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Sample records for acetonitrile mobile phase

  1. Isotherm parameters and intraparticle mass transfer kinetics on molecularly imprinted polymers in acetonitrile/buffer mobile phases

    SciTech Connect

    Kim, Hyunjung; Kaczmarski, Krzysztof; Guiochon, Georges A

    2006-03-01

    The equilibrium isotherm and the intraparticle mass transfer kinetics of the enantiomers of the template were investigated on an Fmoc-L-tryptophan (Fmoc-L-Trp) imprinted polymer at different pHs and water concentrations in acetonitrile/aqueous buffer mobile phases. The equilibrium isotherm data were measured using frontal analysis at 25 {+-} 2 C. The adsorption energy distribution was found to be trimodal, with narrow modes. Consistent with this distribution, the adsorption data were modeled using a tri-Langmuir isotherm equation and the best estimates of the isotherm parameters were determined. The intraparticle mass transfer parameters were derived by comparing the profiles of experimental overloaded bands and the profiles calculated using the isotherm model and the lumped pore diffusion (POR) model of chromatography. These results showed that different adsorption and mass transfer mechanisms exist in mobile phases made of acetonitrile/aqueous buffer and of acetonitrile/acetic acid solutions.

  2. Microchip electrospray: cone-jet stability analysis for water-acetonitrile and water-methanol mobile phases.

    PubMed

    Jung, Stephanie; Effelsberg, Uwe; Tallarek, Ulrich

    2011-03-25

    Changes in mobile phase composition during high performance liquid chromatography (HPLC) gradient elution coupled to mass spectrometry (MS) sensitively affect electrospray operation modes. In this work, we identify the influences of dynamic changes in bulk conductivity on the cone-jet stability island for aqueous acetonitrile and aqueous methanol mobile phases commonly used in reversed-phase HPLC. Bulk conductivities of the mobile phases were varied by adding different amounts of formic acid. A commercial microchip-HPLC/ESI-MS configuration was modified to enable in situ electrospray diagnostics by frequency analysis of the microchip emitter current and spray imaging. This approach facilitated the detection of different spray modes together with their onset potentials. The established spray modes are described and the differences in onset potentials and stability regions explained by the physicochemical properties of the electrosprayed liquid. PMID:21333298

  3. On-column nitrosation of amines observed in liquid chromatography impurity separations employing ammonium hydroxide and acetonitrile as mobile phase.

    PubMed

    Myers, David P; Hetrick, Evan M; Liang, Zhongming; Hadden, Chad E; Bandy, Steven; Kemp, Craig A; Harris, Thomas M; Baertschi, Steven W

    2013-12-01

    The availability of high performance liquid chromatography (HPLC) columns capable of operation at pH values up to 12 has allowed a greater selectivity space to be explored for method development in pharmaceutical analysis. Ammonium hydroxide is of particular value in the mobile phase because it is compatible with direct interfacing to electrospray mass spectrometers. This paper reports an unexpected N-nitrosation reaction that occurs with analytes containing primary and secondary amines when ammonium hydroxide is used to achieve the high pH and acetonitrile is used as the organic modifier. The nitrosation reaction has generality. It has been observed on multiple columns from different vendors and with multiple amine-containing analytes. Ammonia was established to be the source of the nitroso nitrogen. The stainless steel column frit and metal ablated from the frit have been shown to be the sites of the reactions. The process is initiated by removal of the chromium oxide protective film from the stainless steel by acetonitrile. It is hypothesized that the highly active, freshly exposed metals catalyze room temperature oxidation of ammonia to NO but that the actual nitrosating agent is likely N(2)O(3). PMID:24182763

  4. Greening pharmaceutical applications of liquid chromatography through using propylene carbonate-ethanol mixtures instead of acetonitrile as organic modifier in the mobile phases.

    PubMed

    Tache, Florentin; Udrescu, Stefan; Albu, Florin; Micăle, Florina; Medvedovici, Andrei

    2013-03-01

    Substitution of acetonitrile (ACN) as organic modifier in mobile phases for liquid chromatography by mixtures of propylene carbonate (PC) and ethanol (EtOH) may be considered a greener approach for pharmaceutical applications. Such a replacement is achievable without any major compromise in terms of elution order, chromatographic retention, efficiency and peak symmetry. This has been equally demonstrated for reverse phase (RP), ion pair formation (IP) and hydrophilic interaction liquid chromatography (HILIC) separation modes. The impact on the sensitivity induced by the replacement between these organic solvents is discussed for UV-vis and mass spectrometric detection. A comparison between Van Deemter plots obtained under elution conditions based on ACN and PC/EtOH is presented. The alternative elution modes were also compared in terms of thermodynamic parameters, such as standard enthalpy (ΔH⁰) and entropic contributions to the partition between the mobile and the stationary phases, for some model compounds. Van't Hoff plots demonstrated that differences between the thermodynamic parameters are minor when shifting from ACN/water to PC/EtOH/water elution on an octadecyl chemically modified silicagel stationary phase. As long as large volume injection (LVI) of diluents non-miscible with the mobile phase is a recently developed topic having a high potential of greening the sample preparation procedures through elimination of the solvent evaporation stage, this feature was also assessed in the case of ACN replacement by PC/EtOH. PMID:23277155

  5. Acetonitrile

    Integrated Risk Information System (IRIS)

    Acetonitrile ; CASRN 75 - 05 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  6. Retention of ionisable compounds on high-performance liquid chromatography. XV. Estimation of the pH variation of aqueous buffers with the change of the acetonitrile fraction of the mobile phase.

    PubMed

    Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

    2004-12-01

    The most commonly used mobile phases in reversed-phase high-performance liquid chromatography (RP-HPLC) are hydro-organic mixtures of an aqueous buffer and an organic modifier. The addition of this organic solvent to buffered aqueous solutions involves a variation of the buffer properties (pH and buffer capacity). In this paper, the pH variation is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-citrate, and ammonium-ammonia buffers. The proposed equations allow pH estimation of acetonitrile-water buffered mobile phases up to 60% (v/v) of organic modifier and initial aqueous buffer concentrations between 0.001 and 0.1 mol L(-1), from the initial aqueous pH. The estimated pH variation of the mobile phase and the pKa variation of the analytes allow us to predict the degree of ionisation of the analytes and from this and analyte hydrophobicities, to interpret the relative retention and separation of analyte mixtures. PMID:15628122

  7. Adsorption of water from aqueous acetonitrile on silica-based stationary phases in aqueous normal-phase liquid chromatography.

