversed phase (RP) HPLC columns is important for the purification performance and accuracy of RP HPLC quality control methods. We have investigated the chromatographic behavior and recovery of [(18)F]fluoride as a function of the type and brand of RP HPLC column, the pH and the composition of the mobile phase. Elution and elution profile of [(18)F]fluoride from six RP-HPLC columns (Waters XBridge C18 3 mm × 100 mm 3.5 μm; Grace Platinum EPS C18 4.6 mm × 100 mm, 3 μm; Waters XTerra C18 4.6 mm × 250 mm, 5 μm; Phenomenex C18 4.6 mm × 150 mm, 5 μm; Hamilton PRP-1 column 4.1 mm × 150 mm, 5 μm; Merck KGaA Chromolith Performance C18 3 mm × 100 mm) eluted with mobile phase composed of phosphate or acetate buffers (pH 2, 3, 4, 5, 7.3 and 9) and acetonitrile or ethanol as organic modifier were characterized. The elution profile was determined by on-line radioactivity measurement in the column eluate and recovery was calculated by comparison of radioactivity eluted with the HPLC column present or absent in the chromatographic flow path. Interestingly, [(18)F]fluoride recovery increased with increasing pH. At pH 3 all packed silica-based columns showed significant retention of fluorine-18, whereas almost no retention was observed on a polymeric PRP-1 column. However at pH 5, [(18)F]fluoride recovery was above 90% for each tested column. In addition, small differences were observed when changing the composition of the mobile phase. We therefore recommend to use a mobile phase with pH > 5 for silica based C18 columns for both quality control and semi-preparative HPLC of fluorine-18 labeled PET radiopharmaceuticals. If required a lower pH can be used in combination with a polymer based HPLC column.

  9. Accurate and efficient calculation of excitation energies with the active-space particle-particle random phase approximation

    NASA Astrophysics Data System (ADS)

    Zhang, Du; Yang, Weitao

    2016-10-01

    An efficient method for calculating excitation energies based on the particle-particle random phase approximation (ppRPA) is presented. Neglecting the contributions from the high-lying virtual states and the low-lying core states leads to the significantly smaller active-space ppRPA matrix while keeping the error to within 0.05 eV from the corresponding full ppRPA excitation energies. The resulting computational cost is significantly reduced and becomes less than the construction of the non-local Fock exchange potential matrix in the self-consistent-field (SCF) procedure. With only a modest number of active orbitals, the original ppRPA singlet-triplet (ST) gaps as well as the low-lying single and double excitation energies can be accurately reproduced at much reduced computational costs, up to 100 times faster than the iterative Davidson diagonalization of the original full ppRPA matrix. For high-lying Rydberg excitations where the Davidson algorithm fails, the computational savings of active-space ppRPA with respect to the direct diagonalization is even more dramatic. The virtues of the underlying full ppRPA combined with the significantly lower computational cost of the active-space approach will significantly expand the applicability of the ppRPA method to calculate excitation energies at a cost of O(K4), with a prefactor much smaller than a single SCF Hartree-Fock (HF)/hybrid functional calculation, thus opening up new possibilities for the quantum mechanical study of excited state electronic structure of large systems.

  10. Accurate and efficient calculation of excitation energies with the active-space particle-particle random phase approximation

    DOE PAGES

    Zhang, Du; Yang, Weitao

    2016-10-13

    An efficient method for calculating excitation energies based on the particle-particle random phase approximation (ppRPA) is presented. Neglecting the contributions from the high-lying virtual states and the low-lying core states leads to the significantly smaller active-space ppRPA matrix while keeping the error to within 0.05 eV from the corresponding full ppRPA excitation energies. The resulting computational cost is significantly reduced and becomes less than the construction of the non-local Fock exchange potential matrix in the self-consistent-field (SCF) procedure. With only a modest number of active orbitals, the original ppRPA singlet-triplet (ST) gaps as well as the low-lying single and doublemore » excitation energies can be accurately reproduced at much reduced computational costs, up to 100 times faster than the iterative Davidson diagonalization of the original full ppRPA matrix. For high-lying Rydberg excitations where the Davidson algorithm fails, the computational savings of active-space ppRPA with respect to the direct diagonalization is even more dramatic. The virtues of the underlying full ppRPA combined with the significantly lower computational cost of the active-space approach will significantly expand the applicability of the ppRPA method to calculate excitation energies at a cost of O(K^{4}), with a prefactor much smaller than a single SCF Hartree-Fock (HF)/hybrid functional calculation, thus opening up new possibilities for the quantum mechanical study of excited state electronic structure of large systems.« less

  11. Purification of nattokinase by reverse micelles extraction from fermentation broth: effect of temperature and phase volume ratio.

    PubMed

    Liu, Jun-Guo; Xing, Jian-Min; Chang, Tian-Shi; Liu, Hui-Zhou

    2006-03-01

    Nattokinase is a novel fibrinolytic enzyme that is considered to be a promising agent for thrombosis therapy. In this study, reverse micelles extraction was applied to purify and concentrate nattokinase from fermentation broth. The effects of temperature and phase volume ratio used for the forward and backward extraction on the extraction process were examined. The optimal temperature for forward and backward extraction were 25 degrees C and 35 degrees C respectively. Nattokinase became more thermosensitive during reverse micelles extraction. And it could be enriched in the stripping phase eight times during backward extraction. It was found that nattokinase could be purified by AOT reverse micelles with up to 80% activity recovery and with a purification factor of 3.9.

  12. Rapid High-pH Reverse Phase StageTip for Sensitive Small-Scale Membrane Proteomic Profiling.

    PubMed

    Dimayacyac-Esleta, Baby Rorielyn T; Tsai, Chia-Feng; Kitata, Reta Birhanu; Lin, Pei-Yi; Choong, Wai-Kok; Lin, Tai-Du; Wang, Yi-Ting; Weng, Shao-Hsing; Yang, Pan-Chyr; Arco, Susan D; Sung, Ting-Yi; Chen, Yu-Ju

    2015-12-15

    Membrane proteins are crucial targets for cancer biomarker discovery and drug development. However, in addition to the inherent challenges of hydrophobicity and low abundance, complete membrane proteome coverage of clinical specimen is usually hindered by the requirement of large amount of starting materials. Toward comprehensive membrane proteomic profiling for small amounts of samples (10 μg), we developed high-pH reverse phase (Hp-RP) combined with stop-and-go extraction tip (StageTip) technique, as a fast (∼15 min.), sensitive, reproducible, high-resolution and multiplexed fractionation method suitable for accurate quantification of the membrane proteome. This approach provided almost 2-fold enhanced detection of peptides encompassing transmembrane helix (TMH) domain, as compared with strong anion exchange (SAX) and strong cation exchange (SCX) StageTip techniques. Almost 5000 proteins (∼60% membrane proteins) can be identified in only 10 μg of membrane protein digests, showing the superior sensitivity of the Hp-RP StageTip approach. The method allowed up to 9- and 6-fold increase in the identification of unique hydrophobic and hydrophilic peptides, respectively. The Hp-RP StageTip method enabled in-depth membrane proteome profiling of 11 lung cancer cell lines harboring different EGFR mutation status, which resulted in the identification of 3983 annotated membrane proteins. This provides the largest collection of reference peptide spectral data for lung cancer membrane subproteome. Finally, relative quantification of membrane proteins between Gefitinib-resistant and -sensitive lung cancer cell lines revealed several up-regulated membrane proteins with key roles in lung cancer progression.

  13. Preparation and application of reversed phase chromatorotor for the isolation of natural products by centrifugal preparative chromatography

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A method of preparation of Chromatorotor or plates with a reversed phase (RP) solid silica gel sorbent layer has been developed for preparative centrifugal chromatography. The RP-rotor plates consist of binder free RP solid SiO2 sorbent layers of different thicknesses paked between two supported cir...

  14. Simultaneous quantitative trace analysis of anionic and nonionic surfactant mixtures by reversed-phase liquid chromatography.

    PubMed

    Portet, F I; Treiner, C; Desbène, P L

    2000-05-01

    The aim of this work was to simultaneously analyse mixtures of a polydisperse polyethylene oxide (PEO) nonionic surfactant and an anionic surfactant (sodium dodecylsulphate, SDS) in water containing sodium chloride in order to quantify trace amounts of these mixtures after their adsorption at water-solid interfaces. A fractional factorial design was then used to optimise the separation by ion-pair reversed-phase liquid chromatography as a function of six factors: the chain length of the tetraalkylammonium salt used as ion-pairing reagent which varied from methyl (C1) to n-propyl (C3); the concentration of this ion-pairing salt; the acetonitrile percentage in water used as organic modifier; the flow-rate; the temperature of analysis and also the sodium chloride concentration. The factorial design enabled in a limited number of analyses, not only to determine which factors had significant effects on retention times or on resolution between a pair of nonionic oligomers, but also to modelize and then find the interesting and rugged area where this resolution was optimal as well as the conditions where time of analysis was not prohibitive. After optimisation of HPLC analysis, we used a trace enrichment procedure to quantify very low concentrations of SDS and C12E9 polydisperse PEO in water. A C18 cartridge and a strong anionic exchange cartridge were coupled and the conditions of elution were optimised in order to obtain concentrated samples which were injected in the same eluent than the HPLC mobile phase. Under such conditions, we were able to quantify, in a single run, mixtures of anionic and nonionic surfactants at concentrations as low as 3.6 microg l(-1) for SDS and 2.5 microg l(-1) for each PEO oligomer in water. PMID:10843549

  15. Efficient Nanosecond Dual-Signal Optical Parametric Generator with a Periodically Phase Reversed PPMgLN

    NASA Astrophysics Data System (ADS)

    Ji, Feng; Li, Xi-Fu; Zhang, Bai-Gang; Zhang, Tie-Li; Wang, Peng; Xu, De-Gang; Yao, Jian-Quan

    2007-11-01

    We report an efficient nanosecond optical parametric generator (OPG) with a periodically-phase-reversed periodically poled MgO:LiNbO3(ppr-PPMgLN), which produces two pairs of signal and idler waves. The OPG is pumped by a 1.064 μm Q-switched Nd:YVO4 laser. When the repetition rate is set at 10 kHz, the maximum average total output power of 570 mW is achieved, including 410 mW of dual-signal radiations and 160 mW of dual-idler radiations. The total conversion efficiency is 32.5%. The tunable dual-signal wavelengths in the range of 1.474-1.518 μm and 1.490-1.539 μm and the dual-idler of 3.826-3.558 μm and 3.726-3.451 μm are obtained by changing the crystal temperature from 30°C to 200°C.

  16. Expanded separation technique for chlorophyll metabolites in Oriental tobacco leaf using non aqueous reversed phase chromatography.

    PubMed

    Ishida, Naoyuki

    2011-08-26

    An improved separation method for chlorophyll metabolites in Oriental tobacco leaf was developed. While Oriental leaf still gives the green color even after the curing process, little attention has been paid to the detailed composition of the remaining green pigments. This study aimed to identify the green pigments using non aqueous reversed phase chromatography (NARPC). To this end, liquid chromatograph (LC) equipped with a photo diode array detector (DAD) and an atmospheric pressure chemical ionization/mass spectrometer (APCI/MSD) was selected, because it is useful for detecting low polar non-volatile compounds giving green color such as pheophytin a. Identification was based on the wavelength spectrum, mass spectrum and retention time, comparing the analytes in Oriental leaf with the commercially available and synthesized components. Consequently, several chlorophyll metabolites such as hydroxypheophytin a, solanesyl pheophorbide a and solanesyl hydroxypheophorbide a were newly identified, in addition to typical green pigments such as chlorophyll a and pheophytin a. Chlorophyll metabolites bound to solanesol were considered the tobacco specific components. NARPC expanded the number of detectable low polar chlorophyll metabolites in Oriental tobacco leaf. PMID:21782189

  17. Reconstruction of Protein Networks Using Reverse-Phase Protein Array Data.

    PubMed

    von der Heyde, Silvia; Sonntag, Johanna; Kramer, Frank; Bender, Christian; Korf, Ulrike; Beißbarth, Tim

    2016-01-01

    In this chapter, we describe an approach to reconstruct cellular signaling networks based on measurements of protein activation after different stimulation experiments. As experimental platform reverse-phase protein arrays (RPPA) are used. RPPA allow the measurement of proteins and phosphoproteins across many samples in parallel with minimal sample consumption using a panel of highly target protein-specific antibodies. Functional interactions of proteins are modeled using a Boolean network. We describe the Boolean network reconstruction approach ddepn (dynamic deterministic effects propagation networks), which uses time course data to derive protein interactions based on perturbation experiments. We explain how the method works, give a practical application example, and describe how the results can be interpreted. Furthermore prior knowledge on signaling pathways is essential for network reconstruction. Here we describe the use of our software rBiopaxParser to integrate prior knowledge on protein signaling available in public databases. All applied methods are freely available as open-source R software packages. We describe the preparation of RPPA data as well as all relevant programming steps to format the RPPA data, to infer the prior knowledge, and to reconstruct and analyze the protein signaling networks. PMID:26519181

  18. Reverse phase protein arrays in signaling pathways: a data integration perspective

    PubMed Central

    Creighton, Chad J; Huang, Shixia

    2015-01-01

    The reverse phase protein array (RPPA) data platform provides expression data for a prespecified set of proteins, across a set of tissue or cell line samples. Being able to measure either total proteins or posttranslationally modified proteins, even ones present at lower abundances, RPPA represents an excellent way to capture the state of key signaling transduction pathways in normal or diseased cells. RPPA data can be combined with those of other molecular profiling platforms, in order to obtain a more complete molecular picture of the cell. This review offers perspective on the use of RPPA as a component of integrative molecular analysis, using recent case examples from The Cancer Genome Altas consortium, showing how RPPA may provide additional insight into cancer besides what other data platforms may provide. There also exists a clear need for effective visualization approaches to RPPA-based proteomic results; this was highlighted by the recent challenge, put forth by the HPN-DREAM consortium, to develop visualization methods for a highly complex RPPA dataset involving many cancer cell lines, stimuli, and inhibitors applied over time course. In this review, we put forth a number of general guidelines for effective visualization of complex molecular datasets, namely, showing the data, ordering data elements deliberately, enabling generalization, focusing on relevant specifics, and putting things into context. We give examples of how these principles can be utilized in visualizing the intrinsic subtypes of breast cancer and in meaningfully displaying the entire HPN-DREAM RPPA dataset within a single page. PMID:26185419

  19. Efficient Microscale Basic Reverse Phase Peptide Fractionation for Global and Targeted Proteomics.

    PubMed

    Lee, Hyoung-Joo; Kim, Hye-Jung; Liebler, Daniel C

    2016-07-01

    Analysis of small biological samples would benefit from an efficient microscale fractionation strategy that minimizes sample handling, transfer steps, and accompanying losses. Here we describe a microscale basic reverse phase liquid chromatographic (bRPLC) fractionation method that offers high reproducibility and efficiency for peptide mixtures from small (5-20 μg) samples. We applied our platform to detect differentially expressed proteins from lung tumor cell lines that are sensitive (11-18) and resistant (11-18R) to the tyrosine kinase inhibitor erlotinib. Label-free analyses of 5-20 μg samples yielded identifications of approximately 3,200 to 4,000 proteins with coefficients of variation of 1.9-8.9% in replicate analyses. iTRAQ analyses produced similar protein inventories. Label-free and iTRAQ analyses displayed high concordance in identifications of proteins differentially expressed in 11-18 and 11-18R cells. Micro-bRPLC fractionation of cell proteomes increased sensitivity by an average of 4.5-fold in targeted quantitation using parallel reaction monitoring for three representative receptor tyrosine kinases (EGFR, PDGFRA, and BMX), which are present at low abundance in 11-18 and 11-18R cells. These data illustrate the broad utility of micro-bRPLC fractionation for global and targeted proteomic analyses. Data are available through Proteome eXchange Accession PXD003604. PMID:27255222

  20. Reverse phase protein arrays in signaling pathways: a data integration perspective.

    PubMed

    Creighton, Chad J; Huang, Shixia

    2015-01-01

    The reverse phase protein array (RPPA) data platform provides expression data for a prespecified set of proteins, across a set of tissue or cell line samples. Being able to measure either total proteins or posttranslationally modified proteins, even ones present at lower abundances, RPPA represents an excellent way to capture the state of key signaling transduction pathways in normal or diseased cells. RPPA data can be combined with those of other molecular profiling platforms, in order to obtain a more complete molecular picture of the cell. This review offers perspective on the use of RPPA as a component of integrative molecular analysis, using recent case examples from The Cancer Genome Altas consortium, showing how RPPA may provide additional insight into cancer besides what other data platforms may provide. There also exists a clear need for effective visualization approaches to RPPA-based proteomic results; this was highlighted by the recent challenge, put forth by the HPN-DREAM consortium, to develop visualization methods for a highly complex RPPA dataset involving many cancer cell lines, stimuli, and inhibitors applied over time course. In this review, we put forth a number of general guidelines for effective visualization of complex molecular datasets, namely, showing the data, ordering data elements deliberately, enabling generalization, focusing on relevant specifics, and putting things into context. We give examples of how these principles can be utilized in visualizing the intrinsic subtypes of breast cancer and in meaningfully displaying the entire HPN-DREAM RPPA dataset within a single page. PMID:26185419

  1. Simple method for the analysis of food dyes on reversed-phase thin-layer plates.

    PubMed

    Oka, H; Ikai, Y; Kawamura, N; Yamada, M; Inoue, H; Ohno, T; Inagaki, K; Kuno, A; Yamamoto, N

    1987-12-18

    A technique for the determination of food dyes using reversed-phase thin-layer chromatography on octadecyl-modified silica is described. A solvent system containing 5.0% aqueous sodium sulphate solution enables good separation of the food dyes. Their separation is dependent on the pH of the solvent system, good separation among all dyes being obtained between pH 6.0 and 7.0. The determination of thirteen dyes can be achieved by a combination of methanol-acetonitrile-5.0% aqueous sodium sulphate solution (3:3:10) (solvent system A) and methanol-methyl ethyl ketone-5.0% aqueous sodium sulphate solution (1:1:1) (solvent system B). Solvent system A was used for the determination of Tartrazine, Amaranth, Indigo Carmine, New Coccine, Sunset Yellow FCF, Allura Red AC, Fast Green FCF and Brilliant Blue FCF and for the screening of Acid Red (R-106), Eosin (R-103), Erythrosin (R-3), Rose Bengale (R-105) and Phloxine (R-104). When the spots of R-3, R-103, R-104, R-105 and R-106 appear on the plate, their determination can be achieved by using solvent system B. Each calibration graph was linear between 0.2 and 1.0 micrograms.

  2. Analysis of Reverse Phase Protein Array Data: From Experimental Design towards Targeted Biomarker Discovery

    PubMed Central

    Wachter, Astrid; Bernhardt, Stephan; Beissbarth, Tim; Korf, Ulrike

    2015-01-01

    Mastering the systematic analysis of tumor tissues on a large scale has long been a technical challenge for proteomics. In 2001, reverse phase protein arrays (RPPA) were added to the repertoire of existing immunoassays, which, for the first time, allowed a profiling of minute amounts of tumor lysates even after microdissection. A characteristic feature of RPPA is its outstanding sample capacity permitting the analysis of thousands of samples in parallel as a routine task. Until today, the RPPA approach has matured to a robust and highly sensitive high-throughput platform, which is ideally suited for biomarker discovery. Concomitant with technical advancements, new bioinformatic tools were developed for data normalization and data analysis as outlined in detail in this review. Furthermore, biomarker signatures obtained by different RPPA screens were compared with another or with that obtained by other proteomic formats, if possible. Options for overcoming the downside of RPPA, which is the need to steadily validate new antibody batches, will be discussed. Finally, a debate on using RPPA to advance personalized medicine will conclude this article. PMID:27600238

  3. Separation and purification of hydrolyzable tannin from Geranium wilfordii Maxim by reversed-phase and normal-phase high-speed counter-current chromatography.

    PubMed

    Liu, Dan; Su, Zhiguo; Wang, Changhai; Gu, Ming; Xing, Siliang

    2010-08-01

    Three hydrolyzable tannins, geraniin, corilagin and gallic acid, main active components of Geranium wilfordii Maxim, have been separated and purified in one-step by both reversed-phase and normal-phase high-speed counter-current chromatography. Gallic acid, corilagin and geraniin were purified from 70% aqueous acetone extract of G. wilfordii Maxim with solvent system n-hexane-ethyl acetate-methanol-acetic acid-water (1:10:0.2:0.2:20) by reversed-phase high-speed counter-current chromatography at purities of 94.2, 91.0 and 91.3%, at yields of 89.3, 82.9 and 91.7%, respectively. Gallic acid, corilagin and geraniin were purified with solvent system n-hexane-ethyl acetate-methanol-acetic acid-water (0.2:10:2:1:5) by normal-phase high-speed counter-current chromatography at purities of 85.9, 92.2 and 87.6%, at yields of 87.4, 94.6 and 94.3%, respectively. It was successful for both reversed-phase and normal-phase high-speed counter-current chromatography to separate high-polarity of low-molecular-weight substances.

  4. Lipophilicity data for some preservatives estimated by reversed-phase liquid chromatography and different computation methods.

    PubMed

    Casoni, Dorina; Kot-Wasik, Agata; Namieśnik, Jacek; Sârbu, Costel

    2009-03-20

    The chromatographic behavior of some preservatives was performed by reversed-phase high-performance liquid chromatography on C18 (LiChroCART, Purosphere RP-18e), C8 (Zorbax, Eclipse XDB-C8), CN100 (Säulentechnik, Lichrosphere) and NH(2) (Supelcosil LC-NH(2)) columns. The lipophilicity estimated for the first time on the first three columns are comparable and very well correlated. The mobile phase was a mixture of methanol-water (0.1% formic acid) in different volume proportions from 40% to 60% (v/v) for RP-C18, RP-C8 and RP-CN100 column (exception for parabens on RP-C8 column-the methanol concentrations being from 55% to 65%) and from 30% to 50% (v/v) for RP-NH(2). Highly significant correlations were obtained between different experimental indices of lipophilicity (logk(w), S, phi(0), mean of k and logk, and scores of k and logk corresponding to the first principal component) and computed logP values, and C8 column seems to be more suited for estimating the lipophilicity of the investigated compounds. These direct correlations offer a very good opportunity to derive powerful predictive models via Collander-type equations. The reliability of scores values as lipophilic indices is shown by their high correlation with the logK(ow) obtained using classical "shake-flask" technique, logk(w) and also some of the computed logP values. In addition, the results obtained applying PCA to the retention data may be used in interpreting the molecular mechanism of interactions between eluents and stationary phases with different polarity and to explain the chromatographic behavior of compounds. Finally, the "congeneric lipophilicity chart" described by the scores corresponding to the first principal component has the effect of separating compounds from each other more effectively from congeneric ((dis)similarity) point of view. The parabens and tert-butylhydroquinone appeared to be the most lipophilic preservatives.

  5. Direct enantioselective separation of bevantolol by high-performance liquid chromatography on normal and reverse cellulose chiral stationary phases.

    PubMed

    Aboul-Enein, H Y; Serignese, V

    1994-01-01

    A direct, isocratic and simple chromatographic method is described for the enantiomeric separation of bevantolol (BEV) using normal and reverse cellulose tris (3,5-dimethylphenylcarbamate) chiral stationary phases (CSPs) known as Chiralcel OD and Chiralcel OD-R, respectively. The effect of various alcohols present in the mobile phase on the separation factor (a) and resolution factor (Rs) has been studied. The method has been used to determine and identify the BEV enantiomers in human urine after oral administration of racemic BEV. The chiral recognition mechanism(s) between the analyte and these chiral stationary phases is proposed.

  6. Development and validation of a reversed-phase liquid chromatographic method for analysis of estradiol valerate and medroxyprogesterone acetate in a tablet formulation.

    PubMed

    Segall, A; Hormaechea, F; Vitale, M; Perez, V; Pizzorno, M T

    1999-04-01

    A simple and accurate liquid chromatographic method was developed for estimation of estradiol valerate and medroxyprogesterone acetate in pharmaceuticals. Drugs were chromatographed on a reverse phase C18 column, using a mixture (30:70) of ammonium nitrate buffer and acetonitrile and eluants monitored at a wavelength of 280 nm. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The method was statistically validated for its linearity, accuracy, precision and selectivity. Due to its simplicity and accuracy, the authors believe that the method may be used for routine quality control analysis. It does not require any specific sample preparation except the use of a column guard before the analytical column and suitable prefilter attached to the syringe prior to injection.

  7. Strain-assisted current-induced magnetization reversal in magnetic tunnel junctions: A micromagnetic study with phase-field microelasticity

    SciTech Connect

    Huang, H. B.; Hu, J. M.; Yang, T. N.; Chen, L. Q.; Ma, X. Q.

    2014-09-22

    Effect of substrate misfit strain on current-induced in-plane magnetization reversal in CoFeB-MgO based magnetic tunnel junctions is investigated by combining micromagnetic simulations with phase-field microelasticity theory. It is found that the critical current density for in-plane magnetization reversal decreases dramatically with an increasing substrate strain, since the effective elastic field can drag the magnetization to one of the four in-plane diagonal directions. A potential strain-assisted multilevel bit spin transfer magnetization switching device using substrate misfit strain is also proposed.

  8. Clinical utility of reverse phase protein array for molecular classification of breast cancer.

    PubMed

    Negm, Ola H; Muftah, Abir A; Aleskandarany, Mohammed A; Hamed, Mohamed R; Ahmad, Dena A J; Nolan, Christopher C; Diez-Rodriguez, Maria; Tighe, Patrick J; Ellis, Ian O; Rakha, Emad A; Green, Andrew R

    2016-01-01

    Reverse Phase Protein Array (RPPA) represents a sensitive and high-throughput technique allowing simultaneous quantitation of protein expression levels in biological samples. This study aimed to confirm the ability of RPPA to classify archival formalin-fixed paraffin-embedded (FFPE) breast cancer tissues into molecular classes used in the Nottingham prognostic index plus (NPI+) determined by immunohistochemistry (IHC). Proteins were extracted from FFPE breast cancer tissues using three extraction protocols: the Q-proteome FFPE Tissue Kit (Qiagen, Hilden, Germany) and two in-house methods using Laemmli buffer with either incubation for 20 min or 2 h at 105 °C. Two preparation methods, full-face sections and macrodissection, were used to assess the yield and quality of protein extracts. Ten biomarkers used for the NPI+ (ER, PgR, HER2, Cytokeratins 5/6 and 7/8, EGFR, HER3, HER4, p53 and Mucin 1) were quantified using RPPA and compared to results determined by IHC. The Q-proteome FFPE Tissue Kit produced significantly higher protein concentration and signal intensities. The intra- and inter-array reproducibility assessment indicated that RPPA using FFPE lysates was a highly reproducible and robust technique. Expression of the biomarkers individually and in combination using RPPA was highly consistent with IHC results. Macrodissection of the invasive tumour component gave more reliable results with the majority of biomarkers determined by IHC, (80 % concordance) compared with full-face sections (60 % concordance). Our results provide evidence for the technical feasibility of RPPA for high-throughput protein expression profiling of FFPE breast cancer tissues. The sensitivity of the technique is related to the quality of extracted protein and purity of tumour tissue. RPPA could provide a quantitative technique alternative to IHC for the biomarkers used in the NPI+.

  9. Clinical utility of reverse phase protein array for molecular classification of breast cancer.

    PubMed

    Negm, Ola H; Muftah, Abir A; Aleskandarany, Mohammed A; Hamed, Mohamed R; Ahmad, Dena A J; Nolan, Christopher C; Diez-Rodriguez, Maria; Tighe, Patrick J; Ellis, Ian O; Rakha, Emad A; Green, Andrew R

    2016-01-01

    Reverse Phase Protein Array (RPPA) represents a sensitive and high-throughput technique allowing simultaneous quantitation of protein expression levels in biological samples. This study aimed to confirm the ability of RPPA to classify archival formalin-fixed paraffin-embedded (FFPE) breast cancer tissues into molecular classes used in the Nottingham prognostic index plus (NPI+) determined by immunohistochemistry (IHC). Proteins were extracted from FFPE breast cancer tissues using three extraction protocols: the Q-proteome FFPE Tissue Kit (Qiagen, Hilden, Germany) and two in-house methods using Laemmli buffer with either incubation for 20 min or 2 h at 105 °C. Two preparation methods, full-face sections and macrodissection, were used to assess the yield and quality of protein extracts. Ten biomarkers used for the NPI+ (ER, PgR, HER2, Cytokeratins 5/6 and 7/8, EGFR, HER3, HER4, p53 and Mucin 1) were quantified using RPPA and compared to results determined by IHC. The Q-proteome FFPE Tissue Kit produced significantly higher protein concentration and signal intensities. The intra- and inter-array reproducibility assessment indicated that RPPA using FFPE lysates was a highly reproducible and robust technique. Expression of the biomarkers individually and in combination using RPPA was highly consistent with IHC results. Macrodissection of the invasive tumour component gave more reliable results with the majority of biomarkers determined by IHC, (80 % concordance) compared with full-face sections (60 % concordance). Our results provide evidence for the technical feasibility of RPPA for high-throughput protein expression profiling of FFPE breast cancer tissues. The sensitivity of the technique is related to the quality of extracted protein and purity of tumour tissue. RPPA could provide a quantitative technique alternative to IHC for the biomarkers used in the NPI+. PMID:26661092

  10. Analysis of histidine and urocanic acid isomers by reversed-phase high-performance liquid chromatography.

    PubMed

    Hermann, K; Abeck, D

    2001-01-01

    The qualitative separation performance of a C18, C8 and C4 reversed-phase column was investigated for the separation of histidine and its metabolites histamine, 1-methyihistamine and trans- and cis-urocanic acid. Trans- and cis-urocanic acid were baseline separated from their precursor histidine on all three columns using isocratic elution with a mobile phase composed of 0.01 M aqueous TEAP pH 3.0 and acetonitrile at a ratio of 98:2 (v/v). However, histidine was not separated from histamine and 1-methyihistamine. Selecting the C8 column and introducing 0.005 M of the ion pairing reagent 1-octanesulfonic acid sodium salt into the aqueous solution and acetonitrile at a ratio of 90:10 (v/v), significantly improved the separation. The separation was also followed by a change in the retention times and the order of elution. The sequence of elution was histidine, cis-urocanic acid, trans-urocanic acid, histamine and 1-methylhistamine with retention times of 5.58 +/- 0.07, 7.03 +/- 0.15, 7.92 +/- 0.18, 18.77 +/- 0.24 and 20.79 +/- 0.21 min (mean +/- SD; n=5). The separation on the C8 column in the presence of the ion-pairing reagent was further improved with gradient elution that resulted in a reduction in the retention times and elution volumes of histamine and 1-methylhistamine. The detection limits of histidine and trans-urocanic acid at a wavelength of 210 nm and an injection volume of 0.05 ml were 5 x 10(-8) mol l(-1) (n=3). The kinetic of the in-vitro conversion of trans- into the cis-isomer after UV irradiation was depending on the time of exposure and the energy of the light source. UVB light induced a significantly faster conversion than UVA light. TUCA and cUCA samples kept at -25 degrees C were stable for up to 50 weeks. Samples, eluted from human skin showed various concentrations of histidine and trans- and cis-urocanic acid with an average of 1.69 +/- 0.33 x 10(-5) mol l(-1), 1.17 +/- 0.43 x 10(-5) mol l(-1) and 1.67 +/- 0.33 x 10(-5) mol l(-1), respectively

  11. Development of a novel amide-silica stationary phase for the reversed-phase HPLC separation of different classes of phytohormones.

    PubMed

    Aral, Hayriye; Aral, Tarık; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

    2013-11-15

    A novel amide-bonded silica stationary phase was prepared starting from N-Boc-phenylalanine, cyclohexylamine and spherical silica gel (4 µm, 60 Å). The amide ligand was synthesised with high yield. The resulting amide bonded stationary phase was characterised by SEM, IR and elemental analysis. The resulting selector bearing a polar amide group is used for the reversed-phase chromatography separation of different classes of thirteen phytohormones (plant hormones). The chromatographic behaviours of these analytes on the amide-silica stationary phase were compared with those of RP-C18 column under same conditions. The effects of different separation conditions, such as mobile phase, pH value, flow rate and temperature, on the separation and retention behaviours of the 13 phytohormones in this system were studied. The optimum separation was achieved using reversed-phase HPLC gradient elution with an aqueous mobile phase containing pH=6.85 potassium phosphate buffer (20 mM) and acetonitrile with a 22 °C column temperature. Under these experimental conditions, the 12 phytohormones could be separated and detected at 230 or 270 nm within 26 min.

  12. Purification of flavonoids from licorice using an off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method.

    PubMed

    Fan, Yunpeng; Fu, Yanhui; Fu, Qing; Cai, Jianfeng; Xin, Huaxia; Dai, Mei; Jin, Yu

    2016-07-01

    An orthogonal (71.9%) off-line preparative two-dimensional normal-phase liquid chromatography/reversed-phase liquid chromatography method coupled with effective sample pretreatment was developed for separation and purification of flavonoids from licorice. Most of the nonflavonoids were firstly removed using a self-made Click TE-Cys (60 μm) solid-phase extraction. In the first dimension, an industrial grade preparative chromatography was employed to purify the crude flavonoids. Click TE-Cys (10 μm) was selected as the stationary phase that provided an excellent separation with high reproducibility. Ethyl acetate/ethanol was selected as the mobile phase owing to their excellent solubility for flavonoids. Flavonoids co-eluted in the first dimension were selected for further purification using reversed-phase liquid chromatography. Multiple compounds could be isolated from one normal-phase fraction and some compounds with bad resolution in one-dimensional liquid chromatography could be prepared in this two-dimensional system owing to the orthogonal separation. Moreover, this two-dimensional liquid chromatography method was beneficial for the preparation of relatively trace flavonoid compounds, which were enriched in the first dimension and further purified in the second dimension. Totally, 24 flavonoid compounds with high purity were obtained. The results demonstrated that the off-line two-dimensional liquid chromatography method was effective for the preparative separation and purification of flavonoids from licorice.

  13. Roflumilast - A reversible single-crystal to single-crystal phase transition at 50 °C

    NASA Astrophysics Data System (ADS)

    Viertelhaus, Martin; Holst, Hans Christof; Volz, Jürgen; Hummel, Rolf-Peter

    2013-01-01

    Roflumilast is a selective phosphodiesterase type 4 inhibitor and is marketed under the brand names Daxas®, Daliresp® and Libertec®. A phase transition of the drug substance roflumilast was observed at 50 °C. The low temperature form, the high temperature form and the phase transition were characterised by differential scanning calorimetry, variable temperature powder X-ray diffraction and single crystal X-ray diffraction, Raman spectroscopy and solid state NMR spectroscopy. The phase transition of roflumilast at 50 °C is completely reversible, the high temperature form cannot be stabilised by quench cooling and the phase transition does not influence the quality of the active pharmaceutical ingredient (API) and the drug product. It was observed to be a single crystal to single crystal phase transition.

  14. The rich phase behavior of the thermopolarization of water: from a reversal in the polarization, to enhancement near criticality conditions.

    PubMed

    Iriarte-Carretero, Irene; Gonzalez, Miguel A; Armstrong, Jeff; Fernandez-Alonso, Felix; Bresme, Fernando

    2016-07-20

    We investigate using non-equilibrium molecular dynamics simulations the polarization of water induced by thermal gradients using the accurate TIP4P/2005 water model. The full dependence of the polarization covering a wide range of thermodynamic states, from near supercritical to ambient conditions, is reported. Our results show a strong dependence of the thermo-polarization field with the thermodynamic state. The field features a strong enhancement near the critical point, which can be rationalized in terms of the large increase and ultimately the divergence of the thermal expansion of the fluid at the critical temperature. We also show that the TIP4P/2005 model features a reversal in the sign of the thermal polarization at densities ∼1 g cm(-3). The latter result is consistent with the recent observation of this reversal phenomenon in SPC/E water and points the existence of this general physical phenomenon in water. PMID:27397622

  15. Reduction of Solvent Effect in Reverse Phase Gradient Elution LC-ICP-MS

    SciTech Connect

    Sullivan, Patrick Allen

    2005-12-17

    Quantification in liquid chromatography (LC) is becoming very important as more researchers are using LC, not as an analytical tool itself, but as a sample introduction system for other analytical instruments. The ability of LC instrumentation to quickly separate a wide variety of compounds makes it ideal for analysis of complex mixtures. For elemental speciation, LC is joined with inductively coupled plasma mass spectrometry (ICP-MS) to separate and detect metal-containing, organic compounds in complex mixtures, such as biological samples. Often, the solvent gradients required to perform complex separations will cause matrix effects within the plasma. This limits the sensitivity of the ICP-MS and the quantification methods available for use in such analyses. Traditionally, isotope dilution has been the method of choice for LC-ICP-MS quantification. The use of naturally abundant isotopes of a single element in quantification corrects for most of the effects that LC solvent gradients produce within the plasma. However, not all elements of interest in speciation studies have multiple naturally occurring isotopes; and polyatomic interferences for a given isotope can develop within the plasma, depending on the solvent matrix. This is the case for reverse phase LC separations, where increasing amounts of organic solvent are required. For such separations, an alternative to isotope dilution for quantification would be is needed. To this end, a new method was developed using the Apex-Q desolvation system (ESI, Omaha, NE) to couple LC instrumentation with an ICP-MS device. The desolvation power of the system allowed greater concentrations of methanol to be introduced to the plasma prior to destabilization than with direct methanol injection into the plasma. Studies were performed, using simulated and actual linear methanol gradients, to find analyte-internal standard (AIS) pairs whose ratio remains consistent (deviations {+-} 10%) over methanol concentration ranges of 5

  16. Size exclusion chromatography of synthetic polymers and biopolymers on common reversed phase and hydrophilic interaction chromatography columns.

    PubMed

    Caltabiano, Anna M; Foley, Joe P; Barth, Howard G

    2016-03-11

    This work describes the applicability of common reversed phase and HILIC columns for size exclusion chromatography of synthetic and natural polymers. Depending on the nature of the solute and column stationary phase, a "non-retention" condition must be created with the aid of the mobile phase to achieve a unique size-based separation in isocratic mode. The various bonded phases show remarkable differences in size separations that are controlled by mobile phase conditions. Polymer-mobile phase and column-mobile phase solvation interactions determine polymer hydrodynamic volume (or solute bulkiness) and polymer-column steric interaction. Solvation interactions in turn depend on polymer, mobile phase and stationary phase polarities. Column-mobile phase solvation interactions determine the structural order of the bonded ligands that can vary from ordered (extended, aligned away from the silica substrate) to disordered (folded, pointing toward the silica substrate). Chain order increases with increased solvent penetration into the bonded phase. Increased chain order reduces pore volume, and therefore decreases the size-separation efficiency of a column. Conversely, decreased chain order increases pore volume and therefore increases the size-separation efficiency. The thermodynamic quality of the mobile phase also plays a significant role in the separation of polymers. "Poor" solvents can significantly reduce the hydrodynamic diameter of a solute and thus change their retention behavior. Medium polarity stationary phases, such as fluoro-phenyl and cyano, exhibit a unique retention behavior. With an appropriate polarity mobile phase, polar and non-polar synthetic polymers of the same molecular masses can be eluted at the same retention volumes.

  17. The distribution of highly stable millimeter-wave signals over different optical fiber links with accurate phase-correction

    NASA Astrophysics Data System (ADS)

    Liu, Zhangweiyi; Wang, Xiaocheng; Sun, Dongning; Dong, Yi; Hu, Weisheng

    2015-08-01

    We have demonstrated an optical generation of highly stable millimeter-wave signal distribution system, which transfers a 300GHz signal to two remote ends over different optical fiber links for signal stability comparison. The transmission delay variations of each fiber link caused by temperature and mechanical perturbations are compensated by high-precise phase-correction system. The residual phase noise between two remote end signals is detected by dual-heterodyne phase error transfer and reaches -46dBc/Hz at 1 Hz frequency offset from the carrier. The relative instability is 8×10-17 at 1000s averaging time.

  18. Thermodynamics of the sorption of water-soluble vitamins in reverse-phase high performance liquid chromatography

    NASA Astrophysics Data System (ADS)

    Chirkin, V. A.; Karpov, S. I.; Selemenev, V. F.

    2012-12-01

    The thermodynamics of the sorption of certain water-soluble vitamins on a C18 reverse phase from water-acetonitrile solutions of different compositions is studied. The thermodynamic characteristics of the investigated chromatographic systems are calculated. The dependences of standard molar enthalpy and changes in entropy when the sorbate transfers from the bulk solution to the surface layer on the concentration of the organic component in the mobile phase are analyzed. The boundaries for applying the main retention models describing the sorption of the investigated compounds are discussed.

  19. Evaluation of the Kinetic Performance Differences between Hydrophilic-Interaction Liquid Chromatography and Reversed-Phase Liquid Chromatography under Conditions of Identical Packing Structure.

    PubMed

    Song, Huiying; Desmet, Gert; Cabooter, Deirdre

    2015-12-15

    A protocol using trifluoroacetic acid at a temperature of 60 °C is developed for the adequate removal of the stationary phase of reversed-phase liquid chromatography (RPLC) columns. This procedure allows for studying the same column first under RPLC and subsequently under hydrophilic-interaction liquid chromatography (HILIC) conditions to isolate intrinsic differences between mass transfer properties in HILIC and RPLC from differences in packing quality. The established procedure allows for a complete removal of the stationary phase (confirmed by retention studies and thermogravimetry analyses) while leaving the structure of the packing unaffected (witnessed by an unchanged external porosity and pressure drop). Accurate plate height analysis comparing compounds at the same zone retention factor indicates a significant difference in reduced c-term (typically 40-80% larger under HILIC conditions), despite the columns otherwise being identical. Correcting for the known contributions of longitudinal diffusion (b-term) and mass transfer (cm- and cs-term) to focus on band broadening originating from eddy dispersion, similar strong differences are observed (differences of some h = 0.3 up to 1.2). These findings show that the interior structure and retention mechanism of the particles have a very strong effect on the observed eddy dispersion, a factor typically ascribed to phenomena occurring outside the particles. This also implies that comparing the quality of packings of different particle types is virtually impossible without the availability of a sound model to correct for the intraparticle effect on the observed eddy dispersion.

  20. Evaluation of the Kinetic Performance Differences between Hydrophilic-Interaction Liquid Chromatography and Reversed-Phase Liquid Chromatography under Conditions of Identical Packing Structure.

    PubMed

    Song, Huiying; Desmet, Gert; Cabooter, Deirdre

    2015-12-15

    A protocol using trifluoroacetic acid at a temperature of 60 °C is developed for the adequate removal of the stationary phase of reversed-phase liquid chromatography (RPLC) columns. This procedure allows for studying the same column first under RPLC and subsequently under hydrophilic-interaction liquid chromatography (HILIC) conditions to isolate intrinsic differences between mass transfer properties in HILIC and RPLC from differences in packing quality. The established procedure allows for a complete removal of the stationary phase (confirmed by retention studies and thermogravimetry analyses) while leaving the structure of the packing unaffected (witnessed by an unchanged external porosity and pressure drop). Accurate plate height analysis comparing compounds at the same zone retention factor indicates a significant difference in reduced c-term (typically 40-80% larger under HILIC conditions), despite the columns otherwise being identical. Correcting for the known contributions of longitudinal diffusion (b-term) and mass transfer (cm- and cs-term) to focus on band broadening originating from eddy dispersion, similar strong differences are observed (differences of some h = 0.3 up to 1.2). These findings show that the interior structure and retention mechanism of the particles have a very strong effect on the observed eddy dispersion, a factor typically ascribed to phenomena occurring outside the particles. This also implies that comparing the quality of packings of different particle types is virtually impossible without the availability of a sound model to correct for the intraparticle effect on the observed eddy dispersion. PMID:26595107

  1. Accurate Characterization of the Peptide Linkage in the Gas Phase: A Joint Quantum-Chemical and Rotational Spectroscopy Study of the Glycine Dipeptide Analogue.

    PubMed

    Puzzarini, Cristina; Biczysko, Malgorzata; Barone, Vincenzo; Largo, Laura; Peña, Isabel; Cabezas, Carlos; Alonso, José Luis

    2014-02-01

    Accurate structures of aminoacids in the gas phase have been obtained by joint microwave and quantum-chemical investigations. However, the structure and conformational behavior of α-aminoacids once incorporated into peptide chains are completely different and have not yet been characterized with the same accuracy. To fill this gap, we present here an accurate characterization of the simplest dipeptide analogue (N-acetyl-glycinamide) involving peptidic bonds. State-of-the-art quantum-chemical computations are complemented by a comprehensive study of the rotational spectrum using a combination of Fourier transform microwave spectroscopy with laser ablation. The coexistence of the C7 and C5 conformers has been proved and energetically as well as spectroscopically characterized. This joint theoretical-experimental investigation demonstrated the feasibility of obtaining accurate structures for flexible small biomolecules, thus paving the route to the elucidation of the inherent behavior of peptides.

  2. A reversed-phase HPLC-UV method developed and validated for simultaneous quantification of six alkaloids from Nicotiana spp.

    PubMed

    Moghbel, Nahid; Ryu, BoMi; Steadman, Kathryn J

    2015-08-01

    A reversed-phase HPLC-UV method was developed, optimized, and validated for the separation and quantitation of six target alkaloids from leaves of Nicotiana species (nicotine, nornicotine, anatabine, anabasine, myosmine, and cotinine). A bidentate reversed-phase C18 column was used as stationary phase and an alkaline ammonium formate buffer and acetonitrile as mobile phase. The alkaloids were well separated in a short run time of 13min with mobile phase pH 10.5 and a small gradient of 9-13% acetonitrile, and detected using UV at 260nm. Peak parameters were acceptable for all six closely related alkaloids. The proposed method has enough linearity with correlation coefficient >0.999 within the investigated range for all tested alkaloids. Satisfactory precision was achieved for both intra- and inter-day assay, with RSD less than 2% for all alkaloid standards. Reproducibility was also within the acceptable range of RSD <2%. Limit of detection was 1.6μg/mL for nicotine and below 1μg/mL for all other alkaloids. The limit of quantification was 2.8 and 4.8μg/mL for nornicotine and nicotine respectively, and below 2μg/mL for all other alkaloids. The method was successfully applied for simultaneous analysis of alkaloids in leaves of Nicotiana benthamiana.

  3. Phase coexistence calculations via a unit-cell Gibbs ensemble formalism for melts of reversibly bonded block copolymers

    NASA Astrophysics Data System (ADS)

    Mester, Zoltan; Lynd, Nathaniel; Fredrickson, Glenn

    2013-03-01

    Melts of block copolymer blends can exhibit coexistence between compositionally and morphologically distinct phases. We derived a unit-cell approach for a field theoretic Gibbs ensemble formalism to rapidly map out such coexistence regions. We also developed a canonical ensemble model for the reversible reaction of supramolecular polymers and integrated it into the Gibbs ensemble scheme. This creates a faster method for generating phase diagrams in complex supramolecular systems than the usual grand canonical ensemble method and allows us to specify the system in experimentally accessible volume fractions rather than chemical potentials. The integrated approach is used to calculate phase diagrams for AB diblock copolymers reversibly reacting with B homopolymers to form a new diblocks we term ``ABB.'' For our case, we use a diblock that is sixty percent A monomer and a homopolymer that is the same length as the diblock. In the limits of infinite reaction favorability (large equilibrium constant), the system approaches cases of an ABB diblock-B homopolymer blend when the AB diblock is the limiting reactant and AB diblock-ABB diblock blend when the homopolymer is the limiting reactant. As reaction favorability is decreased, the phase boundaries shift towards higher homopolymer compositions so that sufficient reaction can take place to produce the ABB diblock that has a deciding role stabilizing the observed phases.

  4. Accurate and self-consistent procedure for determining pH in seawater desalination brines and its manifestation in reverse osmosis modeling.

    PubMed

    Nir, Oded; Marvin, Esra; Lahav, Ori

    2014-11-01

    Measuring and modeling pH in concentrated aqueous solutions in an accurate and consistent manner is of paramount importance to many R&D and industrial applications, including RO desalination. Nevertheless, unified definitions and standard procedures have yet to be developed for solutions with ionic strength higher than ∼0.7 M, while implementation of conventional pH determination approaches may lead to significant errors. In this work a systematic yet simple methodology for measuring pH in concentrated solutions (dominated by Na(+)/Cl(-)) was developed and evaluated, with the aim of achieving consistency with the Pitzer ion-interaction approach. Results indicate that the addition of 0.75 M of NaCl to NIST buffers, followed by assigning a new standard pH (calculated based on the Pitzer approach), enabled reducing measured errors to below 0.03 pH units in seawater RO brines (ionic strength up to 2 M). To facilitate its use, the method was developed to be both conceptually and practically analogous to the conventional pH measurement procedure. The method was used to measure the pH of seawater RO retentates obtained at varying recovery ratios. The results matched better the pH values predicted by an accurate RO transport model. Calibrating the model by the measured pH values enabled better boron transport prediction. A Donnan-induced phenomenon, affecting pH in both retentate and permeate streams, was identified and quantified.

  5. On-line comprehensive two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography for preparative isolation of Peucedanum praeruptorum.

    PubMed

    Wang, Xin-Yuan; Li, Jia-Fu; Jian, Ya-Mei; Wu, Zhen; Fang, Mei-Juan; Qiu, Ying-Kun

    2015-03-27

    A new on-line comprehensive preparative two-dimensional normal-phase liquid chromatography × reversed-phase liquid chromatography (2D NPLC × RPLC) system was developed for the separation of complicated natural products. It was based on the use of a silica gel packed medium-pressure column as the first dimension and an ODS preparative HPLC column as the second dimension. The two dimensions were connected with normal-phase (NP) and reversed-phase (RP) enrichment units, involving a newly developed airflow assisted adsorption (AAA) technique. The instrument operation and the performance of this NPLC × RPLC separation method were illustrated by gram-scale isolation of ethanol extract from the roots of Peucedanum praeruptorum. In total, 19 compounds with high purity were obtained via automated multi-step preparative separation in a short period of time using this system, and their structures were comprehensively characterized by ESI-MS, (1)H NMR, and (13)C NMR. Including two new compounds, five isomers in two groups with identical HPLC and TLC retention values were also obtained and identified by 1D NMR and 2D NMR. This is the first report of an NPLC × RPLC system successfully applied in an on-line preparative process. This system not only solved the interfacing problem of mobile-phase immiscibility caused by NP and RP separation, it also exhibited apparent advantages in separation efficiency and sample treatment capacity compared with conventional methods.

  6. [[Chiral separation of five arylpropionic acid drugs and determination of their enantiomers in pharmaceutical preparations by reversed-phase high performance liquid chromatography with cellulose-tris-(4-methylbenzoate) stationary phase

    PubMed

    Luo, An; Wan, Qiang; Fan, Huajun; Chen, Zhi; Wu, Xuehao; Huang, Xiaowen; Zang, Linquan

    2014-09-01

    Chromatographic behaviors for enantiomeric separation of arylpropionic acid drugs were systematically developed by reversed phase-high performance liquid chromatography (RP-HPLC) using cellulose-tris-(4-methylbenzoate) (CTMB) as chiral stationary phase (CSP). The effects of the composition of the mobile phase, additives and temperature on chiral separation of flurbiprofen, pranoprofen, naproxen, ibuprofen and loxoprofen were further investigated. The enantiomers had been successfully separated on CSP of CTMB by the mobile phase of methanol-0.1% (v/v) formic acid except naproxen by acetonitrile-0.1% (v/v) formic acid at 25 °C. The mechanisms of the racemic resolution for the above mentioned five drugs are discussed thermodynamically and structurally. The resolutions between respective enantiomers for arylpropionic acid drugs on CTMB had significant differences due to their chromatographic behaviors. The order of resolutions ranked pranoprofen, loxoprofen, flurbiprofen, ibuprofen and naproxen. The method established has been successfully applied to the determination of the enantiomers of the five drugs in commercial preparations under the optimized conditions. It proved that the method is simple, reliable and accurate.

  7. Synthesis of a mixed-model stationary phase derived from glutamine for HPLC separation of structurally different biologically active compounds: HILIC and reversed-phase applications.

    PubMed

    Aral, Tarık; Aral, Hayriye; Ziyadanoğulları, Berrin; Ziyadanoğulları, Recep

    2015-01-01

    A novel mixed-mode stationary phase was synthesised starting from N-Boc-glutamine, aniline and spherical silica gel (4 µm, 60 Å). The prepared stationary phase was characterized by IR and elemental analysis. The new stationary phase bears an embedded amide group into phenyl ring, highly polar a terminal amide group and non-polar groups (phenyl and alkyl groups). At first, this new mixed-mode stationary phase was used for HILIC separation of four nucleotides and five nucleosides. The effects of different separation conditions, such as pH value, mobile phase and temperature, on the separation process were investigated. The optimum separation for nucleotides was achieved using HILIC isocratic elution with aqueous mobile phase and acetonitrile with 20°C column temperature. Under these conditions, the four nucleotides could be separated and detected at 265 nm within 14 min. Five nucleosides were separated under HILIC isocratic elution with aqueous mobile phase containing pH=3.25 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 265 nm within 14 min. Chromatographic parameters as retention factor, selectivity, theoretical plate number and peak asymmetry factor were calculated for the effect of temperature and water content in mobile phase on the separation process. The new column was also tested for nucleotides and nucleosides mixture and six analytes were separated in 10min. The chromatographic behaviours of these polar analytes on the new mixed-model stationary phase were compared with those of HILIC columns under similar conditions. Further, phytohormones and phenolic compounds were separated in order to see influence of the new stationary phase in reverse phase conditions. Eleven plant phytohormones were separated within 13 min using RP-HPLC gradient elution with aqueous mobile phase containing pH=2.5 phosphate buffer (10mM) and acetonitrile with 20°C column temperature and detected at 230 or 278 nm. The best separation

  8. Electron processes in AOT reverse micelles. Part 2. Influence of oil phase. Pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Gebicki, J. L.; Bednarek, P.

    2000-11-01

    Reverse micellar systems formed of AOT, i.e. sodium bis(2-ethyl-1-hexyl) sulfo-succinate, in different hydrocarbons, without water, dry micelles, and in the presence of water, wet micelles, have been studied by means of pulse radiolysis. Different localization sites of hydrated electron within wet reverse micelle including a triad e aq-/Na +/SO 3- rad (absorption band peaking around 610 nm) are proposed and discussed to explain the influence of the ratio [water]/[AOT] and of the kind of alkane on the position and half-width of the absorption spectrum of the hydrated electron. Sulfite radical, necessary to form such triad, is released as a result of electron interaction with AOT molecule within reverse micelles (RM) containing water. A product of direct electron attachment to AOT molecule, AOT radical anion, has been observed spectrophotometrically only in dry AOT RM at ambient temperature (absorption band peaking around 330 nm).

  9. Macroscopic time-reversal symmetry breaking at a nonequilibrium phase transition.

    PubMed

    Shim, Pyoung-Seop; Chun, Hyun-Myung; Noh, Jae Dong

    2016-01-01

    We study the entropy production in a globally coupled Brownian particles system that undergoes an order-disorder phase transition. Entropy production is a characteristic feature of nonequilibrium dynamics with broken detailed balance. We find that the entropy production rate is subextensive in the disordered phase and extensive in the ordered phase. It is found that the entropy production rate per particle vanishes in the disordered phase and becomes positive in the ordered phase following critical scaling laws. We derive the scaling relations for associated critical exponents. The disordered phase exemplifies a case where the entropy production is subextensive with the broken detailed balance. PMID:26871030

  10. Resolution and identification of the protein components of the photosystem II antenna system of higher plants by reversed-phase liquid chromatography with electrospray-mass spectrometric detection.

    PubMed

    Corradini, D; Huber, C G; Timperio, A M; Zolla, L

    2000-07-21

    Reversed-phase liquid chromatography (RPLC) was interfaced to mass spectrometry (MS) with an electrospray ion (ESI) source for the separation and accurate molecular mass determination of the individual intrinsic membrane proteins that comprise the photosystem II (PS II) major light-harvesting complex (LHC II) and minor (CP24, CP26 and CP29) antenna system, whose molecular masses range between 22,000 and 29,000. PS II is a supramolecular complex intrinsic of the thylacoid membrane, which plays the important role in photosynthesis of capturing solar energy, and transferring it to photochemical reaction centers where energy conversion occurs. The protein components of the PS II major and minor antenna systems were extracted from spinach thylacoid membranes and separated using a butyl-silica column eluted by an acetonitrile gradient in 0.05% (v/v) aqueous trifluoroacetic acid. On-line electrospray MS allowed accurate molecular mass determination and identification of the protein components of PS II major and minor antenna system. The proposed RPLC-ESI-MS method holds several advantages over sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the conventional technique for studying membrane proteins, including a better protein separation, mass accuracy, speed and efficiency.

  11. Accurate and practical identification of 20 Fusarium species by seven-locus sequence analysis and reverse line blot hybridization, and an in vitro antifungal susceptibility study.

    PubMed

    Wang, He; Xiao, Meng; Kong, Fanrong; Chen, Sharon; Dou, Hong-Tao; Sorrell, Tania; Li, Ruo-Yu; Xu, Ying-Chun

    2011-05-01

    Eleven reference and 25 clinical isolates of Fusarium were subject to multilocus DNA sequence analysis to determine the species and haplotypes of the fusarial isolates from Beijing and Shandong, China. Seven loci were analyzed: the translation elongation factor 1 alpha gene (EF-1α); the nuclear rRNA internal transcribed spacer (ITS), large subunit (LSU), and intergenic spacer (IGS) regions; the second largest subunit of the RNA polymerase gene (RPB2); the calmodulin gene (CAM); and the mitochondrial small subunit (mtSSU) rRNA gene. We also evaluated an IGS-targeted PCR/reverse line blot (RLB) assay for species/haplotype identification of Fusarium. Twenty Fusarium species and seven species complexes were identified. Of 25 clinical isolates (10 species), the Gibberella (Fusarium) fujikuroi species complex was the commonest (40%) and was followed by the Fusarium solani species complex (FSSC) (36%) and the F. incarnatum-F. equiseti species complex (12%). Six FSSC isolates were identified to the species level as FSSC-3+4, and three as FSSC-5. Twenty-nine IGS, 27 EF-1α, 26 RPB2, 24 CAM, 18 ITS, 19 LSU, and 18 mtSSU haplotypes were identified; 29 were unique, and haplotypes for 24 clinical strains were novel. By parsimony informative character analysis, the IGS locus was the most phylogenetically informative, and the rRNA gene regions were the least. Results by RLB were concordant with multilocus sequence analysis for all isolates. Amphotericin B was the most active drug against all species. Voriconazole MICs were high (>8 μg/ml) for 15 (42%) isolates, including FSSC. Analysis of larger numbers of isolates is required to determine the clinical utility of the seven-locus sequence analysis and RLB assay in species classification of fusaria. PMID:21389150

  12. Normal and Reversed-Phase Thin Layer Chromatography of Green Leaf Extracts

    ERIC Educational Resources Information Center

    Sjursnes, Birte Johanne; Kvittingen, Lise; Schmid, Rudolf

    2015-01-01

    Introductory experiments of chromatography are often conducted by separating colored samples, such as inks, dyes, and plant extracts, using filter paper, chalk, or thin layer chromatography (TLC) plates with various solvent systems. Many simple experiments have been reported. The relationship between normal chromatography and reversed-phase…

  13. Study of bicontinuous phase in (TTAB+pentanol)/water/n-octane reverse micellar system using positron lifetime spectroscopy

    NASA Astrophysics Data System (ADS)

    Chandramani Singh, K.; Yadav, R.; Khani, P. H.

    2013-06-01

    A phase diagram of (TTAB+pentanol)/water/n-octane has been mapped by using optical method. It exhibits a reverse micellar (L2) phase extending over a wide range of concentrations of the constituents. To investigate the fine structure of the L2 phase, a series of (TTAB+pentanol)/n-octane ternary mixtures having initial concentrations of (TTAB+pentanol) (1:1) in n-octane as 35%, 50% and 65% by weight were prepared. In each of these mixtures, positron lifetime measurements were performed as a function of the concentration of water, using a standard lifetime spectrometer. At water concentrations of 11.8%, 8.5% and 8.4% by weight respectively for the above systems, the o-Ps pick-off lifetime τ3 shows an oscillatory behaviour while I3 representing the Ps formation exhibits an abrupt change. These changes in the positron annihilation parameters have been explained on the basis of onset of bicontinuity in the microemulsion phase. The positron annihilation technique thus suggests the existence of droplet-like and bicontinuous structures in the L2 phase which is otherwise considered optically to be a single phase as the system remains clear and isotropic throughout this phase. Supporting evidence has been provided by the electrical conductivity measurements performed in these systems. These results are presented in this paper.

  14. Comparison of the sensitivity of evaporative universal detectors and LC/MS in the HILIC and the reversed-phase HPLC modes.

    PubMed

    Mitchell, Clifford R; Bao, Ye; Benz, Nancy J; Zhang, Shuhong

    2009-12-15

    It was hypothesized that the hydrophilic interaction liquid interface chromatography (HILIC) mode should produce more response than the reversed-phase HPLC mode on detectors with an evaporative component to the detection process. HILIC mobile phases are mostly composed of polar organic solvent and are more volatile than reversed-phase mobile phases. Therefore the more easily evaporated HILIC mobile phases should produce greater sensitivity for those detectors that remove mobile phase by evaporation. The responses of 12 compounds were measured in the reversed-phase mode and the HILIC mode with three detectors: evaporative light scattering detector (ELSD), corona charged aerosol detector (cCAD), and electrospray mass spectrometry (ESI-MS). The compounds studied were very polar compounds that were retained in the HILIC mode. Generally, the HILIC mode was able to achieve greater sensitivity than the reversed-phase mode for these compounds. The increases in sensitivity observed can be attributed to the more volatile HILIC mobile phase. For the ELSD, the HILIC mode produced slightly greater sensitivity than the reversed-phase mode. The cCAD was approximately 10 times more sensitive in the HILIC mode and the ESI-MS was approximately 5-10 times more sensitive in the HILIC mode. There was one instance in the study where a compound produced more response in the reversed-phase mode. Thymine yielded more sensitivity in the reversed-phase mode with the ESI-MS detector. In a given mode of operation, there was significant variation in the measured response factors for all compounds on each detector. While this is not unexpected for the ESI-MS detector, variation in the response factors between compounds indicates that the cCAD and ELSD are not truly universal detectors in the sense that all compounds have identical responses.

  15. Accurate relative-phase and time-delay maps all over the emission cone of hyperentangled photon source

    NASA Astrophysics Data System (ADS)

    Hegazy, Salem F.; El-Azab, Jala; Badr, Yehia A.; Obayya, Salah S. A.

    2016-04-01

    High flux of hyperentangled photons entails collecting the two-photon emission over relatively wide extent in frequency and transverse space within which the photon pairs are simultaneously entangled in multiple degrees of freedom. In this paper, we present a numerical approach to determining the spatial-spectral relative-phase and time-delay maps of hyperentangled photons all over the spontaneous parametric down conversion (SPDC) emission cone. We consider the hyperentangled-photons produced by superimposing noncollinear SPDC emissions of two crossed and coherentlypumped nonlinear crystals. We adopt a vectorial representation for all parameters of concern. This enables us to study special settings such as the self-compensation via oblique pump incidence. While rigorous quantum treatment of SPDC emission requires Gaussian state representation, in low-gain regime (like the case of the study), it is well approximated to the first order to superposition of vacuum and two-photon states. The relative phase and time-delay maps are then calculated between the two-photon wavepackets created along symmetrical locations of the crystals. Assuming monochromatic plane-wave pump field, the mutual signal-idler relations like energy conservation and transversemomentum conservation define well one of the two-photon with reference to its conjugate. The weaker conservation of longitudinal momentum (due to relatively thin crystals) allows two-photon emission directions coplanar with the pump beam while spreading around the perfect phase-matching direction. While prior works often adopt first-order approximation, it is shown that the relative-phase map is a very well approximated to a quadratic function in the polar angle of the two-photon emission while negligibly varying with the azimuthal angle.

  16. Analysis of pharmaceutical dosage forms for oxfendazole: I. Reverse phase liquid chromatographic determination of oxfendazole in swine premix.

    PubMed

    Fleitman, J; Neu, D; Visor, G

    1986-01-01

    A reverse phase liquid chromatographic (LC) procedure is described for quantitating oxfendazole (2-(methoxycarbonylamino)-5-phenylsulfinylbenzimidazole] in swine premix. Sample preparation consists of extracting oxfendazole with an acetone-methanol mixture. An aliquot of the extract is then centrifuged to separate undissolved premix excipients. Internal standard is added to the supernate and the sample is further diluted with water-acetonitrile-phosphoric acid (80 + 20 + 1). Oxfendazole is quantitatively determined using a Partisil-5-ODS-3 column with acetonitrile-0.01 M phosphate buffer (pH 6.0) as the mobile phase. The method is stability specific and yields a mean recovery of 101.1 +/- 0.4% for the 1.35% premix formulation. The dependence of chromatographic performance characteristics on mobile phase organic content, pH, and buffer concentration is also reported.

  17. Development and validation of a reversed-phase HPLC method for determination of alkaloids from Papaver somniferum L. (Papaveraceae).

    PubMed

    Acevska, Jelena; Dimitrovska, Aneta; Stefkov, Gjoshe; Brezovska, Katerina; Karapandzova, Marija; Kulevanova, Svetlana

    2012-01-01

    An HPLC method for the separation of six target alkaloids from Papaver somniferum L. (morphine, codeine, oripavine, thebaine, papaverine, and noscapine) was developed, optimized, and validated. The chromatographic behavior of these alkaloids was investigated using a reversed-phase chromatography at acidic and alkaline pH. The effects of ion-pairing agents, pH value of the mobile phase, concentration of the buffer components, mobile phase organic modifier, and column temperature were studied. Regardless of the large differences in their pKa values, all alkaloids were separated within a close retention window, and good peak shape was achieved for each of the six alkaloids. The proposed method has adequate selectivity, linearity, accuracy, precision, and reproducibility and is applicable for poppy straw.

  18. Simultaneous determination of four anti-dandruff agents including octopirox in shampoo products by reversed-phase liquid chromatography.

    PubMed

    Chao, L

    2001-06-01

    A method based on reversed-phase liquid chromatography (HPLC) has been developed for the simultaneous identification and quantitative determination of four anti-dandruff agents such as salicylic acid, ketoconazole, climbazole, octopirox in commercial anti-dandruff shampoo products. A symmetry C18 column (5 microm, 250 mm x 4.6 mm i.d.) was used at temperature of 35 degrees C, mobile phase with flow rate of 0.8 mL min(-1) was acetonitrile: water (containing 10 mm potassium dihydrogen phosphate, pH 4.0, adjusted with orthophosphoric acid) = 60 : 40 (V/V) and UV detection at 224 nm and 305 nm. Samples were extracted with mobile phase by stirring and ultrasonic method. The average recoveries of four anti-dandruff agents were 98.0-104.1%. The relative standard deviations for samples were 0.11-0.90%. The method is simple, rapid and reproducible. PMID:18498472

  19. Determination of seven artificial sweeteners in diet food preparations by reverse-phase liquid chromatography with absorbance detection.

    PubMed

    Lawrence, J F; Charbonneau, C F

    1988-01-01

    The artificial sweeteners aspartame, saccharin, cyclamate, alitame, acesulfam-K, sucralose, and dulcin are determined in diet soft drinks and tabletop sweetener preparations. Samples are diluted, filtered, and analyzed directly by liquid chromatography on a C-18 reverse-phase column with a mobile phase gradient ranging from 3% acetonitrile in 0.02M KH2PO4 (pH 5) to 20% acetonitrile in 0.02M KH2PO4 (pH 3.5). Diet puddings and dessert toppings are extracted with ethanol, filtered, and diluted with mobile phase for analysis. The sweeteners, except sucralose and cyclamate, were detected by UV absorbance at either 200 or 210 nm. Sucralose was determined at 200 nm or by refractive index. Cyclamate was determined after post-column ion-pair extraction. The sweeteners stevioside and talin were not detected. Additives such as caffeine, sorbic acid, and benzoic acid did not interfere.

  20. The type IIP supernova 2012aw in M95: Hydrodynamical modeling of the photospheric phase from accurate spectrophotometric monitoring

    SciTech Connect

    Dall'Ora, M.; Botticella, M. T.; Della Valle, M.; Pumo, M. L.; Zampieri, L.; Tomasella, L.; Cappellaro, E.; Benetti, S.; Pignata, G.; Bufano, F.; Bayless, A. J.; Pritchard, T. A.; Taubenberger, S.; Benitez, S.; Kotak, R.; Inserra, C.; Fraser, M.; Elias-Rosa, N.; Haislip, J. B.; Harutyunyan, A.; and others

    2014-06-01

    We present an extensive optical and near-infrared photometric and spectroscopic campaign of the Type IIP supernova SN 2012aw. The data set densely covers the evolution of SN 2012aw shortly after the explosion through the end of the photospheric phase, with two additional photometric observations collected during the nebular phase, to fit the radioactive tail and estimate the {sup 56}Ni mass. Also included in our analysis is the previously published Swift UV data, therefore providing a complete view of the ultraviolet-optical-infrared evolution of the photospheric phase. On the basis of our data set, we estimate all the relevant physical parameters of SN 2012aw with our radiation-hydrodynamics code: envelope mass M {sub env} ∼ 20 M {sub ☉}, progenitor radius R ∼ 3 × 10{sup 13} cm (∼430 R {sub ☉}), explosion energy E ∼ 1.5 foe, and initial {sup 56}Ni mass ∼0.06 M {sub ☉}. These mass and radius values are reasonably well supported by independent evolutionary models of the progenitor, and may suggest a progenitor mass higher than the observational limit of 16.5 ± 1.5 M {sub ☉} of the Type IIP events.

  1. Phase contrast imaging measurements of reversed shear Alfvén eigenmodes during sawteeth in Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Edlund, E. M.; Porkolab, M.; Kramer, G. J.; Lin, L.; Lin, Y.; Wukitch, S. J.

    2009-05-01

    Reversed shear Alfvén eigenmodes (RSAEs) have been observed with the phase contrast imaging diagnostic and Mirnov coils during the sawtooth cycle in Alcator C-mod [M. Greenwald et al., Nucl. Fusion 45, S109 (2005)] plasmas with minority ion-cyclotron resonance heating. Both down-chirping RSAEs and up-chirping RSAEs have been observed during the sawtooth cycle. Experimental measurements of the spatial structure of the RSAEs are compared to theoretical models based on the code NOVA [C. Z. Cheng and M. S. Chance, J. Comput. Phys. 71, 124 (1987)] and used to derive constraints on the q profile. It is shown that the observed RSAEs can be understood by assuming a reversed shear q profile (up chirping) or a q profile with a local maximum (down chirping) with q ≈1.

  2. Imidazolium-embedded iodoacetamide-functionalized silica-based stationary phase for hydrophilic interaction/reversed-phase mixed-mode chromatography.

    PubMed

    Wang, Huizhen; Zhang, Lu; Ma, Teng; Zhang, Liyuan; Qiao, Xiaoqiang

    2016-09-01

    A novel imidazolium-embedded iodoacetamide-functionalized silica-based stationary phase has been prepared by surface radical chain-transfer polymerization. The stationary phase was characterized by Fourier transform infrared spectrometry, thermogravimetric analysis, and element analysis. Fast and efficient separations of polar analytes, such as nucleosides and nucleic acid bases, water-soluble vitamins and saponins, were well achieved in hydrophilic interaction chromatography mode. Additionally, a mixed mode of hydrophilic interaction and reversed-phase could be also obtained in the analysis of polar and nonpolar compounds, including weak acidic phenols, basic anilines and positional isomers, with high resolution and molecular-planarity selectivity, outperforming the commercially available amino column. Moreover, simultaneous separation of polar and nonpolar compounds was also achieved. In conclusion, the multimodal retention capabilities of the imidazolium-embedded iodoacetamide-functionalized silica-based column could offer a wide range of retention behavior and flexible selectivity toward hydrophilic and hydrophobic compounds. PMID:27470879

  3. Separation of diastereomers, structural isomers, and homologs of η5-cyclopentadienylcobalt and dinuclear molybdenum complexes by reverse phase high performance liquid chromatography using deoxygenated solvents

    SciTech Connect

    Huggins, John M.; King, Jr., Joseph A.; Peter, K.; Vollhardt, C.; J. Winter, Mark

    1981-03-17

    High performance liquid chromatography (HPLC) is being used in this study as an analytical and preparative tool for the characterization and isolation of a series of air-sensitive organometallic compounds. In addition, reversed phase chromatography with octadecylsilyl-modified silica (ODS) as a stationary phase and polar mobile phases saturated with argon are employed in the separation of products.

  4. Ultimately accurate SRAF replacement for practical phases using an adaptive search algorithm based on the optimal gradient method

    NASA Astrophysics Data System (ADS)

    Maeda, Shimon; Nosato, Hirokazu; Matsunawa, Tetsuaki; Miyairi, Masahiro; Nojima, Shigeki; Tanaka, Satoshi; Sakanashi, Hidenori; Murakawa, Masahiro; Saito, Tamaki; Higuchi, Tetsuya; Inoue, Soichi

    2010-04-01

    SRAF (Sub Resolution Assist Feature) technique has been widely used for DOF enhancement. Below 40nm design node, even in the case of using the SRAF technique, the resolution limit is approached due to the use of hyper NA imaging or low k1 lithography conditions especially for the contact layer. As a result, complex layout patterns or random patterns like logic data or intermediate pitch patterns become increasingly sensitive to photo-resist pattern fidelity. This means that the need for more accurate resolution technique is increasing in order to cope with lithographic patterning fidelity issues in low k1 lithography conditions. To face with these issues, new SRAF technique like model based SRAF using an interference map or inverse lithography technique has been proposed. But these approaches don't have enough assurance for accuracy or performance, because the ideal mask generated by these techniques is lost when switching to a manufacturable mask with Manhattan structures. As a result it might be very hard to put these things into practice and production flow. In this paper, we propose the novel method for extremely accurate SRAF placement using an adaptive search algorithm. In this method, the initial position of SRAF is generated by the traditional SRAF placement such as rule based SRAF, and it is adjusted by adaptive algorithm using the evaluation of lithography simulation. This method has three advantages which are preciseness, efficiency and industrial applicability. That is, firstly, the lithography simulation uses actual computational model considering process window, thus our proposed method can precisely adjust the SRAF positions, and consequently we can acquire the best SRAF positions. Secondly, because our adaptive algorithm is based on optimal gradient method, which is very simple algorithm and rectilinear search, the SRAF positions can be adjusted with high efficiency. Thirdly, our proposed method, which utilizes the traditional SRAF placement, is

  5. Spectrophotometric and reversed-phase high-performance liquid chromatographic methods for simultaneous determination of escitalopram oxalate and clonazepam in combined tablet dosage form.

    PubMed

    Gandhi, Santosh Vilashchand; Dhavale, Nilesh Dnyandev; Jadhav, Vijay Yeshawantrao; Sabnis, Shweta Sadanand

    2008-01-01

    Simple, accurate, precise, and sensitive ultraviolet spectrophotometric and reversed-phase high-performance liquid chromatographic (RP-HPLC) methods for simultaneous estimation of escitalopram oxalate (ESC) and clonazepam (CLO) in combined tablet dosage form have been developed and validated. The spectroscopic method employs an absorbance correction method using 238.6 and 308 nm as 2 wavelengths for estimation with methanol and water as solvents. Beer's law is obeyed in the concentration range of 10.0-50.0 and 0.5-3.0 micro/mL for ESC and CLO, respectively. The RP-HPLC method uses a Jasco HPLC system with HiQ SiL C18 column (250 x 4.6 mm id) acetonitrile-0.005 M tetrabutylammonium hydrogen sulfate (55 + 45, v/v) as the mobile phase, and satranidazole as an internal standard. The detection was carried out using an ultraviolet detector set at 287 nm. For the HPLC method, Beer's law is obeyed in the concentration range of 10.0-60.0 and 0.5-3.0 microg/mL for ESC and CLO, respectively. Both methods have been successfully applied for the analysis of the drugs in a pharmaceutical formulation. Results of analysis were validated statistically and by recovery studies. PMID:18376583

  6. Development and validation of reversed phase high-performance liquid chromatography method for estimation of lercanidipine HCl in pure form and from nanosuspension formulation

    PubMed Central

    Chonkar, Ankita D.; Managuli, Renuka S.; Rao, Josyula Venkata; Udupa, Nayanabhirama

    2015-01-01

    Aim: Quantitative estimation of lercanidipine HCl in bulk material as well as from nanosuspension formulations via a developed reverse phase HPLC method. Materials and Methods: Optimized chromatographic condition was used to achieve separation on a Kromasil (100-5c18 250 × 4.6 mm) column using Shimadzu HPLC system. The mobile phase consisted of a mixture of acetate buffer (20 mM pH 4.5) and acetonitrile in the ratio of 10:90, v/v. It is pumped through the chromatographic system at a flow rate of 1 ml/min. The detection was carried out at 240 nm using ultraviolet-visible spectrophotometry detector. The method was validated as per Q2 (R1) guidelines, and suitability of the developed method was established by optimized nanosuspension formulation. Results: The method is specific to lercanidipine (RT: 7.7 min), and has ability to resolve the analyte peak from excipient interferences. It is linear (regression coefficient: 0.9993), accurate (average recovery: 100%), and passed all the system suitability requirements. Conclusion: Developed method was found applicable for evaluation of drug content, content uniformity, and analyzing samples of dissolution studies of nanosuspension. PMID:26792958

  7. Quantitative analysis of ripasudil hydrochloride hydrate and its impurities by reversed-phase high-performance liquid chromatography after precolumn derivatization: Identification of four impurities.

    PubMed

    Hui, Wenkai; Sun, Lili; Zhang, Hui; Zou, Liang; Zou, Qiaogen; Ouyang, Pingkai

    2016-09-01

    We report the development and validation of a stability-indicating reversed-phase high-performance liquid chromatography method with precolumn derivatization for the separation and identification of the impurities of ripasudil hydrochloride hydrate, a novel protein kinase inhibitor. 2,3,4,6-Tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate was chosen as the derivatizing reagent and triethylamine was added as catalyst. 200 μL sample solution (1 mg/mL), 600 μL derivatizing reagent (1 mg/mL), and 200 μL triethylamine solution (1%, v/v) were mixed and reacted at 40°C for 30 min. The separation was achieved on an Inertsil C18 ODS-3 (250 mm × 4.6 mm, 5 μm) column using mobile phases including 10 mmol monopotassium phosphate buffer (pH 3.0) and methanol in gradient mode. The column temperature was adjusted at 25°C and the flow rate at 1 mL/min. The detection was carried out at 220 nm. Different precolumn derivatization conditions as well as the high-performance liquid chromatography conditions were optimized. Ripasudil hydrochloride hydrate and its four impurities were detected and quantitated, among which two new compounds were characterized. The proposed method was validated and proven to be selective, accurate, and precise and suitable for the quantitative analysis of ripasudil hydrochloride hydrate. PMID:27390135

  8. Development and validation of a reversed-phase HPLC method for simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet dosage form.

    PubMed

    Shaikh, K A; Patil, S D; Devkhile, A B

    2008-12-15

    A simple, precise and accurate reversed-phase liquid chromatographic method has been developed for the simultaneous estimation of ambroxol hydrochloride and azithromycin in tablet formulations. The chromatographic separation was achieved on a Xterra RP18 (250 mm x 4.6 mm, 5 microm) analytical column. A Mixture of acetonitrile-dipotassium phosphate (30 mM) (50:50, v/v) (pH 9.0) was used as the mobile phase, at a flow rate of 1.7 ml/min and detector wavelength at 215 nm. The retention time of ambroxol and azithromycin was found to be 5.0 and 11.5 min, respectively. The validation of the proposed method was carried out for specificity, linearity, accuracy, precision, limit of detection, limit of quantitation and robustness. The linear dynamic ranges were from 30-180 to 250-1500 microg/ml for ambroxol hydrochloride and azithromycin, respectively. The percentage recovery obtained for ambroxol hydrochloride and azithromycin were 99.40 and 99.90%, respectively. Limit of detection and quantification for azithromycin were 0.8 and 2.3 microg/ml, for ambroxol hydrochloride 0.004 and 0.01 microg/ml, respectively. The developed method can be used for routine quality control analysis of titled drugs in combination in tablet formulation.

  9. Selection of reversed-phase liquid chromatographic columns with diverse selectivity towards the potential separation of impurities in drugs.

    PubMed

    Van Gyseghem, E; Jimidar, M; Sneyers, R; Redlich, D; Verhoeven, E; Massart, D L; Vander Heyden, Y

    2004-07-01

    To select appropriate stationary phases from the continuously expanding supply of potentially suitable HPLC columns, the properties of 28 frequently applied stationary phases were determined by measuring several chromatographic parameters. From these results, based on chromatographic expertise, eight stationary phases with different properties and selectivities were selected. The aim of this study is to apply chemometric tools to evaluate the initially selected set of columns, i.e. a more systematic approach for making such a selection is examined. Starting from the information obtained on the 28 stationary phases, the re-evaluation was performed independently based on the chemometric techniques Pareto-optimality, principal component analysis (PCA), and Derringer's desirability functions. The aim was to select a set of efficient columns exhibiting large selectivity differences. The chemometrically selected stationary phases were divided in groups based on hydrophobicity, a critical retention-determining property in reversed-phase chromatography. This allowed to further reducing the selection to three columns. It is demonstrated that the selection by the chemometric approaches in general is fairly comparable with the initial selection.

  10. A reversed-phase high performance liquid chromatography method for quantification of methotrexate in cancer patients serum.

    PubMed

    Li, Yuan-dong; Li, Yan; Liang, Ning-sheng; Yang, Fan; Kuang, Zhi-peng

    2015-10-01

    A simple, rapid and sensitive reversed-phase high performance liquid chromatography (HPLC) method has been developed for the determination of methotrexate in human serum. After deproteinization of the serum with 40% silver nitrate solution, methotrexate and internal standard (IS) were separated on a reversed-phase column with a mobile phase consisting of 10mM sodium phosphate buffer (pH6.40)-methanol (78:22%, v/v) and ultraviolet detection at 310nm. The linearity is evaluated by a calibration curve in the concentration range of 0.05-10.0μg/mL and presented a correlation coefficient of 0.9995. The absolute recoveries were 97.52±3.9% and 96.87±3.7% for methotrexate and ferulic acid (internal standard), respectively. The intra- and inter-day precision were less 6.19 and 5.89%, respectively (n=6). The limit of quantitation was 0.02μg/mL and the limit of detection was 0.006μg/mL. The complete analysis was achieved less than 10min with no interference from endogenous components or 22 examined drugs. This method was validated by using serum samples from high-dose methotrexate treated patients with osteosarcoma, breast cancer, acute leukemia and lymphoma. The method was demonstrated to be a simple, rapid and reliable approach in quantification of methotrexate in serum samples from patients with high-dose methotrexate therapy.

  11. A coupled phase-field and volume-of-fluid method for accurate representation of limiting water wave deformation

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Yu, Xiping

    2016-09-01

    A coupled phase-field and volume-of-fluid method is developed to study the sensitive behavior of water waves during breaking. The THINC model is employed to solve the volume-of-fluid function over the entire domain covered by a relatively coarse grid while the phase-field model based on Allen-Cahn equation is applied over the fine grid. A special algorithm that takes into account the sharpness of the diffuse-interface is introduced to correlate the order parameter obtained on the fine grid and the volume-of-fluid function obtained on the coarse grid. The coupled model is then applied to the study of water waves generated by moving pressures on the free surface. The deformation process of the wave crest during the initial stage of breaking is discussed in details. It is shown that there is a significant variation of the free nappe developed at the front side of the wave crest as the wave steepness differs. It is of a plunging type at large wave steepness while of a spilling type at small wave steepness. The numerical results also indicate that breaking occurs later and the duration of breaking is shorter for waves of smaller steepness and vice versa. Neglecting the capillary effect leads to wave breaking with a sharper nappe and a more dynamic plunging process. The surface tension also has an effect to prevent the formation of a free nappe at the front side of the wave crest in some cases.

  12. An accurate projector gamma correction method for phase-measuring profilometry based on direct optical power detection

    NASA Astrophysics Data System (ADS)

    Liu, Miao; Yin, Shibin; Yang, Shourui; Zhang, Zonghua

    2015-10-01

    Digital projector is frequently applied to generate fringe pattern in phase calculation-based three dimensional (3D) imaging systems. Digital projector often works with camera in this kind of systems so the intensity response of a projector should be linear in order to ensure the measurement precision especially in Phase-Measuring Profilometry (PMP). Some correction methods are often applied to cope with the non-linear intensity response of the digital projector. These methods usually rely on camera and gamma function is often applied to compensate the non-linear response so the correction performance is restricted by the dynamic range of camera. In addition, the gamma function is not suitable to compensate the nonmonotonicity intensity response. This paper propose a gamma correction method by the precisely detecting the optical energy instead of using a plate and camera. A photodiode with high dynamic range and linear response is used to directly capture the light optical from the digital projector. After obtaining the real gamma curve precisely by photodiode, a gray level look-up table (LUT) is generated to correct the image to be projected. Finally, this proposed method is verified experimentally.

  13. Using accurate phase space coordinates of ~100,00 halo field stars to constrain the Milky Way halo

    NASA Astrophysics Data System (ADS)

    Valluri, Monica

    2015-08-01

    The current cosmological paradigm predicts that dark matter halos are triaxial overall, but oblate in regions where baryons dominate. However recent measurements of the shape of the Milky Way dark matter halo find it to be very triaxial with a shape and orientation that are significantly at odds with theoretical predictions. The ESA’s Gaia satellite will soon map the entire Milky Way giving us six phase-space coordinates, ages and abundances for hundreds of thousands of halo stars. I will report progress on a new code based on the Schwarzschild orbit superposition method and orbital frequency mapping, to determine the global shape of the Milky Way's dark matter halo using field stars from Gaia. This technique will simultaneously yield the self-consistent phase-space distribution function of the stellar halo in the inner 20-30kpc region. Detailed analysis of correlations between the chemical abundances, ages and orbits of halo stars in this distribution function will enable us to extract clues to the formation history of the Milky Way that are encoded in orbital properties of halo stars.

  14. Preparation, characterization and application of a reversed phase liquid chromatography/hydrophilic interaction chromatography mixed-mode C18-DTT stationary phase.

    PubMed

    Wang, Qing; Long, Yao; Yao, Lin; Xu, Li; Shi, Zhi-Guo; Xu, Lanying

    2016-01-01

    A mixed-mode chromatographic stationary phase, C18-DTT (dithiothreitol) silica (SiO2) was prepared through "thiol-ene" click chemistry. The obtained material was characterized by fourier transform infrared spectroscope, nitrogen adsorption analysis and contact angle analysis. Chromatographic performance of the C18-DTT was systemically evaluated by studying the effect of acetonitrile content, pH, buffer concentration of the mobile phase and column temperature. It was demonstrated that the novel stationary phase possessed reversed phase liquid chromatography (RPLC)/hydrophilic interaction liquid chromatography (HILIC) mixed-mode property. The stop-flow test revealed that C18-DTT exhibited excellent compatibility with 100% aqueous mobile phase. Additionally, the stability and column-to-column reproducibility of the C18-DTT material were satisfactory, with relative standard deviations of retention factor of the tested analytes (verapamil, fenbufen, guanine, tetrandrine and nicotinic acid) in the range of 1.82-3.72% and 0.85-1.93%, respectively. Finally, the application of C18-DTT column was demonstrated in the separation of non-steroidal anti-inflammatory drugs, aromatic carboxylic acids, alkaloids, nucleo-analytes and polycyclic aromatic hydrocarbons. It had great resolving power in the analysis of various compounds in HILIC and RPLC chromatographic conditions and was a promising RPLC/HILIC mixed-mode stationary phase. PMID:26695288

  15. Preparation, characterization and application of a reversed phase liquid chromatography/hydrophilic interaction chromatography mixed-mode C18-DTT stationary phase.

    PubMed

    Wang, Qing; Long, Yao; Yao, Lin; Xu, Li; Shi, Zhi-Guo; Xu, Lanying

    2016-01-01

    A mixed-mode chromatographic stationary phase, C18-DTT (dithiothreitol) silica (SiO2) was prepared through "thiol-ene" click chemistry. The obtained material was characterized by fourier transform infrared spectroscope, nitrogen adsorption analysis and contact angle analysis. Chromatographic performance of the C18-DTT was systemically evaluated by studying the effect of acetonitrile content, pH, buffer concentration of the mobile phase and column temperature. It was demonstrated that the novel stationary phase possessed reversed phase liquid chromatography (RPLC)/hydrophilic interaction liquid chromatography (HILIC) mixed-mode property. The stop-flow test revealed that C18-DTT exhibited excellent compatibility with 100% aqueous mobile phase. Additionally, the stability and column-to-column reproducibility of the C18-DTT material were satisfactory, with relative standard deviations of retention factor of the tested analytes (verapamil, fenbufen, guanine, tetrandrine and nicotinic acid) in the range of 1.82-3.72% and 0.85-1.93%, respectively. Finally, the application of C18-DTT column was demonstrated in the separation of non-steroidal anti-inflammatory drugs, aromatic carboxylic acids, alkaloids, nucleo-analytes and polycyclic aromatic hydrocarbons. It had great resolving power in the analysis of various compounds in HILIC and RPLC chromatographic conditions and was a promising RPLC/HILIC mixed-mode stationary phase.

  16. One-pot synthesized functionalized mesoporous silica as a reversed-phase sorbent for solid-phase extraction of endocrine disrupting compounds in milks.

    PubMed

    Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Marina, María Luisa; Sierra, Isabel

    2016-01-01

    A new procedure for the determination of 12 naturally occurring hormones and some related synthetic chemicals in milk, commonly used as growth promoters in cattle, is reported. The method is based on liquid-liquid extraction followed by solid-phase extraction (SPE) using a new one-pot synthesized ordered mesoporous silica (of the SBA-15 type) functionalized with octadecyl groups (denoted as SBA-15-C18-CO) as reversed-phase sorbent. The analytes were eluted with methanol and then submitted to HPLC with diode array detection. Under optimal conditions, the method quantification limit for the analytes ranged from 0.023 to 1.36μg/mL. The sorbent affored the extraction of estrone, 17β-estradiol, estriol, progesterone, hexestrol, diethylstilbestrol, 4-androstene-3,17-dione, ethinylestradiol, 17α-methyltestosterone, nandrolone, prednisolone and testosterone with mean recoveries ranging from 72% to 105% (except for diethylstilbestrol) with RSD<11%. These results were comparable and, in some cases, even better than those obtained with other extraction methods, therefore SBA-15-C18-CO mesoporous silica possess a high potential as a reversed-phase sorbent for SPE of the 12 mentioned endocrine disrupting compounds in milk samples.

  17. One-pot synthesized functionalized mesoporous silica as a reversed-phase sorbent for solid-phase extraction of endocrine disrupting compounds in milks.

    PubMed

    Gañán, Judith; Morante-Zarcero, Sonia; Pérez-Quintanilla, Damián; Marina, María Luisa; Sierra, Isabel

    2016-01-01

    A new procedure for the determination of 12 naturally occurring hormones and some related synthetic chemicals in milk, commonly used as growth promoters in cattle, is reported. The method is based on liquid-liquid extraction followed by solid-phase extraction (SPE) using a new one-pot synthesized ordered mesoporous silica (of the SBA-15 type) functionalized with octadecyl groups (denoted as SBA-15-C18-CO) as reversed-phase sorbent. The analytes were eluted with methanol and then submitted to HPLC with diode array detection. Under optimal conditions, the method quantification limit for the analytes ranged from 0.023 to 1.36μg/mL. The sorbent affored the extraction of estrone, 17β-estradiol, estriol, progesterone, hexestrol, diethylstilbestrol, 4-androstene-3,17-dione, ethinylestradiol, 17α-methyltestosterone, nandrolone, prednisolone and testosterone with mean recoveries ranging from 72% to 105% (except for diethylstilbestrol) with RSD<11%. These results were comparable and, in some cases, even better than those obtained with other extraction methods, therefore SBA-15-C18-CO mesoporous silica possess a high potential as a reversed-phase sorbent for SPE of the 12 mentioned endocrine disrupting compounds in milk samples. PMID:26362809

  18. Simultaneous determination of caffeine, theophylline and theobromine in human plasma by on-line solid-phase extraction coupled to reversed-phase chromatography.

    PubMed

    Emara, Samy

    2004-10-01

    A reversed-phase liquid chromatographic column switching system was described for the determination of caffeine (CF), theophylline (TH) and theobromine (TB) in human plasma with a direct injection procedure. A short protein-coated mu Bondapak CN silica pre-column (20 x 3 mm, i.d.) was used for enrichment of the drugs and clean up from weakly retained plasma components using phosphate buffer saline pH 7.4. After washing step, the retained drugs were flushed into a reversed-phase column (5 microm TSK gel ODS-80 TM, 150 x 4.6 mm i.d.) with a mobile phase of methanol-0.01 M phosphate buffer, pH 3.5 (30:70, v/v) for the final separation. The eluent was monitored with a UV detector at 275 nm. The resulting chromatograms showed no interference from endogenous plasma components. A linear relationship between the concentration of drug and peak height was confirmed in the range of 0.5-20 microg/mL for all drugs. High extraction recoveries from plasma ranging from 96.12 to 100.32% were achieved. Validation of the method was examined performing intra- and inter-day accuracy and precision and was found to be satisfactory. The coefficients of variation of the three drugs were less than 3% for intra-day and less than 4% for inter-day run assays.

  19. HPLC in reversed phase mode: Tool for investigation of kinetics of blackcurrant seed oil lipolysis in supercritical carbon dioxide.

    PubMed

    Bártlová, Milena; Bernásek, Prokop; Sýkora, Jan; Sovová, Helena

    2006-07-24

    Blackcurrant (Ribes nigrum) seed oil is rich in alpha- and gamma-linolenic acids, the latter in particular being of potential use in medicine. The enzymatic hydrolysis of the oil was carried out in supercritical carbon dioxide using lipase Lipozyme as catalyst and changes in the composition of acylglycerols were recorded. Mono-, di-, and triacylglycerols and free fatty acids were separated by non-aqueous high-performance liquid chromatography in reversed phase mode and detected by UV diode array and 1H NMR detectors. Lipozyme was found to exert low specificity to individual fatty acids in the hydrolysed oil. PMID:16597516

  20. Ion pair-reversed phase HPLC approach facilitates subcloning of PCR products and screening of recombinant colonies.

    PubMed

    Shaw-Bruha, C M; Lamb, K A

    2000-04-01

    The isolation of a single DNA molecule for cloning is technically difficult, and the subsequent screening of colonies for recombinant DNA clones is time consuming. Ion pair-reversed phase HPLC (IP-RP-HPLC) analysis of nucleic acids improves the resolution and isolation of PCR products to be cloned. We demonstrate that PCR products analyzed and collected using the IP-RP-HPLC approach (WAVE DNA Fragment Analysis System) can be cloned directly into a plasmid vector. In addition, we demonstrate that when IP-RP-HPLC analysis is extended to the colony screening process, the time required for these procedures is reduced.

  1. Reversible phase transition and relaxor behavior in Te2V2O9 single crystals grown by Czochralski technique

    NASA Astrophysics Data System (ADS)

    Shet, Tukaram; Varma, K. B. R.

    2016-09-01

    Te2V2O9 single crystals were grown along the polar c-axis via the Czochralski crystal growth technique. Dielectric studies carried out along the polar axis in a wide temperature range at different frequencies confirmed the relaxor nature of the Te2V2O9 single crystals. Temperature dependent polarized light optical microscopy along a-axis established a reversible phase transition around 614 K. Relaxor nature of Te2V2O9 was attributed to the compositional heterogeneity at micro/nano scale within the grown crystal as vanadium was observed to be present in different oxidation states by X-ray photoelectron spectroscopic studies.

  2. Determination of conjugated bile acids in human bile and duodenal fluid by reverse-phase high-performance liquid chromatography.

    PubMed

    Bloch, C A; Watkins, J B

    1978-05-01

    A simple mehtod using reverse-phase liquid chromatography is presented for resolution and quantitation of the major conjugated bile acids of man, including the glycine and taurine conjugates of the dihydroxy bile acids, chenodeoxycholic and deoxycholic acid. Using modern, high-performance chromatographic equipment, analysis time is less than 30 minutes. The quantitative range of the method, with detection by refractive index, is 0.05 to 0.1 mumol of bile acid and the limit of detection for an injection sample is 0.01 mumol. This provides a sensitivity sufficient for analysis of dilute duodenal and gallbladder bile with minimal sample preparation.