    PubMed

    Soukup, Jan; Jandera, Pavel

    2014-12-29

    Excess adsorption of water from aqueous acetonitrile mobile phases was investigated on 16 stationary phases using the frontal analysis method and coulometric Karl-Fischer titration. The stationary phases include silica gel and silica-bonded phases with different polarities, octadecyl and cholesterol, phenyl, nitrile, pentafluorophenylpropyl, diol and zwitterionic sulfobetaine and phosphorylcholine ligands bonded on silica, hybrid organic-silica and hydrosilated matrices. Both fully porous and core-shell column types were included. Preferential uptake of water by the columns can be described by Langmuir isotherms. Even though a diffuse rather than a compact adsorbed discrete layer of water on the adsorbent surface can be formed because of the unlimited miscibility of water with acetonitrile, for convenience, the preferentially adsorbed water was expressed in terms of a hypothetical monomolecular water layer equivalent in the inner pores. The uptake of water strongly depends on the polarity and type of the column. Less than one monomolecular water layer equivalent was adsorbed on moderate polar silica hydride-based stationary phases, Ascentis Express F5 and Ascentis Express CN column at the saturation capacity, while on more polar stationary phases, several water layer equivalents were up-taken from the mobile phase. The strongest affinity to water was observed on the ZIC cHILIC stationary phases, where more than nine water layer equivalents were adsorbed onto its surface at its saturation capacity. Columns with bonded hydroxyl and diol ligands show stronger water adsorption in comparison to bare silica. Columns based on hydrosilated silica generally show significantly decreased water uptake in comparison to stationary phases bonded on ordinary silica. Significant correlations were found between the water uptake and the separation selectivity for compounds with strong polarity differences. PMID:25544246

  8. Aqueous Two-Phase Systems formed by Biocompatible and Biodegradable Polysaccharides and Acetonitrile

    PubMed Central

    de Brito Cardoso, Gustavo; Souza, Isabela Nascimento; Pereira, Matheus M.; Freire, Mara G.; Soares, Cleide Mara Faria; Lima, Álvaro Silva

    2015-01-01

    In this work, it is shown that novel aqueous two-phase systems can be formed by the combination of acetonitrile and polysaccharides, namely dextran. Several ternary phase diagrams were determined at 25 °C for the systems composed of water + acetonitrile + dextran. The effect of the dextran molecular weight (6,000, 40,000 and 100,000 g.mol−1) was ascertained toward their ability to undergo liquid-liquid demixing. An increase in the dextran molecular weight favors the phase separation. Furthermore, the effect of temperature (25, 35 and 45 °C) was evaluated for the system constituted by the dextran of higher molecular weight. Lower temperatures are favorable for phase separation since lower amounts of dextran and acetonitrile are required for the creation of aqueous two-phase systems. In general, acetonitrile is enriched in the top phase while dextran is majorly concentrated in the bottom phase. The applicability of this new type of two-phase systems as liquid-liquid extraction approaches was also evaluated by the study of the partition behavior of a well-known antioxidant – vanillin - and used here as a model biomolecule. The optimized conditions led to an extraction efficiency of vanillin of 95% at the acetonitrile-rich phase. PMID:25729320

  9. Effect of phase symmetry on the NMR spectrum of acetonitrile oriented in a uniaxial-biaxial-uniaxial phase

    NASA Astrophysics Data System (ADS)

    Deepak, H. S. Vinay; Yelamaggad, C. V.; Khetrapal, C. L.; Ramanathan, K. V.

    2016-09-01

    We report here the measurement of the Csbnd H and the Hsbnd H dipolar couplings of the methyl group of acetonitrile oriented in the biaxial liquid crystal potassium laurate/1-decanol/water system. These parameters show large variations when measured as a function of temperature. The variations follow the symmetry of the phase as the liquid crystal goes through the sequence of uniaxial - biaxial - uniaxial phases and show a close correspondence to the phase changes that occur in the liquid crystalline solvent coinciding with the onset of biaxiality. The Hsbnd Csbnd H bond angle calculated after incorporating vibrational corrections to the dipolar couplings is discussed in terms of contributions in the case of the biaxial liquid crystal arising from vibration-rotation interaction effects.

  10. [Deep eutectic solvent: a new kind of mobile phase modifier for hydrophilic interaction liquid chromatography].

    PubMed

    Tan, Ting; Qiao, Xin; Wan, Yiqun; Qiu, Hongdeng

    2015-09-01

    Deep eutectic solvents (DESs) were used as a new kind of mobile phase modifier in hydrophilic interaction liquid chromatography (HILIC). In our experiment, a SiO2 column (150 mm x 4.6 mm, 3 µm) was selected to separate several nucleobases and nucleosides by using the mixed solution of acetonitrile and DES (choline chloride-ethylene glycol (1:3, mol/mol) ) as mobile phase. Subsequently, the concentrations of DESs in acetonitrile and the column temperature on the effect of separation were investigated. According to the experimental results, better separation of nucleobases and nucleosides was obtained by using acetonitrile and DESs mixed solution as mobile phase than that using traditional water-based solution. For example, a baseline separation between cytosine and cytidine cannot be achieved by HILIC with water-based mobile phase, however, greater improvement was gained by HILIC with modified DES-acetonitrile mobile phase. Meanwhile, the retention times of nucleobases and nucleosides decreased as the proportion of DESs in acetonitrile increased, the most significant decrease of which was with cytidine. Similar retention behavior took place with the effect of column temperature. Decreased retention times of the analytes were observed as column temperature increased. The experimental results indicated that this new method may solve some separation difficulties in traditional water-based HILIC, which also successfully verify the feasibility of DESs as mobile phase modifiers. PMID:26753279

  11. Photochemical oxidation of thiophene by O2 in an oil/acetonitrile two-phase extraction system.

    PubMed

    Li, Fa-Tang; Zhao, Di-Shun; Li, Hong-Xia; Liu, Rui-Hong

    2008-10-01

    Photochemical oxidation of thiophene in an n-octane/acetonitrile extraction system using O(2) as oxidant was studied. Results obtained here can be used as a reference for desulfurization of gasoline, because thiophene is one of the main components containing sulfur in fluid catalytic cracking gasoline. A 500-W high-pressure mercury lamp was used as a light source for irradiation, and air was introduced by a gas pump to supply O(2). Thiophene dissolved in nopolar n-octane solvent was photodecomposed and removed into the polar acetonitrile phase. The desulfurization rate of thiophene in n-octane was 65.2% under photoirradiation for 5 h under the conditions of air flow at 150 mL min(-1), and V(n-octane):V(acetonitrile) = 1:1. This can be improved to 96.5% by adding 0.15 g Na-ZSM-5 zeolite into the 100-mL reaction system, which is the absorbent for O(2) and thiophene. Under such conditions, the photooxidation kinetics of thiophene with O(2) and Na-ZSM-5 zeolite is first-order with an apparent rate constant of 0.6297 h(-1) and half-time of 1.10 h. The sulfur content can be reduced from 800 microL L(-1) to 28 microL L(-1). PMID:18991938

  12. An analytical method for the determination of perfluorinated compounds in whole blood using acetonitrile and solid phase extraction methods.