  3. Separation of guinea-pig pancreatic juice proteins by reversed-phase high-performance liquid chromatography.

    PubMed

    Padfield, P J; Griffin, M; Case, R M

    1986-11-01

    Using a Protesil 300 octyl reversed-phase column with a multistage water-acetonitrile solvent gradient system, it was possible to obtain a well-resolved separation of the nine major proteins present in guinea-pig pancreatic juice. The protein present in each peak of the pancreatic juice chromatogram could only be identified by molecular weight analysis as the acetonitrile denaturated the enzymes and altered their isoelectric points. However, using sodium dodecyl sulphate gel electrophoresis the protein fractions obtained by high-performance liquid chromatography were characterised. Preliminary work has indicated that this system may be capable of separating other complex biological protein mixtures, i.e., saliva. PMID:3793824

  4. Simultaneous determination of diprophylline, proxyphylline and theophylline in serum by reversed-phase high-performance liquid chromatography.

    PubMed

    Wenk, M; Eggs, B; Follath, F

    1983-09-01

    A selective and reliable high-performance liquid chromatographic assay for the simultaneous determination of diprophylline, proxyphylline and theophylline is described. The method involves a single extraction procedure followed by separation on an ODS reversed-phase column using a ternary solvent system. The assay is sufficiently rapid and sensitive to be applied for pharmacokinetic studies as well as for routine monitoring of patient's serum after therapeutic doses of the combined preparation. The practicability and utility of the proposed method is demonstrated in a pharmacokinetic study on four healthy volunteers.

  5. Self-referenced, accurate and sensitive optical frequency comb spectroscopy with a virtually imaged phased array spectrometer.

    PubMed

    Kowzan, Grzegorz; Lee, Kevin F; Paradowska, Magdalena; Borkowski, Mateusz; Ablewski, Piotr; Wójtewicz, Szymon; Stec, Kamila; Lisak, Daniel; Fermann, Martin E; Trawiński, Ryszard S; Masłowski, Piotr

    2016-03-01

    We present a cavity-enhanced direct optical frequency comb spectroscopy system with a virtually imaged phased array (VIPA) spectrometer and either a dither or a Pound-Drever-Hall (PDH) locking scheme used for stable transmission of the comb through the cavity. A self-referenced scheme for frequency axis calibration is shown along with an analysis of its accuracy. A careful comparison between both locking schemes is performed based on near-IR measurements of the carbon monoxide ν=3←0 band P branch transitions in a gas sample with known composition. The noise-equivalent absorptions (NEA) for the PDH and dither schemes are 9.9×10(-10) cm(-1) and 5.3×10(-9) cm(-1), respectively.

  6. Distribution or adsorption: the major dilemma in reversed-phase HPLC

    NASA Astrophysics Data System (ADS)

    Deineka, V. I.

    2008-06-01

    A method is suggested for analyzing the dependences obtained for different compositions of mobile eluent system phases, their slopes and intercepts, log k( i, B) = a + b log k ( i, A), where a is the intercept for the A and B stationary phases and b is the proportionality factor. An analysis requires parallel investigation of sorbate retention on at least three stationary phases with different lengths of grafted hydrocarbon radicals. The dependence of correlation parameters on the sorbate retention mechanism is discussed. It is shown that the hypothetical dependences coincide with the experimental dependences for surface sorption of resveratrol and volume distribution of triglycerides.

  7. Rapid determination of alpha tocopherol in olive oil adulterated with sunflower oil by reversed phase high-performance liquid chromatography.

    PubMed

    Bakre, S M; Gadmale, D K; Toche, R B; Gaikwad, V B

    2015-05-01

    A new method is developed to determine the presence of sunflower oil in olive oil. α-tocopherol is selected as discriminating parameter for detecting sunflower oil adulterant in olive oil. Admixtures of olive oil and sunflower oil (5 %, 10 %, 15 % and 20 % sunflower oil in olive oil) are prepared. These admixtures are analysed by reversed phase high pressure liquid chromatography coupled with fluorescence detector. The sample preparation does not require saponification or addition of antioxidant. The chromatographic system consists of a C18 column with methanol: acetonitrile (50:50) mobile phase. Fluorescence detector excitation wavelength is set at 290 nm and emission wavelength is set at 330 nm. The α tocopherol concentration increases linearly in olive oil adulterated with sunflower oil. The method is simple, selective, sensitive and is precise (RSD = 2.65 %) for α tocopherol. The present method can precisely detect 5 % sunflower oil in olive oil.

  8. Development and validation of a reversed-phase HPLC method for the determination of ezetimibe in pharmaceutical dosage forms.

    PubMed

    Sistla, R; Tata, V S S K; Kashyap, Y V; Chandrasekar, D; Diwan, P V

    2005-09-15

    Ezetimibe belongs to a group of selective and very effective 2-azetidione cholesterol absorption inhibitors that act on the level of cholesterol entry into enterocytes. A rapid, specific reversed-phase HPLC method has been developed for assaying ezetimibe in pharmaceutical dosage forms. The assay involved an isocratic elution of ezetimibe in a Kromasil 100 C18 column using a mobile phase composition of water (pH 6.8, 0.05%, w/v 1-heptane sulfonic acid) and acetonitrile (30:70, v/v). The flow rate was 0.5 ml/min and the analyte monitored at 232 nm. The assay method was found to be linear from 0.5 to 50 microg/ml. All the validation parameters were within the acceptance range. The developed method was successfully applied to estimate the amount of ezetimibe in tablets.

  9. Phase Transition to a Time-Reversal Symmetry-Breaking State in d-Wave Superconducting Films with Rough Surfaces

    NASA Astrophysics Data System (ADS)

    Higashitani, Seiji; Miyawaki, Nobumi

    2015-03-01

    The normal-superconducting phase transition in d-wave superconducting films is discussed with a focus on the effect of diffuse surface scattering. A specularity parameter S characterizing the boundary condition is introduced for systematic analysis of the surface effect. When S = 1 (the specular limit), the film can exhibit a novel superconductivity that spontaneously breaks time-reversal symmetry, as was shown by Vorontsov [Phys. Rev. Lett. 102, 177001 (2009)]. We find that this superconducting phase is suppressed as the degree of surface roughness increases, i.e., as the specularity S decreases. In particular, it is completely suppressed when S = 0 (the diffusive limit). Those results are explained from the viewpoint of surface odd-frequency pairing.

  10. Dynamic phase reversal of photo-induced precession of magnetization in ferromagnetic (Ga,Mn)As thin film

    NASA Astrophysics Data System (ADS)

    Li, Hang; Zhang, Xinhui; Liu, Xinyu; Furdyna, Jacek K.

    2015-11-01

    Ultrafast laser-triggered coherent magnetization dynamics in ferromagnetic (Ga,Mn)As films have been investigated by time-resolved magneto-optical spectroscopy. Dynamic phase reversal in the magnetic precession process is observed when the ambient temperature or the external magnetic field is varied. This phenomenon is found to be sensitive to the spontaneous magnetization orientation, and is attributed to the giant magnetic linear dichroism (MLD) effect in (Ga,Mn)As. Our findings suggest that this effect will enable the sensitive measurement of the dynamic phase of in-plane magnetization precession on picosecond time scale in the collective spin excitation in (Ga,Mn)As, thus enabling efficient and ultrafast magneto-optical detection for magnetization dynamics in ferromagnetic semiconductor-based spintronic devices.

  11. [Separation of zoledronic acid and its related substances by ion-pair reversed-phase high performance liquid chromatography].

    PubMed

    Zhang, Xiaoqing; Jiang, Ye; Xu, Zhiru

    2004-07-01

    A rapid and simple ion-pair reversed-phase high performance liquid chromatographic method (HPLC) has been established for the routine analysis of zoledronic acid and its related substances. The chromatographic conditions were optimized based on the satisfactory separation of zoledronic acid from imidazol-1-ylacetic acid, their retention times and peak shape. The excellent separation of zoledronic acid from its related substances, including the remaining imidazol-1-ylacetic acid used in the synthesis of zoledronic acid and other impurities of oxidation and decomposition, was achieved within 9 min on a Hypersil C8 column with UV detection at 220 nm. The mobile phase was a mixture of methanol (20%) and 5 mmo/L phosphate buffer (80%) that contains 6 mmol/L tetrabutylammonium bromide. The resolution factor of zoledronic acid from its adjacent peak was more than 2.5. This is a simple and rapid method for the routine assay of zoledronic acid.

  12. Performance of different C18 columns in reversed-phase liquid chromatography with hydro-organic and micellar-organic mobile phases.

    PubMed

    Ruiz-Angel, M J; Pous-Torres, S; Carda-Broch, S; García-Alvarez-Coque, M C

    2014-05-30

    Column selection in reversed-phase liquid chromatography (RPLC) can become a challenge if the target compounds interact with the silica-based packing. One of such interactions is the attraction of cationic solutes to the free silanols in silica-based columns, which is a slow sorption-desorption interaction process that gives rise to tailed and broad peaks. The effect of silanols is minimised by the addition of a competing agent in the mobile phase, such as the anionic surfactant sodium dodecyl sulphate (SDS). In micellar-organic RPLC, the adsorption of an approximately fixed amount of SDS monomers gives rise to a stable modified stationary phase, with properties remarkably different from those of the underlying bonded phase. The chromatographic behaviour (in terms of selectivity, analysis time and peak shape) of eight C18 columns in the analysis of weakly acidic phenols and basic β-blockers was examined with hydro-organic and micellar-organic mobile phases. The behaviour of the columns differed significantly when the cationic basic drugs were eluted with hydro-organic mobile phases. With micellar-organic mobile phases, the adsorption of surfactant, instead of making the columns similar, gave rise to a greater diversity of behaviours (especially in terms of selectivity and analysis time), for both groups of phenols and β-blockers, which should be explained by the residual effect of the underlying bonded stationary phase and the different amount of surfactant covering the packing. Therefore, the implementation of a micellar-organic procedure in RPLC will depend significantly on the selected type of C18 column.

  13. Reversed-phase high-performance liquid chromatography of unsubstituted aminobenzoic acids

    USGS Publications Warehouse

    Abidi, S.L.

    1989-01-01

    High-performance liquid chromatographic (HPLC) characteristics of three position isomers of aminobenzoic acids (potential metabolites of important anesthetic drugs), were delineated with respect to their interactions with various mobile phases and stationary phases. HPLC with five hydrocarbonaceous phase, I?-cyclodextrin silica (CDS), macrophase MP-1 polymer (MP), macroporous polystyrene/divinylbenzene (MPD), octadecylsilica (ODS), and propylphenylsilica (PPS), yielded results explicable in terms of substituent effects derived from the bifunctional amino- and carboxy groups. For cases where mobile phases contained sulfonates or quaternary ammonium salts both having longer chain alkyls, retention of analytes on all but CDS appeared to proceed predominantly via an ion-pairing mechanism. The extent of the corresponding counter-ion effects decreased in the order: MPD > ODS > PPS > MP, while the analyte retention order paralleled thier pH2 values. On the other hand, an inverse relationship between the magnitude of capacity factors (k') and pK1 values of the title compounds was observed in experiments that produced retention data incompatible with ion-pair interaction rationales. The unique HPLC results obtained with the CDS phase are compared with those obtained with other phases.

  14. Comparison of zirconia- and silica-based reversed stationary phases for separation of enkephalins.

    PubMed

    Soukupová, K; Krafková, E; Suchánková, Jana; Tesarová, E

    2005-09-16

    In this study, the separation of biologically active peptides on two zirconia-based phases, polybutadiene (PBD)-ZrO2 and polystyrene (PS)-ZrO2, and a silica-based phase C18 was compared. Basic differences in interactions on both types of phases led to quite different selectivity. The retention characteristics were investigated in detail using a variety of organic modifiers, buffers, and temperatures. These parameters affected retention, separation efficiency, resolution and symmetry of peaks. Separation systems consisting of Discovery PBD-Zr column and mobile phase composed of a mixture of acetonitrile and phosphate buffer, pH 2.0 (45:55, v/v) at 70 degrees C and Discovery PS-Zr with acetonitrile and phosphate buffer, pH 3.5 in the same (v/v) ratio at 40 degrees C were suitable for a good resolution of enkephalin related peptides. Mobile phase composed of acetonitrile and phosphate buffer, pH 5.0 (22:78, v/v) was appropriate for separation of enkephalins on Supelcosil C18 stationary phase. PMID:16130703

  15. Influence of mobile phase composition on electroosmotic flow velocity, solute retention and column efficiency in open-tubular reversed-phase capillary electrochromatography.

    PubMed

    Crego, A L; Martínez, J; Marina, M L

    2000-02-11

    The effects of some experimental parameters, such as the volume fraction and type of organic modifier in the mobile phase, and the concentration, type and pH of the buffer on the electroosmotic flow velocity, the retention behavior of test solutes, and the column efficiency have been investigated in capillary electrochromatography (CEC) using an open-tubular column of 9.60 microm I.D. with a porous silica layer chemically modified with C18 as stationary phase. The retention of a group of polycyclic aromatic hydrocarbons (PAHs) used as a test mixture varied significantly by changing the organic modifier content in the hydroorganic mobile phase according to the reversed-phase-like selectivity of the stationary phase. In addition, an increase in the percentage of organic modifier resulted in a slight increase in the linear velocity of the EOF. On the other hand, when the phosphate buffer concentration was increased over the range 1-50 mM, the electroosmotic mobility fell dramatically, the retention of the solutes decreased steadily, and the plate height showed a significant increase. The results obtained with phosphate, trishydroxymethylaminomethane or 2-morpholinoethanesulfonic acid as buffers were similar when pH remained constant. Optimization in CEC was essential to achieve further enhancement of separation performance, because the analysis time and separation resolution are essentially affected when varying operating parameters. Separations of seven PAHs with more than 100000 plates are presented within 4 min analysis time.

  16. Automated gas-phase purification for accurate, multiplexed quantification on a stand-alone ion trap mass spectrometer

    PubMed Central

    Vincent, Catherine E.; Rensvold, Jarred W.; Westphall, Michael S.; Pagliarini, David J.; Coon, Joshua J.

    2012-01-01

    Isobaric tagging enables the acquisition of highly-multiplexed proteome quantification but is hindered by the pervasive problem of precursor interference. The elimination of co-isolated contaminants prior to reporter tag generation can be achieved through the use of gas-phase purification via proton transfer ion/ion reactions (QuantMode); however, the original QuantMode technique was implemented on the high resolution linear ion trap-Orbitrap hybrid mass spectrometer enabled with electron transfer dissociation (ETD). Here we extend this technology to stand-alone linear ion trap systems (trapQuantMode). Facilitated by the use of inlet beam-type activation (i.e., trapHCD) for production and observation of the low mass-to-charge reporter region, this scan sequence comprises three separate events to maximize peptide identifications, minimize duty cycle requirements, and increase quantitative accuracy, precision, and dynamic range. Significant improvements in quantitative accuracy were attained over standard methods when using trapQuantMode (trapQM) to analyze an interference model system comprising tryptic peptides of yeast that we contaminated with human peptides. Finally, we demonstrate practical benefits of this method by analysis of the proteomic changes that occur during mouse skeletal muscle myoblast differentiation. While trapQM’s reduced duty cycle led to the identification of fewer proteins than conventional operation (4,050 vs. 2,964), trapQM identified more significant differences (>1.5 fold, 1,362 vs 1,132, respectively; P<0.05) between the proteomes of undifferentiated myoblasts and differentiated myotubes and nearly ten-fold more differences with changes greater than 5-fold (96 vs. 12). We further show that our trapQM dataset is superior for identifying changes in protein abundance that are consistent with the metabolic and structural changes known to accompany myotube formation. PMID:23046161

  17. On-line comprehensive two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography for preparative isolation of toad venom.

    PubMed

    Li, Jia-Fu; Fang, Hua; Yan, Xia; Chang, Fang-Rong; Wu, Zhen; Wu, Yun-Long; Qiu, Ying-Kun

    2016-07-22

    An on-line comprehensive preparative two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography (2D NPLC×RPLC) system was constructed with a newly developed vacuum evaporation assisted adsorption (VEAA) interface, allowing fast removal of NPLC solvent in the vacuum condition and successfully solving the solvent incompatibility problem between NPLC and RPLC. The system achieved on-line solvent exchange within the two dimensions and its performance was illustrated by gram-scale isolation of crude extract from the venom of Bufo bufo gargarizans. Within separation time of ∼20h, 19 compounds were obtained with high purity in a single run. With the VEAA interface, the 2D system exhibited apparent advantages in separation efficiency and automation compared with conventional methods, indicating its promising application in the routine separation process for complicated natural products. PMID:27328884

  18. A "reverse" solid-phase radio-immuno-assay for IgM-antibodies to hepatitis A virus.

    PubMed

    Meurman, O H; Matter, L; Krishna, R V; Krech, U H

    1981-04-01

    A "reverse"solid-phase radio-immuno-assay for IgM antibodies to hepatitis A virus (HAV) was developed. Anti-human IgM immunoglobulins were bound on the wells of polyvinylchloride microtiter plates. Serum specimens were incubated in the anti-human IgM coated wells and bound IgM antibodies were then assayed for antigen specificity by subsequent incubations with HAV antigen and 125I-labelled human anti-HAV IgG. The test showed a high sensitivity and specificity for anti-HAV IgM antibodies. No false-positive reactions were observed either in the sera from patients with hepatobiliary disorders other than HAV infection or in the sera containing both rheumatoid factor and anti-HAV IgG antibodies. In acute HAV infections specific IgM antibodies were present already in the first specimens taken within a few days after the onset of jaundice. The persistence of the IgM antibodies was from 4 to 6 months. IgM antibody titers up to 1,000,000 were observed in the acute phase of HAV infection. In routine diagnostic work the titration of the sea was not necessary, since a reliable qualitative result was obtained by testing the sera in a single dilution of 1:100. A similar "reverse" immuno-assay principle may be adaptable for the diagnostic determination of IgM antibodies to different viral and microbial antigens.

  19. Reversed-phase high-performance liquid chromatography of the stable electrophoretic fractions of soil humic acids

    NASA Astrophysics Data System (ADS)

    Trubetskoi, O. A.; Trubetskaya, O. E.

    2015-02-01

    Reversed-phase high-performance liquid chromatography (RP-HPLC) has been used for the hydrophobicity analysis of soil humic acids and their stable electrophoretic fractions A, B, and C + D preliminarily prepared by the combination of gel permeation chromatography on Sephadex with polyacrylamide gel electrophoresis. In two humic acid preparations of different genesis, the electrophoretic fraction A of the larger molecular size was the most hydrophobic (60-73% of the fraction was irreversibly adsorbed on a hydrophobic reversed-phase (RF) column C18), and the fraction C + D of the smallest molecular size was the most hydrophilic. The fraction B of medium size occupied an intermediate position (33-47% of the fraction was irreversibly adsorbed on the column). The use of RP-HPLC allowed for the first time detecting the hydrophobic electrophoretic fraction A of the largest molecular size mainly composed of aliphatic long-chained hydrocarbon, protein, and carbohydrate fragments in soil humic acids. Data on the degree of hydrophobicity and the earlier obtained physicochemical characteristics of stable electrophoretic fractions are discussed in terms of the supramolecular and macromolecular structure of soil humic acids.

  20. Short communication: determination of lactoferrin in Feta cheese whey with reversed-phase high-performance liquid chromatography.

    PubMed

    Tsakali, E; Petrotos, K; Chatzilazarou, A; Stamatopoulos, K; D'Alessandro, A G; Goulas, P; Massouras, T; Van Impe, J F M

    2014-01-01

    In the current paper, a method is introduced to determine lactoferrin in sweet whey using reversed-phase HPLC without any pretreatment of the samples or use of a separation technique. As a starting point, the most common HPLC protocols for acid whey, which included pretreatment of the whey along with a sodium dodecyl sulfate-PAGE step, were tested. By skipping the pretreatment and the separation steps while altering the gradient profile, different chromatographs were obtained that proved to be equally efficient to determine lactoferrin. For this novel 1-step reversed-phase HPLC method, repeatability was very high over a wide range of concentrations (1.88% intraday to 5.89% interday). The limit of detection was 35.46μg/mL [signal:noise ratio (S/N)=3], whereas the limit of quantification was 50.86μg/mL (S/N=10). Omitting the pretreatment step caused a degradation of the column's lifetime (to approximately 2,000 samples). As a result, the lactoferrin elution time changed, but neither the accuracy nor the separation ability of the method was significantly influenced. We observed that this degradation could be easily avoided or detained by centrifuging the samples to remove fat or by extensive cleaning of the column after every 5 samples. PMID:24856983

  1. Determination of hydrophobicity of non-homologous series of anticancer drugs by reversed-phase high-performance liquid chromatography.

    PubMed

    Forgács, E; Cserháti, T

    1995-02-01

    The hydrophobicity and specific hydrophobic surface area of 21 commercial anticancer drugs were determined by reversed-phase high-performance liquid chromatography on an octadecyl-silica column using methanol-water mixtures as eluents. Linear correlations were calculated between the log k' values and the methanol concentration of the eluent, the intercept and slope were considered as the best estimation of the hydrophobicity and specific hydrophobic surface area. The relationship between retention characteristics and physicochemical parameters of drugs was evaluated by multivariate mathematical statistical methods, such as principal component analysis followed by two-dimensional non-linear mapping, varimax rotation and by cluster analysis. Anticancer drugs can be well separated by reversed-phase HPLC. Various multivariate mathematical statistical calculations indicate that the retention of the investigated drugs is mainly governed by hydrophobic and steric parameters. The results suggest that the use of principal component analysis followed by two-dimensional non-linear mapping is superior to cluster analysis for the evaluation of large retention data matrices.

  2. Phase-insensitive storage of coherences by reversible mapping onto long-lived populations

    NASA Astrophysics Data System (ADS)

    Mieth, Simon; Genov, Genko T.; Yatsenko, Leonid P.; Vitanov, Nikolay V.; Halfmann, Thomas

    2016-01-01

    We theoretically develop and experimentally demonstrate a coherence population mapping (CPM) protocol to store atomic coherences in long-lived populations, enabling storage times far beyond the typically very short decoherence times of quantum systems. The amplitude and phase of an atomic coherence is written onto the populations of a three-state system by specifically designed sequences of radiation pulses from two coupling fields. As an important feature, the CPM sequences enable a retrieval efficiency, which is insensitive to the phase of the initial coherence. The information is preserved in every individual atom of the medium, enabling applications in purely homogeneously or inhomogeneously broadened ensembles even when stochastic phase jumps are the main source of decoherence. We experimentally confirm the theoretical predictions by applying CPM for storage of atomic coherences in a doped solid, reaching storage times in the regime of 1 min.

  3. Reverse-phase HPLC of benzylpropionitrile dithiocarbamate complexes for the determination of priority pollutant metals

    SciTech Connect

    Park, Y.J.

    1990-01-01

    A new dithiocarbamate, benzylpropionitrile dithiocarbamate (BPDTC), has been synthesized for use in metal analysis. The HPLC behavior of metal chelates of BPDTC has been investigated for the simultaneous determination of antimony, cadmium, chromium, copper, mercury, nickel, lead, selenium, thallium, and zinc, all of which are on the Environmental Protection Agency's list of priority pollutant metals. Metals are extracted into dichloromethane as BPDTC chelates, and then separated on a C-18 column. Cobalt is added as an internal standard. The effects of pH and of three organic modifiers (methanol, acetonitrile, tetrahydrofuran) of the mobile phase on retention time have been investigated. Addition of dichloromethane to the mobile phase increases solubility and chelate stability, and improves the separation of metal BPDTC complexes. BPDTC is added to the aqueous mobile phase to reduce on-column dissociation of the complexes. Detection limits at 260 nm are in the range of 0.1 to 3 ppb using a 1 liter sample.

  4. Separations of substituted benzenes and polycyclic aromatic hydrocarbons using normal- and reverse-phase high performance liquid chromatography with UiO-66 as the stationary phase.

    PubMed

    Zhao, Wei-Wei; Zhang, Chao-Yan; Yan, Zeng-Guang; Bai, Li-Ping; Wang, Xiayan; Huang, Hongliang; Zhou, You-Ya; Xie, Yabo; Li, Fa-Sheng; Li, Jian-Rong

    2014-11-28

    Metal-organic frameworks (MOFs) have great potential for applications in chromatography due to their highly tailorable porous structures and unique properties. In this work, the stable MOF UiO-66 was evaluated as both a normal-phase (NP-) and a reverse-phase (RP-) stationary phase in the high performance liquid chromatography (HPLC) to separate substituted benzenes (SBs) and polycyclic aromatic hydrocarbons (PAHs). It was found that the mobile phase composition has a significant effect on the HPLC separation. Baseline RP-HPLC separations of xylene isomers; naphthalene and anthracene; naphthalene and chrysene; and naphthalene, fluorene, and chrysene were achieved using MeOH/H2O ratios of 80:20, 75:25, 85:15, and 75:25, respectively, on the UiO-66 column. Similarly, baseline NP-HPLC separations of xylene isomers and ethylbenzene; ethylbenzene, styrene, o-xylene, and m-xylene; and several PAHs were also obtained on the UiO-66 column with different mobile phase compositions. The relative standard deviations (RSDs) of retention time, peak height, peak area, and half peak width for five replicate separations of the tested analytes were within the ranges 0.2-0.4%, 0.2-1.6%, 0.7-3.9%, 0.4-1.1%, respectively. We also evaluated other critical HPLC parameters, including injected sample mass, column temperature, and the thermodynamic characters of both the RP-HPLC and the NP-HPLC separation processes. It was confirmed that the separation of SBs on a UiO-66 column was an exothermic process, controlled by both enthalpy change (ΔH) and entropy change (ΔS). The reverse shape selectivity, size selectivity, stacking effect, and electrostatic force played vital roles in the separations of these analytes. To the best of our knowledge, this method is one of the very few examples of using MOFs as the stationary phase in both NP-HPLC and RP-HPLC. MOF-based stationary phases may thus be applied in the separations and analyses of SBs and PAHs in environmental samples.

  5. Deep sequencing analysis of HIV-1 reverse transcriptase at baseline and time of failure in patients receiving rilpivirine in the phase III studies ECHO and THRIVE.

    PubMed

    Van Eygen, Veerle; Thys, Kim; Van Hove, Carl; Rimsky, Laurence T; De Meyer, Sandra; Aerssens, Jeroen; Picchio, Gaston; Vingerhoets, Johan

    2016-05-01

    Minority variants (1.0-25.0%) were evaluated by deep sequencing (DS) at baseline and virological failure (VF) in a selection of antiretroviral treatment-naïve, HIV-1-infected patients from the rilpivirine ECHO/THRIVE phase III studies. Linkage between frequently emerging resistance-associated mutations (RAMs) was determined. DS (llIumina®) and population sequencing (PS) results were available at baseline for 47 VFs and time of failure for 48 VFs; and at baseline for 49 responders matched for baseline characteristics. Minority mutations were accurately detected at frequencies down to 1.2% of the HIV-1 quasispecies. No baseline minority rilpivirine RAMs were detected in VFs; one responder carried 1.9% F227C. Baseline minority mutations associated with resistance to other non-nucleoside reverse transcriptase inhibitors (NNRTIs) were detected in 8/47 VFs (17.0%) and 7/49 responders (14.3%). Baseline minority nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) RAMs M184V and L210W were each detected in one VF (none in responders). At failure, two patients without NNRTI RAMs by PS carried minority rilpivirine RAMs K101E and/or E138K; and five additional patients carried other minority NNRTI RAMs V90I, V106I, V179I, V189I, and Y188H. Overall at failure, minority NNRTI RAMs and NRTI RAMs were found in 29/48 (60.4%) and 16/48 VFs (33.3%), respectively. Linkage analysis showed that E138K and K101E were usually not observed on the same viral genome. In conclusion, baseline minority rilpivirine RAMs and other NNRTI/NRTI RAMs were uncommon in the rilpivirine arm of the ECHO and THRIVE studies. DS at failure showed emerging NNRTI resistant minority variants in seven rilpivirine VFs who had no detectable NNRTI RAMs by PS. PMID:26412111

  6. Electrically driven reversible insulator-metal phase transition in 1T-TaS2.

    PubMed

    Hollander, Matthew J; Liu, Yu; Lu, Wen-Jian; Li, Li-Jun; Sun, Yu-Ping; Robinson, Joshua A; Datta, Suman

    2015-03-11

    In this work, we demonstrate abrupt, reversible switching of resistance in 1T-TaS2 using dc and pulsed sources, corresponding to an insulator-metal transition between the insulating Mott and equilibrium metallic states. This transition occurs at a constant critical resistivity of 7 mohm-cm regardless of temperature or bias conditions and the transition time is significantly smaller than abrupt transitions by avalanche breakdown in other small gap Mott insulating materials. Furthermore, this critical resistivity corresponds to a carrier density of 4.5 × 10(19) cm(-3), which compares well with the critical carrier density for the commensurate to nearly commensurate charge density wave transition. These results suggest that the transition is facilitated by a carrier driven collapse of the Mott gap in 1T-TaS2, which results in fast (3 ns) switching.

  7. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    SciTech Connect

    Hou, Guangjin E-mail: tpolenov@udel.edu; Lu, Xingyu E-mail: lexvega@comcast.net; Vega, Alexander J. E-mail: lexvega@comcast.net; Polenova, Tatyana E-mail: tpolenov@udel.edu

    2014-09-14

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear {sup 1}H-X (X = {sup 13}C, {sup 15}N, {sup 31}P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the {sup 1}H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the {sup 1}H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from {sup 1}H chemical shift anisotropy, while keeping the {sup 1}H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [{sup 15}N]-N-acetyl-valine and [U-{sup 13}C,{sup 15}N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate {sup 1}H-{sup 15}N dipolar couplings in the context of 3D experiments is presented on U-{sup 13}C,{sup 15}N-enriched dynein light chain protein LC8.

  8. Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hou, Guangjin; Lu, Xingyu; Vega, Alexander J.; Polenova, Tatyana

    2014-09-01

    We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear 1H-X (X = 13C, 15N, 31P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the 1H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the 1H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from 1H chemical shift anisotropy, while keeping the 1H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [15N]-N-acetyl-valine and [U-13C,15N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate 1H-15N dipolar couplings in the context of 3D experiments is presented on U-13C,15N-enriched dynein light chain protein LC8.

  9. Mixed-mode reversed-phase and ion-exchange separations of cationic analytes on polybutadiene-coated zirconia.

    PubMed

    Hu, Yue; Yang, Xiqin; Carr, Peter W

    2002-08-30

    The retention and selectivity of the chromatographic separation of basic (cationic) analytes on a polybutadiene-coated zirconia (PBD-ZrO2) stationary phase have been studied in greater detail than in previous studies. These separations are strongly influenced by the chemistry of the accessible surface of zirconia. In the presence of buffers which contain hard Lewis bases (e.g., phosphate, fluoride, carboxylic acids) zirconia's surface becomes negatively charged due to adsorption of the buffer anion at the hard Lewis acid sites. Consequently, under most conditions (e.g., neutral pH), cationic analytes undergo both hydrophobic and cation-exchange interactions. This mixed-mode retention process generally leads to greater retention factors for cations relative to those on silica-based reversed phases despite the lower surface areas of the zirconia phase, but, more importantly, adsorption of hard Lewis bases can be used to control the chromatographic selectivity for cationic analytes on these zirconia-based stationary phases. In contrast to our prior work, here we show that when mixed-mode retention takes place, both retention and selectivity are easily adjusted by changing the type of hard Lewis base buffer anion, the type of buffer counter-ion (e.g., sodium, potassium, ammonium), the pH, and the ionic strength of the eluent as well as the type and amount of organic modifier. PMID:12236500

  10. First order reversal curve investigation of the hard and soft magnetic phases of annealed CoFeCu nanowire arrays

    NASA Astrophysics Data System (ADS)

    Almasi-Kashi, M.; Ramazani, A.; Golafshan, E.; Arefpour, M.; Jafari-Khamse, E.

    2013-11-01

    (CoFe)1-xCux (x=0.12-0.84) nanowire arrays were ac-pulse electrodeposited into anodic aluminum oxide templates. The electrodeposition was performed in a constant electrolyte while Cu content was controlled by off-time between pulses. Nanowires with 30 nm diameter and the certain lengths with the both bcc-CoFe and fcc-Cu phases were obtained. Magnetization and coercivity of the nanowires decreased with increasing the Cu content. Annealing improved the coercivity and a remarkable increase in magnetization of nanowires with high Cu contents was observed. A two-phase treatment was seen for annealed samples with high Cu contents. First order reversal curves showed a hard magnetic phase with almost constant magnetic properties and coercivity of ~2500 Oe. The results showed that main source of the various magnetic behaviors of the samples may be attributed to increase in soft magnetic phase. A single domain treatment with a narrow interacting field and coercive field distributions was also observed for the annealed samples with high Cu content.

  11. Overload for ionized solutes in reversed-phase high-performance liquid chromatography.

    PubMed

    McCalley, David V

    2006-04-15

    Overloading occurs for submicrogram quantities of ionized solutes particularly when using low ionic strength mobile phases at low pH (e.g., formic acid), even with highly inert silica RP-HPLC columns of normal dimensions. Much higher loads can produce a sharp L-shaped peak with retention above the column void volume, in line with the hypothesis that a small number of high-energy sites fill first and are rapidly overloaded, followed by a much larger number of weaker sites. However, charged acids and bases show identical overloading behavior; overloading is reduced as the mobile-phase ionic strength is increased. These findings raise questions about the physical nature of the strong sites. The rapid overloading of silica and purely polymeric phases could be explained by mutual repulsion of ionic species or their inability to fully penetrate the hydrophobic structure of the phase. However, these alternative hypotheses cannot readily explain the high total saturation capacities obtained using frontal analysis. Ion pairing with trifluoroacetic acid may reduce overload, while the effect is less important for formate or phosphate buffers. A surface layer of acetonitrile is not a prerequisite for rapid overloading, as shown by studies using purely aqueous buffers. PMID:16615761

  12. In drastic reversal, Sweden looks to halt nuclear phase-out

    SciTech Connect

    2009-04-15

    In early February, Sweden's coalition government announced that it would introduce a bill in the parliament in March to halt the nuclear phase-out. The bill would also make it possible to build new nuclear plants. Similar sentiments are appearing elsewhere in Europe.

  13. New reversed-phase/anion-exchange/hydrophilic interaction mixed-mode stationary phase based on dendritic polymer-modified porous silica.

    PubMed

    Li, Yun; Yang, Jiajia; Jin, Jing; Sun, Xiaoli; Wang, Longxing; Chen, Jiping

    2014-04-11

    A novel dendritic polymer-modified silica (DPS) stationary phase was prepared by a divergent synthesis scheme starting from propylamine on silica by consecutive amine-epoxy reactions with 1,4-butanedioldiglycidyl ether and aniline. Both elemental analysis and infrared spectra data shows the successful growth of dendritic polymer on silica particles. The carbon and nitrogen contents increased with an increasing number of reaction cycles and achieved 25.2% and 2.1% (w/w) after 11 reaction cycles. The combination of a phenyl ring with a quaternary ammonium, or a tertiary amine at the branch point along with embedded polar functionalities (including ether and hydroxyl groups) in the branch, generated hydrophobic, electrostatic, as well as hydrophilic interactive domains. Depending on solute structure and mobile phase composition, the DPS stationary phase provided multiple retention mechanisms, including reversed phase (RP), anion-exchange (AEX), and hydrophilic interactions. The RP capability achieved separation of polycyclic aromatic hydrocarbons. Basic, neutral and acidic molecules were well separated under RP/AEX mixed mode. Effective separation of small polar compounds (such as nucleobases and nucleosides) was also obtained under hydrophilic interaction liquid chromatography (HILIC) mode. PMID:24630062

  14. [Determination of alliin and its related substances in garlic using pre-column derivatization and reversed-phase high performance liquid chromatography].

    PubMed

    Yuan, Yaozuo; Hang, Taijun; Ji, Yu; Zhang, Zhengxing

    2008-03-01

    A reversed-phase high performance liquid chromatographic method with pre-column derivatization for the determination of alliin and its related substances, which are the precursors of garlic's active components, was established. Alliin was derivatized with 6-aminoquinolyl-N-hydroxysuccinimicly carbamate (AQC). The reaction of derivatization was very fast and the derivative was stable. The analysis was carried out on a Kromasil C18 column (250 mm x 4.6 mm, 5 microm) with a gradientelution and detection at 248 nm. The mobile ph ase consisted of 0.1% acetamide (0.03% acetic acid) (A) and the mixture of water and acetonitrile (40: 60, v/v) (B), and the flow rate was set at 1.0 mL/min. The linear calibration was found for alliin within the range of 1.171 9 -1 500 microg/mL (r = 0.999 8). The inter-day and intra-day precision were good with relative standard deviation (RSD) less than 1.8% (n = 5). The recovery was 99.1% with the RSD of 1.9%. The limit of detection was 0.15 microg/mL. The method established is accurate, simple and rapid and suitable for the determination of alliin and related substances. PMID:18581860

  15. Identification of hydroxyl radical oxidation products of N-hexanoyl-homoserine lactone by reversed-phase high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

    PubMed

    Cui, Yiling; Frey, Rebecca L; Ferry, John L; Ferguson, P Lee

    2009-04-01

    A reversed-phase high-performance liquid chromatography/electrospray tandem mass spectrometry method was developed for the characterization of hydroxyl radical oxidation products of N-hexanoyl-homoserine lactone (C6-HSL), a member of the N-acylhomoserine lactone (AHL) class of microbial quorum-sensing signaling molecules identified in many Gram-negative strains of bacteria. Six products were identified: four with molecular weight (MW) of 213 and two with MW of 260. The characteristic product ions formed through collision-induced dissociation (CID) provided diagnostic structural information. One of the photolysis products was determined to be N-(3-oxohexanoyl)homoserine lactone (3OC6-HSL), a highly active quorum-sensing signal, by comparison with a reference standard. Three structural isomers with the same mass as 3OC6-HSL were identified as acyl side chain oxidized C6-HSL (keto/enol functionalized) by accurate mass measurement and the structures of these products were proposed from CID spectral interpretation. Two structural isomers formed from concurrent oxidation and nitration of C6-HSL were also observed and their structures were postulated based on CID spectra. In addition to the six hydroxyl radical oxidation products formed from the C6-HSL precursor, five additional compounds generated from combined oxidation and lactonolysis of C6-HSL were identified and structures were postulated.

  16. Monolithic stationary phases with incorporated fumed silica nanoparticles. Part II. Polymethacrylate-based monolithic column with "covalently" incorporated modified octadecyl fumed silica nanoparticles for reversed-phase chromatography.

    PubMed

    Aydoğan, Cemil; El Rassi, Ziad

    2016-05-01

    This study is concerned with the incorporation of surface modified fumed silica nanoparticles (FSNPs) into polymethacrylate based monolithic columns for use in reversed phase chromatography (RPC) of small solutes and proteins. First, FSNPs were modified with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) to yield the "hybrid" methacryloyl fumed silica nanoparticle (MFSNP) monomer. The resulting MFSNP was then mixed with glyceryl monomethacrylate (GMM) and ethylene dimethacrylate (EDMA) in a binary porogenic solvent composed of cyclohexanol and dodecanol, and the in situ copolymerization of MFSNP, GMM and EDMA was performed in a stainless steel column of 4.6 mm i.d. The silanol groups of the hybrid monolith thus obtained were grafted with octadecyl ligands by perfusing the hybrid monolithic column with a solution of 4% w/v of dimethyloctadecylchlorosilane (DODCS) in toluene while the column was maintained at 110°C for 6h (in a heated HPLC oven). One of the originalities of this study was to demonstrate MFSNP as a novel derivatized "hybrid monomer" in making RPC monolithic columns with surface bound octadecyl ligands. In this respect, the RPC behavior of the monolithic column with "covalently" incorporated FNSPs having surface grafted octadecyl ligands was evaluated with alkylbenzenes, aniline derivatives and phenolic compounds. The results showed that the hybrid poly(GMA-EDMA-MFSNP) having surface bound octadecyl ligands exhibited hydrophobic interactions under reversed phase elution conditions. Furthermore, six standard proteins were baseline separated on the column using a 10min linear gradient elution at increasing ACN concentration in the mobile phase at a flow rate of 1.0mL/min using a 10 cm×4.6mm i.d. column. The relative standard deviations (RSDs) for the retention times of the tested solutes were lower than 2.1% and 2.4% under isocratic elution and gradient elution conditions, respectively. PMID:27059396

  17. Monolithic stationary phases with incorporated fumed silica nanoparticles. Part II. Polymethacrylate-based monolithic column with "covalently" incorporated modified octadecyl fumed silica nanoparticles for reversed-phase chromatography.

    PubMed

    Aydoğan, Cemil; El Rassi, Ziad

    2016-05-01

    This study is concerned with the incorporation of surface modified fumed silica nanoparticles (FSNPs) into polymethacrylate based monolithic columns for use in reversed phase chromatography (RPC) of small solutes and proteins. First, FSNPs were modified with 3-(trimethoxysilyl)propylmethacrylate (TMSPM) to yield the "hybrid" methacryloyl fumed silica nanoparticle (MFSNP) monomer. The resulting MFSNP was then mixed with glyceryl monomethacrylate (GMM) and ethylene dimethacrylate (EDMA) in a binary porogenic solvent composed of cyclohexanol and dodecanol, and the in situ copolymerization of MFSNP, GMM and EDMA was performed in a stainless steel column of 4.6 mm i.d. The silanol groups of the hybrid monolith thus obtained were grafted with octadecyl ligands by perfusing the hybrid monolithic column with a solution of 4% w/v of dimethyloctadecylchlorosilane (DODCS) in toluene while the column was maintained at 110°C for 6h (in a heated HPLC oven). One of the originalities of this study was to demonstrate MFSNP as a novel derivatized "hybrid monomer" in making RPC monolithic columns with surface bound octadecyl ligands. In this respect, the RPC behavior of the monolithic column with "covalently" incorporated FNSPs having surface grafted octadecyl ligands was evaluated with alkylbenzenes, aniline derivatives and phenolic compounds. The results showed that the hybrid poly(GMA-EDMA-MFSNP) having surface bound octadecyl ligands exhibited hydrophobic interactions under reversed phase elution conditions. Furthermore, six standard proteins were baseline separated on the column using a 10min linear gradient elution at increasing ACN concentration in the mobile phase at a flow rate of 1.0mL/min using a 10 cm×4.6mm i.d. column. The relative standard deviations (RSDs) for the retention times of the tested solutes were lower than 2.1% and 2.4% under isocratic elution and gradient elution conditions, respectively.

  18. How to select equivalent and complimentary reversed phase liquid chromatography columns from column characterization databases.

    PubMed

    Borges, Endler M

    2014-01-01

    Three RP-LC column characterization protocols [Tanaka et al. (1989), Snyder et al. (PQRI, 2002), and NIST SRM 870 (2000)] were evaluated using both Euclidian distance and Principal Components Analysis to evaluate effectiveness at identifying equivalent columns. These databases utilize specific chromatographic properties such as hydrophobicity, hydrogen bonding, shape/steric selectivity, and ion exchange capacity of stationary phases. The chromatographic parameters of each test were shown to be uncorrelated. Despite this, the three protocols were equally successful in identifying similar and/or dissimilar stationary phases. The veracity of the results has been supported by some real life pharmaceutical separations. The use of Principal Component Analysis to identify similar/dissimilar phases appears to have some limitations in terms of loss of information. In contrast, the use of Euclidian distances is a much more convenient and reliable approach. The use of auto scaled data is favoured over the use of weighted factors as the former data transformation is less affected by the addition or removal of columns from the database. The use of these free databases and their corresponding software tools shown to be valid for identifying similar columns with equivalent chromatographic selectivity and retention as a "backup column". In addition, dissimilar columns with complimentary chromatographic selectivity can be identified for method development screening strategies.

  19. In situ observation of quasimelting of diamond and reversible graphite-diamond phase transformations.

    PubMed

    Huang, J Y

    2007-08-01

    Because of technique difficulties in achieving the extreme high-pressure and high-temperature (HPHT) simultaneously, direct observation of the structures of carbon at extreme HPHT conditions has not been possible. Banhart and Ajayan discovered remarkably that carbon onions can act as nanoscopic pressure cells to generate high pressures. By heating carbon onions to approximately 700 degrees C and under electron beam irradiation, the graphite-to-diamond transformation was observed in situ by transmission electron microscopy (TEM). However, the highest achievable temperature in a TEM heating holder is less than 1000 degrees C. Here we report that, by using carbon nanotubes as heaters and carbon onions as high-pressure cells, temperatures higher than 2000 degrees C and pressures higher than 40 GPa were achieved simultaneously in carbon onions. At such HPHT conditions and facilitated by electron beam irradiation, the diamond formed in the carbon onion cores frequently changed its shape, size, orientation, and internal structure and moved like a fluid, implying that it was in a quasimelting state. The fluctuation between the solid phase of diamond and the fluid/amorphous phase of diamond-like carbon, and the changes of the shape, size, and orientation of the solid diamond, were attributed to the dynamic crystallization of diamond crystal from the quasimolten state and the dynamic graphite-diamond phase transformations. Our discovery offers unprecedented opportunities to studying the nanostructures of carbon at extreme conditions in situ and at an atomic scale.

  20. Instrument Parameters Controlling Retention Precision in Gradient Elution Reversed-Phase Liquid Chromatography

    PubMed Central

    Beyaz, Ayse; Fan, Wenzhe; Carr, Peter W.; Schellinger, Adam P.

    2014-01-01

    The precision of retention time in RPLC is important for compound identification, for setting peak integration time windows and in fundamental studies of retention. In this work, we studied the effect of temperature (T), initial (ϕ0) and final mobile phase (ϕf)composition, gradient time (tG), and flow rate (F) on the retention time precision under gradient elution conditions for various types of low MW solutes. We determined the retention factor in pure water (k′w) and the solute-dependent solvent strength (S) parameters of Snyder's linear solvent strength theory (LSST) as a function of temperature for three different groups of solutes. The effect of small changes in the chromatographic variables (T, ϕ0, ϕf, tG and F) by use of the LSST gradient retention equation were estimated. Peaks at different positions in the chromatogram have different sensitivities to changes in these instrument parameters. In general, absolute fluctuations in retention time are larger at longer gradient times. Drugs showed less sensitivity to changes in temperature compared to relatively less polar solutes, non-ionogenic solutes. Surprisingly we observed that fluctuations in temperature, mobile phase composition and flow rate had less effect on retention time under gradient conditions as compared to isocratic conditions. Overall temperature and the initial mobile phase composition are the more important variables affecting retention reproducibility in gradient elution chromatography. PMID:25459648

  1. Improved quality-by-design compliant methodology for method development in reversed-phase liquid chromatography.

    PubMed

    Debrus, Benjamin; Guillarme, Davy; Rudaz, Serge

    2013-10-01

    A complete strategy dedicated to quality-by-design (QbD) compliant method development using design of experiments (DOE), multiple linear regressions responses modelling and Monte Carlo simulations for error propagation was evaluated for liquid chromatography (LC). The proposed approach includes four main steps: (i) the initial screening of column chemistry, mobile phase pH and organic modifier, (ii) the selectivity optimization through changes in gradient time and mobile phase temperature, (iii) the adaptation of column geometry to reach sufficient resolution, and (iv) the robust resolution optimization and identification of the method design space. This procedure was employed to obtain a complex chromatographic separation of 15 antipsychotic basic drugs, widely prescribed. To fully automate and expedite the QbD method development procedure, short columns packed with sub-2 μm particles were employed, together with a UHPLC system possessing columns and solvents selection valves. Through this example, the possibilities of the proposed QbD method development workflow were exposed and the different steps of the automated strategy were critically discussed. A baseline separation of the mixture of antipsychotic drugs was achieved with an analysis time of less than 15 min and the robustness of the method was demonstrated simultaneously with the method development phase.

  2. Magnetic phase transitions and magnetization reversal in MnRuP

    NASA Astrophysics Data System (ADS)

    Lampen-Kelley, P.; Mandrus, D.

    The ternary phosphide MnRuP is an incommensurate antiferromagnetic metal crystallizing in the non-centrosymmetric Fe2P-type crystal structure. Below the Neel transition at 250 K, MnRuP exhibits hysteretic anomalies in resistivity and magnetic susceptibility curves as the propagation vectors of the spiral spin structure change discontinuously across T1 = 180 K and T2 = 100 K. Temperature-dependent X-ray diffraction data indicate that the first-order spin reorientation occurs in the absence of a structural transition. A strong magnetization reversal (MR) effect is observed upon cooling the system through TN in moderate dc magnetic fields. Positive magnetization is recovered on further cooling through T1 and maintained in subsequent warming curves. The field dependence and training of the MR effect in MnRuP will be discussed in terms of the underlying magnetic structures and compared to anomalous MR observed in vanadate systems. This work is supported by the Gordon and Betty Moore Foundation GBMF4416 and U.S. DOE, Office of Science, BES, Materials Science and Engineering Division.

  3. Reversal of the late phase of spike frequency adaptation in cat spinal motoneurons during fictive locomotion

    PubMed Central

    Brownstone, Robert M.; Krawitz, Sherry; Jordan, Larry M.

    2016-01-01

    In spinal motoneurons, late spike frequency adaptation (SFA) is defined as the slowing of the firing rate over tens of seconds and can be seen during sustained or intermittent current injection. Although the function of late SFA is not known, it may result in a decrease in force production over time, or muscle fatigue. Because locomotion can persist for long periods of time without fatigue, late SFA was studied using intracellular recordings from adult cat motoneurons during fictive locomotion. Of eight lumbar motoneurons studied, all showed late adaptation during control conditions, but none demonstrated late adaptation during locomotor activity. The most consistent properties that correlated with the presence or absence of late SFA were those related to availability of fast, inactivating sodium channels, particularly action potential rate of rise. Evidence of the reversal of late SFA during locomotion was present for several minutes following locomotor trials, consistent with the suggestion that SFA is modulated through slow metabotropic pathways. The abolition of late adaptation in spinal motoneurons during fictive locomotion is an example of a state-dependent change in the “intrinsic” properties of mammalian motoneurons. This change contributes to increased excitability of motoneurons during locomotion and results in robust firing during sustained locomotion. PMID:21177992

  4. Reversal of the late phase of spike frequency adaptation in cat spinal motoneurons during fictive locomotion.

    PubMed

    Brownstone, Robert M; Krawitz, Sherry; Jordan, Larry M

    2011-03-01

    In spinal motoneurons, late spike frequency adaptation (SFA) is defined as the slowing of the firing rate over tens of seconds and can be seen during sustained or intermittent current injection. Although the function of late SFA is not known, it may result in a decrease in force production over time, or muscle fatigue. Because locomotion can persist for long periods of time without fatigue, late SFA was studied using intracellular recordings from adult cat motoneurons during fictive locomotion. Of eight lumbar motoneurons studied, all showed late adaptation during control conditions, but none demonstrated late adaptation during locomotor activity. The most consistent properties that correlated with the presence or absence of late SFA were those related to availability of fast, inactivating sodium channels, particularly action potential rate of rise. Evidence of the reversal of late SFA during locomotion was present for several minutes following locomotor trials, consistent with the suggestion that SFA is modulated through slow metabotropic pathways. The abolition of late adaptation in spinal motoneurons during fictive locomotion is an example of a state-dependent change in the "intrinsic" properties of mammalian motoneurons. This change contributes to increased excitability of motoneurons during locomotion and results in robust firing during sustained locomotion. PMID:21177992

  5. Green synthesis and reversible dispersion of a giant fluorescent cluster in solid and liquid phase.

    PubMed

    Ganguly, Mainak; Pal, Jaya; Das, Sancharini; Mondal, Chanchal; Pal, Anjali; Negishi, Yuichi; Pal, Tarasankar

    2013-08-27

    A water-soluble highly fluorescent silver cluster on Au(I) surface has been synthesized with green chemistry under sunlight. The evolution of the silver cluster is synergistic, demanding gold and glutathione. The fluorescent Au(I)core-Ag(0)shell particles are huge in size and at the same time they are robust. That is why they become a deliverable fluorescing solid upon drying. Again, the giant particles run into common water miscible solvents. As a result, the fluorescence intensity increases to a great extent without any alteration of emission maxima. In this respect, acetone has been found to be the best-suited solvent. To have a universal applicability of the fluorescent clusters, the particles in the water pool of a reverse micelle have been prepared to transfer the particles into different water immiscible solvents. The comparatively lower fluorescence intensity of the particles has been ascribed to a space confinement effect. Finally, giant-cluster-impregnated yellow-orange fluorescent polymer film and fluorescent cotton wool, as well as paper substrate, have been prepared. The antibacterial activity of the fluorescent particle has also been tested involving modified cotton wool and paper substrate for Gram-negative and -positive Escherichia coli and Staphylococcus aureus, respectively.

  6. Determination of UV active inorganic anions in potable and high salinity water by ion pair reversed phase liquid chromatography.

    PubMed

    Sadiq Khan, Sadaf; Riaz, M

    2014-05-01

    Reversed phase column was dynamically modified into anion exchange column using various types of tetraalkylammonium salts as ion pair reagents (IPRs) for the separation and quantification of toxic anions such as nitrite, bromate, bromide and nitrate in potable and high salinity water. Various chromatographic parameters such as types and concentration of IPRs, concentration of organic modifier, phosphate buffer and mobile phase pH were optimized for the base-line separation of anions. The lowest detection limits (LDLs) were 0.2 for nitrate and nitrite, 0.6 µg ml(-1)for bromate and bromide respectively for potable water samples. NaCl and Na₂SO₄ were incorporated in the mobile phase for the analysis of high salinity water samples to minimize matrix interferences. This has resulted in change in elution order of anions, better tolerance of matrix anions such as chloride and sulphate. The developed method was successfully utilized for analysis of anions in potable, high salinity and sea water samples.

  7. The origin of nanoscale phase stability reversals in titanium oxide polymorphs

    SciTech Connect

    Hummer, Daniel R.; Kubicki, James D.; Heaney, Peter; Kent, Paul R; Post, Jeffrey E.

    2009-01-01

    We have monitored the hydrothermal crystallization of titania nanoparticles by in situ X-ray diffraction, and our refined average structures cannot account for the stabilization of nano-anatase relative to nano-rutile. However, quantum mechanical calculations on model nanoparticles do generate lower surface energies for anatase than for rutile. These total surface energies derived not from 2-dimensional surface structure alone, as previously thought, but contained large contributions from defects associated with edges and corners of nanocrystals. This study quantifies for the first time the critical role of edge and vertex energies in determining the relative phase stabilities of polymorphic nanoparticles.

  8. Molecular-level characterization of crude oil compounds combining reversed-phase high-performance liquid chromatography with off-line high-resolution mass spectrometry

    USGS Publications Warehouse

    Sim, Arum; Cho, Yunju; Kim, Daae; Witt, Matthias; Birdwell, Justin E.; Kim, Byung Ju; Kim, Sunghwan

    2014-01-01

    A reversed-phase separation technique was developed in a previous study (Loegel et al., 2012) and successfully applied to the de-asphalted fraction of crude oil. However, to the best of our knowledge, the molecular-level characterization of oil fractions obtained by reversed-phase high-performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (MS) has not yet been reported. A detailed characterization of the oil fractions prepared by reversed-phase HPLC was performed in this study. HPLC fractionation was carried out on conventional crude oil and an oil shale pyrolysate. The analyses of the fractions showed that the carbon number of alkyl chains and the double bond equivalent (DBE) value were the major factors determining elution order. The compounds with larger DBE (presumably more condensed aromatic structures) and smaller carbon number (presumably compounds with short side chains) were eluted earlier but those compounds with lower DBE values (presumably less aromatic structures) and higher carbon number (presumably compounds with longer alkyl chains) eluted later in the chromatograms. This separation behavior is in good agreement with that expected from the principles of reversed-phase separation. The data presented in this study show that reversed-phase chromatography is effective in separating crude oil compounds and can be combined with ultrahigh-resolution MS data to better understand natural oils and oil shale pyrolysates.

  9. High-repetition-rate dual-signal intracavity optical parametric generator based on periodically-phase-reversal PPMgLN

    NASA Astrophysics Data System (ADS)

    Ji, Feng; Yao, Jianquan; Zheng, Fanghua; Li, Enbang; Zhang, Tieli; Zhao, Pu; Wang, Peng; Zhang, Baigang

    2007-10-01

    A high-repetition-rate dual-signal intracavity optical parametric generator (IOPG) inside a diode-end-pumped acousto-optically (AO) Q-switched Nd:YVO4 laser is presented. The nonlinear material is a periodically-phase-reversal periodically poled MgO-doped lithium niobate (ppr-PPMgLN). At an incident diode pump power of 6.1 W and a Q-switch repetition rate of 20 kHz, an average dual-signal output power of 0.44 W is achieved. The dual-signal wavelengths of 1477 and 1491 nm are obtained at a crystal temperature of 40 °C. The measurements of the beam quality factor of 1.4 and the pulse duration of 77 ns show good spatial and temporal overlaps for the dual-signal radiation.

  10. Reversed-phase high-performance liquid chromatography method with fluorescence detection to screen nitric oxide synthases inhibitors.

    PubMed

    Maccallini, Cristina; Di Matteo, Mauro; Ammazzalorso, Alessandra; D'Angelo, Alessandra; De Filippis, Barbara; Di Silvestre, Sara; Fantacuzzi, Marialuigia; Giampietro, Letizia; Pandolfi, Assunta; Amoroso, Rosa

    2014-06-01

    Nitric oxide synthase (NOS) inhibitors are potential drug candidates due to the critical role of an excessive production of nitric oxide in a range of diseases. At present, the radiometric detection of L-[(3)H]-citrulline produced from L-[(3)H]-arginine during the enzymatic reaction is one of the most accepted methods to assess the in vitro activity of NOS inhibitors. Here we report a fast, easy, and cheap reversed-phase high-performance liquid chromatography method with fluorescence detection, based on the precolumn derivatization of L-citrulline with o-phthaldialdehyde/N-acetyl cysteine, for the in vitro screening of NOS inhibitors. To evaluate enzyme inhibition by the developed method, N-[3-(aminomethyl)benzyl]acetamidine, a potent and selective inhibitor of inducible NOS, was used as a test compound. The half maximal inhibitory concentration obtained was comparable to that derived by the well-established radiometric assay. PMID:24687974

  11. Comparison of preparative reversed phase liquid chromatography and countercurrent chromatography for the kilogram scale purification of crude spinetoram insecticide.

    PubMed

    DeAmicis, Carl; Edwards, Neil A; Giles, Michael B; Harris, Guy H; Hewitson, Peter; Janaway, Lee; Ignatova, Svetlana

    2011-09-01

    Reversed phase HPLC (RP-HPLC) and high performance countercurrent chromatography (HPCCC) were compared for the pilot scale purification of two semi-synthetic spinosyns, spinetoram-J and spinetoram-L, the major components of the commercial insecticide spinetoram. Two, independently performed, 1 kg, purification campaigns were compared. Each method resulted in the isolation of both components at a purity of >97% and yields for spinetoram-J and spinetoram-L of >93% and ≥ 63% of theoretical, respectively. The HPCCC process produced a 2-fold higher throughput and consumed approximately 70% less solvent than preparative scale RP-HPLC, the volume of product containing fractions from HPCCC amounted to 7% of that produced by HPLC and so required much less post-run processing.

  12. Determination of the triacylglycerol composition of coffee beans by reverse-phase high-performance liquid chromatography.

    PubMed

    Jham, Gulab N; Nikolova-Damyavova, Boryana; Viera, Mirtes; Natalino, Ricardo; Rodrigues, Augusto Cezar

    2003-01-01

    Reverse-phase HPLC with refractive index and light scattering detectors in isocratic and gradient elution modes, respectively, was applied for the separation of the major triacylglycerols (TAG) in coffee lipids. Twelve TAG species could be identified and determined using a linear gradient of acetonitrile in dichloromethane: dichloroethane. The quantitative evaluation was based on the relative area percentages derived directly from a data-station. The procedure was applied to determine the TAG composition of three types of coffee beans harvested in two coffee producing areas in Brazil and dried by two commonly used procedures. No significant differences in the TAG compositions due to the type, origin and drying procedure were found. PMID:14516004

  13. REVERSED-PHASE HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY STUDY OF LIPOPHILICITY OF IMIDAZO[2,1-F]THEOPHYLLINE DERIVATIVES.

    PubMed

    Zagórska, Agnieszka; Czopek, Anna; Pełka, Karolina; Bajda, Marek; Stanisz-Wallis, Krystyna; Pawłowski, Maciej

    2015-01-01

    The present study is a part of our physicochemical and pharmacological studies in a group of tricyclic theophylline derivatives. The investigated compounds exhibit different pharmacological profiles in comparison to theophylline and have been tested as potential antidepressant and/or antipsychotic agents. The differences in pharmacological action between theophylline and their tricyclic derivatives can be explained by their various physicochemical properties, especially lipophilicity. The chromatographic behavior of twenty three derivatives of imidazo[2,1-ƒ]theophylline was investigated, using reversed-phase high performance liquid chromatography (RP-HPLC) method. Moreover, partition coefficients and selected pharmacokinetic parameters were calculated computationally. Principal component analysis (PCA) method was used to establish the relationship between obtained experimental and computational parameters.

  14. Discovery of lung cancer pathways using reverse phase protein microarray and prior-knowledge based Bayesian networks.

    PubMed

    Kim, Dong-Chul; Yang, Chin-Rang; Wang, Xiaoyu; Zhang, Baoju; Wu, Xiaorong; Gao, Jean

    2011-01-01

    The goal of this paper is to infer the signaling pathway related to lung cancer using Reverse Phase Protein Microarray (RPPM), which provides information on post-translational phosphorylation events. The computational inferring of pathways is obtained by performing Bayesian network in combination with prior knowledge from Protein-Protein Interaction (PPI). A clustering based Linear Programming Relaxation is developed for the searching of optimal networks. The PPI prior knowledge is incorporated into a new scoring function definition based on minimum description length (MDL). In the experiment, we first evaluate the algorithm performance with synthetic networks and associated data. Then we show our signaling network inference for lung cancer using RPPM data. Through the study, we expect to derive new signalling pathways and insight on protein regulatory relationships, which are yet to be known for lung cancer study.

  15. [Chiral separation of five beta-blockers using di-n-hexyl L-tartrate-boric acid complex as mobile phase additive by reversed-phase liquid chromatography].

    PubMed

    Yang, Juan; Wang, Lijuan; Guo, Qiaoling; Yang, Gengliang

    2012-03-01

    A reversed-phase high performance liquid chromatographic (HPLC) method using the di-n-hexyl L-tartrate-boric acid complex as a chiral mobile phase additive was developed for the enantioseparation of five beta-blockers including propranolol, esmolol, metoprolol, bisoprolol and sotalol. In order to obtain a better enantioseparation, the influences of concentrations of di-n-butyl L-tartrate and boric acid, the type, concentration and pH of the buffer, methanol content as well as the molecular structure of analytes were extensively investigated. The separation of the analytes was performed on a Venusil MP-C18 column (250 mm x 4.6 mm, 5 microm). The mobile phase was 15 mmol/L ammonium acetate-methanol containing 60 mmol/L boric acid, 70 mmol/L di-n-hexyl L-tartrate (pH 6.00). The volume ratios of 15 mmol/L ammonium acetate to methanol were 20: 80 for propranolol, esmolol, metoprolol, bisoprolol and 30: 70 for sotalol. The flow rate was 0.5 mL/min and the detection wavelength was set at 214 nm. Under the optimized conditions, baseline enantioseparation was obtained separately for the five pairs of analytes.

  16. Common Protein Biomarkers Assessed by Reverse Phase Protein Arrays Show Considerable Intratumoral Heterogeneity in Breast Cancer Tissues

    PubMed Central

    Buchner, Theresa; Thulke, Sabrina; Wolff, Claudia; Höfler, Heinz; Becker, Karl-Friedrich; Avril, Stefanie

    2012-01-01

    Proteins are used as prognostic and predictive biomarkers in breast cancer. However, the variability of protein expression within the same tumor is not well studied. The aim of this study was to assess intratumoral heterogeneity in protein expression levels by reverse-phase-protein-arrays (RPPA) (i) within primary breast cancers and (ii) between axillary lymph node metastases from the same patient. Protein was extracted from 106 paraffin-embedded samples from 15 large (≥3 cm) primary invasive breast cancers, including different zones within the primary tumor (peripheral, intermediate, central) as well as 2–5 axillary lymph node metastases in 8 cases. Expression of 35 proteins including 15 phosphorylated proteins representing the HER2, EGFR, and uPA/PAI-1 signaling pathways was assessed using reverse-phase-protein-arrays. All 35 proteins showed considerable intratumoral heterogeneity within primary breast cancers with a mean coefficient of variation (CV) of 31% (range 22–43%). There were no significant differences between phosphorylated (CV 32%) and non-phosphorylated proteins (CV 31%) and in the extent of intratumoral heterogeneity within a defined tumor zone (CV 28%, range18–38%) or between different tumor zones (CV 24%, range 17–38%). Lymph node metastases from the same patient showed a similar heterogeneity in protein expression (CV 27%, range 18–34%). In comparison, the variation amongst different patients was higher in primary tumors (CV 51%, range 29–98%) and lymph node metastases (CV 65%, range 40–146%). Several proteins showed significant differential expression between different tumor stages, grades, histological subtypes and hormone receptor status. Commonly used protein biomarkers of breast cancer, including proteins from HER2, uPA/PAI-1 and EGFR signaling pathways showed higher than previously reported intratumoral heterogeneity of expression levels both within primary breast cancers and between lymph node metastases from the same

  17. Common protein biomarkers assessed by reverse phase protein arrays show considerable intratumoral heterogeneity in breast cancer tissues.

    PubMed

    Malinowsky, Katharina; Raychaudhuri, Mithu; Buchner, Theresa; Thulke, Sabrina; Wolff, Claudia; Höfler, Heinz; Becker, Karl-Friedrich; Avril, Stefanie

    2012-01-01

    Proteins are used as prognostic and predictive biomarkers in breast cancer. However, the variability of protein expression within the same tumor is not well studied. The aim of this study was to assess intratumoral heterogeneity in protein expression levels by reverse-phase-protein-arrays (RPPA) (i) within primary breast cancers and (ii) between axillary lymph node metastases from the same patient. Protein was extracted from 106 paraffin-embedded samples from 15 large (≥3 cm) primary invasive breast cancers, including different zones within the primary tumor (peripheral, intermediate, central) as well as 2-5 axillary lymph node metastases in 8 cases. Expression of 35 proteins including 15 phosphorylated proteins representing the HER2, EGFR, and uPA/PAI-1 signaling pathways was assessed using reverse-phase-protein-arrays. All 35 proteins showed considerable intratumoral heterogeneity within primary breast cancers with a mean coefficient of variation (CV) of 31% (range 22-43%). There were no significant differences between phosphorylated (CV 32%) and non-phosphorylated proteins (CV 31%) and in the extent of intratumoral heterogeneity within a defined tumor zone (CV 28%, range 18-38%) or between different tumor zones (CV 24%, range 17-38%). Lymph node metastases from the same patient showed a similar heterogeneity in protein expression (CV 27%, range 18-34%). In comparison, the variation amongst different patients was higher in primary tumors (CV 51%, range 29-98%) and lymph node metastases (CV 65%, range 40-146%). Several proteins showed significant differential expression between different tumor stages, grades, histological subtypes and hormone receptor status. Commonly used protein biomarkers of breast cancer, including proteins from HER2, uPA/PAI-1 and EGFR signaling pathways showed higher than previously reported intratumoral heterogeneity of expression levels both within primary breast cancers and between lymph node metastases from the same patient. Assessment

  18. Coupled reversed-phase and ion chromatographic system for the simultaneous identification of inorganic and organic explosives.

    PubMed

    Tyrrell, Eadaoin; Dicinoski, Greg W; Hilder, Emily F; Shellie, Robert A; Breadmore, Michael C; Pohl, Christopher A; Haddad, Paul R

    2011-05-20

    There are many methods available to detect and positively identify either organic or inorganic explosives separately, however no one method has been developed which can detect both types of explosive species simultaneously from a single sample. In this work, a unique coupled-chromatographic system is reported for the simultaneous determination of both organic and inorganic explosive species and is used for pre-blast analysis/identification purposes. This novel approach is based on the combination of reversed-phase high performance liquid chromatography and ion chromatography which allows trace levels of organic and inorganic explosives to be determined simultaneously from a single sample. Using this procedure, a 20 min reversed-phase separation of organic explosives is coupled to a 16 min ion-exchange separation of anions present in inorganic explosives, providing a complete pre-blast analysis/identification system for the separation and detection of a complex mixture containing organic and/or inorganic explosive species. The total analysis time, including sufficient column re-equilibration between runs, was <25 min using the coupled system. By this method, the minimum resolution for the organic separation was 1.16 between nitroglycerin and tetryl and the detection limits ranged from 0.31 mg L(-1) for cyclotetramethylene tetranitramine (HMX) and 1.54 mg L(-1) for pentaerythrite tetranitrate (PETN), while the minimum resolution for the inorganic separation was 0.99 between azide and nitrate, and the detection limits ranged from 7.70 μg L(-1) for fluoride and 159.50 μg L(-1) for benzoate.

  19. Development and validation of a simple and isocratic reversed-phase HPLC method for the determination of rilpivirine from tablets, nanoparticles and HeLa cell lysates

    PubMed Central

    Date, Abhijit A.; Shibata, Annemarie; Bruck, Patrick; Destache, Christopher J.

    2015-01-01

    In the present investigation, a simple and isocratic HPLC-UV method was developed and validated for determination of rilpivirine (RPV) from dosage forms (tablets and nanoparticles) and biological matrices like HeLa cell lysates. The separation and analysis of RPV was carried out under isocratic conditions using (a) a Gemini reversed-phase C18 column (5 μm; 4.6 × 150 mm) maintained at 35°C, (b) a mobile phase consisting of a mixture of acetonitrile and 25 mM potassium dihydrogen phosphate (in the ratio 50:50 v/v) at a flow rate of 0.6 mL/min and (c) atazanavir as an internal standard. The total run time was 17 min and the analysis of RPV and internal standard was carried out at 290 nm. The method was found to be linear (r2 value > 0.998), specific, accurate and precise over the concentration range of 0.025–2 μg/mL. The lower limit of quantification was 0.025 μg/mL, the limit of detection was 0.008 μg/mL and the recovery of RPV was >90%. The stability of the RPV analytical method was confirmed at various conditions such as room temperature (24 h), −20°C (7 days), three freeze–thaw cycles and storage in an autosampler (4°C for 48 h). The method was successfully applied for the determination of RPV from conventional dosage forms like tablets, from polymeric nanoparticles and from biological matrices like HeLa cell lysates. PMID:25298145

  20. Determination of the four major surfactant classes in cleaning products by reversed-phase liquid chromatography using serially connected UV and evaporative light-scattering detection.

    PubMed

    Escrig-Doménech, Aarón; Simó-Alfonso, Ernesto F; Ramis-Ramos, Guillermo

    2016-08-17

    A method for the simultaneous determination of the most frequently used surfactant families -linear alkyl benzenesulphonates (LAS), alkyl ether sulphates (AES), fatty alcohol ethoxylates (FAE) and oleins (soaps, fatty acid salts) - in cleaning products, has been developed. The common reversed phase octyl (C8), pentafluorophenyl and biphenyl columns were not capable of separating the anionic LAS and AES classes; however, since only LAS absorbs in the UV, these two classes were independently quantified using a C8 column and serially connected UV and ELSD detection. The best compromise to resolve the four surfactant classes and the oligomers within the classes was achieved with a C8 column and an ACN/water gradient. To enhance retention of the anionic surfactants, ammonium acetate, as an ion-pairing agent compatible with ELSD detection, was used. Also, to shift the olein peaks with respect to that of the FAE oligomers, acetic acid was used. In the optimized method, modulation of the mobile phase, using ammonium acetate during elution of LAS and AES, and acetic acid after elution of LAS and AES, was provided. Quantitation of the overlapped LAS and AES classes was achieved by using the UV detector to quantitate LAS and the ELSD to determine AES by difference. Accuracy in the determination of AES was achieved by using a quadratic model, and by correcting the predicted AES concentration according to the LAS concentration previously established using the UV chromatogram. Another approach also leading to accurate predictions of the AES concentration was to increase the AES concentrations in the samples by adding a standard solution. In the samples reinforced with AES, correction of the predicted AES concentration was not required. FAE and olein were quantified using also quadratic calibration. PMID:27286775

  1. A reversal phase arrest uncoupling the bone formation and resorption contributes to the bone loss in glucocorticoid treated ovariectomised aged sheep.

    PubMed

    Andreasen, Christina M; Ding, Ming; Overgaard, Søren; Bollen, Peter; Andersen, Thomas L

    2015-06-01

    Large animals as sheep are often used as models for human osteoporosis. Our aim was therefore to determine how glucocorticoid treatment of ovariectomised sheep affects the cancellous bone, determining the cellular events within the bone remodelling process that contributes to their bone loss. Twenty female sheep were assigned for two groups; an untreated control group and an ovariectomised group treated with glucocorticoids (0.6 mg/kg/day, 5 times weekly) for 7 months. At 7 months the glucocorticoid-treated ovariectomised sheep showed a significant change in the bone microstructure revealed by a decreased trabecular bone volume and thickness compared to the control sheep. The treatment led to a temporary elevation of the bone resorption marker CTX (c-terminal collagen telopeptide), while the bone formation marker osteocalcin remained suppressed all 7 months. Histomorphometrically, the treated sheep had a complete absence of osteoid surfaces, and a 5-fold increase in the extent of eroded/reversal surfaces after 7 months. Most of these reversal surfaces were actually arrested reversal surfaces, defined as reversal surfaces without the presence of neighbouring osteoid surfaces or osteoclasts, which is classically observed next to active reversal surfaces. As in humans, these arrested reversal surfaces had compared to active reversal surfaces a reduced canopy coverage, a significantly decreased cell density, and a decreased immunoreactivity for the osteoblastic markers osterix, runx2 and smooth muscle actin in the mononuclear reversal cells colonising the surfaces. In conclusion, glucocorticoid treatment of ovariectomised sheep induced a significant bone loss, caused by an arrest of the reversal phase, resulting in an uncoupling of the bone formation and resorption during the reversal phase, as recently demonstrated in postmenopausal women with glucocorticoid-induced osteoporosis. This supports the relevance of the sheep model to the pathophysiology of glucocorticoid

  2. Dynamic phase transition phenomena and magnetization reversal process in uniaxial ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Yüksel, Yusuf

    2015-09-01

    By utilizing the Monte Carlo simulation technique with Metropolis algorithm, we have studied the dynamic phase transition properties such as dynamic hysteresis loops and frequency dispersion of their area in the presence of externally applied oscillating magnetic fields. Particular attention has been paid on the variation of the hysteresis loop area (HLA) curves and their maximal behavior at different temperature regimes. In order to understand the physical mechanism behind the maximum lossy point observed in HLA curves, time series of instantaneous magnetization, as well as micromagnetic domain structures have been provided. Most of the qualitative aspects of the results reported in the present work are shown to be not model-specific type but common phenomenon observed in dynamic magnetic systems.

  3. Panoramic infrared-imaging spectroradiometer model with reverse phase-modulated beam broadcasting.

    PubMed

    Carrieri, A H

    1997-03-20

    The optical design of a passive remote sensor, a panoramic spectroradiometer (PANSPEC), and its computer-simulated image performance are presented. PANSPEC monitors the surrounding infrared environment for chemical clouds, detecting a presence once absorption or emission spectra characteristic of the chemical species are resolved. PANSPEC broadcasts chemical presence and cloud heading when equipped with a laser transmitter that projects a polarized laser beam source with phase encryption back through the optical system into object space. Various merit functions were programmed and accessed during computer optimization runs for shaping and positioning of the instrument's semishell entrance window, collector, collimator, interferometer, and imager. The result is a balanced near-diffraction-limited circular image, 6.3 mm across with 10-line pairs/mm spatial resolution at 50% modulation, and an f/2.3 working speed.

  4. Determination of lipophilicity of chlorinated alicyclic compounds by reversed-phase high performance liquid chromatography

    SciTech Connect

    Liu, J.; Coats, J.R. . Dept. of Entomology); Chambers, J.E. . Coll. of Veterinary Medicine)

    1994-01-01

    A RP-HPLC procedure has been developed for measuring the capacity factor (k[prime]) of a series of chlorinated alicyclic compounds. The chromatographic behavior measured on a 4.5 mm i.d. [times] 3.3 cm C-18 column with methanol/water as the mobile phase was related to the volume fraction of methanol ([phi]). A linear relationship was found between log k[prime] and [phi], showing the correlation coefficient [lambda] > 0.99, for each of the 15 chlorinated alicyclic compounds tested. The log k[sub w], the capacity factor obtained by extrapolation of the retention data from binary effluents to 100% water, was chosen as a measure of the solute lipophilicity. Since log k[sub w] is considered as a valuable index of the lipophilicity of a compound, the determined values will be used for the quantitative structure-activity relationship studies of the chlorinated alicyclic compounds.

  5. Diagonal reverse-phase chromatography applications in peptide-centric proteomics: ahead of catalogue-omics?

    PubMed

    Gevaert, Kris; Van Damme, Petra; Martens, Lennart; Vandekerckhove, Joël

    2005-10-01

    Diagonal electrophoresis/chromatography was described 40 years ago and was used to isolate specific sets of peptides from simple peptide mixtures such as protease digests of purified proteins. Recently, we have adapted the core technology of diagonal chromatography so that the technique can be used in so-called gel-free, peptide-centric proteome studies. Here we review the different procedures we have developed over the past few years, sorting of methionyl, cysteinyl, amino terminal, and phosphorylated peptides. We illustrate the power of the technique, termed COFRADIC (combined fractional diagonal chromatography), in the case of a peptide-centric analysis of a sputum sol phase sample of a patient suffering from chronic obstructive pulmonary disease (COPD). We were able to identify an unexpectedly high number of intracellular proteins next to known biomarkers.

  6. Reverse phase liquid chromatographic determination of aspartame in beverages and beverage mixes.

    PubMed

    Webb, N G; Beckman, D D

    1984-01-01

    A method is described for determining the artificial sweetener aspartame in beverages and beverage mixes by liquid chromatography. Aspartame is separated on a microC18 column, using a mobile phase of acetic acid, water, and isopropyl alcohol at pH 3.0 and UV detection at 254 nm. Beverages are filtered through 0.45 micron filters and injected directly into the chromatograph. Aspartame is eluted in approximately 7 min. Detection of aspartame is confirmed by a UV scan of the trapped peak. Aspartame is quantitated in the presence of other beverage additives such as saccharin, caffeine, sodium benzoate, artificial colors, and artificial flavors. Results are presented for spiked soda beverages, beverages from fruit-flavored mixes, instant tea, reconstituted presweetened drink mixes, and a powdered tabletop sweetener.

  7. Reverse-phase liquid chromatographic determination of benzoic and sorbic acids in foods.

    PubMed

    Bui, L V; Cooper, C

    1987-01-01

    An isocratic liquid chromatographic (LC) technique is described for the determination of benzoic acid and sorbic acid in foods such as beverages, fruits, seafood, vegetables, sauces, and dairy, bakery, and confectionery products. A C18 column is used with methanol-phosphate buffer (5 + 95) as mobile phase and 4-hydroxyacetanilide or 3,5-dinitrobenzoic acid as internal standard. Sample preparation is simple, rapid, and produces a sample extract that has a minimum effect on the column performance and life. Specificity of the method was checked against common food additives such as L-ascorbic acid, caffeine, artificial sweeteners (saccharin, cyclamate, aspartame), antioxidants (BHT, BHA) and artificial colors. Also described are 2 procedures for confirmation of the preservatives, using either redox reaction of sorbic acid with potassium permanganate or gas chromatography/mass spectrometry. Mean recoveries of 90-105% were obtained with a precision of 1-6% and a detection limit of 20 mg/kg for the 2 preservatives.

  8. Crowding-Induced Mixing Behavior of Lipid Bilayers: Examination of Mixing Energy, Phase, Packing Geometry, and Reversibility.

    PubMed

    Zeno, Wade F; Rystov, Alice; Sasaki, Darryl Y; Risbud, Subhash H; Longo, Marjorie L

    2016-05-10

    In an effort to develop a general thermodynamic model from first-principles to describe the mixing behavior of lipid membranes, we examined lipid mixing induced by targeted binding of small (Green Fluorescent Protein (GFP)) and large (nanolipoprotein particles (NLPs)) structures to specific phases of phase-separated lipid bilayers. Phases were targeted by incorporation of phase-partitioning iminodiacetic acid (IDA)-functionalized lipids into ternary lipid mixtures consisting of DPPC, DOPC, and cholesterol. GFP and NLPs, containing histidine tags, bound the IDA portion of these lipids via a metal, Cu(2+), chelating mechanism. In giant unilamellar vesicles (GUVs), GFP and NLPs bound to the Lo domains of bilayers containing DPIDA, and bound to the Ld region of bilayers containing DOIDA. At sufficiently large concentrations of DPIDA or DOIDA, lipid mixing was induced by bound GFP and NLPs. The validity of the thermodynamic model was confirmed when it was found that the statistical mixing distribution as a function of crowding energy for smaller GFP and larger NLPs collapsed to the same trend line for each GUV composition. Moreover, results of this analysis show that the free energy of mixing for a ternary lipid bilayer consisting of DOPC, DPPC, and cholesterol varied from 7.9 × 10(-22) to 1.5 × 10(-20) J/lipid at the compositions observed, decreasing as the relative cholesterol concentration was increased. It was discovered that there appears to be a maximum packing density, and associated maximum crowding pressure, of the NLPs, suggestive of circular packing. A similarity in mixing induced by NLP1 and NLP3 despite large difference in projected areas was analytically consistent with monovalent (one histidine tag) versus divalent (two histidine tags) surface interactions, respectively. In addition to GUVs, binding and induced mixing behavior of NLPs was also observed on planar, supported lipid multibilayers. The mixing process was reversible, with Lo domains

  9. Crowding-induced mixing behavior of lipid bilayers: Examination of mixing energy, phase, packing geometry, and reversibility

    DOE PAGES

    Zeno, Wade F.; Rystov, Alice; Sasaki, Darryl Y.; Risbud, Subhash H.; Longo, Marjorie L.

    2016-04-20

    In an effort to develop a general thermodynamic model from first-principles to describe the mixing behavior of lipid membranes, we examined lipid mixing induced by targeted binding of small (Green Fluorescent Protein (GFP)) and large (nanolipoprotein particles (NLPs)) structures to specific phases of phase-separated lipid bilayers. Phases were targeted by incorporation of phase-partitioning iminodiacetic acid (IDA)-functionalized lipids into ternary lipid mixtures consisting of DPPC, DOPC, and cholesterol. GFP and NLPs, containing histidine tags, bound the IDA portion of these lipids via a metal, Cu2+, chelating mechanism. In giant unilamellar vesicles (GUVs), GFP and NLPs bound to the Lo domains ofmore » bilayers containing DPIDA, and bound to the Ld region of bilayers containing DOIDA. At sufficiently large concentrations of DPIDA or DOIDA, lipid mixing was induced by bound GFP and NLPs. The validity of the thermodynamic model was confirmed when it was found that the statistical mixing distribution as a function of crowding energy for smaller GFP and larger NLPs collapsed to the same trend line for each GUV composition. Moreover, results of this analysis show that the free energy of mixing for a ternary lipid bilayer consisting of DOPC, DPPC, and cholesterol varied from 7.9 × 10–22 to 1.5 × 10–20 J/lipid at the compositions observed, decreasing as the relative cholesterol concentration was increased. It was discovered that there appears to be a maximum packing density, and associated maximum crowding pressure, of the NLPs, suggestive of circular packing. A similarity in mixing induced by NLP1 and NLP3 despite large difference in projected areas was analytically consistent with monovalent (one histidine tag) versus divalent (two histidine tags) surface interactions, respectively. In addition to GUVs, binding and induced mixing behavior of NLPs was also observed on planar, supported lipid multibilayers. Furthermore, the mixing process was reversible, with

  10. Retention prediction of highly polar ionizable solutes under gradient conditions on a mixed-mode reversed-phase and weak anion-exchange stationary phase.

    PubMed

    Balkatzopoulou, P; Fasoula, S; Gika, H; Nikitas, P; Pappa-Louisi, A

    2015-05-29

    In the present work the retention of three highly polar and ionizable solutes - uric acid, nicotinic acid and ascorbic acid - was investigated on a mixed-mode reversed-phase and weak anion-exchange (RP/WAX) stationary phase in buffered aqueous acetonitrile (ACN) mobile phases. A U-shaped retention behavior was observed for all solutes with respect to the eluent organic modifier content studied in a range of 5-95% (v/v). This retention behavior clearly demonstrates the presence of a HILIC-type retention mechanism at ACN-rich hydro-organic eluents and an RP-like retention at aqueous-rich hydro-organic eluents. Hence, this column should be promising for application under both RP and HILIC gradient elution modes. For this reason, a series of programmed elution runs were carried out with increasing (RP) and decreasing (HILIC) organic solvent concentration in the mobile phase. This dual gradient process was successfully modeled by two retention models exhibiting a quadratic or a cubic dependence of the logarithm of the solute retention factor (lnk) upon the organic modifier volume fraction (φ). It was found that both models produced by gradient retention data allow the prediction of solute retention times for both types of programmed elution on the mixed-mode column. Four, in the case of the quadratic model, or five, in the case of the cubic model, initial HILIC- and RP-type gradient runs gave satisfactory retention predictions of any similar kind elution program, even with different flow rate, with an overall error of only 2.5 or 1.7%, respectively.

  11. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

    PubMed

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-12-01

    Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number.

  12. Numerical Simulation of Natural Convection of a Nanofluid in an Inclined Heated Enclosure Using Two-Phase Lattice Boltzmann Method: Accurate Effects of Thermophoresis and Brownian Forces.

    PubMed

    Ahmed, Mahmoud; Eslamian, Morteza

    2015-12-01

    Laminar natural convection in differentially heated (β = 0°, where β is the inclination angle), inclined (β = 30° and 60°), and bottom-heated (β = 90°) square enclosures filled with a nanofluid is investigated, using a two-phase lattice Boltzmann simulation approach. The effects of the inclination angle on Nu number and convection heat transfer coefficient are studied. The effects of thermophoresis and Brownian forces which create a relative drift or slip velocity between the particles and the base fluid are included in the simulation. The effect of thermophoresis is considered using an accurate and quantitative formula proposed by the authors. Some of the existing results on natural convection are erroneous due to using wrong thermophoresis models or simply ignoring the effect. Here we show that thermophoresis has a considerable effect on heat transfer augmentation in laminar natural convection. Our non-homogenous modeling approach shows that heat transfer in nanofluids is a function of the inclination angle and Ra number. It also reveals some details of flow behavior which cannot be captured by single-phase models. The minimum heat transfer rate is associated with β = 90° (bottom-heated) and the maximum heat transfer rate occurs in an inclination angle which varies with the Ra number. PMID:26183389

  13. Determination of caffeine, theobromine, and theophylline in standard reference material 2384, baking chocolate, using reversed-phase liquid chromatography.

    PubMed

    Thomas, Jeanice Brown; Yen, James H; Schantz, Michele M; Porter, Barbara J; Sharpless, Katherine E

    2004-06-01

    A rapid and selective isocratic reversed-phase liquid chromatographic method has been developed at the National Institute of Standards and Technology to simultaneously measure caffeine, theobromine, and theophylline in a food-matrix standard reference material (SRM) 2384, Baking Chocolate. The method uses isocratic elution with a mobile phase composition (volume fractions) of 10% acetronitrile/90% water (pH adjusted to 2.5 using acetic acid) at a flow rate of 1.5 mL/min with ultraviolet absorbance detection (274 nm). Total elution time for these analytes is less than 15 min. Concentration levels of caffeine, theobromine, and theophylline were measured in single 1-g samples taken from each of eight bars of chocolate over an eight-day period. Samples were defatted with hexane, and beta-hydroxyethyltheophylline was added as the internal standard. The repeatability for the caffeine, theobromine, and theophylline measurements was 5.1, 2.3, and 1.9%, respectively. The limit of quantitation for all analytes was <100 ng/mL. The measurements from this method were used in the value-assignment of caffeine, theobromine, and theophylline in SRM 2384.

  14. Rapid Determination of Bile Acids in Bile from Various Mammals by Reversed-Phase Ultra-Fast Liquid Chromatography.

    PubMed

    Si, Gu Leng Ri; Yao, Peng; Shi, Luwen

    2015-08-01

    A valid and efficient reversed-phase ultra-fast liquid chromatography method was developed for the simultaneous determination of 13 bile acids in the bile of three mammal species, including rat, pig and human gallstone patients. Chromatographic separation was performed with a Shim-pack XR-ODS column, and the mobile phase consisted of acetonitrile and potassium phosphate buffer (pH 2.6) at a flow rate of 0.5 mL min(-1). The linear detection range of most bile acids ranged from 2 to 600 ng µL(-1) with a good correlation coefficient (>0.9995). The precision of each bile acid was <1.8% for intraday and <4.8% for interday. All bile acids were separated in 15 min with satisfactory resolution, and the total analysis time was 18 min, including equilibration. The method was successfully applied in rapid screening of bile samples from the three mammals. Significant metabolic frameworks of bile acids among various species were observed, whereas considerable quantitative variations in both inter- and intraspecies were also observed, especially for gallstone patients. Our results suggest that detecting the change of bile acid profiles could be applied for the diagnosis of gallstone disease. PMID:25520305

  15. Investigation of noise properties in grating-based x-ray phase tomography with reverse projection method

    NASA Astrophysics Data System (ADS)

    Bao, Yuan; Wang, Yan; Gao, Kun; Wang, Zhi-Li; Zhu, Pei-Ping; Wu, Zi-Yu

    2015-10-01

    The relationship between noise variance and spatial resolution in grating-based x-ray phase computed tomography (PCT) imaging is investigated with reverse projection extraction method, and the noise variances of the reconstructed absorption coefficient and refractive index decrement are compared. For the differential phase contrast method, the noise variance in the differential projection images follows the same inverse-square law with spatial resolution as in conventional absorption-based x-ray imaging projections. However, both theoretical analysis and simulations demonstrate that in PCT the noise variance of the reconstructed refractive index decrement scales with spatial resolution follows an inverse linear relationship at fixed slice thickness, while the noise variance of the reconstructed absorption coefficient conforms with the inverse cubic law. The results indicate that, for the same noise variance level, PCT imaging may enable higher spatial resolution than conventional absorption computed tomography (ACT), while ACT benefits more from degraded spatial resolution. This could be a useful guidance in imaging the inner structure of the sample in higher spatial resolution. Project supported by the National Basic Research Program of China (Grant No. 2012CB825800), the Science Fund for Creative Research Groups, the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant Nos. KJCX2-YW-N42 and Y4545320Y2), the National Natural Science Foundation of China (Grant Nos. 11475170, 11205157, 11305173, 11205189, 11375225, 11321503, 11179004, and U1332109).

  16. 3D printed titanium micro-bore columns containing polymer monoliths for reversed-phase liquid chromatography.

    PubMed

    Gupta, Vipul; Talebi, Mohammad; Deverell, Jeremy; Sandron, Sara; Nesterenko, Pavel N; Heery, Brendan; Thompson, Fletcher; Beirne, Stephen; Wallace, Gordon G; Paull, Brett

    2016-03-01

    The potential of 3D selective laser melting (SLM) technology to produce compact, temperature and pressure stable titanium alloy chromatographic columns is explored. A micro bore channel (0.9 mm I.D. × 600 mm long) was produced within a 5 × 30 × 30 mm titanium alloy (Ti-6Al-4V) cuboid, in form of a double handed spiral. A poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) (BuMA-co-EDMA) monolithic stationary phase was thermally polymerised within the channel for application in reversed-phase high-performance liquid chromatography. The prepared monolithic column was applied to the liquid chromatographic separation of intact proteins and peptides. Peak capacities of 69-76 (for 6-8 proteins respectively) were observed during isothermal separation of proteins at 44 °C which were further increased to 73-77 using a thermal step gradient with programmed temperature from 60 °C to 35 °C using an in-house built direct-contact heater/cooler platform based upon matching sized Peltier thermoelectric modules. Rapid temperature gradients were possible due to direct-contact between the planar metal column and the Peltier module, and the high thermal conductivity of the titanium column as compared to a similar stainless steel printed column. The separation of peptides released from a digestion of E.coli was also achieved in less than 35 min with ca. 40 distinguishable peaks at 210 nm. PMID:26873472

  17. Comprehensive analysis of pharmaceutical products using simultaneous mixed-mode (ion-exchange/reversed-phase) and hydrophilic interaction liquid chromatography.

    PubMed

    Kazarian, Artaches A; Nesterenko, Pavel N; Soisungnoen, Phimpha; Burakham, Rodjana; Srijaranai, Supalax; Paull, Brett

    2014-08-01

    Liquid chromatographic assays were developed using a mixed-mode column coupled in sequence with a hydrophilic interaction liquid chromatography column to allow the simultaneous comprehensive analysis of inorganic/organic anions and cations, active pharmaceutical ingredients, and excipients (carbohydrates). The approach utilized dual sample injection and valve-mediated column switching and was based upon a single high-performance liquid chromatography gradient pump. The separation consisted of three distinct sequential separation mechanisms, namely, (i) ion-exchange, (ii) mixed-mode interactions under an applied dual gradient (reversed-phase/ion-exchange), and (iii) hydrophilic interaction chromatography. Upon first injection, the Scherzo SS C18 column (Imtakt) provided resolution of inorganic anions and cations under isocratic conditions, followed by a dual organic/salt gradient to elute active pharmaceutical ingredients and their respective organic counterions and potential degradants. At the top of the mixed-mode gradient (high acetonitrile content), the mobile phase flow was switched to a preconditioned hydrophilic interaction liquid chromatography column, and the standard/sample was reinjected for the separation of hydrophilic carbohydrates, some of which are commonly known excipients in drug formulations. The approach afforded reproducible separation and resolution of up to 23 chemically diverse solutes in a single run. The method was applied to investigate the composition of commercial cough syrups (Robitussin®), allowing resolution and determination of inorganic ions, active pharmaceutical ingredients, excipients, and numerous well-resolved unknown peaks. PMID:24890905

  18. 3D printed titanium micro-bore columns containing polymer monoliths for reversed-phase liquid chromatography.

    PubMed

    Gupta, Vipul; Talebi, Mohammad; Deverell, Jeremy; Sandron, Sara; Nesterenko, Pavel N; Heery, Brendan; Thompson, Fletcher; Beirne, Stephen; Wallace, Gordon G; Paull, Brett

    2016-03-01

    The potential of 3D selective laser melting (SLM) technology to produce compact, temperature and pressure stable titanium alloy chromatographic columns is explored. A micro bore channel (0.9 mm I.D. × 600 mm long) was produced within a 5 × 30 × 30 mm titanium alloy (Ti-6Al-4V) cuboid, in form of a double handed spiral. A poly(butyl methacrylate-co-ethyleneglycoldimethacrylate) (BuMA-co-EDMA) monolithic stationary phase was thermally polymerised within the channel for application in reversed-phase high-performance liquid chromatography. The prepared monolithic column was applied to the liquid chromatographic separation of intact proteins and peptides. Peak capacities of 69-76 (for 6-8 proteins respectively) were observed during isothermal separation of proteins at 44 °C which were further increased to 73-77 using a thermal step gradient with programmed temperature from 60 °C to 35 °C using an in-house built direct-contact heater/cooler platform based upon matching sized Peltier thermoelectric modules. Rapid temperature gradients were possible due to direct-contact between the planar metal column and the Peltier module, and the high thermal conductivity of the titanium column as compared to a similar stainless steel printed column. The separation of peptides released from a digestion of E.coli was also achieved in less than 35 min with ca. 40 distinguishable peaks at 210 nm.

  19. [Determination of arsanilic acid and sulfanilic acid as adulterant in feed additives by reversed-phase high performance liquid chromatography].

    PubMed

    Xu, Jinping; He, Heng; Xu, Mengyi; Qu, Yanhua

    2010-02-01

    A reversed-phase high performance liquid chromatographic (RP-HPLC) method was established for the determination of arsanilic acid and sulfanilic acid as adulterant in the feed additives. The separation was carried out on a Waters Bondapak C18 column, and methanol-water (pH 2.9 adjusted by 0.01 mol/L phosphoric acid) (1 : 4, v/v) was used as the mobile phase with a flow rate of 1.0 mL/min. A diode array detector was used at 244 nm as the detection wavelength. Arsanilic acid and sulfanilic acid were separated within 3 min. The linear ranges all were 5 - 200 mg/L and the detection limits (S/N = 3) were 0.20 and 0.15 mg/L for arsanilic acid and sulfanilic acid, respectively. This method is simple and rapid, and suitable for the simultaneous determination of arsanilic acid and sulfanilic acid in feed additives.

  20. [A reversed-phase high performance liquid chromatographic method for the determination of pinoresinol diglucopyranoside in Eucommia Ulmoides Oliv].