    PubMed

    Yeung, Leo W Y; Taniyasu, Sachi; Kannan, Kurunthachalam; Xu, Della Z Y; Guruge, Keerthi S; Lam, Paul K S; Yamashita, Nobuyoshi

    2009-06-19

    A method for the analysis of perfluorinated compounds (perfluoroalkyl sulfonates: C4, C6, C8, C10; perfluoroalkyl sulfinates: C6, C8, C10; perfluorooctanesulfonamide, N-ethyl perfluorooctanesulfonamide, N-ethyl perfluorooctanesulfonamidoacetate, perfluorocarboxylates: C4-C14; fluorotelomer carboxylate (7:3, 8:2) in whole blood using acetonitrile and OASIS WAX solid phase extraction (SPE) cartridge was developed. Separation of target compounds in two HPLC columns (ion exchange JJ50-2D and C18 Betasil columns) was examined. Matrix recoveries of the developed methods ranged from 70% to 120%. Separation of possible inferences such as taurodeoxycholic acid (TDC) was accomplished using an ion exchange JJ50-2D column, and this separation was validated using whole blood of different animals. PMID:19439311

  13. Study of the mechanism of acetonitrile stacking and its application for directly combining liquid-phase microextraction with micellar electrokinetic chromatography.

    PubMed

    Sun, Jingru; Feng, Jing; Shi, Ludi; Liu, Laping; He, Hui; Fan, Yingying; Hu, Shibin; Liu, Shuhui

    2016-08-26

    Acetonitrile stacking is an online concentration method that is distinctive due to its inclusion of a high proportion of organic solvent in sample matrices. We previously designed a universal methodology for the combination of liquid-phase microextraction (LPME) and capillary electrophoresis (CE) using acetonitrile stacking and micellar electrokinetic chromatography (MEKC) mode, thereby achieving large-volume injection of the diluted LPME extractant and the online concentration. In this report, the methodology was extended to the analysis of highly substituted hydrophobic chlorophenols in wines using diethyl carbonate as the extractant. Additionally, the mechanism of acetonitrile stacking was studied. The results indicated that the combination of LPME and MEKC exhibited good analytical performance: with ∼40-fold concentration by LPME, a 20-cm (33% of the total length) sample plug injection of an eight-fold dilution of diethyl carbonate with the organic solvent-saline solution produced enrichments higher by a factor of 260-791. Limits of qualification ranged from 5.5 to 16.0ng/mL. Acceptable reproducibilities of lower than 1.8% for migration time and 8.6% for peak areas were obtained. A dual stacking mechanism of acetonitrile stacking was revealed, involving transient isotachophoresis plus pH-junction stacking. The latter was associated with a pH shift induced by the presence of acetonitrile. The pseudo-stationary phase (Brij-35) played an important role in reducing the CE running time by weakening the isotachophoretic migration of the analyte ions following Cl(-) ions. The combination of acetonitrile stacking and nonionic micelle-based MEKC appears to be a perfect match for introducing water-immiscible LPME extractants into an aqueous CE system and can thus significantly expand the application of LPME-CE in green analytical chemistry. PMID:27451260

  14. A new insight into the photochemistry of avobenzone in gas phase and acetonitrile from ab initio calculations.

    PubMed

    Kojić, Marko; Petković, Milena; Etinski, Mihajlo

    2016-08-10

    Avobenzone (4-tert-butyl-4'-methoxydibenzoylmethane, AB) is one of the most widely used filters in sunscreens for skin photoprotection in the UVA band. The photochemistry of AB includes keto-enol tautomerization, cis-trans isomerization, rotation about the single bond and α bond cleavages of carbonyl groups. In this contribution we study chelated and non-chelated enol, rotamers Z and E, and keto tautomers of AB in the ground and excited states in gas phase and acetonitrile by means of a coupled cluster method. Our findings suggest that torsion around the double C2-C3 bond of photoexcited chelated enol leads to internal conversion to the ground state and formation of rotamer E. In addition, opening of the chelated hydrogen ring by torsion of the hydroxyl group creates non-chelated enol. The possible mechanisms of rotamer Z formation are discussed. The solvent dependent photolability is related to the relative order of the lowest triplet ππ* and nπ* states of the keto tautomer. PMID:27443629

  15. Acetonitrile extraction and dual-layer solid phase extraction clean-up for pesticide residue analysis in propolis.

    PubMed

    Oellig, Claudia

    2016-05-01

    Propolis is a very complex mixture of substances that is produced by honey bees and is known to be a rather challenging matrix for residue analysis. Besides resins, flavonoids and phenols, high amount of wax is co-extracted resulting in immense matrix effects. Therefore a suitable clean-up is crucial and indispensable. In this study, a reliable solid phase extraction (SPE) clean-up was developed for pesticide residue analysis in propolis. The clean-up success was quickly and easily monitored by high-performance thin-layer chromatography with different detection possibilities. The final method consists of the extraction of propolis with acetonitrile according to the QuEChERS method followed by an effective extract purification on dual-layer SPE cartridges with spherical hydrophobic polystyrene-divinylbenzene resin/primary secondary amine as sorbent and a mixture of toluene/acetone (95:5, v/v) for elution. Besides fat-soluble components like waxes, flavonoids, and terpenoids, more polar compounds like organic acids, fatty acids, sugars and anthocyanins were also removed to large extent. Method performance was assessed by recovery experiments at spiking levels of 0.5 and 1mg/kg (n=5) for fourteen pesticides that are relevant for propolis. Mean recoveries determined by HPLC-MS against solvent standards were between 40 and 101%, while calculation against matrix-matched standards provided recoveries of 79-104%. Precision of recovery, assessed by relative standard deviations, were below 9%. Thus, the developed dual-layer SPE clean-up enables the reliable pesticide residue analysis in propolis and provides a suitable alternative to time-consuming clean-up procedures proposed in literature. PMID:27059398

  16. Comparison of iso-eluotropic mobile phases at different temperatures for the separation of triacylglycerols in Non-Aqueous Reversed Phase Liquid Chromatography.