    PubMed

    Qi, X; Zhang, S

    1998-03-01

    A reversed-phase high performance liquid chromatographic method for the determination of (+)-pinoresinol-di-O-beta-D-glucopyranoside in the bark of Eucommia Ulmoides was established. The air-dried bark of E. Ulmoides was ground into powder and extracted continuously with methanol. The extract was evaporated under reduced pressure, then suspended in water. This suspension being subjected to column chromatography was eluted successively with water, 30%, 50% and 90% aqueous solution of ethanol. The 30% EtOH eluate was concentrated and then injected into HPLC system. The conditions of HPLC were: YWG-C18 column (250 mm x 4.6 mm i.d. 10 microns); 28%(V/V) methanol mobile phase and UV detector at 232 nm. The calibration curve was linear in the range of 0.068 microgram-0.68 microgram of(+)-pinoresinol-di-O-beta-D-glucopyranoside with correlation coefficient of 0.9999. The coefficient of variation and average recovery were 0.50%-0.74% (n = 5) and 99.22% (n = 3) respectively.

  1. Reversible optical switching of highly confined phonon-polaritons with an ultrathin phase-change material.

    PubMed

    Li, Peining; Yang, Xiaosheng; Maß, Tobias W W; Hanss, Julian; Lewin, Martin; Michel, Ann-Katrin U; Wuttig, Matthias; Taubner, Thomas

    2016-08-01

    Surface phonon-polaritons (SPhPs), collective excitations of photons coupled with phonons in polar crystals, enable strong light-matter interaction and numerous infrared nanophotonic applications. However, as the lattice vibrations are determined by the crystal structure, the dynamical control of SPhPs remains challenging. Here, we realize the all-optical, non-volatile, and reversible switching of SPhPs by controlling the structural phase of a phase-change material (PCM) employed as a switchable dielectric environment. We experimentally demonstrate optical switching of an ultrathin PCM film (down to 7 nm, <λ/1,200) with single laser pulses and detect ultra-confined SPhPs (polariton wavevector kp > 70k0, k0 = 2π/λ) in quartz. Our proof of concept allows the preparation of all-dielectric, rewritable SPhP resonators without the need for complex fabrication methods. With optimized materials and parallelized optical addressing we foresee application potential for switchable infrared nanophotonic elements, for example, imaging elements such as superlenses and hyperlenses, as well as reconfigurable metasurfaces and sensors. PMID:27213955

  2. Rapid determination of alpha tocopherol in olive oil adulterated with sunflower oil by reversed phase high-performance liquid chromatography.

    PubMed

    Bakre, S M; Gadmale, D K; Toche, R B; Gaikwad, V B

    2015-05-01

    A new method is developed to determine the presence of sunflower oil in olive oil. α-tocopherol is selected as discriminating parameter for detecting sunflower oil adulterant in olive oil. Admixtures of olive oil and sunflower oil (5 %, 10 %, 15 % and 20 % sunflower oil in olive oil) are prepared. These admixtures are analysed by reversed phase high pressure liquid chromatography coupled with fluorescence detector. The sample preparation does not require saponification or addition of antioxidant. The chromatographic system consists of a C18 column with methanol: acetonitrile (50:50) mobile phase. Fluorescence detector excitation wavelength is set at 290 nm and emission wavelength is set at 330 nm. The α tocopherol concentration increases linearly in olive oil adulterated with sunflower oil. The method is simple, selective, sensitive and is precise (RSD = 2.65 %) for α tocopherol. The present method can precisely detect 5 % sunflower oil in olive oil. PMID:25892814

  3. High resolution reversed phase analysis of recombinant monoclonal antibodies by ultra-high pressure liquid chromatography column coupling.

    PubMed

    Fekete, Szabolcs; Dong, Michael W; Zhang, Taylor; Guillarme, Davy

    2013-09-01

    Monoclonal antibodies (mAbs) represent one of the fastest growing areas of new drug development. However, their analytical characterization is complex and generally requires an array of orthogonal analytical techniques. Reversed phase liquid chromatography is a valuable strategy due to its high resolving power and straightforward compatibility to mass spectrometry. The present study demonstrates that high peak capacity can be attained with intact mAb of ~150 kDa, reduced mAb fragments of ~25-50 kDa and also digested mAb generating numerous peptides of ~0.5-3 kDa. Several long columns packed with fully porous wide-pore sub-2 μm particles were coupled in series to evaluate the effect of column length on peak capacity. By using three columns of 150 mm length, a mobile phase temperature of 80 °C and a gradient time of around 20 min, peak capacities of 117 and 128 were obtained for a commercial intact mAb and its reduced mAb fragments, respectively. On the other hand, when peptide mapping was performed at 50 °C, with a gradient time of 270 min and a column length of 450 mm, a peak capacity of more than 700 was achieved.

  4. [Synthesis of porous spherical silicon oxynitride material and evaluation of its properties in reversed-phase chromatographic separation].

    PubMed

    Zhong, Hongmin; Zhang, Hua; Wan, Huihui

    2013-04-01

    Silica has been widely used as HPLC column packing material. However, the fact that base can attack the silanol and dissolve the silica embarrasses the utilization of silica stationary phase in high pH mobile phases (pH >8). In our previous research, the use of porous spherical silicon oxynitride (sph-SiON) material from high temperature nitridation of silica microspheres as stationary phase for HPLC has been explored, and the sph-SiON is stable to alkaline mobile phases and demonstrates excellent separation of a variety of polar compounds in hydrophilic interaction liquid chromatography (HILIC) mode. Herein, the degree of nitridation was studied as a function of temperature of nitridation at 750-1 050 degrees C, yielding the silicon oxynitride with 0.40%-12.0% (mass fraction) nitrogen from elemental analysis. At the temperature of 1 050 degrees C, the nitrogen content increased from 12.0% to 24.5% with the nitridation time increasing from 20 h to 120 h. The sph-SiON is stable when disposed in different pH aqueous solutions for one week. The sph-SiON material can be modified to give hydrophobic surface through the reaction of surface Si-NHx with dimethyloctadecylchlorosilane. Elemental analysis and 13C cross-polarization magic-angle spinning (CP/MAS) NMR spectrum of C18-sph-SiON prove the integration of C18 alkyl groups attached onto the sph-SiON surface. The chromatographic evaluation of C18-sph-SiON in reversed-phase separation mode was performed with alkylbenzenes as hydrophobic probes. Three alkylbenzene compounds can be separated and retained well on C18-sph-SiON even in the mobile phase of methanol/H2O (70/30, v/v) with 78 507 plates/m, and an excellent tailing factor (0.95) can be obtained for ethylbenzene. In comparison with C18-SiO2, C18-sph-SiON shows distinct differences with respect to different classes of analytes, i. e. neutral analyte naphthalene, acidic analyte ibuprofen, and basic analyte amitriptyline.

  5. Two-step ion-exchange chromatographic purification combined with reversed-phase chromatography to isolate C-peptide for mass spectrometric analysis.

    PubMed

    Kabytaev, Kuanysh; Durairaj, Anita; Shin, Dmitriy; Rohlfing, Curt L; Connolly, Shawn; Little, Randie R; Stoyanov, Alexander V

    2016-02-01

    A liquid chromatography with mass spectrometry on-line platform that includes the orthogonal techniques of ion exchange and reversed phase chromatography is applied for C-peptide analysis. Additional improvement is achieved by the subsequent application of cation- and anion-exchange purification steps that allow for isolating components that have their isoelectric points in a narrow pH range before final reversed-phase mass spectrometry analysis. The utility of this approach for isolating fractions in the desired "pI window" for profiling complex mixtures is discussed.

  6. Determination of azide impurity in sartans using reversed-phase HPLC with UV detection.

    PubMed

    Gričar, Maja; Andrenšek, Samo

    2016-06-01

    A simple and robust, gradient HPLC method was developed for determination of azide ppm (μgg(-1)) levels in different sartans (irbesartan, candesartan, valsartan). The sartan was dissolved in 0.1M NaOH. Then pH was adjusted to 4.5 with 20% H3PO4 followed by dilution with water. Precipitated API was removed by filtration using 0.45μm membrane PVDF (Polyvinylidene Fluoride) membrane filter, and supernatant was analyzed by gradient elution HPLC at room temperature with Hydro RP HPLC 250×4.6mm, 4μm column and UV detection at 205nm. The best sensitivity was achieved by UV detection cell with 60mm optical path length: LOD 0.17μgg(-1) and LOQ 0.84μgg(-1) for azide. The USP requirement for maximum azide content in irbesartan is 10μgg(-1). The analytical method was validated as per International Conference on Harmonization (ICH) guidelines with respect to system precision, intraday precision (repeatability), intermediate precision (ruggedness), linearity, quantitation limit, detection limit, accuracy, standard and sample solution stability, robustness and selectivity/specificity. The method was linear in the range from LOQ (0.84μgg(-1)) to 101μgg(-1) of azide. The correlation coefficient was 0.9999 and bias on y-axis for 84μgg(-1) test concentration was 0.33%. The accuracy of the method was established based on the recovery obtained between 94.0% and 103.0% for azide. Standard and sample solutions were stable for at least 48h at room temperature and in refrigerator. The method was found to be robust for variation in column temperature (±5°C) and mobile phase flow rate (±0.2mLmin(-1)) and selective for anions such as bromide, nitrate, nitrite, formate and acetate. PMID:26999319

  7. Proanthocyanidins in wild sea buckthorn (Hippophaë rhamnoides) berries analyzed by reversed-phase, normal-phase, and hydrophilic interaction liquid chromatography with UV and MS detection.

    PubMed

    Kallio, Heikki; Yang, Wei; Liu, Pengzhan; Yang, Baoru

    2014-08-01

    A rapid and sensitive method for profiling of proanthocyanidins (PAs) of sea buckthorn (Hippophaë rhamnoides) berries was established based on aqueous, acidified acetone extraction. The extract was purified by Sephadex column chromatography and analyzed using reversed-phase, normal-phase, and hydrophilic interaction liquid chromatography (HILIC). Negative ion electrospray ionization mass spectrometry (ESI-MS) in single ion recording (SIR) and full scan modes combined with UV detection were used to define the combinations and ratios of PA oligomer classes. PAs with degree of polymerization from 2 to 11 were detected by HILIC-ESI-MS. Quantification of dimeric, trimeric, and tetrameric PAs was carried out with ESI-MS-SIR, and their molar proportions were 40, 40, and 20%, respectively. Only B-type PAs were found, and (epi)gallocatechins were the main monomeric units. More than 60 combinations of (epi)catechins and (epi)gallocatechins of proanthocyanidin dimers and trimers were found. A majority of the PAs were shown to be higher polymers based on the HILIC-UV analysis.

  8. Separation and characterization of bufadienolides in toad skin using two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography coupled with mass spectrometry.

    PubMed

    Zhang, Yun; Jin, Hongli; Li, Xiaolong; Zhao, Jianqiang; Guo, Xiujie; Wang, Jixia; Guo, Zhimou; Zhang, Xiuli; Tao, Yanduo; Liu, Yanfang; Chen, Deliang; Liang, Xinmiao

    2016-07-15

    Bufadienolides possess various bioactivities especially antitumor. Due to the high structural diversity, the separation of bufadienolides often suffers from coelution problem on conventional RP columns. In this work, an off-line two-dimensional normal-phase liquid chromatography×reversed-phase liquid chromatography (2D-NPLC×RPLC) method was developed to separate and characterize bufadienolides in toad skin. Several RP and NP columns were evaluated with five reference bufadienlides. The XUnion C18 and XAmide columns exhibited superior chromatographic performances for bufadienlide separation, and were selected in RPLC and NPLC, respectively. RPLC was used in the second-dimension for the good compatibility with MS, while NPLC was adopted in the first-dimension. The orthogonality of the 2D-NPLC×RPLC system was investigated by the geometric approach using fifteen bufadienolide mixtures. The result was 49.6%, demonstrating reasonable orthogonality of this 2D-LC system. By combining the 2D-LC system with MS, 64 bufadienlides including 33 minor ones and 11 pairs of isomers in toad skin were identified. This off-line 2D-NPLC×RPLC allowed to solve the coelution problem of bufadienlides in one-dimension RPLC, and thus facilitated the identification significantly.

  9. Separation of peptides and intact proteins by electrostatic repulsion reversed phase liquid chromatography.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2014-12-29

    A new brand of BEH-C18 hybrid particles chemically bonded to a leash carrying an amine group permits the implementation of electrostatic repulsive interactions chromatography. Using columns packed with this material, the influence of the concentration of positive charges bonded to the BEH-C18 surface on the overloaded band profiles of a few positively charged peptides and proteins was investigated in the gradient elution mode. Three columns packed with endcapped BEH-C18 particles bonded with three different surface-charge densities (LOW, MEDIUM and HIGH) were used and compared with those provided by a column packed with non-doped, endcapped BEH-C18 particles. The surface concentrations of fixed charges in the LOW, MEDIUM and HIGH columns were estimated at 0.029, 0.050, and 0.064μmol/m(2), for example, about two orders of magnitude smaller than the surface density of bonded C18 chains (2.1μmol/m(2)). Three different mobile phase additives (0.1% v/v of trifluoro-acetic, phosphoric, and formic acid) were used to optimize the purification levels of proteins under different loading conditions. The weak ion-pairing ions (formate and phosphate) generate smaller retention but broader, more fronting band profiles than those eluted with a stronger ion-pairing ion (trifluoroactate). This effect is worse in the presence of fixed charges at the surface of the BEH-C18 particles. This was explained by an enhanced anti-Langmuirian adsorption behavior of the charged proteins in the presence of fixed surface charges. As the protein concentration increases in the bulk, so does the internal ionic strength, the electrostatic repulsive interactions weaken, and retention increases. Band fronting is mostly eliminated by replacing weak ion-pairing acids with TFA with which the adsorption isotherm remains weakly langmuirian. Faster but still complete gradient separation of insulin and myoglobin were achieved with the HIGH column than with the reference neutral column, despite a measurable

  10. Comparison of chromatographic band profiles obtained under microwave irradiated and non-irradiated reversed-phase liquid chromatography column

    SciTech Connect

    Galinada, Wilmer; Guiochon, Georges A

    2005-08-01

    The possible influence of the application of microwave energy to a reversed-phase liquid chromatography column on the mass transfer kinetics and the thermodynamics of equilibrium between mobile and stationary phases was examined. Chromatograms of propylbenzene and phenol were recorded under the same experimental conditions, on the same column, successively irradiated and not. The effect of microwave irradiation on the mass transfer kinetics was determined by measuring the second moment of small pulses of propylbenzene in a 70:30 (v/v) solution of methanol in water and microwave outputs of 15 and 30 W. The effect of microwave irradiation on the equilibrium thermodynamics was determined by measuring the elution time of breakthrough curves of phenol at high concentrations in a 20:80 (v/v) solution of methanol and water and microwave outputs of 15, 50, and 150 W. A qualitative comparison of the profiles of the propylbenzene peaks obtained with and without irradiation suggests that this irradiation affects significantly the peak shapes. However, a qualitative comparison of the profiles of the breakthrough curves of phenol obtained with and without irradiation suggests that this irradiation has no significant effect on their shapes. The peak sharpening observed may be due to an increase in the diffusivity, resulting from the dielectric polarization under microwave irradiation. This effect is directly related to an increase of the rate of mass transfers in the column. In contrast, the similarity of the overloaded band profiles at high concentrations suggests that the equilibrium thermodynamics is unaffected by microwave irradiation. This may be explained by the transparence of the stationary phase to microwaves at 2.45 GHz. The column temperature was measured at the column outlet under irradiation powers of 15, 30, 50, and 150 W. It increases with increasing power, the corresponding effluent temperatures being 25 {+-} 1, 30 {+-} 1, 35 {+-} 1, and 45 {+-} 1 C, respectively.

  11. Comparison of chromatographic band profiles obtained under microwave irradiated and non-irradiated reversed-phase liquid chromatography column.

    PubMed

    Galinada, Wilmer A; Guiochon, Georges

    2005-10-28

    The possible influence of the application of microwave energy to a reversed-phase liquid chromatography column on the mass transfer kinetics and the thermodynamics of equilibrium between mobile and stationary phases was examined. Chromatograms of propylbenzene and phenol were recorded under the same experimental conditions, on the same column, successively irradiated and not. The effect of microwave irradiation on the mass transfer kinetics was determined by measuring the second moment of small pulses of propylbenzene in a 70:30 (v/v) solution of methanol in water and microwave outputs of 15 and 30 W. The effect of microwave irradiation on the equilibrium thermodynamics was determined by measuring the elution time of breakthrough curves of phenol at high concentrations in a 20:80 (v/v) solution of methanol and water and microwave outputs of 15, 50, and 150 W. A qualitative comparison of the profiles of the propylbenzene peaks obtained with and without irradiation suggests that this irradiation affects significantly the peak shapes. However, a qualitative comparison of the profiles of the breakthrough curves of phenol obtained with and without irradiation suggests that this irradiation has no significant effect on their shapes. The peak sharpening observed may be due to an increase in the diffusivity, resulting from the dielectric polarization under microwave irradiation. This effect is directly related to an increase of the rate of mass transfers in the column. In contrast, the similarity of the overloaded band profiles at high concentrations suggests that the equilibrium thermodynamics is unaffected by microwave irradiation. This may be explained by the transparence of the stationary phase to microwaves at 2.45 GHz. The column temperature was measured at the column outlet under irradiation powers of 15, 30, 50, and 150 W. It increases with increasing power, the corresponding effluent temperatures being 25+/-1, 30+/-1, 35+/-1, and 45+/-1 degrees C, respectively.

  12. Liquid Hybridization and Solid Phase Detection: A Highly Sensitive and Accurate Strategy for MicroRNA Detection in Plants and Animals.

    PubMed

    Li, Fosheng; Mei, Lanju; Zhan, Cheng; Mao, Qiang; Yao, Min; Wang, Shenghua; Tang, Lin; Chen, Fang

    2016-01-01

    MicroRNAs (miRNAs) play important roles in nearly every aspect of biology, including physiological, biochemical, developmental and pathological processes. Therefore, a highly sensitive and accurate method of detection of miRNAs has great potential in research on theory and application, such as the clinical approach to medicine, animal and plant production, as well as stress response. Here, we report a strategic method to detect miRNAs from multicellular organisms, which mainly includes liquid hybridization and solid phase detection (LHSPD); it has been verified in various species and is much more sensitive than traditional biotin-labeled Northern blots. By using this strategy and chemiluminescent detection with digoxigenin (DIG)-labeled or biotin-labeled oligonucleotide probes, as low as 0.01-0.25 fmol [for DIG-CDP Star (disodium2-chloro-5-(4-methoxyspiro{1,2-dioxetane-3,2'-(5'-chloro)tricyclo[3.3.1.13,7]decan}-4-yl)phenyl phosphate) system], 0.005-0.1 fmol (for biotin-CDP Star system), or 0.05-0.5 fmol (for biotin-luminol system) of miRNA can be detected and one-base difference can be distinguished between miRNA sequences. Moreover, LHSPD performed very well in the quantitative analysis of miRNAs, and the whole process can be completed within about 9 h. The strategy of LHSPD provides an effective solution for rapid, accurate, and sensitive detection and quantitative analysis of miRNAs in plants and animals. PMID:27598139

  13. Liquid Hybridization and Solid Phase Detection: A Highly Sensitive and Accurate Strategy for MicroRNA Detection in Plants and Animals

    PubMed Central

    Li, Fosheng; Mei, Lanju; Zhan, Cheng; Mao, Qiang; Yao, Min; Wang, Shenghua; Tang, Lin; Chen, Fang

    2016-01-01

    MicroRNAs (miRNAs) play important roles in nearly every aspect of biology, including physiological, biochemical, developmental and pathological processes. Therefore, a highly sensitive and accurate method of detection of miRNAs has great potential in research on theory and application, such as the clinical approach to medicine, animal and plant production, as well as stress response. Here, we report a strategic method to detect miRNAs from multicellular organisms, which mainly includes liquid hybridization and solid phase detection (LHSPD); it has been verified in various species and is much more sensitive than traditional biotin-labeled Northern blots. By using this strategy and chemiluminescent detection with digoxigenin (DIG)-labeled or biotin-labeled oligonucleotide probes, as low as 0.01–0.25 fmol [for DIG-CDP Star (disodium2-chloro-5-(4-methoxyspiro{1,2-dioxetane-3,2′-(5′-chloro)tricyclo[3.3.1.13,7]decan}-4-yl)phenyl phosphate) system], 0.005–0.1 fmol (for biotin-CDP Star system), or 0.05–0.5 fmol (for biotin-luminol system) of miRNA can be detected and one-base difference can be distinguished between miRNA sequences. Moreover, LHSPD performed very well in the quantitative analysis of miRNAs, and the whole process can be completed within about 9 h. The strategy of LHSPD provides an effective solution for rapid, accurate, and sensitive detection and quantitative analysis of miRNAs in plants and animals. PMID:27598139

  14. Combined effects of potassium chloride and ethanol as mobile phase modulators on hydrophobic interaction and reversed-phase chromatography of three insulin variants.

    PubMed

    Johansson, Karolina; Frederiksen, Søren S; Degerman, Marcus; Breil, Martin P; Mollerup, Jørgen M; Nilsson, Bernt

    2015-02-13

    The two main chromatographic modes based on hydrophobicity, hydrophobic interaction chromatography (HIC) and reversed-phase chromatography (RPC), are widely used for both analytical and preparative chromatography of proteins in the pharmaceutical industry. Despite the extensive application of these separation methods, and the vast amount of studies performed on HIC and RPC over the decades, the underlying phenomena remain elusive. As part of a systematic study of the influence of mobile phase modulators in hydrophobicity-based chromatography, we have investigated the effects of both KCl and ethanol on the retention of three insulin variants on two HIC adsorbents and two RPC adsorbents. The focus was on the linear adsorption range, separating the modulator effects from the capacity effects, but some complementary experiments at higher load were included to further investigate observed phenomena. The results show that the modulators have the same effect on the two RPC adsorbents in the linear range, indicating that the modulator concentration only affects the activity of the solute in the mobile phase, and not that of the solute-ligand complex, or that of the ligand. Unfortunately, the HIC adsorbents did not show the same behavior. However, the insulin variants displayed a strong tendency toward self-association on both HIC adsorbents; on one in particular. Since this causes peak fronting, the retention is affected, and this could probably explain the lack of congruity. This conclusion was supported by the results from the non-linear range experiments which were indicative of double-layer adsorption on the HIC adsorbents, while the RPC adsorbents gave the anticipated increased tailing at higher load.

  15. Lewisite Metabolites in Urine by Solid Phase Extraction-Dual Column Reversed-Phase Liquid Chromatography-Isotope Dilution Tandem Mass Spectrometry.

    PubMed

    Palcic, Jason D; Donovan, Stephen F; Jones, Janet S; Flagg, E Lindsay; Salonga, Redentor A; Mock, Walter E; Asirvatham, Victor S

    2016-07-01

    Lewisite (2-chlorovinyldichloroarsine) is a chemical warfare agent developed during World War I. A quantitative method using solid phase extraction (SPE) followed by dual column liquid chromatography (LC)-isotope dilution tandem mass spectrometry (MS-MS) was developed for the determination of (2-chlorovinyl)arsonic acid (CVAOA), a metabolite of Lewisite, in human urine. The sample was treated with hydrogen peroxide to oxidize any (2-chlorovinyl)arsonous acid (CVAA) that remained in the trivalent arsenic oxidation state. There was 1.19% (arsenic purity) of bis-(2-chlorovinyl)arsinic acid (BCVAOA), a minor Lewisite metabolite, in the stock CVAA material. The high-throughput method qualitatively assessed BCVAOA simultaneously utilizing normal-phase silica SPE followed by reversed-phase C18 LC for an orthogonal separation. The chromatographic method results in a 5.8-min cycle time with adequate retention (k' = 2.4) of CVAOA. The mass spectrometer was operated in positive electrospray ionization mode with quantitative m/z 186.9→61.0 and confirmation 186.9→91.0 mass transitions. This selective method demonstrated linearity, accuracy and reproducibility for the clinically relevant calibration range (25-3,200 µg/L as CVAA). The method detection limit was 3.3 µg/L as CVAA from a 10 µL injection. This LC-MS-MS emergency response method has a throughput of >240 samples (2.5 extracted 96-well plates) per day. PMID:27339483

  16. Linear modeling of the soil-water partition coefficient normalized to organic carbon content by reversed-phase thin-layer chromatography.

    PubMed

    Andrić, Filip; Šegan, Sandra; Dramićanin, Aleksandra; Majstorović, Helena; Milojković-Opsenica, Dušanka

    2016-08-01

    Soil-water partition coefficient normalized to the organic carbon content (KOC) is one of the crucial properties influencing the fate of organic compounds in the environment. Chromatographic methods are well established alternative for direct sorption techniques used for KOC determination. The present work proposes reversed-phase thin-layer chromatography (RP-TLC) as a simpler, yet equally accurate method as officially recommended HPLC technique. Several TLC systems were studied including octadecyl-(RP18) and cyano-(CN) modified silica layers in combination with methanol-water and acetonitrile-water mixtures as mobile phases. In total 50 compounds of different molecular shape, size, and various ability to establish specific interactions were selected (phenols, beznodiazepines, triazine herbicides, and polyaromatic hydrocarbons). Calibration set of 29 compounds with known logKOC values determined by sorption experiments was used to build simple univariate calibrations, Principal Component Regression (PCR) and Partial Least Squares (PLS) models between logKOC and TLC retention parameters. Models exhibit good statistical performance, indicating that CN-layers contribute better to logKOC modeling than RP18-silica. The most promising TLC methods, officially recommended HPLC method, and four in silico estimation approaches have been compared by non-parametric Sum of Ranking Differences approach (SRD). The best estimations of logKOC values were achieved by simple univariate calibration of TLC retention data involving CN-silica layers and moderate content of methanol (40-50%v/v). They were ranked far well compared to the officially recommended HPLC method which was ranked in the middle. The worst estimates have been obtained from in silico computations based on octanol-water partition coefficient. Linear Solvation Energy Relationship study revealed that increased polarity of CN-layers over RP18 in combination with methanol-water mixtures is the key to better modeling of

  17. Development and validation of a sensitive solid phase extraction/hydrophilic interaction liquid chromatography/mass spectrometry method for the accurate determination of glucosamine in dog plasma.

    PubMed

    Hubert, C; Houari, S; Lecomte, F; Houbart, V; De Bleye, C; Fillet, M; Piel, G; Rozet, E; Hubert, Ph

    2010-05-01

    A sensitive and accurate LC/MS method was developed for the monitoring of glucosamine (GLcN) dog plasmatic concentration. In this scope, relatively low plasmatic concentrations of GLcN were expected, ranging from 50 to 1000 ng/mL. Liquid chromatography coupled to simple quadrupole mass spectrometry detection (LC/MS) was selected bringing the selectivity and the sensitivity needed for this application. Additionally, a solid phase extraction (SPE) step was performed to reduce matrix and ion suppression effects. Due to the ionisable character of the compound of interest, a mixed-mode strong cation exchange (Plexa PCX) disposable extraction cartridge (DEC) was selected. The separation was carried out on a Zorbax SB-CN column (5 microm, 4.6mm i.d. x 250 mm), considering hydrophilic interaction liquid chromatography (HILIC). Indeed, the mobile phase was made of methanol and 5mM ammonium hydrogen carbonate buffer at pH 7.5 (95/5, v/v). The detection was led at m/z ratios of 180.0 and 417.0, for GLcN and IS, respectively. Reliability of the results was demonstrated through the validation of the method using an approach based on the accuracy profile allowing managing the risk associated to the use of these methods in routine analysis: it is thus guaranteed that each future result will fall in the +/-30% acceptance limits with a probability of at least 90%. Successful application of the method to a preliminary pharmacokinetic study illustrated the usefulness of the method for pre-clinical studies.

  18. Systematic evaluation of matrix effects in hydrophilic interaction chromatography versus reversed phase liquid chromatography coupled to mass spectrometry.

    PubMed

    Periat, Aurélie; Kohler, Isabelle; Thomas, Aurélien; Nicoli, Raul; Boccard, Julien; Veuthey, Jean-Luc; Schappler, Julie; Guillarme, Davy

    2016-03-25

    Reversed phase liquid chromatography (RPLC) coupled to mass spectrometry (MS) is the gold standard technique in bioanalysis. However, hydrophilic interaction chromatography (HILIC) could represent a viable alternative to RPLC for the analysis of polar and/or ionizable compounds, as it often provides higher MS sensitivity and alternative selectivity. Nevertheless, this technique can be also prone to matrix effects (ME). ME are one of the major issues in quantitative LC-MS bioanalysis. To ensure acceptable method performance (i.e., trueness and precision), a careful evaluation and minimization of ME is required. In the present study, the incidence of ME in HILIC-MS/MS and RPLC-MS/MS was compared for plasma and urine samples using two representative sets of 38 pharmaceutical compounds and 40 doping agents, respectively. The optimal generic chromatographic conditions in terms of selectivity with respect to interfering compounds were established in both chromatographic modes by testing three different stationary phases in each mode with different mobile phase pH. A second step involved the assessment of ME in RPLC and HILIC under the best generic conditions, using the post-extraction addition method. Biological samples were prepared using two different sample pre-treatments, i.e., a non-selective sample clean-up procedure (protein precipitation and simple dilution for plasma and urine samples, respectively) and a selective sample preparation, i.e., solid phase extraction for both matrices. The non-selective pretreatments led to significantly less ME in RPLC vs. HILIC conditions regardless of the matrix. On the contrary, HILIC appeared as a valuable alternative to RPLC for plasma and urine samples treated by a selective sample preparation. Indeed, in the case of selective sample preparation, the compounds influenced by ME were different in HILIC and RPLC, and lower and similar ME occurrence was generally observed in RPLC vs. HILIC for urine and plasma samples

  19. Chromatographic models to predict the elution of ionizable analytes by organic modifier gradient in reversed phase liquid chromatography.

    PubMed

    Andrés, Axel; Téllez, Adolfo; Rosés, Martí; Bosch, Elisabeth

    2012-07-20

    The retention of an ionizable analyte under RP-HPLC organic modifier gradient elution is strongly affected by its ionization degree which, in turn, depends on its pK(a) and on the pH of the mobile phase. The values of both parameters change depending on the mobile phase composition and thus retention becomes a parameter quite difficult to predict, particularly when working in gradient mode. In this work, an equation describing the retention of ionizable analytes has been combined with three different models of different complexity, developed for gradient elution of neutral compounds (1, 2, or 3 fitting parameters), in order to predict retention of compounds with acid-base properties with particular buffers. All models have been tested under 16 different gradient patterns (4 linear gradients, 4 concave gradients, 4 convex gradients and 4 combinations between them) for the prediction of the retention time of 12 acid-base compounds (pK(a) values from 4 to 9) in 3 different buffered mobile phases (pH 5, pH 7 and pH 9) with acetonitrile as organic modifier. The agreement between the experimental and calculated retention times is good for all models. The best results are obtained through the model that depends on three parameters and the accuracy of the two-parameter model is slightly lower but very acceptable too. On the other hand, the predictions performed with the one-parameter model are the less accurate, but good enough to become a valid model taking into account that it requires very little experimental work.

  20. Reversed Phase SPE and GC-MS Study of Polycyclic Aromatic Hydrocarbons in Water Samples from the River Buriganga, Bangladesh

    PubMed Central

    Nawaz, Md. Saddam; Ferdousi, Farhana Khanam; Alam, A. M. Shafiqul

    2014-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are semivolatile organic compounds (SVOCs) categorized as persistent organic pollutants (POPs). PAHs are ubiquitous in terrestrial, atmospheric, and particularly aquatic environments throughout the world and have been detected in lakes, ground waters, and rivers. This research work involved the analysis of five PAHs, anthracene, fluorene, naphthalene, phenanthrene, and pyrene, in water sample collected from the river Buriganga, Bangladesh. The extraction of water samples was carried out by reversed phase solid-phase extraction (RP-SPE) technique with C-18 SPE cartridges. A solvent mixture of dichloromethane and hexane (1 : 2) with a flow rate of 0.5 mL/min was used as eluent. Percentage recoveries of five PAHs for this technique were in the range of 81.47 ± 1.16 to 98.60 ± 0.61%. PAHs quantification was achieved by using an ion trap gas chromatography mass spectrometer (GC-MS) interfaced to gas chromatography (GC) equipped with a fused silica capillary column. Helium was used as carrier gas with a flow rate of 1.0 mL/min. The commonly detected PAH compounds in the river water were anthracene, naphthalene, and phenanthrene at the concentration ranges of 0.451 to 3.201, 0.033 to 3.1131, and 0.320 to 2.546 μg/mL, respectively. The results reflect that PAHs presented in this river water were mostly from petrogenic and pyrogenic sources. PMID:27340687

  1. A novel reverse phase high-performance liquid chromatography method for standardization of Orthosiphon stamineus leaf extracts

    PubMed Central

    Saidan, Noor Hafizoh; Aisha, Abdalrahim F.A.; Hamil, Mohd Shahrul Ridzuan; Majid, Amin Malik Shah Abdul; Ismail, Zhari

    2015-01-01

    Background: Orthosiphon stamineus Benth. (Lamiaceae) is a traditional medicinal plant which has been used in treating various ailments such as kidney diseases, bladder inflammation, arthritis and diabetes. The leaves contain high concentration of phenolic compounds, thus, rosmarinic acid (RA), 3’-hydroxy-5, 6, 7, 4’-tetramethoxyflavone (TMF), sinensetin (SIN) and eupatorin (EUP) were chosen as a marker compounds for standardization of various O. stamineus leaf extracts. Objective: The aim was to develop and validate a new high-performance liquid chromatography (HPLC) method for quantification of 4 marker compounds (RA, TMF, SIN, EUP) in various O. stamineus leaf extracts. Materials and Methods: The method was developed and validated using RP-HPLC-diode-array detection at 320 nm for accuracy, precision and limits of detection and was applied for quantification of it markers in five different extracts prepared in solvents with increasing polarity, using a gradient mobile phase 0.1% formic acid: Acetonitrile at a flow rate of 1 ml/min on reverse phase acclaim polar advantage II C18 column (3 μm, 3 × 150 mm) with 18 min separation time. Results: The developed method provided satisfactory precision, and the accuracy of this method was in the range of 90.2% to 105.5%. All of 4 compounds showed good linearity at R2 > 0.999. Conclusion: The developed method is a simple, cost effective with shorter run time (18 min) in comparison to previous methods (30 min) and utilization of environmental-friendly solvents system. Therefore, this method has the potential to replace currently used methods in the routine standardization work of O. stamineus extracts, raw materials and its commercial products. PMID:25598631

  2. Controlling granule size through breakage in a novel reverse-phase wet granulation process: the effect of impeller speed and binder liquid viscosity.

    PubMed

    Wade, J B; Martin, G P; Long, D F

    2015-01-30

    The feasibility of a novel reverse-phase wet granulation process has been established previously highlighting several potential advantages over the conventional wet granulation process and making recommendations for further development of the approach. The feasibility study showed that in the reverse-phase process granule formation proceeds via a controlled breakage mechanism. Consequently, the aim of the present study was to investigate the effect of impeller speeds and binder liquid viscosity on the size distribution and intragranular porosity of granules using this novel process. Impeller tip speed was found to have different effects on the granules produced by a conventional as opposed to a reverse-phase granulation process. For the conventional process, an increase in impeller speed from 1.57 to 3.14 ms(-1) had minimal effect on granule size distribution. However, a further increase in impeller tip speed to 3.93 and 4.71 ms(-1) resulted in a decrease in intragranular porosity and a corresponding increase in mean granule size. In contrast when the reverse-phase process was used, an increase in impeller speed from 1.57 to 4.71 ms(-1) resulted in increased granule breakage and a decrease in the mean granule size. This was postulated to be due to the fact that the granulation process begins with fully saturated pores. Under these conditions further consolidation of granules at increased impeller tip speeds is limited and rebound or breakage occurs. Based on these results and analysis of the modified capillary number the conventional process appears to be driven by viscous forces whereas the reverse-phase process appears to be driven by capillary forces. Additionally, in the reverse-phase process a critical impeller speed, represented by the equilibrium between centrifugal and gravitational forces, appears to represent the point above which breakage of large wet agglomerates and mechanical dispersion of binder liquid take place. In contrast the conventional process

  3. Simultaneous achiral-chiral analysis of pharmaceutical compounds using two-dimensional reversed phase liquid chromatography-supercritical fluid chromatography.

    PubMed

    Venkatramani, C J; Al-Sayah, Mohammad; Li, Guannan; Goel, Meenakshi; Girotti, James; Zang, Lisa; Wigman, Larry; Yehl, Peter; Chetwyn, Nik

    2016-02-01

    A new interface was designed to enable the coupling of reversed phase liquid chromatography (RPLC) and supercritical fluid chromatography (SFC). This online two-dimensional chromatographic system utilizing RPLC in the first dimension and SFC in the second was developed to achieve simultaneous achiral and chiral analysis of pharmaceutical compounds. The interface consists of an eight-port, dual-position switching valve with small volume C-18 trapping columns. The peaks of interest eluting from the first RPLC dimension column were effectively focused as sharp concentration pulses on small volume C-18 trapping column/s and then injected onto the second dimension SFC column. The first dimension RPLC separation provides the achiral purity result, and the second dimension SFC separation provides the chiral purity result (enantiomeric excess). The results are quantitative enabling simultaneous achiral, chiral analysis of compounds. The interface design and proof of concept demonstration are presented. Additionally, comparative studies to conventional SFC and case studies of the applications of 2D LC-SFC in pharmaceutical analysis is presented.

  4. Preparation of Nonionic Vesicles Using the Supercritical Carbon Dioxide Reverse Phase Evaporation Method and Analysis of Their Solution Properties.

    PubMed

    Yamaguchi, Shunsuke; Tsuchiya, Koji; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2016-01-01

    We have previously reported a new preparation method for liposomes using supercritical carbon dioxide (scCO2) as a solvent, referred to as the supercritical carbon dioxide reverse phase evaporation (scRPE) method. In our previous work, addition of ethanol to scCO2 as a co-solvent was needed, because lipid molecules had to be dissolved in scCO2 to form liposomes. In this new study, niosomes (nonionic surfactant vesicles) were prepared from various nonionic surfactants using the scRPE method. Among the nonionic surfactants tested were polyoxyethylene (6) stearylether (C18EO6), polyoxyethylene (5) phytosterolether (BPS-5), polyoxyethylene (6) sorbitan stearylester (TS-106V), and polyoxyethylene (4) sorbitan stearylester (Tween 61). All these surfactants have hydrophilic-lipophilic balance values (HLBs) around 9.5 to 9.9, and they can all form niosomes using the scRPE method even in the absence of ethanol. The high solubility of these surfactants in scCO2 was shown to be an important factor in yielding niosomes without ethanol addition. The niosomes prepared with the scRPE method had higher trapping efficiencies than those prepared using the conventional Bangham method, since the scRPE method gives a large number of unilamellar vesicles while the Bangham method gives multilamellar vesicles. Polyoxyethylene-type nonionic surfactants with HLB values from 9.5 to 9.9 were shown to be optimal for the preparation of niosomes with the scRPE method.

  5. A reverse-phase protein microarray-based screen identifies host signaling dynamics upon Burkholderia spp. infection

    PubMed Central

    Chiang, Chih-Yuan; Uzoma, Ijeoma; Lane, Douglas J.; Memišević, Vesna; Alem, Farhang; Yao, Kuan; Kota, Krishna P.; Bavari, Sina; Wallqvist, Anders; Hakami, Ramin M.; Panchal, Rekha G.

    2015-01-01

    Burkholderia is a diverse genus of gram-negative bacteria that causes high mortality rate in humans, equines and cattle. The lack of effective therapeutic treatments poses serious public health threats. Developing insights toward host-Burkholderia spp. interaction is critical for understanding the pathogenesis of infection as well as identifying therapeutic targets for drug development. Reverse-phase protein microarray technology was previously proven to identify and characterize novel biomarkers and molecular signatures associated with infectious disease and cancer. In the present study, this technology was utilized to interrogate changes in host protein expression and phosphorylation events in macrophages infected with a collection of geographically diverse strains of Burkholderia spp. The expression or phosphorylation state of 25 proteins was altered during Burkholderia spp. infections of which eight proteins were selected for further characterization by immunoblotting. Increased phosphorylation of AMPK-α1, Src, and GSK3β suggested the importance of their roles in regulating Burkholderia spp. mediated innate immune response. Modulating the inflammatory response by perturbing their activities may provide therapeutic routes for future treatments. PMID:26284031

  6. Reverse-phase high-performance liquid chromatography of nerve growth factor receptor-like proteins identified with monoclonal antibodies

    SciTech Connect

    Shan, D.E.; Beck, C.E.; Werrbach-Perez, K.; Perez-Polo, J.R. )

    1990-12-01

    Human neuroblastoma SK-N-SH-SY5Y (SY5Y) and rat pheochromocytoma PC12 cells are model cell lines used in the study of nerve growth factor (NGF) effect. The effects of NGF are initiated by binding to cell surface receptors (NGFR). The amino acid sequence for NGFR has been deduced based on the identification of a single gene for NGFR. However, there are two kinds of NGF binding activities and several reported molecular weights of NGFR. We report here on the demonstration of NGFR-like proteins from PC12 and SY5Y cells by sequential lectin chromatography, reverse-phase HPLC, and SDS-PAGE analysis of immunoprecipitates obtained with NGFR-specific monoclonal antibodies. For both human and rodent NGFR, there was a tendency for the higher molecular-weight species of NGFR-like proteins to be eluted in more hydrophobic fractions. Also, the expression of different species of NGFR could be modified by treatment with retinoic acid (RA). These results are consistent with the hypothesis that the different molecular species of NGFR may result from the generation of a truncated form of NGFR, the presence of sugar residues on the NGFR protein, dimer formation between NGFR, or the association of NGFR with a receptor-associated protein.

  7. Use of reverse phase protein microarrays and reference standard development for molecular network analysis of metastatic ovarian carcinoma.

    PubMed

    Sheehan, Katherine M; Calvert, Valerie S; Kay, Elaine W; Lu, Yiling; Fishman, David; Espina, Virginia; Aquino, Joy; Speer, Runa; Araujo, Robyn; Mills, Gordon B; Liotta, Lance A; Petricoin, Emanuel F; Wulfkuhle, Julia D

    2005-04-01

    Cancer can be defined as a deregulation or hyperactivity in the ongoing network of intracellular and extracellular signaling events. Reverse phase protein microarray technology may offer a new opportunity to measure and profile these signaling pathways, providing data on post-translational phosphorylation events not obtainable by gene microarray analysis. Treatment of ovarian epithelial carcinoma almost always takes place in a metastatic setting since unfortunately the disease is often not detected until later stages. Thus, in addition to elucidation of the molecular network within a tumor specimen, critical questions are to what extent do signaling changes occur upon metastasis and are there common pathway elements that arise in the metastatic microenvironment. For individualized combinatorial therapy, ideal therapeutic selection based on proteomic mapping of phosphorylation end points may require evaluation of the patient's metastatic tissue. Extending these findings to the bedside will require the development of optimized protocols and reference standards. We have developed a reference standard based on a mixture of phosphorylated peptides to begin to address this challenge.

  8. Diet-related reference values for plasma amino acids in newborns measured by reversed-phase HPLC.

    PubMed

    Scott, P H; Sandham, S; Balmer, S E; Wharton, B A

    1990-11-01

    We have measured by reversed-phase HPLC concentrations of amino acids in plasma in groups of 80 normal appropriate-weight term babies fed from birth either a casein formula (WhiteCap SMA, n = 26), a whey formula (Gold Cap SMA, n = 26), or breast milk (n = 28). They were studied from day 11 to week 15 postpartum. The trend was towards an increase in amino acid concentrations in plasma with age, more marked in formula-fed than in breast-fed infants. Reference values were derived for each group. Both formula-fed groups showed several differences from the breast-fed group. Detailed examination indicated that tyrosine, phenylalanine, and methionine concentrations were increased in the casein-fed group greater than 20% of the time, but only threonine was similarly increased in the whey-fed group. Other amino acids, different ones for each formula group, were increased less frequently. There were no consistent correlations with any aspect of infant growth. Appropriate reference values are important for interpreting amino acid concentrations in plasma from newborns and for evaluating the effects of any future dietary modifications to infant formulas. HPLC analysis provides a suitable highly sensitive method for undertaking such studies.

  9. Preparation and application of reversed phase Chromatorotor for the isolation of natural products by centrifugal preparative chromatography.

    PubMed

    Muhammad, Ilias; Samoylenko, Volodymyr; Machumi, Francis; Zakia, Mohamed Ahmed; Mohammed, Rabab; Hetta, Mona H; Gillum, Van

    2013-03-01

    A method of preparation of rotors with a reversed phase (RP) solid silica gel sorbent layer has been developed for centrifugal preparative chromatography (CPC), also known as rotational planar chromatography (RPC). The rotors consist of binder free RP solid SiO2 layers of different thicknesses packed between two supported circular glass discs and can be used in any appropriate device for centrifugal chromatography, like Chromatotron and CycloGraph. Polar and /or semi-polar compounds with close R(f) values, as well as extracts and column fractions were separated and/or purified in a preparative and/or semi-preparative scale using the RP rotors, eluted with mixtures of aqueous-based solvents. We herein report three examples of its application, using RP Chromatorotors, for the isolation of the diastereoisomeric alkaloids banistenosides I and II from Banisteriopsis caapi, saponins III and IV from Fagonia cretica, and the sesquiterpenes artemisinin (V) and artemisinic acid (VI) from Artemisia annua. PMID:23678798

  10. Characterization of organic fouling in reverse osmosis membranes by headspace solid phase microextraction and gas chromatography-mass spectrometry.

    PubMed

    Martínez, C; Gómez, V; Pocurull, E; Borrull, F

    2015-01-01

    Adsorption of organic substances on reverse osmosis (RO) membrane surfaces may form an organic film on the membrane, known as organic fouling, and cause flow-rate loss. This problem is mostly unavoidable as no pretreatment method exists for perfect removal of possible foulants, including organic compounds resulting from undesirable bioactivity. Understanding the characteristics of fouling layers is an essential step towards overall improvement of RO membrane operations. In this study, the organic fouling in RO membranes treating the effluent of a secondary treatment from an urban wastewater treatment plant was characterized. Headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry has been used for the first time, to provide valuable information of organic fouling. Different polarity SPME fibers were tested for this purpose. In addition, the characterization of the organic fouling obtained by HS-SPME was compared with the results obtained by extraction using several organic solvents. The results indicated that more compound families can be identified by HS-SPME than by organic solvent extraction. Moreover, complementary organic analyses were done for better understanding of the organic fouling in RO membranes, such as total organic carbon and loss on ignition.

  11. Magnetoliposomes prepared by reverse-phase followed by sequential extrusion: characterization and possibilities in the treatment of inflammation.

    PubMed

    García-Jimeno, Sonia; Escribano, Elvira; Queralt, Josep; Estelrich, Joan

    2011-02-28

    Anionic ferrofluid was encapsulated in 200nm-diameter liposomes. The process involved phase-reverse evaporation followed by sequential extrusion. Magnetoliposomes were characterized by transmission electron microscopy, Doppler laser electrophoresis, SQUID magnetometry, dynamic light scattering and iron content by atomic absorption spectrophotometry. The absence of hysteresis of the magnetic power of particles at room temperature is characteristic of a material with superparamagnetic properties. The encapsulation efficiency was determined for several iron/phospholipid ratios, and this parameter ranged from 0.016 to 0.024mg iron per mmole of phospholipids, depending on the initial magnetite concentration. In comparison with magnetoliposomes that were obtained solely by extrusion, this method afforded significantly better encapsulation (P=0.0002). Magnetic particles were intravenously administered to healthy or inflammation-induced mice. After 1h, the content of iron was determined in exudates, liver, spleen and plasma. Magnetoliposomes accumulated in the exudates collected from the inflammation site, which suggests that these particles could be loaded with the drugs needed to treat some inflammatory processes. PMID:21129463

  12. Improved peptide elution time prediction for reversed-phase liquid chromatography-MS by incorporating peptide sequence information

    SciTech Connect

    Petritis, Konstantinos; Kangas, Lars J.; Yan, Bo; Monroe, Matthew E.; Strittmatter, Eric F.; Qian, Weijun; Adkins, Joshua N.; Moore, Ronald J.; Xu, Ying; Lipton, Mary S.; Camp, David G.; Smith, Richard D.

    2006-07-15

    We describe an improved artificial neural network (ANN)-based method for predicting peptide retention times in reversed phase liquid chromatography. In addition to the peptide amino acid composition, this study investigated several other peptide descriptors to improve the predictive capability, such as peptide length, sequence, hydrophobicity and hydrophobic moment, and nearest neighbor amino acid, as well as peptide predicted structural configurations (i.e., helix, sheet, coil). An ANN architecture that consisted of 1052 input nodes, 24 hidden nodes, and 1 output node was used to fully consider the amino acid residue sequence in each peptide. The network was trained using {approx}345,000 non-redundant peptides identified from a total of 12,059 LC-MS/MS analyses of more than 20 different organisms, and the predictive capability of the model was tested using 1303 confidently identified peptides that were not included in the training set. The model demonstrated an average elution time precision of {approx}1.5% and was able to distinguish among isomeric peptides based upon the inclusion of peptide sequence information. The prediction power represents a significant improvement over our earlier report (Petritis et al., Anal. Chem. 2003, 75, 1039-1048) and other previously reported models.

  13. Spatial discordance and phase reversals during alternate pacing in discrete-time kinematic and cardiomyocyte ionic models

    NASA Astrophysics Data System (ADS)

    Weinberg, Seth H.

    2015-10-01

    Alternans, a beat-to-beat alternation in the cardiac action potential duration (APD), is a dynamical instability linked with the initiation of arrhythmias and sudden cardiac death, and arises via a period-doubling bifurcation when myocytes are stimulated at fast rates. In this study, we analyze the stability of a propagating electrical wave in a one-dimensional cardiac myocyte model in response to an arrhythmogenic rhythm known as alternate pacing. Using a discrete-time kinematic model and complex frequency (Z) domain analysis, we derive analytical expressions to predict phase reversals and spatial discordance in the interbeat interval (IBI) and APD, which, importantly, cannot be predicted with a model that neglects the influence of cell coupling on repolarization. We identify key dimensionless parameters that determine the transition from spatial concordance to discordance. Finally, we show that the theoretical predictions agree closely with numerical simulations of an ionic myocyte model, over a wide range of parameters, including variable IBI, altered ionic current gating, and reduced cell coupling. We demonstrate a novel approach to predict instability in cardiac tissue during alternate pacing and further illustrate how this approach can be generalized to more detail models of myocyte dynamics.

  14. A well-based reverse-phase protein array of formalin-fixed paraffin-embedded tissue.

    PubMed

    Chung, Joon-Yong; Hewitt, Stephen M

    2015-01-01

    Biomarkers from tissue-based proteomic studies directly contribute to defining disease states as well as promise to improve early detection or provide for further targeted therapeutics. In the clinical setting, tissue samples are preserved as formalin-fixed paraffin-embedded (FFPE) tissue blocks for histological examination. However, proteomic analysis of FFPE tissue is complicated due to the high level of covalently cross-linked proteins arising from formalin fixation. To address these challenges, we developed well-based reverse-phase protein array (RPPA). This approach is a robust protein isolation methodology (29.44 ± 7.8 μg per 1 mm(3) of FFPE tissue) paired with a novel on electrochemiluminescence detection system. Protein samples derived from FFPE tissue by means of laser capture dissection, with as few as 500 shots, demonstrate measurable signal differences for different proteins. The lysates coated to the array plate, dried up and vacuum-sealed, remain stable up to 2 months at room temperature. This methodology is directly applicable to FFPE tissue and presents the direct opportunity of addressing hypothesis within clinical trials and well-annotated clinical tissue repositories.

  15. A well-based reverse-phase protein array of formalin-fixed paraffin-embedded tissue.

    PubMed

    Chung, Joon-Yong; Hewitt, Stephen M

    2015-01-01

    Biomarkers from tissue-based proteomic studies directly contribute to defining disease states as well as promise to improve early detection or provide for further targeted therapeutics. In the clinical setting, tissue samples are preserved as formalin-fixed paraffin-embedded (FFPE) tissue blocks for histological examination. However, proteomic analysis of FFPE tissue is complicated due to the high level of covalently cross-linked proteins arising from formalin fixation. To address these challenges, we developed well-based reverse-phase protein array (RPPA). This approach is a robust protein isolation methodology (29.44 ± 7.8 μg per 1 mm(3) of FFPE tissue) paired with a novel on electrochemiluminescence detection system. Protein samples derived from FFPE tissue by means of laser capture dissection, with as few as 500 shots, demonstrate measurable signal differences for different proteins. The lysates coated to the array plate, dried up and vacuum-sealed, remain stable up to 2 months at room temperature. This methodology is directly applicable to FFPE tissue and presents the direct opportunity of addressing hypothesis within clinical trials and well-annotated clinical tissue repositories. PMID:26043998

  16. Interferon-alpha 2b quantification in inclusion bodies using reversed phase-ultra performance liquid chromatography (RP-UPLC).

    PubMed

    Cueto-Rojas, H F; Pérez, N O; Pérez-Sánchez, G; Ocampo-Juárez, I; Medina-Rivero, E

    2010-04-15

    Interferon-alpha 2b (IFN-alpha 2b) is a recombinant therapeutic cytokine produced as inclusion bodies using a strain of Escherichia coli as expression system. After fermentation and recovery, it is necessary to know the amount of recombinant IFN-alpha 2b, in order to determine the yield and the load for solubilization, and chromatographic protein purification steps. The present work details the validation of a new short run-time and fast sample-preparation method to quantify IFN-alpha 2b in inclusion bodies using Reversed Phase-Ultra Performance Liquid Chromatography (RP-UPLC). The developed method demonstrated an accuracy of 100.28%; the relative standard deviations for method precision, repeatability and inter-day precision tests were found to be 0.57%, 1.54% and 1.83%, respectively. Linearity of the method was assessed in the range of concentrations from 0.05 mg/mL to 0.5 mg/mL, the curve obtained had a determination coefficient (r(2)) of 0.9989. Detection and quantification limits were found to be 0.008 mg/mL and 0.025 mg/mL, respectively. The method also demonstrated robustness for changes in column temperature, and specificity against host proteins and other recombinant protein expressed in the same E. coli strain. PMID:20299292

  17. Simultaneous determination of triple therapy for Helicobacter pylori in human plasma by reversed phase chromatography with online wavelength switching

    NASA Astrophysics Data System (ADS)

    Ahmed, Sameh; Atia, Noha N.

    2015-02-01

    The infection of gastric mucosa by Helicobacter pylori (HP) is an essential cofactor in the aetiology of gastroduodenal ulcer and gastric carcinoma. Because of the bacterial resistance, combination therapy containing omeprazole (OME), tinidazole (TNZ) and clarithromycin (CLA) is commonly used for eradication of HP. However, the simultaneous determination of the triple therapy in human plasma was not reported. A simple, reproducible, and selective HPLC method was developed for the simultaneous determination of the triple therapy mixture used for management of HP infections in human plasma. An HPLC procedure based on a liquid-liquid extraction, enrichment of the analytes and subsequent reversed-phase chromatography with UV detection was used. To enable sensitive and selective detection, the method involved the use of online wavelength switching detection, with two different detection wavelengths; 280 nm for detection of OME and TNZ and 210 nm for detection of CLA. Separations were performed on C18 analytical column with acetonitrile-10 mM phosphate buffer of pH = 3.0 at flow rate of 1.0 mL min-1. The linear ranges in human plasma were 0.05-10 μg mL-1 with correlation coefficients >0.9990. The detection limits in human plasma were 0.02-0.07 μg mL-1. Validation parameters were assessed in compliance with US-FDA guidelines. The method proved to be valuable for the therapeutic drug monitoring after oral administration of triple therapy tablets.

  18. Reversed-phase liquid chromatographic profile of free amino acids in strawberry-tree (Arbutus unedo L.) honey.

    PubMed

    Spano, Nadia; Piras, Irene; Ciulu, Marco; Floris, Ignazio; Panzanelli, Angelo; Pilo, Maria I; Piu, Paola C; Sanna, Gavino

    2009-01-01

    The typical profile of the free amino acids contained in strawberry-tree (Arbutus unedo L.) honey is reported for the first time. An optimized reversed-phase liquid chromatographic (RP-LC) method with phenyl isothiocyanate precolumn derivatization was used. Fourteen free amino acids were identified and quantified in 16 analytical samples. Proline (65.63%) was found to be the most abundant free amino acid, followed by glutamic acid (6.49%), arginine (5.21%), alanine (5.17%), and phenylalanine (4.97%). The total free amino acid content of strawberry-tree honey (average value, 436 mg/kg) was found to be low in comparison to amounts cited in the literature concerning unifloral honeys. The analytical method was optimized and fully validated in terms of detection and quantitation limits, precision (by testing repeatability and reproducibility), linearity, and bias (by means of recovery tests). The acceptability of the validation protocol results was verified using Horwitz's mathematical model and AOAC guidelines. PMID:19714983

  19. A reverse-phase protein microarray-based screen identifies host signaling dynamics upon Burkholderia spp. infection.

    PubMed

    Chiang, Chih-Yuan; Uzoma, Ijeoma; Lane, Douglas J; Memišević, Vesna; Alem, Farhang; Yao, Kuan; Kota, Krishna P; Bavari, Sina; Wallqvist, Anders; Hakami, Ramin M; Panchal, Rekha G

    2015-01-01

    Burkholderia is a diverse genus of gram-negative bacteria that causes high mortality rate in humans, equines and cattle. The lack of effective therapeutic treatments poses serious public health threats. Developing insights toward host-Burkholderia spp. interaction is critical for understanding the pathogenesis of infection as well as identifying therapeutic targets for drug development. Reverse-phase protein microarray technology was previously proven to identify and characterize novel biomarkers and molecular signatures associated with infectious disease and cancer. In the present study, this technology was utilized to interrogate changes in host protein expression and phosphorylation events in macrophages infected with a collection of geographically diverse strains of Burkholderia spp. The expression or phosphorylation state of 25 proteins was altered during Burkholderia spp. infections of which eight proteins were selected for further characterization by immunoblotting. Increased phosphorylation of AMPK-α1, Src, and GSK3β suggested the importance of their roles in regulating Burkholderia spp. mediated innate immune response. Modulating the inflammatory response by perturbing their activities may provide therapeutic routes for future treatments. PMID:26284031

  20. Reverse-phase HPLC separation of hemp seed (Cannabis sativa L.) protein hydrolysate produced peptide fractions with enhanced antioxidant capacity.

    PubMed

    Girgih, Abraham T; Udenigwe, Chibuike C; Aluko, Rotimi E

    2013-03-01

    Hemp seed protein hydrolysate (HPH) was produced through simulated gastrointestinal tract (GIT) digestion of hemp seed protein isolate followed by partial purification and separation into eight peptide fractions by reverse-phase (RP)-HPLC. The peptide fractions exhibited higher oxygen radical absorbance capacity as well as scavenging of 2,2-diphenyl-1-picrylhydrazyl, superoxide and hydroxyl radicals when compared to HPH. Radical scavenging activities of the fractionated peptides increased as content of hydrophobic amino acids or elution time was increased, with the exception of hydroxyl radical scavenging that showed decreased trend. Glutathione (GSH), HPH and the RP-HPLC peptide fractions possessed low ferric ion reducing ability but all had strong (>60 %) metal chelating activities. Inhibition of linoleic acid oxidation by some of the HPH peptide fractions was higher at 1 mg/ml when compared to that observed at 0.1 mg/ml peptide concentration. Peptide separation resulted in higher concentration of some hydrophobic amino acids (especially proline, leucine and isoleucine) in the fractions (mainly F5 and F8) when compared to HPH. The elution time-dependent increased concentrations of the hydrophobic amino acids coupled with decreased levels of positively charged amino acids may have been responsible for the significantly higher (p < 0.05) antioxidant properties observed for some of the peptide fractions when compared to the unfractionated HPH. In conclusion, the antioxidant activity of HPH after simulated GIT digestion is mainly influenced by the amino acid composition of some of its peptides.

  1. A rapid micromethod for measuring theophylline in serum by reverse-phase high-performance liquid chromatography.

    PubMed

    Soldin, S J; Hill, J G

    1977-04-01

    We describe an assay system for measuring theophylline in 25 microliters of serum. The procedure involves extraction with a 95:5 mixture of chloroform:isopropanol containing beta-hydroxypropyltheophylline as internal standard, and reverse-phase chromatography on a 4 mm x 30 cm column containing "micron Bondapak C18." Theophylline and beta-hydroxypropyltheophylline are eluted with a 90:10 mixture of sodium acetate butter (20 mmoles/litre pH 4.0) and acetonitrile at a flow rate of 1.8 ml/min., are detected by their absorbance at 254 nm, and quantitated by measuring peak areas. Column temperature has not been found to be critical in this analysis. Each analysis requires 9 minutes of chromatography time with a total analysis time of 20 minutes. Analytical recoveries were found to be 71 to 75% for theophylline and 94% for beta-hydroxypropyltheophylline. This difference in recovery is corrected when determining the theophylline concentration in unknown samples. The method has good precision (coefficients of variation between 7.0% and 7.9% for therapeutic and toxic concentrations). The results obtained with this method compare favourably with results obtained by a published cation-exchange high-performance liquid chromatographic method. None of the metabolites of theophylline, common compounds related to theophylline in structure or drugs tested have been found to interfere with the analysis described.

  2. Reversed-Phase Chromatography with Multiple Fraction Concatenation Strategy for Proteome Profiling of Human MCF10A Cells

    SciTech Connect

    Wang, Yuexi; Yang, Feng; Gritsenko, Marina A.; Wang, Yingchun; Clauss, Therese RW; Liu, Tao; Shen, Yufeng; Monroe, Matthew E.; Lopez-Ferrer, Daniel; Reno, Theresa; Moore, Ronald J.; Klemke, Richard L.; Camp, David G.; Smith, Richard D.

    2011-05-01

    Two dimensional liquid chromatography (2D LC) is commonly used for shotgun proteomics to improve the analysis dynamic range. Reversed phase liquid chromatography (RPLC) has been routinely employed as the second dimensional separation prior to the mass spectrometric analysis. Construction of 2D separation with RP-RP arises a concern for the separation orthogonality. In this study, we applied a novel concatenation strategy to improve the orthogonality of 2D RP-RP formed by low pH (i.e., pH 3) and high pH (i.e., pH 10) RPLC. We confidently identified 3753 proteins (18570 unique peptides) and 5907 proteins (37633 unique peptides) from low pH RPLC-RP and high pH RPLC-RP, respectively, for a trypsin-digested human MCF10A cell sample. Compared with SCX-RP, the high pH-low pH RP-RP approach resulted in 1.8-fold and 1.6-fold in the number of peptide and protein identifications, respectively. In addition to the broader identifications, the High pH-low pH RP-RP approach has advantages including the improved protein sequence coverage, the simplified sample processing, and the reduced sample loss. These results demonstrated that the concatenation high pH-low pH RP-RP strategy is an attractive alternative to SCX for 2D LC shotgun proteomic analysis.

  3. Reversed phase and cation exchange liquid chromatography with spectrophotometric and elemental/molecular mass spectrometric detection for S-adenosyl methionine/S-adenosyl homocysteine ratios as methylation index in cell cultures of ovarian cancer.

    PubMed

    Iglesias González, T; Cinti, M; Montes-Bayón, M; Fernández de la Campa, M R; Blanco-González, E

    2015-05-01

    S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are essential compounds in the carbon metabolic cycle that have clinical implications in a broad range of disease conditions. The measurement of the ratio SAM/SAH also called methylation index, has become a way of monitoring the DNA methylation of a cell which is an epigenetic event with important clinical implications in diagnosis; therefore the development of suitable methods to accurately quantify these compounds is mandatory. This work illustrates the comparison of three independent methods for the determination of the methylation index, all of them based on the chromatographic separation of the two species (SAM and SAH) using either ion-pairing reversed phase or cation exchange chromatography. The species detection was conducted using either molecular absorption spectrophotometry (HPLC-UV) or mass spectrometry with electrospray (ESI-MS/MS) as ionization source or inductively coupled plasma (DF-ICP-MS) by monitoring the S-atom contained in both analytes. The analytical performance characteristics of the three methods were critically compared obtaining best features for the combination of reversed phase HPLC with ESI-MS in the MRM mode. In this case, detection limits of about 0.5ngmL(-1) for both targeted analytes permitted the application of the designed strategy to evaluate the effect of cisplatin on the changes of the methylation index among epithelial ovarian cancer cell lines sensitive (A2780) and resistant (A2780CIS) to this drug after exposition to cisplatin.

  4. Reversible and irreversible magnetization of the Chevrel-phase superconductor PbMo{sub 6}S{sub 8}

    SciTech Connect

    Zheng, D.N.; Ramsbottom, H.D.; Hampshire, D.P.

    1995-11-01

    Magnetic measurements have been carried out on the hot-isostatically-pressed Chevrel-phase superconductor PbMo{sub 6}S{sub 8} at temperatures from 4.2 K to {ital T}{sub {ital c}} and for magnetic fields up to 12 T. The results show that for the PbMo{sub 6}S{sub 8} compound there is a wide magnetically reversible region, between the irreversibility field {ital B}{sub irr} and the upper critical field {ital B}{sub {ital c}2}, on the isothermal magnetic hysteresis curves. The {ital B}{sub irr}({ital T}) line, i.e., the irreversibility line, was found to obey a power-law expression: {ital B}{sub irr}={ital B}{sup *}(1{minus}{ital T}/{ital T}{sub {ital c}}){sup {alpha}} with {alpha}{approx}1.5. Magnetic relaxation measurements revealed that the flux-creep effect in the material studied is substantial and is greater than those observed in conventional metallic alloys, but smaller than in high-temperature superconductors. The existence of the irreversibility line and pronounced flux-creep effect in PbMo{sub 6}S{sub 8} is attributed to the short coherence length of the material. From the reversible magnetization data, the values of the penetration depth, the coherence length, and the critical fields are obtained together with the Ginzburg-Landau parameter {kappa}. At 4.2 K, the critical current density {ital J}{sub {ital c}} is 10{sup 9} A m{sup {minus}2} at zero field, and decreases to 2{times}10{sup 8} A m{sup {minus}2} at 10 T. Pinning force curves measured at different temperatures obey a Kramer-scaling law of the form: {ital F}{sub {ital p}}(={ital J}{sub {ital c}}{times}{ital B}){proportional_to}{ital b}{sup 1/2}(1{minus}{ital b}){sup 2}, which indicates that the {ital J}{sub {ital c}} is limited by one predominant flux-pinning mechanism.

  5. Single-step electrotransfer of reverse-stained proteins from sodium dodecyl sulfate-polyacrylamide gel onto reversed-phase minicartridge and subsequent desalting and elution with a conventional high-performance liquid chromatography gradient system for analysis.

    PubMed

    Fernandez-Patron, C; Madrazo, J; Hardy, E; Mendez, E; Frank, R; Castellanos-Serra, L

    1995-06-01

    Isolation of proteins from polyacrylamide electrophoresis gels by a novel combination of techniques is described. A given protein band from a reverse stained (imidazol-sodium dodecyl sulfate--zinc salts) gel can be directly electrotransferred onto a reversed-phase chromatographic support, packed in a self-made minicartridge (2 mm in thickness, 8 mm in internal diameter, made of inert polymeric materials). The minicartridge is then connected to a high-performance liquid chromatography system and the electrotransferred protein eluted by applying an acetonitrile gradient. Proteins elute in a small volume ( < 700 microL) of high-purity volatile solvents (water, trifluoroacetic acid, acetonitrile) and are free of contaminants (gel contaminants, salts, etc). Electrotransferred proteins were efficiently retained, e.g., up to 90% for radioiodinated alpha-lactalbumin, by the octadecyl matrix, and their recovery on elution from the minicartridge was in the range typical for this type of chromatographic support, e.g., 73% for alpha-lactalbumin. The technique was successfully applied to a variety of proteins in the molecular mass range 6-68 kDa, and with amounts between 50 and 2000 pmol. The good mechanical and chemical stability of the developed minicartridges, during electrotransfer and chromatography, allowed their repeated use. This new technique permitted a single-step separation of two proteins unresolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis due to their different elution from the reversed-phase support. The isolated proteins were amenable to analysis by N-terminal sequencing, enzymic digestion and mass spectrometry of their proteolytic fragments. Chromatographic elution of proteins from the reversed-phase mini-cartridge was apparently independent of the specific loading mode employed, i.e., loading by conventional loop injection or by electrotransfer. PMID:7498136

  6. Reversed-phase high-performance liquid chromatography method for the analysis of nitro-arginine in rat plasma and urine.

    PubMed

    Tabrizi-Fard, M A; Fung, H L

    1996-04-26

    Nitro-L-arginine (L-NNA) is an inhibitor of the enzyme nitric oxide synthase (NOS). We developed a simple, sensitive and reproducible reversed-phase high-performance liquid chromatographic method for detection of nitro-arginine (L- and D-enantiomer) in rat plasma and urine. Samples were treated with perchloric acid, neutralized and eluted through a C8 reversed-phase column with a mobile phase of 18.5 mM heptanesulfonic acid-10% methanol in water, using theophylline as an internal standard. Plasma recovery for both isomers was complete, and the sensitivity limit was 0.5 micrograms/ml. This method may be used for disposition studies of L-NNA in small animals.

  7. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-03-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 microL samples of a 50 mM probe solution were injected into C(18)-bonded columns using a series of five buffered mobile phases at (SW)pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C(18)-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C(18)-bonded layer and the bulk phase. PMID:18976999

  8. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2009-03-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 microL samples of a 50 mM probe solution were injected into C(18)-bonded columns using a series of five buffered mobile phases at (SW)pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C(18)-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C(18)-bonded layer and the bulk phase.

  9. Adsorption mechanism of acids and bases in reversed-phase liquid chromatography in weak buffered mobile phases designed for liquid chromatography/mass spectrometry

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    The overloaded band profiles of five acido-basic compounds were measured, using weakly buffered mobile phases. Low buffer concentrations were selected to provide a better understanding of the band profiles recorded in LC/MS analyses, which are often carried out at low buffer concentrations. In this work, 10 {micro}L samples of a 50 mM probe solution were injected into C{sub 18}-bonded columns using a series of five buffered mobile phases at {sub W}{sup S}pH between 2 and 12. The retention times and the shapes of the bands were analyzed based on thermodynamic arguments. A new adsorption model that takes into account the simultaneous adsorption of the acidic and the basic species onto the endcapped adsorbent, predicts accurately the complex experimental profiles recorded. The adsorption mechanism of acido-basic compounds onto RPLC phases seems to be consistent with the following microscopic model. No matter whether the acid or the base is the neutral or the basic species, the neutral species adsorbs onto a large number of weak adsorption sites (their saturation capacity is several tens g/L and their equilibrium constant of the order of 0.1 L/g). In contrast, the ionic species adsorbs strongly onto fewer active sites (their saturation capacity is about 1 g/L and their equilibrium constant of the order of a few L/g). From a microscopic point of view and in agreement with the adsorption isotherm of the compound measured by frontal analysis (FA) and with the results of Monte-Carlo calculations performed by Schure et al., the first type of adsorption sites are most likely located in between C{sub 18}-bonded chains and the second type of adsorption sites are located deeper in contact with the silica surface. The injected concentration (50 mM) was too low to probe the weakest adsorption sites (saturation capacity of a few hundreds g/L with an equilibrium constant of one hundredth of L/g) that are located at the very interface between the C{sub 18}-bonded layer and the bulk

  10. First accurate experimental study of Mu reactivity from a state-selected reactant in the gas phase: the Mu + H2{1} reaction rate at 300 K

    NASA Astrophysics Data System (ADS)

    Bakule, Pavel; Sukhorukov, Oleksandr; Ishida, Katsuhiko; Pratt, Francis; Fleming, Donald; Momose, Takamasa; Matsuda, Yasuyuki; Torikai, Eiko

    2015-02-01

    This paper reports on the experimental background and methodology leading to recent results on the first accurate measurement of the reaction rate of the muonium (Mu) atom from a state-selected reactant in the gas phase: the Mu + H2\\{1\\}\\to MuH + H reaction at 300 K, and its comparison with rigorous quantum rate theory, Bakule et al (2012 J. Phys. Chem. Lett. 3 2755). Stimulated Raman pumping, induced by 532 nm light from the 2nd harmonic of a Nd:YAG laser, was used to produce H2 in its first vibrational (v = 1) state, H2\\{1\\}, in a single Raman/reaction cell. A pulsed muon beam (from ‘ISIS’, at 50 Hz) matched the 25 Hz repetition rate of the laser, allowing data taking in equal ‘Laser-On/Laser-Off’ modes of operation. The signal to noise was improved by over an order of magnitude in comparison with an earlier proof-of-principle experiment. The success of the present experiment also relied on optimizing the overlap of the laser profile with the extended stopping distribution of the muon beam at 50 bar H2 pressure, in which Monte Carlo simulations played a central role. The rate constant, found from the analysis of three separate measurements, which includes a correction for the loss of {{H}2}\\{1\\} concentration due to collisional relaxation with unpumped H2 during the time of each measurement, is {{k}Mu}\\{1\\} = 9.9[(-1.4)(+1.7)] × 10-13 cm3 s-1 at 300 K. This is in good to excellent agreement with rigorous quantum rate calculations on the complete configuration interaction/Born-Huang surface, as reported earlier by Bakule et al, and which are also briefly commented on herein.

  11. Reverse-phase phosphoproteome analysis of signaling pathways induced by Rift valley fever virus in human small airway epithelial cells.

    PubMed

    Popova, Taissia G; Turell, Michael J; Espina, Virginia; Kehn-Hall, Kylene; Kidd, Jessica; Narayanan, Aarthi; Liotta, Lance; Petricoin, Emanuel F; Kashanchi, Fatah; Bailey, Charles; Popov, Serguei G

    2010-01-01

    Rift valley fever virus (RVFV) infection is an emerging zoonotic disease endemic in many countries of sub-Saharan Africa and in Egypt. In this study we show that human small airway epithelial cells are highly susceptible to RVFV virulent strain ZH-501 and the attenuated strain MP-12. We used the reverse-phase protein arrays technology to identify phosphoprotein signaling pathways modulated during infection of cultured airway epithelium. ZH-501 infection induced activation of MAP kinases (p38, JNK and ERK) and downstream transcriptional factors [STAT1 (Y701), ATF2 (T69/71), MSK1 (S360) and CREB (S133)]. NF-κB phosphorylation was also increased. Activation of p53 (S15, S46) correlated with the increased levels of cleaved effector caspase-3, -6 and -7, indicating activation of the extrinsic apoptotic pathway. RVFV infection downregulated phosphorylation of a major anti-apoptotic regulator of survival pathways, AKT (S473), along with phosphorylation of FOX 01/03 (T24/31) which controls cell cycle arrest downstream from AKT. Consistent with this, the level of apoptosis inhibitor XIAP was decreased. However, the intrinsic apoptotic pathway marker, caspase-9, demonstrated only a marginal activation accompanied by an increased level of the inhibitor of apoptosome formation, HSP27. Concentration of the autophagy marker, LC3B, which often accompanies the pro-survival signaling, was decreased. Cumulatively, our analysis of RVFV infection in lung epithelium indicated a viral strategy directed toward the control of cell apoptosis through a number of transcriptional factors. Analyses of MP-12 titers in challenged cells in the presence of MAPK inhibitors indicated that activation of p38 represents a protective cell response while ERK activation controls viral replication. PMID:21072193

  12. Reverse-Phase Microarray Analysis Reveals Novel Targets in Lymph Nodes of Bacillus anthracis Spore-Challenged Mice

    PubMed Central

    Popova, Taissia G.; Espina, Virginia; Liotta, Lance A.; Popov, Serguei G.

    2015-01-01

    Anthrax is a frequently fatal infection of many animal species and men. The causative agent Bacillus anthracis propagates through the lymphatic system of the infected host; however, the specific interactions of the host and microbe within the lymphatics are incompletely understood. We report the first description of the phosphoprotein signaling in the lymph nodes of DBA/2 mice using a novel technique combining the reverse-phase microarray with the laser capture microdissesction. Mice were challenged into foot pads with spores of toxinogenic, unencapsulated Sterne strain. The spores quickly migrated to the regional popliteal lymph nodes and spread to the bloodstream as early as 3 h post challenge. All mice died before 72 h post challenge from the systemic disease accompanied by a widespread LN tissue damage by bacteria, including the hemorrhagic necrotizing lymphadenitis, infiltration of CD11b+ and CD3+ cells, and massive proliferation of bacteria in lymph nodes. A macrophage scavenger receptor CD68/macrosialin was upregulated and found in association with vegetative bacteria likely as a marker of their prior interaction with macrophages. The major signaling findings among the 65 tested proteins included the reduced MAPK signaling, upregulation of STAT transcriptional factors, and altered abundance of a number of pro- and anti-apoptotic proteins with signaling properties opposing each other. Downregulation of ERK1/2 was associated with the response of CD11b+ macrophages/dendritic cells, while upregulation of the pro-apoptotic Puma indicated a targeting of CD3+ T-cells. A robust upregulation of the anti-apoptotic survivin was unexpected because generally it is not observed in adult tissues. Taken together with the activation of STATs it may reflect a new pathogenic mechanism aimed to delay the onset of apoptosis. Our data emphasize a notion that the net biological outcome of disease is determined by a cumulative impact of factors representing the microbial insult and

  13. Chemical anchoring of lauryl methacrylate-based reversed phase monolith to 1/16″ o.d. polyetheretherketone tubing.

    PubMed

    Shu, Shin; Kobayashi, Hiroharu; Okubo, Masaki; Sabarudin, Akhmad; Butsugan, Michio; Umemura, Tomonari

    2012-06-15

    In this paper, we describe a method for the preparation of easy-to-use reversed-phase monolithic microbore columns. Polyetheretherketone (PEEK) tubing with an outer diameter of 1/16″ and an inner diameter of 1.0 mm was used as a column housing (empty column), and in it lauryl methacrylate (LMA) was copolymerized with ethylene dimethacrylate (EDMA). In order to chemically anchor the polymer monolith to the tube wall, the inner wall surface was pretreated by the following two-step procedure. (1) 50% sulfuric acid was filled into the PEEK tubing and left to stand for 6 h to generate sulfonate groups on the surface. (2) After washing with Milli-Q water, the sulfonated PEEK surface was brought into contact with 1 M glycidyl methacrylate in dichloromethane (or acetone) at 40°C for 4 h to introduce methacryloyl groups via the reaction of sulfonate groups and epoxy groups. Mechanical strength and column efficiency of the resulting monoliths were evaluated through the separation of a series of alkylbenzenes in acetonitrile-water (50:50, v/v) eluent over the flow rate range of 50-750 μL/min (corresponding to 1.7-25.5 mm/s). The poly(LMA-co-EDMA) monolith provided acceptable column efficiency of 2000 theoretical plates/10 cm (HETP value of 50 μm) for amylbenzene (separation factor k=40) and low flow resistance of 0.5 MPa/10 cm at a normal flow rate of 50 μL/min. The methacryloylated PEEK tubing tightly held the monolith, and the monolithic column exhibited good pressure resistance up to 15 MPa, allowing rapid separation at a 15-20 fold higher flow rate than normal. PMID:22560348

  14. Retention behavior of lipids in reversed-phase ultrahigh-performance liquid chromatography-electrospray ionization mass spectrometry.

    PubMed

    Ovčačíková, Magdaléna; Lísa, Miroslav; Cífková, Eva; Holčapek, Michal

    2016-06-10

    Reversed-phase ultrahigh-performance liquid chromatography (RP-UHPLC) method using two 15cm sub-2μm particles octadecylsilica gel columns is developed with the goal to separate and unambiguously identify a large number of lipid species in biological samples. The identification is performed by the coupling with high-resolution tandem mass spectrometry (MS/MS) using quadrupole - time-of-flight (QTOF) instrument. Electrospray ionization (ESI) full scan and tandem mass spectra are measured in both polarity modes with the mass accuracy better than 5ppm, which provides a high confidence of lipid identification. Over 400 lipid species covering 14 polar and nonpolar lipid classes from 5 lipid categories are identified in total lipid extracts of human plasma, human urine and porcine brain. The general dependences of relative retention times on relative carbon number or relative double bond number are constructed and fit with the second degree polynomial regression. The regular retention patterns in homologous lipid series provide additional identification point for UHPLC/MS lipidomic analysis, which increases the confidence of lipid identification. The reprocessing of previously published data by our and other groups measured in the RP mode and ultrahigh-performance supercritical fluid chromatography on the silica column shows more generic applicability of the polynomial regression for the description of retention behavior and the prediction of retention times. The novelty of this work is the characterization of general trends in the retention behavior of lipids within logical series with constant fatty acyl length or double bond number, which may be used as an additional criterion to increase the confidence of lipid identification. PMID:27179677

  15. Fragment profiling of low molecular weight heparins using reversed phase ion pair liquid chromatography-electrospray mass spectrometry.

    PubMed

    Xu, Xiaohui; Li, Daoyuan; Chi, Lequan; Du, Xuzhao; Bai, Xue; Chi, Lianli

    2015-04-30

    Low molecular weight heparins (LMWHs) are linear and highly charged carbohydrate polymers prepared by chemical or enzymatic depolymerization of heparin. Compared to unfractionated heparin (UFH), LMWHs are prevalently used as clinical anticoagulant drugs due to their lower side effects and better bioavailability. The work presented herein provides a rapid and powerful fragment mapping method for structural characterization of LMWHs. The chain fragments of two types of LMWHs, enoxaparin and nadroparin, were generated by controlled enzymatic digestion with each of heparinase I (Hep I, Enzyme Commission (EC) # 4.2.2.7), heparinase II (Hep II, no EC # assigned) and heparinase III (Hep III, EC # 4.2.2.8). Reversed phase ion pair high performance liquid chromatography (RPIP-HPLC) coupled with electrospray ion trap time-of-flight mass spectrometry (ESI-IT-TOF-MS) was used to profile the oligosaccharide chains ranging from disaccharides to decasaccharides. A database containing all theoretical structural compositions was established to assist the mass spectra interpretation. The six digests derived by three enzymes from two types of LMWHs exhibited distinguishable fingerprinting patterns. And a total of 94 enoxaparin fragments and 109 nadroparin fragments were detected and identified. Besides the common LMWH oligosaccharides, many components containing characteristic LMWH structures such as saturated L-idopyranosuronic acid, 2,5-anhydro-D-mannitol, 1,6-anhydro-D-aminopyranose, as well as odd number oligosaccharides were also revealed. Quantitative comparison of major components derived from innovator and generic nadroparin products was presented. This approach to profile LMWHs' fragments offers a highly reproducible, high resolution and information-rich tool for evaluating the quality of this category of anticoagulant drugs or comparing structural similarities among samples from various sources.

  16. Comparison of capillary electrophoresis and reversed-phase liquid chromatography methodologies for determination of diazepam in pharmaceutical tablets.

    PubMed

    Aurora Prado, María S; Steppe, Martin; Tavares, Marina F M; Kedor-Hackmann, Erika R M; Santoro, Maria Inês R M

    2005-02-23

    Two novel analytical methodologies using capillary electrophoresis (CE) and reversed-phase high-performance liquid chromatography (RP-HPLC) for the determination of diazepam in commercial and simulated tablet formulations were developed and compared. The CE analysis was carried out in a bare fused-silica capillary with 75 microm i.d. and total length of 50 cm (28 cm to the detector) with a buffer solution containing 20 mmol L(-1) sodium tetraborate and 20 mmolL(-1) sodium dodecylsulfate (SDS), pH 9.23. The applied voltage was 20 kV and bromazepam was used as internal standard (IS). The RP-HPLC analysis was carried out in a LiChrospher((R)) 100 RP-18 (5 microm) column with a mobile phase constituted of methanol, acetonitrile and water (45:25:30) with a flow rate of 0.8 mL/min, using acetaminophen as IS. In both cases, detection was carried out by ultraviolet (UV) absorption at 242 nm. Under the optimized conditions, the CE retention times for the standard diazepam and bromazepam (IS) were 4.08 and 3.43 min, respectively, and the retention times of the RP-HPLC analysis for the standard diazepam and acetaminophen (IS) were 4.86 and 1.58 min, respectively. The resolution and efficiency for CE were 7.4 and 1.18 x 10(5)plates/m and for RP-HPLC, 7.5 and 1.76 x 10(4) plates/m. Analytical curves of peak area versus concentration presented correlation coefficients of 0.9996 for CE and 0.9994 for RP-HPLC. The limits of detection (LOD) and quantitation (LOQ) were 4.24 and 12.85 microg/mL for CE and 1.44 and 4.36 microg/mL for RP-HPLC. Relative standard deviations (R.S.D.) were 1.62 and 0.98% for CE and RP-HPLC, respectively. The percentage recovery determined with CE was 100.27+/-1.25 and with RP-HPLC was 101.12+/-2.48. Although both methodologies were shown to be suitable for the determination of diazepam in tablets, performing in a similar manner with regards to several aspects (linearity, recovery and specificity), CE provided a faster analysis and column efficiency whereas

  17. Elution factors of synthetic oxotriacylglycerols as an aid in identification of peroxidized natural triacylglycerols by reverse-phase high-performance liquid chromatography with electrospray mass spectrometry.

    PubMed

    Sjövall, O; Kuksis, A; Marai, L; Myher, J J

    1997-11-01

    Selected elution factors were determined for model oxotriacylglycerols as an aid in identification of the peroxidation products of natural triacylglycerols by reverse-phase high-performance liquid chromatography (HPLC) with electrospray mass spectrometry (LC/ES/MS). For this purpose synthetic triacylglycerols of known structure were converted to hydroperoxides, hydroxides, epoxides, and core aldehydes and their dinitrophenylhydrazones by published procedures. The oxotriacylglycerols were resolved by normal-phase thin-layer chromatography and reverse-phase HPLC, and the identities of the oxotriacylglycerols confirmed by LC/ES/MS. Elution factors of oxotriacylglycerols were determined in relation to a homologous series of saturated triacylglycerols, ranging from 24 to 54 acyl carbons, and analyzed by reverse-phase HPLC, using a gradient of 20-80% isopropanol in methanol as eluting solvent and an evaporative light-scattering detector. It was shown that the elution times varied with the nature of the functional group and its regiolocation in the triacylglycerol molecule. A total of 31 incremental elution factors were calculated from chromatography of 33 oxygenated and nonoxygenated triacylglycerol species, ranging in carbon number from 36 to 54 and in double-bond number from 0 to 6.

  18. Dendrimer-functionalized mesoporous silica as a reversed-phase/anion-exchange mixed-mode sorbent for solid phase extraction of acid drugs in human urine.

    PubMed

    Li, Yun; Yang, Jiajia; Huang, Chaonan; Wang, Longxing; Wang, Jincheng; Chen, Jiping

    2015-05-01

    A new dendrimer-functionalized mesoporous silica material based on large-pore 3D cubic Korea Advanced Institute of Science and Technology-6 (KIT-6) was synthesized by the growing of dendritic branches inside the mesopores of aminopropyl functionalized KIT-6. Detailed physical characterizations using transmission electron microscopy, nitrogen adsorption-desorption measurements, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis reveal that the multifunctional dendrimers have been grown successfully within the confined spaces of mesopores. Although the 3D ordered mesoporous architecture of KIT-6 was well preserved, there was a significant and continuous decrease in pore size, specific surface area (SBET) and pore volume when increasing dendrimer generation up to six. In order to get a compromise between the SBET, pore size and density of functionalities, the dendrimer-functionalized KIT-6 (DF-KIT-6) for generation 2 (SBET, 314.2 m(2) g(-1); pore size, 7.9 nm; carbon and nitrogen contents, 19.80% and 1.92%) was selected for solid phase extraction (SPE) applications. The DF-KIT-6 was then evaluated as a reversed-phase/anion-exchange mixed-mode sorbent for extraction of the selected acidic drugs (ketoprofen, KEP; naproxen, NAP; and ibuprofen, IBU), since the dendrimers contained both hydrocarbonaceous and amine functionalities. The effective parameters on extraction efficiency such as sample pH and volume, type and volume of eluent and wash solvents were optimized. Under the optimized experimental conditions, the DF-KIT-6 based SPE coupled with HPLC-UV method demonstrated good sensitivity (0.4-4.6 ng mL(-1) detection of limits) and linearity (R(2)>0.990 for 10-2000 ng mL(-1) of KEP and IBU, and 1-200 ng mL(-1) of NAP). The potential use of DF-KIT-6 sorbent for preconcentration and cleanup of acid drugs in human urine samples was also demonstrated. Satisfactory recoveries at two spiking levels (30 and 300 ng mL(-1) for KEP and IBU, 3 and 30 ng mL(-1

  19. Response to {open_quotes}Comment on {open_quote}Reversible work of formation of an embryo of a new phase within a uniform macroscopic mother phase{close_quote}thinsp{close_quotes} [J. Chem. Phys. {bold 111}, 3769 (1999)

    SciTech Connect

    Debenedetti, P.G.; Reiss, H.

    1999-08-01

    External constraints are necessary in order to calculate the energetics of embryo formation when the embryo is not a critical nucleus. The expression for the reversible work of formation obtained in by Debenedetti and Reiss [J. Chem. Phys. {bold 108}, 5498 (1998)] is rigorous and valid regardless of the relative densities of the embryo and mother phase. {copyright} {ital 1999 American Institute of Physics.}

  20. Effects of pH mismatch between the two dimensions of reversed-phase×reversed-phase two-dimensional separations on second dimension separation quality for ionogenic compounds-I. Carboxylic acids.

    PubMed

    Stoll, Dwight R; O'Neill, Kelly; Harmes, David C

    2015-02-27

    Two persistent impediments to wider adoption of two-dimensional liquid chromatography (2D-LC) are the perceptions that 2D methods are generally less sensitive than 1D ones, and that coupling of certain separation modes in a 2D system is difficult because of the negative impact of the effluent of the first separation on the second separation. In this work we address these problems in the specific case where reversed-phase separations are used in both dimensions of a 2D-LC system, but the pH is varied such that the ionization state of carboxylic acid analytes is different (i.e., neutral or negatively charged, in eluents buffered at pH 2 or 7) in the two columns. We first demonstrate that the effect of first dimension ((1)D) effluent on the performance of second dimension ((2)D) separation of ionogenic solutes is much more serious than it is for neutral compounds where the pH of the eluent does not play a role in retention. We have systematically varied the properties of the sample solution injected into the (2)D column (i.e., the (1)D effluent), as well as the (2)D eluent, with the goal of establishing guidelines for conditions that yield acceptable (2)D performance. We find that the organic solvent content of the (1)D effluent and (2)D eluent is not as important as the buffer concentrations in these two solutions, and that the greater the ratio of buffer concentration in the (1)D effluent relative to the (2)D eluent, the smaller the volume one can inject into the (2)D column before dramatic peak splitting occurs. We have then used the information from these simple experiments to guide both 1D experiments that mimic the (2)D separation, and actual 2D separations, to demonstrate that online adjustment of the properties of the (1)D effluent by dilution with a buffered solvent prior to injection into the (2)D column is a very effective solution to the pH mismatch problem. We find that when the buffer capacity of the diluent is high enough to effectively titrate the (1)D

  1. Murine schistosomiasis mansoni: process of blood coagulation at pre-patent, acute and chronic phases, and consequence of chemotherapeutic cure on the reversion of changes.

    PubMed

    Carvalho, Maria G; Mello, Rômulo T; Soares, Anna L; Bicalho, Rosilene S; Lima e Silva, Francisco C; Coelho, Paulo M Z

    2005-10-01

    The present study aims to elucidate in a sequential manner the changes of the blood coagulation process at different phases of experimental schistosomiasis, comprising the pre-patent, acute, intermediate and chronic phases, and the effect of chemotherapeutic cure, at the acute and chronic phases, on reversion of changes related to the coagulation factors. Mice were infected with Schistosoma mansoni cercariae, and were divided into four groups. Blood samples from these groups were collected 32, 70, 100, and 140 days after infection, corresponding to the pre-patent, acute, intermediate and chronic phases, respectively. Simultaneously, other infected groups were given oxamniquine, 70 and 140 days after infection. At the same time as blood collection from infected and/or treated animal groups, other uninfected control animal groups were punctured and maintained under the same conditions as the infected animals. The vitamin-K-dependent clotting factors were found to be more sensitive to infection at different phases, while factors VIII and XI presented hyperactivity. Results obtained 90 days after chemotherapeutic treatment with oxamniquine, administered at the acute and chronic phases, presented noticeable reversion of the main alterations in the coagulation mechanism. The present study provides unquestionable data on the development of hemostatic changes throughout the course of S. mansoni infection.

  2. Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

    SciTech Connect

    Manohara, G.V.; Vishnu Kamath, P.; Milius, Wolfgang

    2012-12-15

    Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2-5 nm-thick tactoids with a radial dimension of 0.2-0.5 {mu}m. - Graphical abstract: Schematic of the hydrated, dehydrated and interstratified phases observed during the hydration-dehydration of Ni/Al-CH{sub 3}COO LDH. Highlights: Black-Right-Pointing-Pointer Ni/Al-acetate LDHs were synthesized by HPFS method by hydrolysis of acetamide. Black-Right-Pointing-Pointer Intercalated acetate ion shows reversible hydration with variation in humidity. Black-Right-Pointing-Pointer An ordered interstratified phase was observed during hydration/dehydration cycle. Black-Right-Pointing-Pointer A solution type equilibrium is observed between hydration-dehydration phases. Black-Right-Pointing-Pointer These LDHs undergo facile aqueous exfoliation.

  3. Improved high performance liquid chromatographic separation of anthocyanin compounds from grapes using a novel mixed-mode ion-exchange reversed-phase column.

    PubMed

    McCallum, Jason L; Yang, Raymond; Young, J Christopher; Strommer, Judith N; Tsao, Rong

    2007-04-27

    A novel mixed mode HPLC method using a column combining both ion-exchange and reversed-phase separation mechanisms has been developed to facilitate analysis of anthocyanins in grapes. Chromatographic performance and subsequent analysis of anthocyanidin diglucosides and acylated compounds are significantly improved using the new column, compared to those associated with conventional C18 reversed-phase methods. The mixed mode column produces a distinctive eluting pattern for the different anthocyanin subgroups, avoiding overlaps found with C18 columns. The enhanced chromatographic resolution provides nearly complete separation of 37 anthocyanin types, and permits detection of delphinidin 3-O-(6''-O-caffeoyl) beta-D-glucoside for the first time in extracts of skins from Concord grapes. PMID:17382950

  4. Separation of aromatic carboxylic acids using quaternary ammonium salts on reversed-phase HPLC. 2. Application for the analysis of Loy Yang coal oxidation products

    SciTech Connect

    Kawamura, K.; Okuwaki, A.; Verheyen, T.V.; Perry, G.J.

    2006-07-01

    In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed-phase HPLC using eluent containing quaternary ammonium salt was optimized using the solvent gradient method. This method was applied for the analysis of Loy Yang coal oxidation products. It was confirmed that the analytical data using this method were consistent with those determined using gas chromatography.

  5. Direct Analysis of Reversed-Phase HPTLC Separated Tryptic Protein Digests using a Liquid Microjunction Surface Sampling Probe/ESI-MS System

    SciTech Connect

    Emory, Joshua F; Walworth, Matthew J; Van Berkel, Gary J; Schulz, Michael; Minarik, susanne

    2010-01-01

    The sampling, ionization and detection of tryptic peptides separated in one-dimension on reversed phase HPTLC plates was performed using liquid microjunction surface sampling probe electrospray ionization mass spectrometry. Tryptic digests of five proteins (cytochrome c., myoglobin, beta-casein, lysozyme, and bovine serum albumin) were spotted on reversed phase HPTLC RP-8 F254s and HPTLC RP-18 F254s plates. The plates were then developed using 70/30 methanol/water with 0.1 M ammonium acetate. A dual purpose extraction/electrospray solution containing 70/30/0.1 water/methanol/formic acid was infused through the sampling probe during analysis of the developed lanes. Both full scan mass spectra and data dependent tandem mass spectra were acquired for each development lane to detect and verify the peptide distributions. Data dependent tandem mass spectra provided both protein identification and sequence coverage information. Highest sequence coverages were achieved for cytochrome c. and myoglobin (62.5% and 58.3%, respectively) on reversed phase RP-8 plates. While the tryptic peptides were separated enough for identification, the peptide bands did show some overlap with most peptides located in the lower half of the development lane. Proteins whose peptides were more separated gave higher sequence coverage. Larger proteins such as beta-casein and BSA which were spotted in lower relative amounts gave much lower sequence coverage than the smaller proteins.

  6. Using reverse-phase protein arrays as pharmacodynamic assays for functional proteomics, biomarker discovery, and drug development in cancer.