    PubMed

    Hmida, Dorra; Abderrabba, Manef; Tchapla, Alain; Héron, Sylvie; Moussa, Fathi

    2015-05-15

    Triacylglycerols (TAGs) are a large class of neutral lipids that naturally occur in both plant and animal oils and fats. Their analyses in Non-Aqueous Reversed Phase Liquid Chromatography (NARP) require a mixture of weak solvent (mostly acetonitrile) and strong solvent. In the present work, we have established eluotropic solvent strength scale of several binary mobile phases on C18 bonded silica at different temperatures (acetonitrile/methylene chloride, acetonitrile/acetone, acetonitrile/ethyl acetate, acetonitrile/propan-2-ol, and acetonitrile/butan-1-ol at 25°C, 43°C, 63°C and 85°C); it is based on the methylene selectivity and the use of homologous series. We show that this scale is well suited to the TAGs analysis. The analysis of nine seed oils (Aleurites fordii, Calophyllum inophyllum, Glycina max, Olea europea, Orbignya olifeira, Pinus koraiensis, Pistacia lentiscus, Punica granatum and Ribes nigrum) in iso-eluotropic conditions leads to propose unambiguously the couple MeCN/BuOH at 25°C as the best system to separate TAGs. The use of butanol, as strong solvent, provides very good TAGs congeners separations and avoids the use of chlorinated solvents which gave to this day the best separations. PMID:25855317

  17. Effect of Mobile Phase on Electrospray Ionization Efficiency

    NASA Astrophysics Data System (ADS)

    Liigand, Jaanus; Kruve, Anneli; Leito, Ivo; Girod, Marion; Antoine, Rodolphe

    2014-08-01

    Electrospray (ESI) ionization efficiencies (IE) of a set of 10 compounds differing by chemical nature, extent of ionization in solution (basicity), and by hydrophobicity (tetrapropylammonium and tetraethylammonium ion, triethylamine, 1-naphthylamine, N,N-dimethylaniline, diphenylphthalate, dimethylphtahalate, piperidine, pyrrolidine, pyridine) have been measured in seven mobile phases (three acetonitrile percentages 20%, 50%, and 80%, and three different pH-adjusting additives, 0.1% formic acid, 1 mM ammonia, pH 5.0 buffer combination) using the relative measurement method. MS parameters were optimized separately for each ion. The resulting relative IE data were converted into comparable logIE values by anchoring them to the logIE of tetrapropylammonium ion taking into account the differences of ionization in different solvents and thereby making the logIE values of the compounds comparable across solvents. The following conclusions were made from analysis of the data. The compounds with pK a values in the range of the solution pH values displayed higher IE at lower pH. The sensitivity of IE towards pH depends on hydrophobicity being very strong with pyridine, weaker with N,N-dimethylaniline, and weakest with 1-naphthylamine. IEs of tetraalkylammonium ions and triethylamine were expectedly insensitive towards solution pH. Surprisingly high IEs of phthalate esters were observed. The differences in solutions with different acetonitrile content and similar pH were smaller compared with the pH effects. These results highlight the importance of hydrophobicity in electrospray and demonstrate that high hydrophobicity can sometimes successfully compensate for low basicity.

  18. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning... compliance with all requirements for receipt of Mobility Fund Phase I support at the time that it...

  19. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning... compliance with all requirements for receipt of Mobility Fund Phase I support at the time that it...

  20. 47 CFR 54.1008 - Mobility Fund Phase I disbursements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 3 2014-10-01 2014-10-01 false Mobility Fund Phase I disbursements. 54.1008 Section 54.1008 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) UNIVERSAL SERVICE Mobility Fund § 54.1008 Mobility Fund Phase I disbursements. (a) A winning bidder for Mobility Fund Phase I...

  1. Influence of the Modifier Type and its Concentration on Electroosmotic Flow of the Mobile Phase in Pressurized Planar Electrochromatography.

    PubMed

    Hałka-Grysińska, Aneta; Płocharz, Paweł W; Torbicz, Andrzej; Skwarek, Ewa; Janusz, Władysław; Dzido, Tadeusz H

    2014-01-01

    The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, N-methylformamide and N,N-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase. During the study we found that there is no linear correlation between EOF velocity of the mobile phase and single variables such as zeta potential or dielectric constant or viscosity. However, there is quite strong linear correlation between EOF velocity of the mobile phase and variable obtained by multiplying zeta potential of the stationary phase-mobile phase interface, by dielectric constant of the mobile phase solution and dividing by viscosity of the mobile phase. Therefore, it could be concluded that the PPEC system fulfilled the Helmholtz-Smoluchowski equation. PMID:25067847

  2. Enhanced extraction yields and mobile phase separations by solvent mixtures for the analysis of metabolites in Annona muricata L. leaves.

    PubMed

    Ribeiro de Souza, Eloana Benassi; da Silva, Renata Reis; Afonso, Sabrina; Scarminio, Ieda Spacino

    2009-12-01

    The effects of five extraction solvents and their mixtures on the yield of metabolites in crude and fractionated extracts of Annona muricata L. leaves were investigated by direct comparison. Extraction media were prepared using simplex centroid mixtures of ethanol, ethyl acetate, dichloromethane, acetone, and chloroform. The effects of the mobile phase solvent strength and the analysis wavelength on the chromatographic separation were also investigated. Solvent mixtures rather than pure solvents were found to be the most efficient extractors for the different fractions. The results indicated that the mobile phase composed of methanol/acetonitrile/water (26:27:47 v/v/v) was most suitable for the basic fraction analysis at 254 nm, whereas the mobile phase composed of methanol/acetonitrile/water (35:35:30 v/v/v) was the most adequate for the organic fraction analysis at 254 nm. The results indicated that the chromatographic profiles and number of peaks were affected by the mobile phase strength and analysis wavelength. PMID:19882621

  3. Multiresidue pesticide analysis of botanical dietary supplements using salt-out acetonitrile extraction, solid-phase extraction cleanup column, and gas chromatography-triple quadrupole mass spectrometry.

    PubMed

    Hayward, Douglas G; Wong, Jon W; Shi, Feng; Zhang, Kai; Lee, Nathaniel S; DiBenedetto, Alex L; Hengel, Mathew J

    2013-05-01

    Dietary supplements form an increasing part of the American diet, yet broadly applicable multiresidue pesticide methods have not been evaluated for many of these supplements. A method for the analysis of 310 pesticides, isomers, and pesticide metabolites in dried botanical dietary supplements has been developed and validated. Sample preparation involved acetonitrile:water added to the botanical along with anhydrous magnesium sulfate and sodium chloride for extraction, followed by cleanup with solid-phase extraction using a tandem cartridge consisting of graphitized carbon black (GCB) and primary-secondary amine sorbent (PSA). Pesticides were measured by gas chromatography-tandem mass spectrometry. Accuracy and precision were evaluated through fortifications of 24 botanicals at 10, 25, 100, and 500 μg/kg. Mean pesticide recoveries and relative standard deviations (RSDs) for all botanicals were 97%, 91%, 90%, and 90% and 15%, 10%, 8%, and 6% at 10, 25, 100, and 500 μg/kg, respectively. The method was applied to 21 incurred botanicals. Quinoxyfen was measured in hops (100-620 μg/kg). Tetraconazole (48 μg/kg), tetramethrin (15 μg/kg), methamidophos (50 μg/kg), and chlorpyrifos (93 μg/kg) were measured in licorice, mallow, tea, and tribulus, respectively. Quintozene, its metabolites and contaminants (pentachloroaniline, pentachlorobenzene, pentachloroanisole, and pentachlorothioanisole and hexachlorobenzene and tecnazene, respectively), with hexachlorocyclohexanes and DDT were identified in ginseng sources along with azoxystrobin, diazinon, and dimethomorph between 0.7 and 2800 μg/kg. Validation with these botanicals demonstrated the extent of this method's applicability for screening 310 pesticides in a wide array of botanical dietary supplements. PMID:23534560

  4. Electronic structure of the acetonitrile and acetonitrile dimer anions: a topological investigation.

    PubMed

    Timerghazin, Qadir K; Peslherbe, Gilles H

    2008-01-17

    . We also report the first multireference electronic structure calculations of the valence-bound-electron acetonitrile monomer and dimer anions, the highest-level calculations of these species to date. The acetonitrile radical anion is unstable in the gas phase and is topologically characterized by a radical-like nonbonded charge concentration located at the cyanide carbon atom. Based on the results of the AIM analysis, the previously proposed resonance description of the valence-bound-electron acetonitrile anion is refined, and a new resonance description of the dimer anion is proposed. Overall, this work demonstrates the rich topological variety of the excess electron interacting with acetonitrile molecules, which manifests itself as charge concentrations, pseudo-atoms, and covalent bonds. PMID:18154288

  5. Effect of HPLC binary mobile phase composition on the analysis of carbonyls.

    PubMed

    Ho, Duy Xuan; Kim, Ki-Hyun

    2011-09-01

    The relative performance of the binary mobile phase in the high-performance liquid chromatography analysis of carbonyl compounds (CCs) was tested using the liquid-phase standards containing 15 aldehyde/ketone-DNPH mixture. The Hichrome column was employed for the analysis of CCs at a flow rate of 1.5 mL min( - 1). The binary mobile phases prepared using both acetonitrile/water (AW) and a possible alternative of methanol:water (MW) mixture were examined by their calibration results. The data derived from these two binary phases were then evaluated in terms of three key variables (i.e., resolution, relative sensitivity, and retention time). The relative water content (or the water to organic solvent ratio (W/A) or (W/M)) of the binary phase was found as the key variable for the performance. The results indicate that the optimal resolution of AW combination was attained consistently for most composition, while MW generally suffered from overpressure problem. The changes of water content in the AW mixture led to the changes of all three variables in the quantitative analysis of CCs. The obtained results confirm that the AW mixture should be the optimal elutant for the CC analysis, as other simple binary compositions like MW are limited in many respects. PMID:21107904

  6. Effect of the mobile phase composition on the adsorption behavior of tryptophan in reversed-phase liquid chromatography

    SciTech Connect

    Ahmad, Tarab; Guiochon, Georges A

    2006-03-01

    Single-component adsorption isotherm data of l-tryptophan on a C{sub 18}-bonded silica column were acquired by frontal analysis (FA), with aqueous mobile phases containing 2.5, 5, and 7.5% of acetonitrile (ACN) or 7, 10, 15, and 20% of methanol (MeOH). Most of these isotherms have two inflection points and three different parts. The low and the high concentration parts exhibit langmuirian behavior. The intermediate part exhibits anti-langmuirian behavior. The inflection points shift toward higher concentrations with increasing mobile phase concentration in ACN or MeOH, which causes the differences in the isotherm profiles. The nature of the organic modifier and its concentration affect only the isotherm profile and the numerical values of its parameters, not the nature of the best model, which is the bi-Moreau model in all cases. The isotherm profiles depend on the experimental conditions because they affect the intensity of the adsorbate-adsorbate interactions. Overloaded band profiles of tryptophan were recorded with the seven mobile phase compositions. They were used to determine the best values of the isotherm coefficients by the inverse method (IM) of chromatography. There is an excellent agreement between the values of these parameters obtained by FA and by IM. Increasing the concentration of either ACN or MeOH in the mobile phase causes a slight decrease in the saturation capacities of the low and the high energy sites, and in the adsorption constant of the low energy sites. The adsorption constant of the high energy sites increases with increasing concentration of either solvent or is little affected. The adsorbate-adsorbate interaction constants of both low and high energy sites increase for both solvents. Saturation capacities of the high energy sites are higher for ACN than for MeOH.

  7. Multiresidue pesticide analysis of ginseng powders using acetonitrile- or acetone-based extraction, solid-phase extraction cleanup, and gas chromatography-mass spectrometry/selective ion monitoring (GC-MS/SIM) or -tandem mass spectrometry (GC-MS/MS).

    PubMed

    Wong, Jon W; Zhang, Kai; Tech, Katherine; Hayward, Douglas G; Krynitsky, Alexander J; Cassias, Irene; Schenck, Frank J; Banerjee, Kaushik; Dasgupta, Soma; Brown, Don