    PubMed

    Lu, Yiling; Ling, Shiyun; Hegde, Apurva M; Byers, Lauren A; Coombes, Kevin; Mills, Gordon B; Akbani, Rehan

    2016-08-01

    The majority of the targeted therapeutic agents in clinical use target proteins and protein function. Although DNA and RNA analyses have been used extensively to identify novel targets and patients likely to benefit from targeted therapies, these are indirect measures of the levels and functions of most therapeutic targets. More importantly, DNA and RNA analysis is ill-suited for determining the pharmacodynamic effects of target inhibition. Assessing changes in protein levels and function is the most efficient way to evaluate the mechanisms underlying sensitivity and resistance to targeted agents. Understanding these mechanisms is necessary to identify patients likely to benefit from treatment and to develop rational drug combinations to prevent or bypass therapeutic resistance. There is an urgent need for a robust approach to assess protein levels and protein function in model systems and across patient samples. While "shot gun" mass spectrometry can provide in-depth analysis of proteins across a limited number of samples, and emerging approaches such as multiple reaction monitoring have the potential to analyze candidate markers, mass spectrometry has not entered into general use because of the high cost, requirement of extensive analysis and support, and relatively large amount of material needed for analysis. Rather, antibody-based technologies, including immunohistochemistry, radioimmunoassays, enzyme-linked immunosorbent assays (ELISAs), and more recently protein arrays, remain the most common approaches for multiplexed protein analysis. Reverse-phase protein array (RPPA) technology has emerged as a robust, sensitive, cost-effective approach to the analysis of large numbers of samples for quantitative assessment of key members of functional pathways that are affected by tumor-targeting therapeutics. The RPPA platform is a powerful approach for identifying and validating targets, classifying tumor subsets, assessing pharmacodynamics, and identifying prognostic

  7. Influence of microwave irradiation on the mass-transfer kinetics of propylbenzene in reversed-phase liquid chromatography

    SciTech Connect

    Galinada, Wilmer; Kaczmarski, Krzysztof; Guiochon, Georges A

    2005-09-01

    The effect of microwave irradiation on the kinetics of mass transfer in reversed-phase liquid chromatography (RPLC) was studied by measuring its influence on the band profile of propylbenzene in a C{sub 18}-silica column eluted with an aqueous solution of methanol and placed inside a microwave oven. The elution peaks were measured by the pulse-response method, under linear conditions. The amount of microwave energy induced into the column was varied based on the microwave input power. The experimental data were analyzed using the conventional method of moment analysis and the lumped pore diffusion model. With input powers of 15 and 30 W, the effluent temperatures were 25 {+-} 1 and 30 {+-} 1 C, respectively. The effect of microwave irradiation on the mass transfer of the studied solute was determined by comparing the band profiles obtained under the same experimental conditions, at the same temperature, with and without irradiation. The values of the intraparticle diffusion coefficient, D{sub e}, measured with microwave irradiation were ca. 20% higher than those obtained without irradiation. Derived from the method of moments, the values of D{sub e} at 15 W (25 {+-} 1 C) and 0 W (25 {+-} 1 C) were 8.408 x 10{sup -6} cm{sup 2} s{sup -1} and 6.947 x 10{sup -6} cm{sup 2} s{sup -1}, respectively, while these values at 30 W (30 {+-} 1 C) and 0 W (30 {+-} 1 C) were 9.389 x 10{sup -6} cm{sup 2} s{sup -1} and 7.848 x 10{sup -6} cm{sup 2} s{sup -1}, respectively. The values of the surface diffusivity, D{sub S}, also increased with increasing power of the microwave irradiation. It is assumed that the increase in intraparticle diffusion for propylbenzene was caused by the molecular excitation of the organic modifier that has a higher dielectric loss than the solute. The values of D{sub e} were also analyzed and determined using the POR model. There was an excellent agreement between the results of the two independent methods. These preliminary results suggest that microwave

  8. Simultaneous determination of alpha-tocopherol and beta-carotene in olive oil by reversed-phase high-performance liquid chromatography.

    PubMed

    Gimeno, E; Calero, E; Castellote, A I; Lamuela-Raventós, R M; de la Torre, M C; López-Sabater, M C

    2000-06-01

    A reversed-phase high-performance liquid chromatographic method was developed for the determination, in one run, of alpha-tocopherol and beta-carotene in virgin olive oil. The method involved a rapid saponification and a later extraction with a mixture of hexane-ethyl acetate. The chromatographic system consists of an ODS-2 column with a mobile phase of methanol-water-butanol and a diode-array detector. Linearity, precision, recovery and sensitivity were satisfactory. The main advantage of the proposed method is the speed and simultaneous determination of both compounds at the same time. PMID:10905709

  9. Analysis of nucleic acids by capillary ion-pair reversed-phase HPLC coupled to negative-ion electrospray ionization mass spectrometry.

    PubMed

    Huber, C G; Krajete, A

    1999-09-01

    Ion-pair reversed-phase high-performance liquid chromatography was successfully coupled to negative-ion electrospray ionization mass spectrometry by using 60 × 0.20 mm i.d. capillary columns packed with 2.3-μm micropellicular, octadecylated poly(styrene/divinylbenzene) particles as stationary phase and gradients of acetonitrile in 50 mM aqueous triethylammonium bicarbonate as mobile phase. Systematic variation of the eluent composition, such as concentration of ion-pair reagent, anion in the ion-pair reagent, solution pH, and acetonitrile concentration led to the conclusion that most parameters have opposite effects on chromatographic and mass spectrometric performances. The use of acetonitrile as sheath liquid enabled the rapid and highly efficient separation and detection of phosphorylated and nonphosphorylated oligonucleotides ranging in size from 8 to 40 nucleotides. High-quality full-scan mass spectra showing little cation adduction were acquired from which the molecular masses of the separated oligonucleotides were calculated with an accuracy of 0.011%. With calibration curves being linear over at least 2 orders of magnitude, the lower limits of detection for a oligodeoxythymidine 16-mer were 104 fmol with full scan and 710 amol with selected-ion-monitoring data acquisition. The potential of ion-pair reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry was demonstrated for mixed-sequence oligomers by the characterization of a reaction mixture from solid-phase synthesis of a 40-mer oligonucleotide.

  10. Interpretation of the excess adsorption isotherms of organic eluent components on the surface of reversed-phase adsorbents. Effect on the analyte retention.

    PubMed

    Kazakevich, Y V; LoBrutto, R; Chan, F; Patel, T

    2001-04-13

    The excess adsorption isotherms of acetonitrile, methanol and tetrahydrofuran from water on reversed-phase packings were studied, using 10 different columns packed with C1-C6, C8, C10, C12, and C18 monomeric phases, bonded on the same type of silica. The interpretation of isotherms on the basis of the theory of excess adsorption shows significant accumulation of the organic eluent component on the adsorbent surface on the top of "collapsed" bonded layer. The accumulated amount was shown to be practically independent of the length of alkyl chains bonded to the silica surface. A model that describes analyte retention on a reversed-phase column from a binary mobile phase is developed. The retention mechanism involves a combination of analyte distribution between the eluent and organic adsorbed layer, followed by analyte adsorption on the surface of the bonded phase. A general retention equation for the model is derived and methods for independent measurements of the involved parameters are suggested. The theory was tested by direct measurement of analyte retention from the eluents of varied composition and comparison of the values obtained with those theoretically calculated values. Experimental and theoretically calculated values are in good agreement.

  11. Retention data from reverse-phase high-performance thin-layer chromatography in characterization of some bis-salicylic acid derivatives.

    PubMed

    Djaković-Sekulić, Tatjana; Perisić-Janjić, Nada; Djurendi, Evgenija

    2009-08-01

    The chromatographic behaviour of salicylic acid derivatives was investigated using reversed-phase high performance thin-layer chromatography (RP HPTLC) with methanol-water and dioxane-water binary mixtures as mobile phase in order to establish relationships between chromatographic data and selected physico-chemical parameters that are related to ADME (absorption, distribution, metabolism and elimination). Some of the investigated compounds were screened for antioxidant activity. Examination of chromatographic behaviour revealed a linear correlation between R(M) values and the volume fraction of mobile phase modifier. Obtained R(M)(0) values were correlated with lipophilicity, solubility, human intestinal absorption, plasma-protein binding, and blood-brain barrier data. The comparison among chromatographic data obtained by two mobile phase was performed with a statistical technique, principle component analysis.

  12. Incorporation of ionic liquid into porous polymer monoliths to enhance the separation of small molecules in reversed-phase high-performance liquid chromatography.

    PubMed

    Wang, Jiafei; Bai, Ligai; Wei, Zhen; Qin, Junxiao; Ma, Yamin; Liu, Haiyan

    2015-06-01

    An ionic liquid was incorporated into the porous polymer monoliths to afford stationary phases with enhanced chromatographic performance for small molecules in reversed-phase high-performance liquid chromatography. The effect of the ionic liquid in the polymerization mixture on the performance of the monoliths was studied in detail. While monoliths without ionic liquid exhibited poor resolution and low efficiency, the addition of ionic liquid to the polymerization mixture provides highly increased resolution and high efficiency. The chromatographic performances of the monoliths were demonstrated by the separations of various small molecules including aromatic hydrocarbons, isomers, and homologues using a binary polar mobile phase. The present column efficiency reached 27 000 plates/m, which showed that the ionic liquid monoliths are alternative stationary phases in the separation of small molecules by high-performance liquid chromatography.

  13. Non-particulate (continuous bed or monolithic) restricted-access reversed-phase media for sample clean-up and separation by capillary-format liquid chromatography.

    PubMed

    Jarmalaviciene, Reda; Kornysova, Olga; Westerlund, Douglas; Maruska, Audrius

    2003-11-01

    Restricted-access reversed-phase non-particulate (continuous bed or monolithic) stationary phases of different hydrophobicity synthesized in 100 microm i.d. fused silica capillaries have been evaluated. A specific property of restricted-access media (RAM) is that they interact with small analytes and exclude big molecules, e.g. proteins, from access to the active sites and adsorption on the surface. This dual property facilitates direct injection of biological fluids for drug or drug-metabolite analysis. Different RAM and RAM-precursor capillary columns were tested to assess the influence of chromatographic bed morphology on loadability. Inverse size-exclusion chromatography was used for investigation of pore structural properties of the capillary-format continuous beds. The data obtained were used to discuss the mechanism of separation of the biological samples using capillary columns and to propose a model for the topochemical architecture of the RAM investigated. Different morphology of the non-particulate reversed-phase precursors resulted in two types of RAM material shielded with hydrophilic polymer, classified as homogeneous or heterogeneous topochemistry stationary phases. Capillary columns were applied for chromatography of biological fluids. High resolution was obtained, without the need for column switching, when capillary columns operated in gradient conditions. Extensive evaluation of the chromatographic properties (hydrophobicity, efficiency, separation impedance, and loadability) of the non-particulate reversed-phase materials was performed before and after shielding with hydrophilic polymer to generate restricted-access properties. Minor changes of hydrophobicity, efficiency, or separation impedance were observed after the shielding. PMID:14513200

  14. The evolution of granule fracture strength as a function of impeller tip speed and granule size for a novel reverse-phase wet granulation process.

    PubMed

    Wade, J B; Martin, G P; Long, D F

    2015-07-01

    The feasibility of a novel reverse-phase wet granulation process has been established previously and several potential advantages over the conventional process have been highlighted (Wade et al., 2014a,b,b). Due to fundamental differences in the growth mechanism and granule consolidation behaviour between the two processes the reverse-phase approach generally formed granules with a greater mass mean diameter and a lower intragranular porosity than those formed by the conventional granulation process under the same liquid saturation and impeller tip speed conditions. The lower intragranular porosity was hypothesised to result in an increase in the granule strength and subsequent decrease in tablet tensile strength. Consequently, the aim of this study was to compare the effect of impeller tip speed and granule size on the strength and compaction properties of granules prepared using both the reverse-phase and conventional granulation processes. For the conventional granulation process an increase in the impeller tip speed from 1.57 to 4.71 ms(-1) (200-600 RPM) resulted in an increase in the mean granule strength (p<0.05) for all granule size fractions and as the granule size fraction increased from 425-600 to 2000-3350 μm the mean fracture strength decreased (p<0.05). For the reverse-phase process an increase in impeller tip speed had no effect (p>0.05) on mean granule strength whereas, like the conventional process, an increase in granule size fraction from 425-600 to 2000-3350 μm resulted in a decrease (p<0.05) in the mean fracture strength. No correlation was found between mean granule fracture strength and the tablet tensile strength (p>0.05) for either granulation approach. These data support the rejection of the original hypothesis which stated that an increase in granule strength may result in a decrease in the tablet tensile strength. The similar tablet tensile strength observed between the conventional and reverse-phase granulation processes indicated that

  15. Reversible Phase Change Characteristics of Cr-Doped Sb2Te3 Films with Different Initial States Induced by Femtosecond Pulses.

    PubMed

    Wang, Qing; Jiang, Minghui; Liu, Bo; Wang, Yang; Zheng, Yonghui; Song, Sannian; Wu, Yiqun; Song, Zhitang; Feng, Songlin

    2016-08-17

    As a kind of chalcogenide alloy, phase change material has been widely used as novel storage medium in optical disk or electrical memory. In this paper, femtosecond pulses are used to study the reversible phase transition processes of Cr-doped Sb2Te3 films with different initial states. The SET processes are all induced by multiple pulses and relate to the increase of crystallized partial in the irradiated spot. When the Cr concentration is 5.3 at % or 10.5 at %, the crystallization mechanism is still growth-dominated as Sb2Te3, which is beneficial for high speed and high density storage, whereas the necessary crystallization energy increases with more Cr-dopants, leading to higher amorphous thermal stability. RESET results by multiple pulses show that Cr-dopants will not increase the power consumption, and the increase in Cr-dopants could greatly increase the antioxidant capacity. Single-pulse experiments show that the RESET process involves the competition of melting/amorphization and recrystallization. The reversible SET/RESET results on different initial states are quite different from each other, which is mainly due to the different surroundings around the irradiated spot. Crystalline surroundings provide higher thermal conductivity and lead to easier crystallization, whereas amorphous surroundings were the reverse. All in all, Cr-doped Sb2Te3 films with suitable composition have advantages for storage with high density, better thermal stability, and lower power consumption; and the suitable initial states could ensure better reversible phase transition performances. PMID:27459421

  16. A mathematical recursive model for accurate description of the phase behavior in the near-critical region by Generalized van der Waals Equation

    NASA Astrophysics Data System (ADS)

    Kim, Jibeom; Jeon, Joonhyeon

    2015-01-01

    Recently, related studies on Equation Of State (EOS) have reported that generalized van der Waals (GvdW) shows poor representations in the near critical region for non-polar and non-sphere molecules. Hence, there are still remains a problem of GvdW parameters to minimize loss in describing saturated vapor densities and vice versa. This paper describes a recursive model GvdW (rGvdW) for an accurate representation of pure fluid materials in the near critical region. For the performance evaluation of rGvdW in the near critical region, other EOS models are also applied together with two pure molecule group: alkane and amine. The comparison results show rGvdW provides much more accurate and reliable predictions of pressure than the others. The calculating model of EOS through this approach gives an additional insight into the physical significance of accurate prediction of pressure in the nearcritical region.

  17. On thermodynamic and microscopic reversibility

    SciTech Connect

    Crooks, Gavin E.

    2011-07-12

    The word 'reversible' has two (apparently) distinct applications in statistical thermodynamics. A thermodynamically reversible process indicates an experimental protocol for which the entropy change is zero, whereas the principle of microscopic reversibility asserts that the probability of any trajectory of a system through phase space equals that of the time reversed trajectory. However, these two terms are actually synonymous: a thermodynamically reversible process is microscopically reversible, and vice versa.

  18. Development and Validation of a Reversed-Phase HPLC Method for the Quantitative Determination of Ten Polyphenols Extracted from Apple Peel.

    PubMed

    Ran, Junjian; Sun, Huadi; Zhu, Mingming; Chen, Juan; Zhao, Ruixiang

    2016-01-01

    A method based on a reversed-phase HPLC method was established, optimized, and validated for the separation and quantitation of 10 polyphenols extracted from the peel of apple species. A bidentate reversed-phase C18 column was used as stationary phase, and an acidified water buffer and methanol were used as mobile phase. The polyphenols were well separated and detected using UV at 280 and 320 nm. Validation parameters, such as linearity, LOD, LOQ, accuracy, and precision, were acceptable for all 10 polyphenols. The proposed method has enough linearity with correlation coefficient >0.99 within the investigated range for all tested polyphenols. The LOD was 0.24 μg/mL for ellagic acid and <0.2 μg/mL for all other polyphenols. The LOQ was 9.39 × 10(-2) μg/mL for chlorogenic acid, and ellagic acid, 2.82 × 10(-2) μg/mL for caffeic acid and >0.1 μg/mL for all other polyphenols. Recovery was within the acceptable range from 98.38 to 100.39% for all polyphenols standards. Satisfactory precision was achieved for both intra- and interday assay, with RSD <2%. The method was successfully applied for simultaneous analysis of polyphenols from apple peel. PMID:26952990

  19. Thermally Induced Reversible Double Phase Transitions in an Organic-Inorganic Hybrid Iodoplumbate C4H12NPbI3 with Symmetry Breaking.

    PubMed

    Liu, Guangfeng; Liu, Jie; Sun, Zhihua; Zhang, Zhenyi; Chang, Lei; Wang, Junling; Tao, Xutang; Zhang, Qichun

    2016-08-15

    A one-dimensional (1D) organic-inorganic hybrid iodoplumbate crystal (1, C4H12NPbI3, TMAPbI3) can undergo two reversible phase transitions as the temperature decreases. Its dynamic phase-transition behaviors were carefully studied by dielectric measurements, thermal analysis, and variable-temperature crystallographic studies. These results indicate that the phase transitions possess a disorder-order feature with a noncentrosymmetrical intermediate phase structure. Due to the existence of the ordered motion and reorientation of the C4H12N(+) cation, 1 undergoes two phase transitions: the first one from space group P63/m at room temperature to Pm at 163 K with symmetry breaking, and the second one from space group Pm at 163 K to P61 at 142 K with partial symmetry restoration. Our results indicate that there is an existence of a transitional structure with a low symmetry space group during the disorder-order-type phase transitions, which can provide us valuable information to deeply understand the disorder-order phase transition in organic-inorganic hybrids. PMID:27459127

  20. Phase-coded microwave signal generation based on a single electro-optical modulator and its application in accurate distance measurement.

    PubMed

    Zhang, Fangzheng; Ge, Xiaozhong; Gao, Bindong; Pan, Shilong

    2015-08-24

    A novel scheme for photonic generation of a phase-coded microwave signal is proposed and its application in one-dimension distance measurement is demonstrated. The proposed signal generator has a simple and compact structure based on a single dual-polarization modulator. Besides, the generated phase-coded signal is stable and free from the DC and low-frequency backgrounds. An experiment is carried out. A 2 Gb/s phase-coded signal at 20 GHz is successfully generated, and the recovered phase information agrees well with the input 13-bit Barker code. To further investigate the performance of the proposed signal generator, its application in one-dimension distance measurement is demonstrated. The measurement accuracy is less than 1.7 centimeters within a measurement range of ~2 meters. The experimental results can verify the feasibility of the proposed phase-coded microwave signal generator and also provide strong evidence to support its practical applications.

  1. Reversible hydration and aqueous exfoliation of the acetate-intercalated layered double hydroxide of Ni and Al: Observation of an ordered interstratified phase

    NASA Astrophysics Data System (ADS)

    Manohara, G. V.; Vishnu Kamath, P.; Milius, Wolfgang

    2012-12-01

    Acetate-intercalated layered double hydroxides (LDHs) of Ni and Al undergo reversible hydration in the solid state in response to the ambient humidity. The LDH with a high layer charge (0.33/formula unit) undergoes facile hydration in a single step, whereas the LDH with a lower layer charge (0.24/formula unit) exhibits an ordered interstratified intermediate, comprising the hydrated and dehydrated layers stacked alternatively. This phase, also known as the staged S-2 phase, coexists with the end members suggesting the existence of a solution-type equilibrium between the S-2 phase and the end members of the hydration cycle. These LDHs also undergo facile aqueous exfoliation into 2-5 nm-thick tactoids with a radial dimension of 0.2-0.5 μm.

  2. Reversible bulk-phase change of anthroyl compounds for photopatterning based on photodimerization in the molten state and thermal back reaction.

    PubMed

    Kihara, Hideyuki; Yoshida, Masaru

    2013-04-10

    As new organic materials for rewritable photopatterning, 2-anthroyl and 9-anthroyl ester compounds were synthesized. Their bulk-phase changes (we use "bulk-phase change" as complete phase change in a mass of a material neither in a surface nor in a small quantity in this study) triggered by photodimerization under melting conditions (melt-photodimerization) and subsequent thermal back reactions were investigated. All the anthroyl compounds exhibited melting points lower than ca. 160 °C, and they were nearly quantitatively converted to the corresponding photodimers by UV irradiation at temperatures of ∼5 °C higher than their respective melting points. We found that there were two kinds of bulk-phase change behaviors through the photoreaction. Two of the anthroyl compounds remained isotropic and lost fluidity during the melt-photodimerization. The obtained photodimers exhibited robust solid-state amorphous phases at room temperature. In contrast, the other three anthroyl compounds showed crystallization during the melt-photodimerization. The resulting photodimers changed from isotropic to crystalline phases, even at high temperature. Various experiments revealed that the bulk phase of the photodimers was affected not by the existence of regioisomers but by their fluidity at the photoirradiation temperature. The latter three photodimers retained enough fluidity, reflecting their high molecular mobilities at the photoirradiation temperature at which the isothermal crystallization occurred. The other two products were not able to crystallize due to low fluidity, resulting in amorphous phases. We also found that all the photodimers reverted to the corresponding monomers by thermal back reaction and recovered their initial photochemical and thermal properties. Using these reversible bulk-phase changes of the anthroyl compounds, we successfully demonstrated rewritable photopatterning in not only negative images but also positive ones, based on the optical contrast

  3. Vibratory hub load data reduction and analysis from the reverse velocity rotor wind tunnel test, phase 2B

    NASA Technical Reports Server (NTRS)

    Taylor, R. B.

    1976-01-01

    The vibratory hub loads data analysis from the reverse velocity rotor wind tunnel test is reported. Vibratory loads were obtained from the rotating hub balance and also by synthesis of generalized coordinates from the blade flap bending moments. Load trends were defined as a function of speed, rotor thrust and 2 per rev cyclic from each of the data methods. These trends were compared to determine the degree of agreement between each method and provide substantiation for the generalized coordinate approach.

  4. Magneto-optical measurements as tests for time-reversal symmetry breaking in the hidden order and superconducting phases of URu2Si2

    NASA Astrophysics Data System (ADS)

    Kapitulnik, Aharon

    It is now experimentally well established that the superconducting (SC) phase of URu2Si2 with Tc =1.5K emerges from the hidden order (HO) phase with THO = 17.5K. Thus, it is of great interest to discern the different symmetries of both phases. In particular, recent theoretical proposals for time-reversal symmetry breaking (TRSB) order parameters of either phases pose the question of whether the HO one drives the SC one, or TRSB appears in the SC phase independently. In this talk we report high resolution polar Kerr effect (PKE) measurements as a function of temperature for several high-quality single crystals of URu2Si2. We find an onset of PKE below the superconducting transition that is consistent with a TRS-breaking order parameter. This effect appears to be independent of an additional, possibly extrinsic, PKE generated in the hidden order phase, and contains structure below Tc suggestive of additional physics within the superconducting state. Work supported by DOE.

  5. Optimum separation and compound class separation of the metabolites of benzo[a]pyrene-DNA adducts with reversed-phase liquid chromatography

    SciTech Connect

    Rozbeh, M.; Hurtubise, R.J. . Dept. of Chemistry)

    1994-01-01

    Mobile phases were optimized for the reversed-phase liquid chromatographic separation of a complex mixtures of fourteen metabolites of benzo[a]pyrene (B[a]P). The metabolites constituted groups of isomers that were difficult to separate. The groups of isomers were tetrols, dihydrodiols, diones, and monohydroxyl-benzo[a]pyrenes. The window diagram optimization approach was used to initially optimize the binary mobile phases. Based on the data obtained from the optimum binary mobile phases, a solubility parameter optimization method was employed to obtain an optimum ternary mobile phase. Both the binary and ternary mobile phases were very effective in separating the metabolites. However, complete baseline resolution of the complex mixture of the metabolites was not achieved under the conditions investigated. Nevertheless, it was possible to obtain a separation of all fourteen of the metabolites with some overlap of the chromatographic bands. Also, compound class separation was obtained with the classes separating in the order of tetrols, diones, dihydrodiols, and monohydroxyl-benzo[a]pyrenes.

  6. Lipophilicity indices derived from the liquid chromatographic behavior observed under bimodal retention conditions (reversed phase/hydrophilic interaction): application to a representative set of pyridinium oximes.

    PubMed

    Voicu, Victor; Sârbu, Costel; Tache, Florentin; Micăle, Florina; Rădulescu, Ştefan Flavian; Sakurada, Koichi; Ohta, Hikoto; Medvedovici, Andrei

    2014-05-01

    The liquid chromatographic behavior observed under bimodal retention conditions (reversed phase and hydrophilic interaction) offers a new basis for the determination of some derived lipophilicity indices. The experiments were carried out on a representative group (30 compounds) of pyridinium oximes, therapeutically tested in acetylcholinesterase reactivation, covering a large range of lipophilic character. The chromatographic behavior was observed on a mixed mode acting stationary phase, resulting from covalent functionalization of high purity spherical silica with long chain alkyl groups terminated by a polar environment created through the vicinal diol substitution at the lasting carbon atoms (Acclaim Mixed Mode HILIC 1 column). Elution was achieved by combining different proportions of 5 mM ammonium formiate solutions in water and acetonitrile. The derived lipophilicity indices were compared with logP values resulting from different computational algorithms. The correlations between experimental and computed data sets are significant. To obtain a better insight on the transition from reversed phase to hydrophilic interaction retention mechanisms, the variation of the thermodynamic parameters determined through the van׳t Hoff approach was also discussed. PMID:24720980

  7. Reversible switching from antiferro- to ferromagnetic behavior by solvent-mediated, thermally-induced phase transitions in a trimorphic MOF-based magnetic sponge system.

    PubMed

    Wriedt, Mario; Yakovenko, Andrey A; Halder, Gregory J; Prosvirin, Andrey V; Dunbar, Kim R; Zhou, Hong-Cai

    2013-03-13

    Hydrothermal reactions of copper(II) acetate, tetrazolate-5-carboxylate (tzc), and the neutral N-donor spacer ligand 1,3-di(4-pyridyl)propane (dpp) lead in a single reaction vial to the simultaneous formation of three different single-crystalline solvates [Cu(tzc)(dpp)]n·0.5C6H14·0.5H2O (1), [Cu(tzc)(dpp)]n·4.5H2O (2), and [Cu(tzc)(dpp)]n·1.25C6H14 (3). All three structures were characterized by single crystal X-ray diffraction. None of these solvates can be prepared as phase-pure bulk materials, but reaction conditions similar to those used for single crystal synthesis yield a phase-pure polycrystalline bulk material of an additional forth solvate phase [Cu(tzc)(dpp)]n·2H2O (4). Investigations of its thermal properties by in situ temperature-dependent synchrotron-based powder diffraction experiments have shown interesting phase transitions upon heating in a helium stream. Initially, the precursor dihydrate 4 transforms to an anhydrous phase [Cu(tzc)(dpp)]n (6I) via the intermediate monohydrate phase [Cu(tzc)(dpp)]n·H2O (5). Upon further heating, phase 6I transforms to a new anhydrous polymorph 6II, which transforms upon cooling to a further new phase 6III. Thermogravimetric measurements performed in tandem with differential scanning calorimetry as well as infrared spectroscopic investigations are in agreement with these findings. The de/resolvation behavior is accompanied by a dramatic change in their magnetic properties: The dihydrate phase shows antiferromagnetic exchange interactions, whereas ferromagnetic properties are observed for the trimorphic anhydrate system. This magnetic sponge-like behavior can be reversibly cycled upon de/resolvation of the material. PMID:23414430

  8. Complementing reversed-phase selectivity with porous graphitized carbon to increase the metabolome coverage in an on-line two-dimensional LC-MS setup for metabolomics.

    PubMed

    Ortmayr, Karin; Hann, Stephan; Koellensperger, Gunda

    2015-05-21

    Efficient and robust separation methods are indispensable in modern LC-MS based metabolomics, where high-resolution mass spectrometers are challenged by isomeric and isobaric metabolites. The optimization of chromatographic separation hence remains an invaluable tool in the comprehensive analysis of the chemically diverse intracellular metabolome. While it is widely accepted that a single method with comprehensive metabolome coverage does not exist, the potential of combining different chromatographic selectivities in two-dimensional liquid chromatography is underestimated in the field. Here, we introduce a novel separation system combining reversed-phase and porous graphitized carbon liquid chromatography in a heart-cut on-line two-dimensional setup for mass spectrometry. The proposed experimental setup can be readily implemented using standard HPLC equipment with only one additional HPLC pump and a two-position six-port valve. The method proved to be robust with excellent retention time stability (average 0.4%) even in the presence of biological matrix. Testing the presented approach on a test mixture of 82 relevant intracellular metabolites, the number of metabolites that are retained could be doubled as compared to reversed-phase liquid chromatography alone. The presented work further demonstrates how the distinct selectivity of porous graphitized carbon complements reversed-phase liquid chromatography and extends the metabolome coverage of conventional LC-MS based methods in metabolomics to biologically important, but analytically challenging compound groups such as sugar phosphates. Both metabolic profiling and metabolic fingerprinting benefit from this method's increased separation capabilities that enhance sample throughput and the biological information content of LC-MS data. An inter-platform comparison with GC- and LC-tandem MS analyses confirmed the validity of the presented two-dimensional approach in the analysis of yeast cell extracts from P

  9. A novel evaluation method for extrapolated retention factor in determination of n-octanol/water partition coefficient of halogenated organic pollutants by reversed-phase high performance liquid chromatography.

    PubMed

    Han, Shu-ying; Liang, Chao; Qiao, Jun-qin; Lian, Hong-zhen; Ge, Xin; Chen, Hong-yuan

    2012-02-01

    The retention factor corresponding to pure water in reversed-phase high performance liquid chromatography (RP-HPLC), k(w), was commonly obtained by extrapolation of retention factor (k) in a mixture of organic modifier and water as mobile phase in tedious experiments. In this paper, a relationship between logk(w) and logk for directly determining k(w) has been proposed for the first time. With a satisfactory validation, the approach was confirmed to enable easy and accurate evaluation of k(w) for compounds in question with similar structure to model compounds. Eight PCB congeners with different degree of chlorination were selected as a training set for modeling the logk(w)-logk correlation on both silica-based C(8) and C(18) stationary phases to evaluate logk(w) of sample compounds including seven PCB, six PBB and eight PBDE congeners. These eight model PCBs were subsequently combined with seven structure-similar benzene derivatives possessing reliable experimental K(ow) values as a whole training set for logK(ow)-logk(w) regressions on the two stationary phases. Consequently, the evaluated logk(w) values of sample compounds were used to determine their logK(ow) by the derived logK(ow)-logk(w) models. The logK(ow) values obtained by these evaluated logk(w) were well comparable with those obtained by experimental-extrapolated logk(w), demonstrating that the proposed method for logk(w) evaluation in this present study could be an effective means in lipophilicity study of environmental contaminants with numerous congeners. As a result, logK(ow) data of many PCBs, PBBs and PBDEs could be offered. These contaminants are considered to widely exist in the environment, but there have been no reliable experimental K(ow) data available yet. PMID:22200319

  10. Simultaneous separation by reversed-phase high-performance liquid chromatography and mass spectral identification of anthocyanins and flavonols in Shiraz grape skin.

    PubMed

    Downey, Mark O; Rochfort, Simone

    2008-08-01

    A limitation of large-scale viticultural trials is the time and cost of comprehensive compositional analysis of the fruit by high-performance liquid chromatography (HPLC). In addition, separate methods have generally been required to identify and quantify different classes of metabolites. To address these shortcomings a reversed-phase HPLC method was developed to simultaneously separate the anthocyanins and flavonols present in grape skins. The method employs a methanol and water gradient acidified with 10% formic acid with a run-time of 48 min including re-equilibration. Identity of anthocyanins and flavonols in Shiraz (Vitis vinifera L.) skin was confirmed by mass spectral analysis. PMID:18573501

  11. Simple method for the extraction and reversed-phase high-performance liquid chromatographic analysis of carotenoid pigments from red yeasts (Basidiomycota, Fungi).

    PubMed

    Weber, Roland W S; Anke, Heidrun; Davoli, Paolo

    2007-03-23

    A simple method for the extraction of carotenoid pigments from frozen wet cells of red yeasts (Basidiomycota) and their analysis by reversed-phase HPLC using a C(18) column and a water/acetone solvent system is described. Typical red yeast carotenoids belonging to an oxidative series from the monocyclic gamma-carotene to 2-hydroxytorularhodin and from the bicyclic beta-carotene to astaxanthin were separated. Pigment identity was confirmed by LC-atmospheric pressure chemical ionisation (APCI) mass spectrometry using similar chromatographic conditions.

  12. Effect of pressure on the selectivity of polymeric C18 and C30 stationary phases in reversed-phase liquid chromatography. Increased separation of isomeric fatty acid methyl esters, triacylglycerols, and tocopherols at high pressure.

    PubMed

    Okusa, Kensuke; Iwasaki, Yuki; Kuroda, Ikuma; Miwa, Shohei; Ohira, Masayoshi; Nagai, Toshiharu; Mizobe, Hoyo; Gotoh, Naohiro; Ikegami, Tohru; McCalley, David V; Tanaka, Nobuo

    2014-04-25

    A high-density, polymeric C18 stationary phase (Inertsil ODS-P) or a polymeric C30 phase (Inertsil C30) provided improved resolution of the isomeric fatty acids (FAs), FA methyl esters (FAMEs), triacylglycerols (TAGs), and tocopherols with an increase in pressure of 20-70MPa in reversed-phase HPLC. With respect to isomeric C18 FAMEs with one cis-double bond, ODS-P phase was effective for recognizing the position of a double bond among petroselinic (methyl 6Z-octadecenoate), oleic (methyl 9Z-octadecenoate), and cis-vaccenic (methyl 11Z-octadecenoate), especially at high pressure, but the differentiation between oleic and cis-vaccenic was not achieved by C30 phase regardless of the pressure. A monomeric C18 phase (InertSustain C18) was not effective for recognizing the position of the double bond in monounsaturated FAME, while the separation of cis- and trans-isomers was achieved by any of the stationary phases. The ODS-P and C30 phases provided increased separation for TAGs and β- and γ-tocopherols at high pressure. The transfer of FA, FAME, or TAG molecules from the mobile phase to the ODS-P stationary phase was accompanied by large volume reduction (-30∼-90mL/mol) resulting in a large increase in retention (up to 100% for an increase of 50MPa) and improved isomer separation at high pressure. For some isomer pairs, the ODS-P and C30 provided the opposite elution order, and in each case higher pressure improved the separation. The two stationary phases showed selectivity for the isomers having rigid structures, but only the ODS-P was effective for differentiating the position of a double bond in monounsaturated FAMEs. The results indicate that the improved isomer separation was provided by the increased dispersion interactions between the solute and the binding site of the stationary phase at high pressure.

  13. Design of Phosphonium-Type Zwitterion as an Additive to Improve Saturated Water Content of Phase-Separated Ionic Liquid from Aqueous Phase toward Reversible Extraction of Proteins

    PubMed Central

    Ito, Yoritsugu; Kohno, Yuki; Nakamura, Nobuhumi; Ohno, Hiroyuki

    2013-01-01

    We designed phosphonium-type zwitterion (ZI) to control the saturated water content of separated ionic liquid (IL) phase in the hydrophobic IL/water biphasic systems. The saturated water content of separated IL phase, 1-butyl-3-methyimidazolium bis(trifluoromethanesulfonyl)imide, was considerably improved from 0.4 wt% to 62.8 wt% by adding N,N,N-tripentyl-4-sulfonyl-1-butanephosphonium-type ZI (P555C4S). In addition, the maximum water content decreased from 62.8 wt% to 34.1 wt% by increasing KH2PO4/K2HPO4 salt content in upper aqueous phosphate buffer phase. Horse heart cytochrome c (cyt.c) was dissolved selectively in IL phase by improving the water content of IL phase, and spectroscopic analysis revealed that the dissolved cyt.c retained its higher ordered structure. Furthermore, cyt. c dissolved in IL phase was re-extracted again from IL phase to aqueous phase by increasing the concentration of inorganic salts of the buffer solution. PMID:24013379

  14. Enzymatic hydrolysis of penicillin and in situ product separation in thermally induced reversible phase-separation of ionic liquids/water mixture.

    PubMed

    Mai, Ngoc Lan; Koo, Yoon-Mo

    2014-09-01

    Enzymatic hydrolysis of penicillin G to produce 6-aminopenicillanic acid, key intermediate for the production of semisynthetic β-lactam antibiotics, is one of the most relevant example of industrial implementation of biocatalysts. The hydrolysis reaction is traditionally carried out in aqueous buffer at pH 7.5-8. However, the aqueous rout exhibits several drawbacks in enzyme stability and product recovery. In this study, several ionic liquids (ILs) have been used as media for enzymatic hydrolysis of penicillin G. The results indicated that hydrophobic ILs/water two-phase system were good media for the reaction. In addition, a novel aqueous two-phase system based on the lower critical solution temperature type phase changes of amino acid based ILs/water mixture was developed for in situ penicillin G hydrolysis and product separation. For instance, hydrolysis yield of 87.13% was obtained in system containing 30 wt% [TBP][Tf-ILe] with pH control (pH 7.6). Since the phase-separation of this medium system can be reversible switched from single to two phases by slightly changing the solution temperature, enzymatic hydrolytic reaction and product recovery were more efficient than those of aqueous system. In addition, the ILs could be reused for at least 5 cycles without significant loss in hydrolysis efficiency. PMID:25039057

  15. Enzymatic hydrolysis of penicillin and in situ product separation in thermally induced reversible phase-separation of ionic liquids/water mixture.

    PubMed

    Mai, Ngoc Lan; Koo, Yoon-Mo

    2014-09-01

    Enzymatic hydrolysis of penicillin G to produce 6-aminopenicillanic acid, key intermediate for the production of semisynthetic β-lactam antibiotics, is one of the most relevant example of industrial implementation of biocatalysts. The hydrolysis reaction is traditionally carried out in aqueous buffer at pH 7.5-8. However, the aqueous rout exhibits several drawbacks in enzyme stability and product recovery. In this study, several ionic liquids (ILs) have been used as media for enzymatic hydrolysis of penicillin G. The results indicated that hydrophobic ILs/water two-phase system were good media for the reaction. In addition, a novel aqueous two-phase system based on the lower critical solution temperature type phase changes of amino acid based ILs/water mixture was developed for in situ penicillin G hydrolysis and product separation. For instance, hydrolysis yield of 87.13% was obtained in system containing 30 wt% [TBP][Tf-ILe] with pH control (pH 7.6). Since the phase-separation of this medium system can be reversible switched from single to two phases by slightly changing the solution temperature, enzymatic hydrolytic reaction and product recovery were more efficient than those of aqueous system. In addition, the ILs could be reused for at least 5 cycles without significant loss in hydrolysis efficiency.

  16. Development of 0.5-5 W, 10K Reverse Brayton Cycle Cryocoolers - Phase II Final Report

    SciTech Connect

    Doty, F. D.; Boman, A.; Arnold, S.; Spitzmesser, J. B.; Jones, D.; McCree, D.; Hacker, L. J.

    2001-10-15

    Miniature cryocoolers for the 8-30 K range are needed to provide 0.5-5 w of cooling to high sensitivity detectors (for long-wave-length IR, magnetism, mm-wave, X-ray, dark matter, and possibly y-ray detection) while maintaining low mass, ultra-low vibration, and good efficiency. This project presents a new approach to eliminating the problems normally encountered in efforts to build low-vibration, fieldable, miniature cryocoolers. Using the reverse Brayton Cycle (RBC), the approach applies and expands on existing spinner technology previously used only in Nuclear Magnetic Resonance (NMR) probes.

  17. Separation of Cinchona alkaloids on a novel strong cation-exchange-type chiral stationary phase-comparison with commercially available strong cation exchanger and reversed-phase packing materials.

    PubMed

    Hoffmann, Christian V; Lämmerhofer, Michael; Lindner, Wolfgang

    2009-02-01

    A recently reported chiral strong cation exchanger (cSCX) type stationary phase was investigated for the LC separation of a series of Cinchona alkaloids and synthetic derivatives thereof to test its usefulness as alternative methodology for the separation of those important pharmaceuticals. The cSCX column-packing material was qualitatively compared on the one hand against a commercially available non-enantioselective SCX-material, PolySulfoethyl-A, and, on the other hand, against a modern C18 reversed-phase stationary phase which is commonly employed for Cinchona alkaloid analysis. Both SCX columns showed no pronounced peak-tailing phenomena which typically hamper Cinchona alkaloid RP analysis and require specific optimization. Thus, the cSCX-based assay provided new feasibilities for the separation of the Cinchona alkaloids in polar organic mode as opposed to conventional reversed-phase methodologies. In particular, a method for the simultaneous determination of eight Cinchona alkaloids (quinine, quinidine, cinchonine, cinchonidine, and their corresponding dihydro analogs) using the cSCX column in HPLC has been developed and exemplarily applied to impurity profiling of a commercial alkaloid sample. Furthermore, both SCX materials allowed successful separation of C9-epi and 10,11-didehydro derivatives from their respective educts in an application in synthetic Cinchona alkaloid chemistry. PMID:19107468

  18. Porous silica particles grafted with an amphiphilic side-chain polymer as a stationary phase in reversed-phase high-performance liquid chromatography.

    PubMed

    Shahruzzaman, Md; Takafuji, Makoto; Ihara, Hirotaka

    2015-07-01

    The amphiphilic polymer-grafted silica was newly prepared as a stationary phase in high-performance liquid chromatography. Poly(4-vinylpyridine) with a trimethoxysilyl group at one end was grafted onto porous silica particles and the pyridyl side chains were quaternized with 1-bromooctadecane. The obtained poly(octadecylpyridinium)-grafted silica was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy and Brunauer-Emmett-Teller analysis. The degree of quaternization of the pyridyl groups on the obtained stationary phase was estimated to be 70%. The selective retention behaviors of polycyclic aromatic hydrocarbons including some positional isomers were investigated using poly(octadecylpyridinium)-grafted silica as an amphiphilic polymer stationary phase in high-performance liquid chromatography and results were compared with commercially available polymeric octadecylated silica and phenyl-bonded silica columns. The results indicate that the selectivity toward polycyclic aromatic hydrocarbons exhibited by the amphiphilic polymer stationary phase is higher than the corresponding selectivity exhibited by a conventional phenyl-bonded silica column. However, compared with the polymeric octadecylated silica phase, the new stationary phase presents similar retention behavior for polycyclic aromatic hydrocarbons but different retention behavior particularly for positional isomers of disubstituted benzenes as the aggregation structure of amphiphilic polymers on the surface of silica substrate has been altered during mobile phase variation.

  19. Qualitative and quantitative determination of sesquiterpenoids in Achillea species by reversed-phase high-performance liquid chromatography, mass-spectrometry and thin-layer chromatography.

    PubMed

    Glasl, S; Kastner, U; Jurenitsch, J; Kubelka, W

    1999-06-11

    A reversed-phase high-performance liquid chromatographic method was developed as a universal analysis system in order to determine and quantify antiphlogistic sesquiterpenoids in different Achillea species. Identification was performed by HPLC and diode array detection as well as by monitoring the HPLC fractions by TLC and MS. Using santonin as internal standard, HPLC separations were achieved with a methanol-water gradient system using RP 8 LiChrospher 100 (5 microm) as stationary phase. For validation, sample analyses were performed, using the two tetraploid species A. collina and A. pratensis. The method allows the identification and quantification of the main compounds achillicin, 8alpha-tigloxy-artabsin, 8alpha-angeloxy-artabsin, arglanin and santamarin with variation coefficients between 3.4 and 4.7% (total content) using santonin as internal standard. For the different compounds recovery was found between 81 and 107% performing multiple analyses of A. collina and A. pratensis.

  20. Mass spectrometric elucidation of triacylglycerol content of Brevoortia tyrannus (menhaden) oil using non-aqueous reversed-phase liquid chromatography under ultra high pressure conditions.

    PubMed

    Dugo, Paola; Beccaria, Marco; Fawzy, Nermeen; Donato, Paola; Cacciola, Francesco; Mondello, Luigi

    2012-10-12

    A non-aqueous reversed phase high performance liquid chromatography method was developed, and optimized for triacylglycerol analysis in a Brevoortia tyrannus (menhaden) oil sample. Four columns were serially coupled to tackle such a task, for a total length of 60 cm of shell-packed stationary phase, and operated under ultra high pressure conditions. As detection, positive-ion atmospheric pressure chemical ionization mass spectrometry was used to attain identification of the analyzed sample components. A number of 137 triacylglycerols containing up to 19 fatty acids, with 14-22 carbon atom alkyl chain length and 0-6 double bonds, were positively identified in the complex lipidic sample. This is the first work that reports an extensive characterization of the triacylglycerol fraction of menhaden oil. PMID:22503927

  1. Determination of 1,7,7-Trimethyl-bicyclo(2,2,1)heptan-2-one in a Cream Pharmaceutical Formulation by Reversed-phase Liquid Chromatography

    PubMed Central

    Shabir, G. A.; Bradshaw, T. K.

    2010-01-01

    A reversed-phase liquid chromatographic method for the determination of 1,7,7-trimethyl-bicyclo(2,2,1)heptan-2-one in a cream formulation is developed and validated. The separation was achieved using an isocratic mobile phase, on a Lichrosorb C8 column. The calibration curve is linear (r2= 0.9999) from 25-175% of the analytical concentration of 1.0 mg/ml. The mean percent standard deviation values for intra-day and inter-day precision studies were <1%. The recovery ranges 99.80-100.06% from a cream formulation. The method can be used reliably in quality control for the analysis of bulk cream samples and final product release. PMID:21969761

  2. Influence of perfluorinated carboxylic acids on ion-pair reversed-phase high-performance liquid chromatographic separation of betacyanins and 17-decarboxy-betacyanins.

    PubMed

    Wybraniec, Sławomir; Mizrahi, Yosef

    2004-03-12

    The ability of trifluoroacetic acid, pentafluoropropionic acid and heptafluorobutyric acid to act as ion-pairing agents for betacyanins and 17-decarboxy-betacyanins during HPLC analysis on a Luna C18(2) reversed-phase column is reported. While the perfluorinated carboxylic acids affect the retention of both groups of compounds by changing the pH of the mobile phase, the possibility of ion-pair chromatography for 17-decarboxy-betacyanins was noticed. In order to explain the accessibility of the positive charge for the counter-anion in decarboxy-betacyanins, the mesomeric structures of the polymethine system at low pH (around a value of 1.5), when the carboxylic group in the 2 position is protonated, should be taken into consideration.

  3. The timing of the human circadian clock is accurately represented by the core body temperature rhythm following phase shifts to a three-cycle light stimulus near the critical zone

    NASA Technical Reports Server (NTRS)

    Jewett, M. E.; Duffy, J. F.; Czeisler, C. A.

    2000-01-01

    A double-stimulus experiment was conducted to evaluate the phase of the underlying circadian clock following light-induced phase shifts of the human circadian system. Circadian phase was assayed by constant routine from the rhythm in core body temperature before and after a three-cycle bright-light stimulus applied near the estimated minimum of the core body temperature rhythm. An identical, consecutive three-cycle light stimulus was then applied, and phase was reassessed. Phase shifts to these consecutive stimuli were no different from those obtained in a previous study following light stimuli applied under steady-state conditions over a range of circadian phases similar to those at which the consecutive stimuli were applied. These data suggest that circadian phase shifts of the core body temperature rhythm in response to a three-cycle stimulus occur within 24 h following the end of the 3-day light stimulus and that this poststimulus temperature rhythm accurately reflects the timing of the underlying circadian clock.

  4. Evaluation of selenium species in selenium-enriched pakchoi (Brassica chinensis Jusl var parachinensis (Bailey) Tsen & Lee) using mixed ion-pair reversed phase HPLC-ICP-MS.

    PubMed

    Thosaikham, Witphon; Jitmanee, Kritsana; Sittipout, Rossukon; Maneetong, Sarunya; Chantiratikul, Anut; Chantiratikul, Piyanete

    2014-02-15

    HPLC-ICP-MS based on ion-paired reversed phase chromatography for the selenium speciation using the mixture of 1-butanesulfonic acid (BA) and trifluoroacetic acid (TFA) as the mixed ion-pairing reagents was developed and applied to selenium-enriched pakchoi (Brassica chinensis Jusl var parachinensis (Bailey) Tsen & Lee). Several conditions of ion-paired reversed phase HPLC-ICP-MS, such as pH of the mobile phase, concentration of ion pairing reagents, types and length of analytical column, and flow rate of the mobile phase, were optimised for five selenium species; selenate (Se(VI)), Selenite (se(IV)), selenocysteine (SeC), Se-methylselenocysteine (SeMC) and selenomethionine (SeM). The results showed that the optimum conditions for pH, BA and TFA condition, type of separating column and flow rate, were 4.5, 8mM, 4mM, C18 (250 mm length × 4.6mm I.D) and 1.2 mL min(-1), respectively. These conditions archived separation of the organic selenium species. The limits of detection (LOD) and quantitation (LOQ) of each selenium species were lower than 5 and 16 ng Se mL(-1), respectively. Furthermore, the recoveries of most selenium species were good, except for SeC. In this research, selenium-enriched pakchoi was cultivated by supplementing inorganic selenium from selenate into sand. The result showed that inorganic selenium, SeMC, SeM and several unknown species were found in selenium-enriched pakchoi sprouts by using the proposed method. Thereby, the biotransformation of selenate in pakchoi was similar to other Brassicaceae plants such as kale and broccoli.

  5. Features of the adsoprtion of naproxen on the chiral stationary phase (S,S)-Whelk-O1 under reversed-phase conditions

    SciTech Connect

    Asnin, Leonid; Gritti, Fabrice; Kaczmarski, Krzysztof; Guiochon, Georges A

    2010-01-01

    Using elution chromatography, we studied the adsorption mechanism of the Naproxen enantiomers on the chiral stationary phase (S,S)-Whelk-O1, from buffered methanol-water solutions. We propose an adsorption mechanism that assumes monolayer adsorption of the more retained enantiomer and the associative adsorption of the less retained one. The effects of the mobile phase composition on the adsorption of Naproxen are discussed. The combination of an elevated column temperature and of the use of an acidic mobile phase led to the degradation of the column and caused a major loss of its separation ability. The use of a moderately acidic mobile phase at temperature slightly above ambient did not produce rapid severe damages but, nevertheless, hampered the experiments and caused a slow gradual deterioration of the column.

  6. A rapid hydrolysis method and DABS-Cl derivatization for complete amino acid analysis of octreotide acetate by reversed phase HPLC.

    PubMed

    Akhlaghi, Yousef; Ghaffari, Solmaz; Attar, Hossein; Alamir Hoor, Amir

    2015-11-01

    Octreotide as a synthetic cyclic octapeptide is a somatostatin analog with longer half-life and more selectivity for inhibition of the growth hormone. The acetate salt of octreotide is currently used for medical treatment of somatostatin-related disorders such as endocrine and carcinoid tumors, acromegaly, and gigantism. Octreotide contains both cysteine and tryptophan residues which make the hydrolysis part of its amino acid analysis procedure very challenging. The current paper introduces a fast and additive-free method which preserves tryptophan and cysteine residues during the hydrolysis. Using only 6 M HCl, this hydrolysis process is completed in 30 min at 150 °C. This fast hydrolysis method followed by pre-column derivatization of the released amino acids with 4-N,N-dimethylaminoazobenzene-4'-sulfonyl chloride (DABS-Cl) which takes only 20 min, makes it possible to do the complete amino acid analysis of an octreotide sample in a few hours. The highly stable-colored DABS-Cl derivatives can be detected in 436 nm in a reversed phase chromatographic system, which eliminates spectral interferences to a great extent. The amino acid analysis of octreotide acetate including hydrolysis, derivatization, and reversed phase HPLC determination was validated according to International Conference of Harmonization (ICH) guidelines.

  7. Chitosan-coated magnetic nanoparticles prepared in one-step by precipitation in a high-aqueous phase content reverse microemulsion.

    PubMed

    Pineda, María Guadalupe; Torres, Silvia; López, Luis Valencia; Enríquez-Medrano, Francisco Javier; de León, Ramón Díaz; Fernández, Salvador; Saade, Hened; López, Raúl Guillermo

    2014-07-02

    Chitosan-coated magnetic nanoparticles (CMNP) were prepared in one-step by precipitation in a high-aqueous phase content reverse microemulsion in the presence of chitosan. The high-aqueous phase concentration led to productivities close to 0.49 g CMNP/100 g microemulsion; much higher than those characteristic of precipitation in reverse microemulsions for preparing magnetic nanoparticles. The obtained nanoparticles present a narrow particle size distribution with an average diameter of 4.5 nm; appearing to be formed of a single crystallite; furthermore they present superparamagnetism and high magnetization values; close to 49 emu/g. Characterization of CMNP suggests that chitosan is present as a non-homogeneous very thin layer; which explains the slight reduction in the magnetization value of CMNP in comparison with that of uncoated magnetic nanoparticles. The prepared nanoparticles show high heavy ion removal capability; as demonstrated by their use in the treatment of Pb2+ aqueous solutions; from which lead ions were completely removed within 10 min.

  8. Reversed-phase ion-pair liquid chromatographic determination of chlorophacinone and diphacinone in steam-rolled oat baits and steam-rolled oat/wax baits.

    PubMed

    Primus, T M; Griffin, D L; Volz, S A; Johnston, J J

    1998-01-01

    A reversed-phase ion-pair liquid chromatographic (LC) method was developed for analysis of steam-rolled oat (SRO) baits fortified with either chlorophacinone or diphacinone. Baits were prepared with and without paraffin wax. Chlorophacinone or diphacinone was extracted from wax-free SRO baits with 5 mM tetrabutylammonium phosphate methanolic ion-pairing solution. Wax baits were initially extracted with petroleum ether and then cleaned up by liquid extraction into methanolic ion-pairing solution containing 20% water. SRO extracts were analyzed with reversed-phase ion-pair LC. Chlorophacinone and diphacinone were quantified by UV absorption at 325 nm. Recoveries from SRO fortified with chlorophacinone at 25 and 150 micrograms/g were 90.7 and 90.8%, respectively, whereas for diphacinone at the same levels, recoveries were 93.5 and 92.3%, respectively. Recoveries from wax baits fortified at 25 and 75 micrograms/g chlorophacinone were 98.5 and 100%, respectively, whereas for diphacinone at the same levels, recoveries were 93.6 and 98.0%, respectively. Method limits of detection for chlorophacinone and diphacinone in SRO baits were estimated to be 1.0 and 0.76 micrograms/g, respectively. Method limits of detection for chlorophacinone and diphacinone in wax baits were estimated to be 4.2 and 2.8 micrograms/g, respectively. PMID:9549068

  9. In vivo biosynthesis of L-(/sup 35/S)Cys-arginine vasopressin, -oxytocin, and -somatostatin: rapid estimation using reversed phase high pressure liquid chromatography. [Rats

    SciTech Connect

    Franco-Bourland, R.E.; Fernstrom, J.D.

    1981-01-01

    L(/sup 35/S)Cys-arginine vasopressin, -oxytocin, and -somatostatin were purified from hypothalami and neurohypophyses 4 h after rats received L(/sup 35/S)Cys via the third ventricle. After acetic acid extraction, Sephadex G-25 filtration, and chemoadsorption to C18-silica (Sep-Pak cartridges), the labeled peptides were rapidly separated by gradient elution, reversed phase, high pressure liquid chromatography (HPLC). The identity and isotopic purity of the labeled peptides were determined by several reversed phase HPLC procedures in conjunction with chemical modification. The labeled peptide fractions were at least 50% radiochemically pure. Using this HPLC isolation procedure, incorporation of L-(/sup 35/S)Cys into each peptide was determined in hydrated and dehydrated rats. Label incorporation into arginine vasopressin and oxytocin in the hypothalamus and the neurohypophysis of dehydrated rats was 2-3 times greater than that in hydrated rats. Incorporation of label into hypothalamic and neurohypophyseal somatostatin was unaffected by the hydration state of the animal. This procedure thus provides a very rapid, but sensitive, set of techniques for studying the control of small peptide biosynthesis in the brain.

  10. A rapid hydrolysis method and DABS-Cl derivatization for complete amino acid analysis of octreotide acetate by reversed phase HPLC.

    PubMed

    Akhlaghi, Yousef; Ghaffari, Solmaz; Attar, Hossein; Alamir Hoor, Amir

    2015-11-01

    Octreotide as a synthetic cyclic octapeptide is a somatostatin analog with longer half-life and more selectivity for inhibition of the growth hormone. The acetate salt of octreotide is currently used for medical treatment of somatostatin-related disorders such as endocrine and carcinoid tumors, acromegaly, and gigantism. Octreotide contains both cysteine and tryptophan residues which make the hydrolysis part of its amino acid analysis procedure very challenging. The current paper introduces a fast and additive-free method which preserves tryptophan and cysteine residues during the hydrolysis. Using only 6 M HCl, this hydrolysis process is completed in 30 min at 150 °C. This fast hydrolysis method followed by pre-column derivatization of the released amino acids with 4-N,N-dimethylaminoazobenzene-4'-sulfonyl chloride (DABS-Cl) which takes only 20 min, makes it possible to do the complete amino acid analysis of an octreotide sample in a few hours. The highly stable-colored DABS-Cl derivatives can be detected in 436 nm in a reversed phase chromatographic system, which eliminates spectral interferences to a great extent. The amino acid analysis of octreotide acetate including hydrolysis, derivatization, and reversed phase HPLC determination was validated according to International Conference of Harmonization (ICH) guidelines. PMID:26002809

  11. A method for identification of diastereomers of 2-decarboxy-betacyanins and 2,17-bidecarboxy-betacyanins in reversed-phase HPLC.

    PubMed

    Wybraniec, Sławomir

    2007-11-01

    A method was developed for identification of diastereomers of 2-decarboxy-betacyanins and 2,17-bidecarboxy-betacyanins chromatographed in reversed-phase high-performance liquid chromatography (HPLC) as pairs of unknown elution order. The method was based on alkaline hydrolysis of selected betacyanin and decarboxylated betacyanin mixtures and subsequent cross-recondensation of the hydrolysates. The arising intermediate derivatives of decarboxylated betalamic acid and cyclo-dopa were stable enough for subsequent recondensation. Generated diagnostic pigments as the recondensation products were monitored by HPLC-diode-array detection-electrospray ionisation mass spectrometry. The isoforms (15R) of 2-decarboxy-betacyanins and 2,17-bidecarboxy-betacyanins were eluted earlier than the 15S forms, in contrast to betacyanins and 17-decarboxy-betacyanins, but in accordance with betaxanthins. 2,17-Bidecarboxy-betanin/2,17-bidecarboxy-isobetanin, being not resolved in reversed-phase HPLC, were partially separated by ion-pair chromatography and under these conditions their order of elution was the same as that of acylated 2,17-bidecarboxy-betacyanins. The method allows complete identification of all the decarboxylated groups of betanin, phyllocactin and hylocerenin as well as other betacyanins in biological or pharmaceutical material.

  12. Accurate determination of the anisotropy factors and the phase differences of Raman polarizabilities in some uniaxial crystals: the case of lithium niobate.

    PubMed

    Djiedeu, N; Mohamadou, B; Bourson, P; Aillerie, M

    2009-01-01

    The present study highlights self-consistently helpful improvements dedicated to overcoming the difficulty resulting from the fitting procedure of integrated Raman intensities recorded according to the rotation crystal method described earlier. To this end, the anisotropy factors of Raman polarizabilities and the corresponding relative phases are determined within the framework of the exact mathematical derivation of the phase factors. These are the relevant parameters of the Raman efficiency relations which are numerically difficult to obtain from the fitting of the integrated areas. The present theoretical approach is then applied to the modes of the A(1) and Ey symmetry species of the lithium niobate (LN) crystal point group. All the expressions of the Raman absolute intensities of the A(1) and Ey irreducible representations initially imply three parameters to be determined from the fitting computations. However, from the derived analytical expressions of the phase differences, the number of parameters involved in the fitting procedure is reduced from 3 to 2, thus improving the statistics of the numerical treatment.

  13. A study of the efficiency of polybutadiene-coated zirconia as a reversed-phase chromatographic support.

    PubMed

    Li, J; Carr, P W

    1997-06-01

    This work describes the dynamic characteristics of columns packed with polybutadiene (PBD)-coated zirconia. Reduced plate height (h) vs reduced velocity (v) data for alkylbenzenes were acquired for three phases coated with different amounts of PBD. Additional data for benzene (k' = 0) on uncoated and four coated phases were also collected. These h vs v plots have a minimum between 4 and 5, indicating good but not excellent column efficiency. By fitting the Knox equation to these data, the A (packing quality), B (axial diffusion), and C (mass transfer resistance) coefficients were determined. The A coefficients were about 2 in all cases, and the B coefficients had values between 2 and 3. The C coefficients varied from 0.05 to 0.2, depending on the polymer load. The data suggest that the quality of packing and the efficiency of mass transfer resistance in the "film" of polymeric stationary phase, not the stagnant mobile phase, are key to further improvements in column performance. The amount of polymer loaded significantly affects the efficiency through the mass transfer resistance in the stationary phase. PMID:9183182

  14. Analysis of β-blockers in groundwater using large-volume injection coupled-column reversed-phase liquid chromatography with fluorescence detection and liquid chromatography time-of-flight mass spectrometry.

    PubMed

    Galera, María M; Vázquez, Piedad P; Vázquez, María del Mar P; García, María Dolores G; Amate, Carmen F

    2011-08-01

    Atenolol, nadolol, metoprolol, bisoprolol and betaxolol were simultaneously determined in groundwater samples by large-volume injection coupled-column reversed-phase liquid chromatography with fluorescence detection (LVI-LC-LC-FD) and liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS). The LVI-LC-LC-FD method combines analyte isolation, preconcentration and determination into a single step. Significant reductions in costs for sample pre-treatment (solvent and solid phases for clean up) and method development times are also achieved. Using LC-TOF-MS, accurate mass measurements within 3 ppm error were obtained for all of the β-blockers studied. Empirical formula information can be obtained by this method, allowing the unequivocal identification of the target compounds in the samples. To increase the sensitivity, a solid-phase extraction step with Oasis MCX cartridge was carried out yielding recoveries of 79-114% (n=5) with RSD 2-7% for the LC-TOF-MS method. SPE gives a high purification of β-blockers compared with the existing methods. A 100% methanol wash was allowed for these compounds with no loss of analytes. Limit of quantification was 1-7 ng/L for LVI-LC-LC-FD and 0.25-5 ng/L for LC-TOF-MS. As a result of selective extraction and effective removal of coextractives, no matrix effect was observed in LVI-LC-LC-FD and LC-TOF-MS analyses. The methods were applied to detect and quantify β-blockers in groundwater samples of Almería (Spain).

  15. Tuning the Hydrophilicity and Hydrophobicity of the Respective Cation and Anion: Reversible Phase Transfer of Ionic Liquids.

    PubMed

    Yao, Wenhui; Wang, Huiyong; Cui, Guokai; Li, Zhiyong; Zhu, Anlian; Zhang, Suojiang; Wang, Jianji

    2016-07-01

    The separation and recycling of catalyst and cocatalyst from the products and solvents are of critical importance. In this work, a class of functionalized ionic liquids (ILs) were designed and synthesized, and by tuning the hydrophilicity and hydrophobicity of cation and anion, respectively, these ILs could reversibly transfer between water and organics triggered upon undergoing a temperature change. From a combination of multiple spectroscopic techniques, it was shown that the driving force behind the transfer was originated from a change in conformation of the PEG chain of the IL upon temperature variation. By utilizing the novel property of this class of ILs, a highly efficient and controllable CuI-catalyzed cycloaddition reaction was achieved wherein the IL was used to entrain, activate, and recycle the catalyst, as well as to control the reaction. PMID:27187750

  16. A chromatographic estimate of the degree of surface heterogeneity of RPLC packing materials. III. Endcapped amido-embedded reversed phase

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2006-01-01

    The difference in adsorption behavior between a conventional monomeric endcapped C{sub 18} stationary phase (3.43 {micro}mol/m{sup 2}) and an endcapped polymeric RP-Amide phase (3.31 {micro}mol/m{sup 2}) was investigated. The adsorption isotherms of four compounds (phenol, caffeine, sodium 2-naphthalene sulfonate, and propranololium chloride) were measured by frontal analysis (FA) and the degree of heterogeneity of each phase for each solute was characterized by their adsorption energy distributions (AED), derived using the Expectation-Maximization method. The results show that only certain analytes (phenol and 2-naphthalene sulfonate) are sensitive to the presence of the polar embedded amide groups within the RP phase. Their binding constants on the amide-bonded phase are significantly higher than on conventional RPLC phases. Furthermore, an additional type of adsorption sites was observed for these two compounds. However, these sites having a low density, their presence does not affect much the retention factors of the two analytes. On the other hand, the adsorption behavior of the other two analytes (caffeine and propranololium chloride) is almost unaffected by the presence of the amide group in the bonded layer. Strong selective interactions may explain these observations. For example, hydrogen-bond interactions between an analyte (e.g., phenol or naphthalene sulfonate) and the carbonyl group (acceptor) or the nitrogen (donor) of the amido-embedded group may take place. No such interactions may take place with either caffeine or the cation propranololium chloride. This study confirms the hypothesis that analytes have ready access to locations deep inside the bonded layer, where the amide groups are present.

  17. Simultaneous analysis of hyoscyamine, scopolamine, 6beta-hydroxyhyoscyamine and apoatropine in Solanaceous hairy roots by reversed-phase high-performance liquid chromatography.

    PubMed

    Kursinszki, László; Hank, Hajnalka; László, Imre; Szoke, Eva

    2005-10-14

    A new high-performance liquid chromatographic method is described for tropane alkaloid analysis in genetically transformed root cultures of Datura innoxia Mill. and Atropa belladonna L. Sample preparation, tropane alkaloid extraction with chloroform-methanol-concentrated ammonia 15:5:1 (v/v/v), was followed by solid-phase extraction on Supelclean LC-18 cartridges. Optimized conditions and careful pH control resulted in high recovery and reproducibility. Simultaneous determination of apoatropine, 6beta-hydroxyhyoscyamine, hyoscyamine and scopolamine was performed by HPLC on C18 (2) reversed-phase column. The application of Luna new-generation silica-based stationary phase resulted in excellent peak shapes using an ion-pair reagent and triethanolamine free mobile phase and allowed to exploit the full power of pH-dependent selectivity. Simplicity and improved selectivity make this method a preferred alternative of published ion-pair chromatographic methods. Validation studies proved that the global method has good repeatability and satisfactory recovery. Absolute limits of detection were 0.6, 0.6, and 0.8 ng for hyoscyamine, 6beta-hydroxyhyoscyamine, and scopolamine respectively.

  18. Design of Experiment (DOE) Utilization to Develop a Simple and Robust Reversed-Phase HPLC Technique for Related Substances’ Estimation of Omeprazole Formulations

    PubMed Central

    Manranjan, Vayeda Chintan; Yadav, Devendra Singh; Jogia, Hitesh Amrutlal; Chauhan, Praful Lalitkumar

    2013-01-01

    A simple, fast, and sensitive reversed-phase HPLC method with UV detection was developed for the quantitation of omeprazole and its eleven related compounds (impurities) in pharmaceutical formulation using the Thermo Accucore C–18 (50 mm × 4.6 mm, 2.6 μm) column. The separation among all the compounds was achieved with a flow rate of 0.8 mL min−1 employing a gradient program of mobile phase A [0.08 M glycine buffer pH 9.0: acetonitrile; 95:05 (v/v)] and mobile phase B [acetonitrile: methanol; 65:35 (v/v)]. The chromatographic detection was carried out at a wavelength of 305 nm. The method was validated for specificity, linearity, and recovery. The huskiness of the method was determined prior to validation using the Design of Experiments (DOE). The ANOVA analysis of DOE with a 95% confidence interval (CI) confirmed the buffer pH of mobile phase A (p <0.0001) and column temperature (p<0.0001) as significant Critical Method Parameters (CMPs). PMID:24482772

  19. Determination of the n-octanol/water partition coefficients of weakly ionizable basic compounds by reversed-phase high-performance liquid chromatography with neutral model compounds.

    PubMed

    Liang, Chao; Han, Shu-ying; Qiao, Jun-qin; Lian, Hong-zhen; Ge, Xin

    2014-11-01

    A strategy to utilize neutral model compounds for lipophilicity measurement of ionizable basic compounds by reversed-phase high-performance liquid chromatography is proposed in this paper. The applicability of the novel protocol was justified by theoretical derivation. Meanwhile, the linear relationships between logarithm of apparent n-octanol/water partition coefficients (logKow '') and logarithm of retention factors corresponding to the 100% aqueous fraction of mobile phase (logkw ) were established for a basic training set, a neutral training set and a mixed training set of these two. As proved in theory, the good linearity and external validation results indicated that the logKow ''-logkw relationships obtained from a neutral model training set were always reliable regardless of mobile phase pH. Afterwards, the above relationships were adopted to determine the logKow of harmaline, a weakly dissociable alkaloid. As far as we know, this is the first report on experimental logKow data for harmaline (logKow = 2.28 ± 0.08). Introducing neutral compounds into a basic model training set or using neutral model compounds alone is recommended to measure the lipophilicity of weakly ionizable basic compounds especially those with high hydrophobicity for the advantages of more suitable model compound choices and convenient mobile phase pH control.

  20. Design of a fully-fiber multi-chord interferometer and a new phase-shift demodulation method for field-reversed configuration

    SciTech Connect

    Fang, Dongfan Sun, Qizhi; Zhao, Xiaoming; Jia, Yuesong

    2014-05-15

    A 633 nm laser interferometer has been designed based on a novel concept, which, without the acousto-optic modulator or the demodulator circuit, adopts the fibers to connect all elements except photodetectors and oscilloscope in this system to make it more compact, portable, and efficient. The noteworthy feature is to mathematically compare the two divided interference signals, which have the same phase-shift caused by the electron density but possess the different initial phase and low angular frequencies. It is possible to read the plasma density directly on the oscilloscope by our original mathematic demodulation method without a camera. Based on the Abel inversion algorithm, the radial electron density profiles versus time can be obtained by using the multi-chord system. The designed measurable phase shift ranges from 0 to 2π rad corresponding to the maximum line integral of electron density less than 3.5 × 10{sup 17} cm{sup −2}, and the phase accuracy is about 0.017 rad corresponding to the line integral of electron density accuracy of 1 × 10{sup 15} cm{sup −2}. After the construction of eight-chord interferometer, it will provide the detailed time resolved information of the spatial distribution of the electron density in the field-reversed configuration (FRC) plasma target produced by the “Yingguang-1” programmed-discharge device, which is being constructed in the Key Laboratory of Pulsed Power, China Academy of Engineering Physics.

  1. A Pure-Phase Homonuclear J-Modulated HMQC Experiment with Tilted Cross-Peak Patterns for an Accurate Determination of Homonuclear Coupling Constants

    NASA Astrophysics Data System (ADS)

    Koź Miń Ski, Wiktor

    1999-11-01

    A new HMQC-based experiment is presented which allows for an efficient determination of accurate homonuclear coupling-constant values. Pure absorption lineshapes with tilted cross-peak patterns are obtained by a combination of the active-coupling-pattern tilting (ACT) scheme with J-scaling. Characteristic features include separate heteronuclear echo and antiecho acquisition with a BIRDy pulse positioned before or after the t1 period, respectively, to refocus I-spin homonuclear coupling evolution. Additionally, due to the incorporation of J-scaling the relative spacing of the S-spin chemical-shift differences and I-spin homonuclear coupling splittings in the F1 domain is largely under experimental control. The most important advantage of the proposed method is that the I-spin homonuclear coupling evolution occurs simultaneously with the evolution of the heteronuclear zero and double-quantum coherences, which exhibit a slower transverse relaxation than I-spin single-quantum coherences. The effectiveness of the new sequence is demonstrated by a determination of the 3JHN,Hα couplings in a peptide sample. Additionally, the broadband property of the new sequence is verified with a sucrose sample.

  2. Effect of the endcapping of reversed-phase high-performance liquid chromatography adsorbents on the adsorption isotherm

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2005-09-01

    The retention mechanisms of n-propylbenzoate, 4-t ert-butylphenol, and caffeine on the endcapped Symmetry-C{sub 18} and the non-endcapped Resolve-C{sub 18} are compared. The adsorption isotherms were measured by frontal analysis (FA), using as the mobile phase mixtures of methanol or acetonitrile and water of various compositions. The isotherm data were modeled and the adsorption energy distributions calculated. The surface heterogeneity increases faster with decreasing methanol concentration on the non-endcapped than on the endcapped adsorbent. For instance, for methanol concentrations exceeding 30% (v/v), the adsorption of caffeine is accounted for by assuming three and two different types of adsorption sites on Resolve-C{sub 18} and Symmetry-C{sub 18}, respectively. This is explained by the effect of the mobile phase composition on the structure of the C{sub 18}-bonded layer. The bare surface of bonded silica appears more accessible to solute molecules at high water contents in the mobile phase. On the other hand, replacing methanol by a stronger organic modifier like acetonitrile dampens the differences between non-endcapped and endcapped stationary phase and decreases the degree of surface heterogeneity of the adsorbent. For instance, at acetonitrile concentrations exceeding 20%, the surface appears nearly homogeneous for the adsorption of caffeine.

  3. Preparative isolation and purification of amides from the fruits of Piper longum L. by upright counter-current chromatography and reversed-phase liquid chromatography.

    PubMed

    Wu, Shihua; Sun, Cuirong; Pei, Saifeng; Lu, Yanbin; Pan, Yuanjiang

    2004-06-25

    A versatile counter-current chromatography (CCC) with upright type-J multilayer coil planet centrifuge, named upright CCC, was applied to the isolation and purification of amides from Piper longum L., which is widely used as an anodyne and a treatment for stomach disease in China. After the saponification by KOH of the ethanol extracts solution of 15 kg of crude drug "Piper Longi Fructus", the fruits of P. longum L., the solution was extracted with light petroleum and 500 g of red crude oil was obtained. Using 2.5 g of red crude oil as sample, the preparative upright CCC with a two-phase system composed of light petroleum (bp 60-90 degrees C)-ethyl acetate-tetrachloromethane-methanol-water (1:1:8:6:1, v/v) was successfully performed, which yielded nine fractions. Then these fractions were further purified by use of reversed-phase liquid chromatography (RPLC) with a glass column of 500 x 10 mm i.d. packed with reversed-phase silica gel. As a result, nine target amides with over 95% purity, i.e., 50 mg of (2E,4E)-N-isobutyl-eicosa-2,4-dienamide, 150 mg of (2E,4E,14Z)-N-isobutyl-eicosa-2,4,14-trienamide, 110 mg of (2E,4E,12Z)-N-isobutyl-ocatadeca-2,4,12-trienamide, 50 mg of guineensine, 60 mg of pipernonaline, 75 mg of pellitorine, 63 mg of piperine, 45 mg of piperanine, and 40 mg of piperlonguminine were isolated, respectively. Structures of all compounds were identified by electrospray ionization MS, electron impact ionization MS, one- and two-dimensional NMR spectra.

  4. Simultaneous screening for lipophilic and hydrophilic toxins in marine harmful algae using a serially coupled reversed-phase and hydrophilic interaction liquid chromatography separation system with high-resolution mass spectrometry.

    PubMed

    Chen, Junhui; Gao, Liyuan; Li, Zhaoyong; Wang, Shuai; Li, Jingxi; Cao, Wei; Sun, Chengjun; Zheng, Li; Wang, Xiaoru

    2016-03-31

    The presence of toxins in harmful algal blooms (HABs) poses considerable concerns because of their potential adverse effects on ecological environments and human health. When marine HABs occur, efficient screening and identification of toxins in different kinds of HAB algae remains a challenge. In this study, the applicability of serial coupling of reversed-phase liquid chromatography (RPLC) and hydrophilic interaction chromatography (HILIC) combined with high resolution mass spectrometry (HR-MS) for the simultaneous screening and identification of various kinds of known lipophilic and hydrophilic toxins in HAB algae was investigated for the first time. Ultrasound-assisted extraction (UAE) was explored to extract both lipophilic and hydrophilic toxins in algae simultaneously. As in most cases, toxin standards were not available; therefore, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, eight known lipophilic toxins and 11 hydrophilic toxins were successfully detected in a single injection, and the proposed method was validated. Satisfactory sensitivity, repeatability (RSD <14.87%) and recovery (89.4-105.8%) of the method were achieved. A major advantage of the proposed method is that it can almost detect members of all eight groups of marine algal toxins in a single run. Using this method, several known toxins in different marine toxigenic algae including Alexandrium tamarense, Alexandrium minutum and Prorocentrum lima were successfully observed and identified. This work demonstrates that RPLC/HILIC-HR-MS combined with an accurate mass list of known marine algal toxins may be used as a powerful tool for screening of different classes of known toxins in marine harmful algae. PMID:26965334

  5. Simultaneous screening for lipophilic and hydrophilic toxins in marine harmful algae using a serially coupled reversed-phase and hydrophilic interaction liquid chromatography separation system with high-resolution mass spectrometry.

    PubMed

    Chen, Junhui; Gao, Liyuan; Li, Zhaoyong; Wang, Shuai; Li, Jingxi; Cao, Wei; Sun, Chengjun; Zheng, Li; Wang, Xiaoru

    2016-03-31

    The presence of toxins in harmful algal blooms (HABs) poses considerable concerns because of their potential adverse effects on ecological environments and human health. When marine HABs occur, efficient screening and identification of toxins in different kinds of HAB algae remains a challenge. In this study, the applicability of serial coupling of reversed-phase liquid chromatography (RPLC) and hydrophilic interaction chromatography (HILIC) combined with high resolution mass spectrometry (HR-MS) for the simultaneous screening and identification of various kinds of known lipophilic and hydrophilic toxins in HAB algae was investigated for the first time. Ultrasound-assisted extraction (UAE) was explored to extract both lipophilic and hydrophilic toxins in algae simultaneously. As in most cases, toxin standards were not available; therefore, an identification procedure based on accurate mass data and chromatographic behavior was proposed. According to this procedure, eight known lipophilic toxins and 11 hydrophilic toxins were successfully detected in a single injection, and the proposed method was validated. Satisfactory sensitivity, repeatability (RSD <14.87%) and recovery (89.4-105.8%) of the method were achieved. A major advantage of the proposed method is that it can almost detect members of all eight groups of marine algal toxins in a single run. Using this method, several known toxins in different marine toxigenic algae including Alexandrium tamarense, Alexandrium minutum and Prorocentrum lima were successfully observed and identified. This work demonstrates that RPLC/HILIC-HR-MS combined with an accurate mass list of known marine algal toxins may be used as a powerful tool for screening of different classes of known toxins in marine harmful algae.

  6. Gradient liquid chromatographic retention time prediction for suspect screening applications: A critical assessment of a generalised artificial neural network-based approach across 10 multi-residue reversed-phase analytical methods.

    PubMed

    Barron, Leon P; McEneff, Gillian L

    2016-01-15

    For the first time, the performance of a generalised artificial neural network (ANN) approach for the prediction of 2492 chromatographic retention times (tR) is presented for a total of 1117 chemically diverse compounds present in a range of complex matrices and across 10 gradient reversed-phase liquid chromatography-(high resolution) mass spectrometry methods. Probabilistic, generalised regression, radial basis function as well as 2- and 3-layer multilayer perceptron-type neural networks were investigated to determine the most robust and accurate model for this purpose. Multi-layer perceptrons most frequently yielded the best correlations in 8 out of 10 methods. Averaged correlations of predicted versus measured tR across all methods were R(2)=0.918, 0.924 and 0.898 for the training, verification and test sets respectively. Predictions of blind test compounds (n=8-84 cases) resulted in an average absolute accuracy of 1.02±0.54min for all methods. Within this variation, absolute accuracy was observed to marginally improve for shorter runtimes, but was found to be relatively consistent with respect to analyte retention ranges (~5%). Finally, optimised and replicated network dependency on molecular descriptor data is presented and critically discussed across all methods. Overall, ANNs were considered especially suitable for suspects screening applications and could potentially be utilised in bracketed-type analyses in combination with high resolution mass spectrometry. PMID:26592605

  7. Gradient liquid chromatographic retention time prediction for suspect screening applications: A critical assessment of a generalised artificial neural network-based approach across 10 multi-residue reversed-phase analytical methods.

    PubMed

    Barron, Leon P; McEneff, Gillian L

    2016-01-15

    For the first time, the performance of a generalised artificial neural network (ANN) approach for the prediction of 2492 chromatographic retention times (tR) is presented for a total of 1117 chemically diverse compounds present in a range of complex matrices and across 10 gradient reversed-phase liquid chromatography-(high resolution) mass spectrometry methods. Probabilistic, generalised regression, radial basis function as well as 2- and 3-layer multilayer perceptron-type neural networks were investigated to determine the most robust and accurate model for this purpose. Multi-layer perceptrons most frequently yielded the best correlations in 8 out of 10 methods. Averaged correlations of predicted versus measured tR across all methods were R(2)=0.918, 0.924 and 0.898 for the training, verification and test sets respectively. Predictions of blind test compounds (n=8-84 cases) resulted in an average absolute accuracy of 1.02±0.54min for all methods. Within this variation, absolute accuracy was observed to marginally improve for shorter runtimes, but was found to be relatively consistent with respect to analyte retention ranges (~5%). Finally, optimised and replicated network dependency on molecular descriptor data is presented and critically discussed across all methods. Overall, ANNs were considered especially suitable for suspects screening applications and could potentially be utilised in bracketed-type analyses in combination with high resolution mass spectrometry.

  8. SISGR -- Domain Microstructures and Mechanisms for Large, Reversible and Anhysteretic Strain Behaviors in Phase Transforming Ferroelectric Materials

    SciTech Connect

    Wang, Yu U.

    2013-12-06

    This four-year project (including one-year no-cost extension) aimed to advance fundamental understanding of field-induced strain behaviors of phase transforming ferroelectrics. We performed meso-scale phase field modeling and computer simulation to study domain evolutions, mechanisms and engineering techniques, and developed computational techniques for nanodomain diffraction analysis; to further support above originally planned tasks, we also carried out preliminary first-principles density functional theory calculations of point defects and domain walls to complement meso-scale computations as well as performed in-situ high-energy synchrotron X-ray single crystal diffraction experiments to guide theoretical development (both without extra cost to the project thanks to XSEDE supercomputers and DOE user facility Advanced Photon Source).

  9. Phase-reversal emulsion catalysis with CNT-TiO2 nanohybrids for the selective oxidation of benzyl alcohol.

    PubMed

    Yu, Chang; Fan, Liman; Yang, Juan; Shan, Yuanyuan; Qiu, Jieshan

    2013-11-25

    Mix it up: Carbon nanotube (CNT)-TiO2 nanohybrids with the potential to control the phase of an emulsion were successfully developed with a simple yet efficient method. When ruthenium was deposited on these CNT-TiO2 nanohybrid supports, they demonstrated catalytic potential for the selective oxidation of benzyl alcohol to benzaldehyde. The relationship between the emulsion properties and the catalytic mechanism is also discussed.

  10. Ion chromatographic determination of hydroxide ion on monolithic reversed-phase silica gel columns coated with nonionic and cationic surfactants.

    PubMed

    Xu, Qun; Mori, Masanobu; Tanaka, Kazuhiko; Ikedo, Mikaru; Hu, Wenzhi; Haddad, Paul R

    2004-07-01

    The determination of hydroxide by ion chromatography (IC) is demonstrated using a monolithic octadecylsilyl (ODS)-silica gel column coated first with a nonionic surfactant (polyoxyethylene (POE)) and then with a cationic surfactant (cetyltrimethylammonium bromide (CTAB)). This stationary phase, when used in conjunction with a 10 mmol/l sodium sulfate eluent at pH 8.2, was found to be suitable for the rapid and efficient separation of hydroxide from some other anions, based on a conventional ion-exchange mechanism. The peak directions and detection responses for these ions were in agreement with their known limiting equivalent ionic conductance values. Under these conditions, a linear calibration plot was obtained for hydroxide ion over the range 16 micromol/l to 15 mmol/l, and the detection limit determined at a signal-to-noise ratio of 3 was 6.4 micromol/l. The double-coated stationary phase described above was shown to be superior to a single coating of cetyltrimethylammonium bromide alone, in terms of separation efficiency and stability of the stationary phase. A range of samples comprising solutions of some strong and weak bases was analyzed by the proposed method and the results obtained were in good agreement with those obtained by conventional potentiometric pH measurement.

  11. Comparison of corrosion properties of passive films formed on phase reversion induced nano/ultrafine-grained 321 stainless steel

    NASA Astrophysics Data System (ADS)

    Jinlong, Lv; Hongyun, Luo

    2013-09-01

    The nano/ultrafine grain (NUG) with an average grain size of 230 nm was obtained by cold rolling down to 94% reduction in thickness and reversion annealing at 800 °C for 200 s. The NUG sample exhibited a lower corrosion resistance than coarse grain (CG) sample in 0.1 M NaCl solution at room temperature, indicating that the passive film formed on the surface of the NUG austenite did not improve corrosion resistance in the solution. However, the corrosion resistance of the former was higher than that of the latter in 0.5 M H2SO4 solution at room temperature, which was proved by electrochemical impedance spectroscopy and Mott-Schottky plots in conjunction with the point defect model. Comparing slightly difference of acceptor density (i.e. cation vacancies) between CG and NUG samples, higher corrosion resistance of NUG sample was probably attributed to significant decreased donor density (i.e. oxygen vacancies and cation interstitials) in 0.5 M H2SO4 solution. Moreover, the corrosion resistance of the passive films formed on CG and NUG samples in borate buffer solution at room temperature showed little difference.

  12. Accurate determination of 2,4,6-trichloroanisole in wines at low parts per trillion by solid-phase microextraction followed by GC-ECD.

    PubMed

    Alzaga, Roberto; Ortiz, Laura; Sánchez-Baeza, Francisco; Marco, M-Pilar; Bayona, Josep Maria

    2003-06-01

    A headspace solid-phase microextraction (HS-SPME) procedure at 30 degrees C with a 100 microm PDMS fiber of a saturated NaCl solution stirred at 1100 rpm combined to GC-ECD for the 2,4,6-trichloroanisol (TCA) determination in wines has been developed. Due to the matrix complexity and ethanol absorption into the fiber, the internal standard selection was crucial to obtain unbiased results. Thus, matrix effects were observed when analyzing different types of Spanish wines (white, early, and vintage red wines) spiked with TCA at low concentration levels (i.e., <40 ng L(-)(1)). In contrast, the use of 2,4,6-tribromoanisole (TBA) as internal standard overcame these matrix effects, whereas the use of 2,4,6-trichlorophenyl ethyl ether led to inconsistent results. The developed HS-SPME-GC-ECD methodology reaches a limit of quantitation for TCA in wine within 2.9-18 ng L(-)(1), with a relative standard deviation of 2.5-13.4%, depending on the TCA concentration level and wine characteristics. This analytical method is comparable to the existing methodologies based on HS-SPME followed by GC-MS in terms of accuracy, precision, length of determination, and length of quantification; however, analysis cost is reduced.

  13. Validated Stability-indicating Reverse-phase Ultra-performance Liquid Chromatography Method for Simultaneous Determination of Sodium Methylparaben, Sodium Propylparaben and Ketorolac Tromethamine in Topical Dosage Forms

    PubMed Central

    Roy, C.; Chakrabarty, J.; Modi, P. B.

    2013-01-01

    A sensitive, fast, and stability-indicating isocratic reverse-phase ultra-performance liquid chromatography method was developed and validated for quantitative simultaneous determination of sodium methylparaben, sodium propylparaben and ketorolac tromethamine in topical dosage forms. Separation of all peaks was achieved by using acquity ethylene bridged hybrid C18 (50×2.1 mm, 1.7 μ) as stationary phase, mobile phase used was triethylamine buffer (pH 2.5):tetrahydrofuran:methanol (665:35:300, v/v/v) with isocratic mode at a flow rate of 0.40 ml/min. All component were detected at 252 nm with 10 min run time. The described method was found to be linear in the concentration range of 248-744 μg/ml for ketorolac tromethamine, 20.8-62.4 μg/ml for sodium methylparaben and 2.38-7.13 μg/ml for sodium propylparaben with correlation coefficients more than 0.999. Method was validated in terms of specificity, linearity, accuracy, precision, solution stability, filter equivalency, and robustness as per International Conference on Harmonization guideline. Formulation was exposed to the stress conditions of peroxide, acid, base, thermal, and photolytic degradation and proven all components were well separated in the presence of degradants. PMID:24019569

  14. Monolithic metal-organic framework MIL-53(Al)-polymethacrylate composite column for the reversed-phase capillary liquid chromatography separation of small aromatics.

    PubMed

    Yusuf, Kareem; Badjah-Hadj-Ahmed, Ahmed Yacine; Aqel, Ahmad; ALOthman, Zeid Abdullah

    2016-03-01

    A monolithic capillary column containing a composite of metal-organic framework MIL-53(Al) incorporated into hexyl methacrylate-co-ethylene dimethacrylate was prepared to enhance the separation of mixtures of small aromatic compounds by using capillary liquid chromatography. The addition of 10 mg/mL MIL-53(Al) microparticles increased the micropore content in the monolithic matrix and increased the Brunauer-Emmett-Teller surface area from 26.92 to 85.12 m(2) /g. The presence of 1,4-benzenedicarboxylate moieties within the structure of MIL-53(Al) as an organic linker greatly influenced the separation of aromatic mixtures through π-π interactions. High-resolution separation was obtained for a series of alkylbenzenes (with resolution factors in the range 0.96-1.75) in less than 8 min, with 14 710 plates/m efficiency for propylbenzene, using a binary polar mobile phase of water/acetonitrile in isocratic mode. A reversed-phase separation mechanism was indicated by the increased retention factor and resolution as the water percentage in the mobile phase increased. A stability study on the composite column showed excellent mechanical stability under various conditions. The higher resolution and faster separation observed at increased temperature indicated an exothermic separation, whereas the negative values for the free energy change of transfer indicated a spontaneous process.

  15. Extension of Toth function from gas-solid to liquid-solid equilibria and application to reversed-phase liquid chromatography systems

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2006-03-01

    The extension of the {Psi} function developed by Toth from equilibria taking place at gas-solid interfaces to those taking place at liquid-solid interfaces was investigated. The results were applied to conventional liquid-solid systems used in reversed-phase liquid chromatography (RPLC). The adsorbents in these systems are made of porous silica having a hydrophobic solid surface obtained by chemically bonding C{sub 18} alkyl chains to a porous silica gel then endcapping the surface with trimethylsilyl groups. The liquid is an aqueous solution of an organic solvent, most often methanol or acetonitrile. The probe compound used here is phenol. Adsorption data of phenol were measured using the dynamic frontal analysis (FA) method. The excess adsorption of the organic solvent was measured using the minor disturbance (MD) method. Activity coefficients in the bulk were estimated through the UNIFAC group contributions. The results show that the {Psi} function predicts 90% of the total free energy of immersion, {Delta}F, of the solid when the concentration of phenol is moderate (typically less than 10 g/L). At higher concentrations, the nonideal behavior of the bulk liquid phase becomes significant and it may contribute up to about 30% of {Delta}F. The high concentration of adsorbed molecules of phenol at the interface decreases the interfacial tension, {sigma}, by about 18 mN/m, independently of the structure of the adsorbed phase and of the nature of the organic solvent.

  16. Stability indicating reversed-phase high-performance liquid chromatographic and thin layer densitometric methods for the determination of ziprasidone in bulk powder and in pharmaceutical formulations.

    PubMed

    El-Sherif, Zeinab A; El-Zeany, Badr; El-Houssini, Ola M; Rashed, Mohamed S; Aboul-Enein, Hassan Y

    2004-04-01

    Two sensitive and reproducible methods were developed and validated for the determination of ziprasidone (ZIP) in the presence of its degradation products in pure form and in pharmaceutical formulations. The fi rst method was based on reversed-phase high-performance liquid chromatography (HPLC), on a Lichrosorb RP C(18) column using water:acetonitrile:phosphoric acid (76:24:0.5 v/v/v) as the mobile phase at a fl ow rate of 1.5 mL min(-1) at ambient temperature. Quantification was achieved with UV detection at 229 nm over a concentration range of 10-500 micro g mL(-1) with mean percentage recovery of 99.71 +/- 0.55. The method retained its accuracy in presence of up to 90% of ZIP degradation products. The second method was based on TLC separation of ZIP from its degradation products followed by densitometric measurement of the intact drug spot at 247 nm. The separation was carried out on aluminium sheet of silica gel 60 F(254) using choloroform:methanol:glacial acetic acid (75:5:4.5 v/v/v) as the mobile phase, over a concentration range of 1-10 micro g per spot and mean percentage recovery of 99.26 +/- 0.39. Both methods were applied successfully to laboratory prepared mixtures and pharmaceutical capsules.

  17. Densitometric HPTLC method for qualitative, quantitative analysis and stability study of Coenzyme Q10 in pharmaceutical formulations utilizing normal and reversed-phase silica gel plates.

    PubMed

    Abdel-Kader, Maged Saad; Alam, Prawez; Alqasoumi, Saleh Ibrahim

    2016-03-01

    Two simple, precise and stability-indicating densitometric HPTLC method were developed and validated for qualitative and quantitative analysis of Coenzyme Q10 in pharmaceutical formulations using normal-phase (Method I) and reversed phase (Method II) silica gel TLC plates. Both methods were developed and validated with 10×20 cm glass-backed plates coated with 0.2 mm layers of either silica gel 60 F254 (E-Merck, Germany) using hexane-ethyl acetate (8.5:1.5 v/v) as developing system (Method I) or RP-18 silica gel 60 F254 (E-Merck, Germany) using methanol-acetone (4:6 v/v) as mobile phase (Method II). Both analyses were scanned with a densitometer at 282 nm. Linearity was found in the ranges 50-800 ng/spot (r(2)=0.9989) and 50-800 ng/spot (r(2)=0.9987) for Method I and Method II respectively. Stability of Coenzyme Q10 was explored by the two methods using acid, base, hydrogen peroxide, temperature and different solvents. Due to the efficiency of the method in separating Coenzyme Q10 from other ingredients including its degradation products, it can be applied for quality control, standardization of different pharmaceutical formulations and stability study.

  18. Development and validation of a new stability indicating reversed phase liquid chromatographic method for the determination of prednisolone acetate and impurities in an ophthalmic suspension.

    PubMed

    Marley, Adrian; Stalcup, Apryll M; Connolly, Damian

    2015-01-01

    A new stability indicating reversed phase high performance liquid chromatography (RP-HPLC) method was developed and validated under current International Conference of Harmonisation (ICH) guidance for the determination of prednisolone acetate (PAC) and impurities in an ophthalmic suspension. The developed method is presented as an alternative to a modified version of the current RP-HPLC method described in the USP monograph for the assay of PAC in an ophthalmic suspension. Along with the assay of PAC, the new method is also capable of identifying and quantifying eight selected PAC impurities and degradation products in an ophthalmic suspension. Using an Agilent Poroshell 120 EC-C18 100 mm × 4.6mm (dp: 2.7 μm) column set to 60°C with step gradient elution generated using mobile phase A: acetonitrile/water (10:90) (v/v) and mobile phase B: acetonitrile delivered at 1.2 mL min(-1), all peaks of interest are eluted in 33 min with resolution of 1.5 between the critical pairs. The developed method was validated for PAC and impurities to ICH recommendations for accuracy, linearity, precision (repeatability), limit of detection, limit of quantitation, robustness and specificity.

  19. Quantifying factors determining the rate of CTL escape and reversion during acute and chronic phases of HIV infection

    SciTech Connect

    Ganusov, Vitaly V; Korber, Bette M; Perelson, Alan S

    2009-01-01

    Human immunodeficiency virus (HIV) often evades cytotoxic T cell (CTL) responses by generating variants that are not recognized by CTLs. However, the importance and quantitative details of CTL escape in humans are poorly understood. In part, this is because most studies looking at escape of HIV from CTL responses are cross-sectional and are limited to early or chronic phases of the infection. We use a novel technique of single genome amplification (SGA) to identify longitudinal changes in the transmitted/founder virus from the establishment of infe