    2010-05-26

    A multiresidue method for the analysis of 168 pesticides in dried powdered ginseng has been developed using acetonitrile or acetone mixture (acetone/cyclohexane/ethyl acetate, 2:1:1 v/v/v) extraction, solid-phase extraction (SPE) cleanup with octyl-bonded silica (C(8)), graphitized carbon black/primary-secondary amine (GCB/PSA) sorbents and toluene, and capillary gas chromatography-mass spectrometry/selective ion monitoring (GC-MS/SIM) or -tandem mass spectrometry (GC-MS/MS). The geometric mean limits of quantitation (LOQs) were 53 and 6 microg/kg for the acetonitrile extraction and 48 and 7 microg/kg for the acetone-based extraction for GC-MS/SIM and GC-MS/MS, respectively. Mean percent recoveries and standard deviations from the ginseng fortified at 25, 100, and 500 microg/kg using GC-MS/SIM were 87 +/- 10, 88 +/- 8, and 86 +/- 10% from acetonitrile extracts and 88 +/- 13, 88 +/- 12, and 88 +/- 14% from acetone mixture extracts, respectively. The mean percent recoveries from the ginseng at the 25, 100, and 500 microg/kg levels using GC-MS/MS were 83 +/- 19, 90 +/- 13, and 89 +/- 11% from acetonitrile extracts and 98 +/- 20, 91 +/- 13, and 88 +/- 14% from acetone extracts, respectively. Twelve dried ginseng products were found to contain one or more of the following pesticides and their metabolites: BHCs (benzene hexachlorides, alpha-, beta-, gamma-, and delta-), chlorothalonil, chlorpyrifos, DDT (dichlorodiphenyl trichloroethane), dacthal, diazinon, iprodione, quintozene, and procymidone ranging from <1 to >4000 microg/kg. No significant differences were found between the two extraction solvents, and GC-MS/MS was found to be more specific and sensitive than GC-MS/SIM. The procedures described were shown to be effective in screening, identifying, confirming, and quantitating pesticides in commercial ginseng products. PMID:20225896

  8. Detection of adulteration in acetonitrile

    NASA Astrophysics Data System (ADS)

    Chen, Guoxiang; Fujimori, Kiyoshi; Lee, Hans; Nashed-Samuel, Yasser; Phillips, Joseph; Rogers, Gary; Shen, Hong; Yee, Chanel

    2011-05-01

    To address the increasing concern that acetonitrile may be intentionally adulterated to meet the shortfall in global supplies resulting from a downturn in its manufacturing, three analytical techniques were examined in this study. Gas Chromatography with Thermal Conductivity Detection (GC-TCD), Near Infrared (NIR) spectroscopy and Fourier Transform Infrared (FT-IR) spectroscopy were assessed for their ability to detect and quantify potential adulterants including water, alternative organic solvents, and by-products associated with the production of acetonitrile. The results of the assessment of the three techniques for acetonitrile adulteration testing are discussed.

  9. Capillary electrokinetic separations: Influence of mobile phase composition on performance

    SciTech Connect

    Sepaniak, M.J.; Swaile, D.F.; Powell, A.C.; Cole, R.O.

    1990-01-01

    The composition of the mobile phase employed in capillary zone electrophoresis and the related technique, micellar electrokinetic capillary chromatography, is an important factor in determining separation performance. The influences of ionic salt, surfactant, and organic solvent mobile phase additives on separation efficiency, retention, and elution range are discussed and demonstrated. 23 refs., 2 figs., 2 tabs.

  10. Influence of mobile phase composition and cross-linking density on the enantiomeric recognition properties of molecularly imprinted polymers.

    PubMed

    Yu, C; Mosbach, K

    2000-08-01

    A series of experiments were conducted to investigate elements which affect the enantiomeric recognition properties of molecularly imprinted polymers (MIPs) in the HPLC mode. Our results show that the recognition properties of MIPs are greatly influenced by the mobile phase used. For a polymer prepared in acetonitrile, a good enantiomeric separation was observed when acetonitrile-based mobile phase was used, when the mobile phase was changed to chloroform-based, no enantiomeric recognition was observed although the sample molecule was retarded. This indicates that the specific co-operative binding interactions between the functional groups at the imprinted polymer's recognition sites and the sample molecule were considerably disrupted and only non-specific interactions remained. When the mobile phase was changed back to acetonitrile-based, the recognition was regained. In contrast, for polymers prepared in chloroform, chloroform-based mobile phase gave much better separation than acetonitrile-based mobile phase. When other solvents were tested, significant solvent effects were generally observed. Based on these observations, the recognition properties of the methacrylic acid (MAA)-co-ethylene glycol dimethacrylate (EGDMA) polymers were reinvestigated, and the results show that by simply using an optimised mobile phase system, significantly improved recognition over previously reported results was observed. For a polymer made against Cbz-L-Trp, 100 microg of Cbz-D,L-Trp was separated with a separation factor (alpha) of 4.23 and a resolution (Rs) of 3.87, whereas in the previous report, 10 microg of Cbz-D,L-Trp was only separated with alpha = 1.67 and Rs = 0.1. It is generally realised that the imprinted polymer's recognition property is also very much influenced by the nature of the polymer network. It was shown that the recognition decreased with a decrease in the apparent degree of cross-linking (molar percentage of cross-linker in the polymerisation mixture

  11. Analytical Enantioseparation of β-Substituted-2-Phenylpropionic Acids by High-Performance Liquid Chromatography with Hydroxypropyl-β-Cyclodextrin as Chiral Mobile Phase Additive.

    PubMed

    Tong, Shengqiang; Zhang, Hu; Yan, Jizhong

    2016-04-01

    Analytical enantioseparation of five β-substituted-2-phenylpropionic acids by high-performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral mobile phase additive was established in this paper, and chromatographic retention mechanism was studied. The effects of various factors such as the organic modifier, different ODS C18 columns and concentration of HP-β-CD were investigated. The chiral mobile phase was composed of methanol or acetonitrile and 0.5% triethylamine acetate buffer at pH 3.0 added with 25 mmol L(-1) of HP-β-CD, and baseline separations could be reached for all racemates. As for chromatographic retention mechanism, it was found that there was a negative correlation between the concentration of HP-β-CD in mobile phase and the retention factor under constant pH value and column temperature. PMID:26755500

  12. MSAT mobile electronically steered phased array antenna development

    NASA Technical Reports Server (NTRS)

    Schmidt, Fred

    1988-01-01

    The Mobile Satellite Experiment (MSAT-X) breadboard antenna design demonstrates the feasibility of using a phased array in a mobile satellite application. An electronically steerable phased array capable of tracking geosynchronous satellites from anywhere in the Continental United States has been developed. The design is reviewed along with the test data. Cost analysis are presented which indicate that this design can be produced at a cost of $1620 per antenna.

  13. Low temperature properties of acetonitrile confined in MCM-41.

    PubMed

    Kittaka, Shigeharu; Iwashita, Takafumi; Serizawa, Akihiro; Kranishi, Miki; Takahara, Shuichi; Kuroda, Yasushige; Mori, Toshinori; Yamaguchi, Toshio

    2005-12-15

    The effect of confinement on the phase changes and dynamics of acetonitrile in mesoporous MCM-41 was studied by use of adsorption, FT-IR, DSC, and quasi-elastic neutron scattering (QENS) measurements. Acetonitrile molecules in a monolayer interact strongly with surface hydroxyls to be registered and perturb the triple bond in the C[triple bond]N group. Adsorbed molecules above the monolayer through to the central part of the cylindrical pores are capillary condensed molecules (cc-acetonitrile), but they do not show the hysteresis loop in adsorption-desorption isotherms, i.e., second order capillary condensation. FT-IR measurements indicated that the condensed phase is very similar to the bulk liquid. The cc-acetonitrile freezes at temperatures that depend on the pore size of the MCM-41 down to 29.1 A (C14), below which it is not frozen. In addition, phase changes between alpha-type and beta-type acetonitriles were observed below the melting points. Application of the Gibbs-Thomson equation, assuming the unfrozen layer thickness to be 0.7 nm, gave the interface free energy differences between the interfaces, i.e., Deltagamma(l/alpha) = 22.4 mJ m(-2) for the liquid/pore surface (ps) and alpha-type/ps, and Deltagamma(alpha/beta) = 3.17 mJ m(-2) for alpha-type/ps and beta-type/ps, respectively. QENS experiments substantiate the differing behaviors of monolayer acetonitrile and cc-acetonitrile. The monolayer acetonitrile molecules are anchored so as not to translate. The two Lorentzian analysis of QENS spectra for cc-acetonitriles showed translational motion but markedly slowed. However, the activation energy for cc-acetonitrile in MCM-41 (C18) is 7.0 kJ mol(-1) compared to the bulk value of 12.7 kJ mol(-1). The relaxation times for tumbling rotational diffusion of cc-acetonitrile are similar to bulk values. PMID:16375278

  14. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive

    PubMed Central

    Peng, Yangfeng; He, Quan Sophia; Cai, Jiang

    2016-01-01

    Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT). PMID:26880921

  15. Enantioseparation of Citalopram by RP-HPLC, Using Sulfobutyl Ether-β-Cyclodextrin as a Chiral Mobile Phase Additive.

    PubMed

    Peng, Yangfeng; He, Quan Sophia; Cai, Jiang

    2016-01-01

    Enantiomeric separation of citalopram (CIT) was developed using a reversed phase HPLC (RP-HPLC) with sulfobutylether-β-cyclodextrin (SBE-β-CD) as a chiral mobile phase additive. The effects of the pH value of aqueous buffer, concentration of chiral additive, composition of mobile phase, and column temperature on the enantioseparation of CIT were investigated on the Hedera ODS-2 C18 column (250 mm × 4.6 mm × 5.0 um). A satisfactory resolution was achieved at 25°C using a mobile phase consisting of a mixture of aqueous buffer (pH of 2.5, 5 mM sodium dihydrogen phosphate, and 12 mM SBE-β-CD), methanol, and acetonitrile with a volumetric ratio of 21 : 3 : 1 and flow rate of 1.0 mL/min. This analytical method was evaluated by examining the precision (lower than 3.0%), linearity (regression coefficients close to 1), limit of detection (0.070 µg/mL for (R)-CIT and 0.076 µg/mL for (S)-CIT), and limit of quantitation (0.235 µg/mL for (R)-CIT and 0.254 µg/mL for (S)-CIT). PMID:26880921

  16. Utilization of deep eutectic solvents as novel mobile phase additives for improving the separation of bioactive quaternary alkaloids.

    PubMed

    Tan, Ting; Zhang, Mingliang; Wan, Yiqun; Qiu, Hongdeng

    2016-03-01

    Deep eutectic solvents (DESs) were used as novel mobile phase additives to improve chromatographic separation of four quaternary alkaloids including coptisine chloride, sanguinarine, berberine chloride and chelerythrine on a C18 column. DESs as a new class of ionic liquids are renewably sourced, environmentally benign, low cost and easy to prepare. Seven DESs were obtained by mixing different hydrogen acceptors and hydrogen-bond donors. The effects of organic solvents, the concentration of DESs, the types of DESs and the pH values of the buffer solution on the separation of the analytes were investigated. The composition of acetonitrile and 1.0% deep eutectic solvents aqueous solution (pH 3.3, adjusted with hydrochloric acid) in a 32:68 (v/v) ratio was used as optimized mobile phase, with which four quaternary alkaloids were well separated. When a small amount of DESs was added in the mobile phase for the separation of alkaloids on the C18 column, noticeable improvements were distinctly observed such as decreasing peak tailing and improving resolution. The separation mechanism mediated by DESs as mobile phase additives can be attributed to combined effect of both hydrogen acceptors and hydrogen-bond donors. For example, choline chloride can effectively cover the residual silanols on silica surface and ethylene glycol can reduce the retention time of analytes. The proposed method has been applied to determine BerbC in Lanqin Chinese herbal oral solution and BerbC tablet. Utilization of DESs in mobile phase can efficiently improve separation and selectivity of analytes from complex samples. PMID:26717817

  17. Investigations of mobile phase contributions to enantioselective anion- and zwitterion-exchange modes on quinine-based zwitterionic chiral stationary phases.

    PubMed

    Hoffmann, Christian V; Reischl, Roland; Maier, Norbert M; Lämmerhofer, Michael; Lindner, Wolfgang

    2009-02-13

    Novel chiral stationary phases (CSPs) based on zwitterionic Cinchona alkaloid-type low-molecular mass chiral selectors (SOs), as they have been reported recently, were investigated in HPLC towards effects on their chromatographic behavior by mobile phase composition. Mobile phase characteristics like acid-to-base ratio and type of acidic and basic additives as well as effect of type of bulk solvents in nonaqueous polar organic and aqueous reversed-phase (RP) eluent systems were varied in order to illustrate the variability and applicability of zwitterionic CSPs with regard to mobile phase aspects. Chiral SOs of the five zwitterionic CSPs investigated herein contained weak and strong cation-exchange (WCX, SCX) sites at C9- and C6'-positions of the Cinchona alkaloid scaffold which itself accommodated the weak anion-exchange (WAX) site. The study focused on zwitterion-exchange (ZX) operational mode and chiral amino acids as target analytes. Besides, also the anion-exchange (AX) mode for chiral N-blocked amino acid analytes was considered, because of the intramolecular counterion (IMCI) property available in AX mode. Overall, most general and successful conditions in ZX mode were found to be weakly acidic methanolic mobile phases. In aqueous eluents RP contributions to retention came into play but only at low organic modifier content because of the highly polar character of zwitterionic analytes. At higher acetonitrile content, HILIC-related retention phenomena were observed. When using weakly basic eluent system in AX mode remarkably fast enantiomer separations involving exclusion phenomena were possible with one enantiomer eluting before and the other after void volume. PMID:19144343

  18. Vitamin D analysis in plasma by high performance liquid chromatography (HPLC) with C(30) reversed phase column and UV detection--easy and acetonitrile-free.

    PubMed

    Hymøller, Lone; Jensen, Søren Krogh

    2011-04-01

    Two physiologically important forms of vitamin D exist: vitamin D(2) and vitamin D(3), which by liver based hydroxylase enzymes are converted to 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3), respectively. These hydroxylated metabolites of vitamin D are measured in plasma to assess the vitamin D status of animals and humans. Therefore cheap and reliable analytical methods are very much in demand in nutritional and physiological research. After saponification and extraction of plasma or serum samples the current method uses reverse phase high performance liquid chromatography on a C(30) column and with UV detection at 265nm for quantifying vitamin D(2), vitamin D(3), 25-hydroxyvitamin D(2), and 25-hydroxyvitamin D(3). The method proved versatile with respect to plasma lipid content, sample amount, and plasma concentration of the vitamin D metabolites as it was tested using plasma from six different species: cattle, pigs, poultry, mink, horses, and humans. In cattle plasma recoveries were between 86.6 and 101.0%, within day error between 0.9 and 5.9%, and between day error between 0.2 and 1.7%. However, depending on species and sample amount error percentages varied. When running the method on standard reference material® 972 "Vitamin D in human serum" from the National Institute of Standards and Technology (NIST) (Gaithersburg, USA) the results for 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) concentrations were within the boundaries provided by NIST, reflected by Z-scores between 0.1 and 0.9. PMID:21342692

  19. Laser synthesis and spectroscopy of acetonitrile/silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Akin, S. T.; Liu, X.; Duncan, M. A.

    2015-11-01

    Silver nanoparticles with acetonitrile ligands are produced in a laser ablation flow reactor. Excimer laser ablation produces gas phase metal clusters which are thermalized with helium or argon collisions in the flowtube, and reactions with acetonitrile vapor coordinate this ligand to the particle surface. The gaseous mixture is captured in a cryogenic trap; warming produces a solution of excess ligand and coated particles. TEM images reveal particle sizes of 10-30 nm diameter. UV-vis absorption and fluorescence spectra are compared to those of standard silver nanoparticles with surfactant coatings. Deep-UV ligand absorption is strongly enhanced by nanoparticle adsorption.

  20. Formation of iron complexs from trifluoroacetic acid based liquid chromatography mobile phases as interference ions in liquid chromatography/electrospray ionization mass spectrometric analysis

    SciTech Connect

    Shukla, Anil K.; Zhang, Rui; Orton, Daniel J.; Zhao, Rui; Clauss, Therese RW; Moore, Ronald J.; Smith, Richard D.

    2011-05-30

    Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are not due to any contamination from solvents and chemicals used for mobile and stationary phases or from the laboratory atmospheric environment. Instead these ions are clusters of trifluoroacetic acid formed in association with acetonitrile, water and iron from the stainless steel union used to connect the column with the electrospray tip and to apply high voltage; the molecular formulae are Fe+((OH)(H2O)2)9(CF3COOH)5 and Fe+((OH)(H2O)2)6 (CF3COOH)5.

  1. The Electrodeposition of Silver from Supercritical Carbon Dioxide/Acetonitrile

    PubMed Central

    Bartlett, Philip N; Perdjon-Abel, Magdalena; Cook, David; Reid, Gillian; Levason, William; Cheng, Fei; Zhang, Wenjian; George, Michael W; Ke, Jie; Beanland, Richard; Sloan, Jeremy

    2014-01-01

    Cyclic voltammetry of silver coordination complexes in acetonitrile and in a single-phase supercritical carbon dioxide/acetonitrile (scCO2/CH3CN) system is reported. Five silver precursors are investigated: (1,5-cyclooctadiene)(hexafluoroacetylacetonato) silver(I) [Ag(hfac)(COD)], (hexafluoroacetylacetonato)(triphenylphosphine) silver(I) [Ag(hfac)(PPh3)], (perfluorooctanoato)bis(triphenylphosphine) silver(I) [Ag(CF3(CF2)6CO2)(PPh3)2], tetrakis(triphenylphosphine) silver(I) tetrafluoroborate [Ag(PPh3)4][BF4] and tetrakis(acetonitrile) silver(I) tetrafluoroborate [Ag(CH3CN)4][BF4]. Of these, [Ag(CH3CN)4][BF4] is found to be the most suitable for electrodeposition of silver from scCO2/CH3CN.

  2. A novel method for the determination of three volatile organic compounds in exhaled breath by solid-phase microextraction-ion mobility spectrometry.

    PubMed

    Allafchian, Ali Reza; Majidian, Zahra; Ielbeigi, Vahideh; Tabrizchi, Mahmoud

    2016-01-01

    A method was carried out for the quantitative determination of the concentrations of volatile organic compounds (VOCs) using solid-phase microextraction and ion mobility spectrometry (SPME-IMS). This method was optimized and evaluated. The best results were obtained at sorption temperature 70 °C, desorption temperature 200 °C, and extraction time 15 min. Under the optimized conditions, the linear dynamic range was found to be 0.01-4.0 ppb (R(2) > 0.995), 2.3-400 ppm (R(2) > 0.994), and 2.5-76 ppb (R(2) > 0.998) for acetone, acetaldehyde, and acetonitrile, respectively. The detection limits for acetone, acetaldehyde, and acetonitrile were 0.001 ppb, 0.18 ppm, and 0.22 ppb, respectively. As a practical application, the method was applied for the determination of acetone, acetaldehyde, and acetonitrile in human breath matrix. Therefore, the proposed method was found to be effective and simple enough to be strongly recommended for real sample analysis. PMID:26558761

  3. Phase transitions in contagion processes mediated by recurrent mobility patterns

    NASA Astrophysics Data System (ADS)

    Balcan, Duygu; Vespignani, Alessandro

    2011-07-01

    Human mobility and activity patterns mediate contagion on many levels, including the spatial spread of infectious diseases, diffusion of rumours, and emergence of consensus. These patterns however are often dominated by specific locations and recurrent flows and poorly modelled by the random diffusive dynamics generally used to study them. Here we develop a theoretical framework to analyse contagion within a network of locations where individuals recall their geographic origins. We find a phase transition between a regime in which the contagion affects a large fraction of the system and one in which only a small fraction is affected. This transition cannot be uncovered by continuous deterministic models because of the stochastic features of the contagion process and defines an invasion threshold that depends on mobility parameters, providing guidance for controlling contagion spread by constraining mobility processes. We recover the threshold behaviour by analysing diffusion processes mediated by real human commuting data.

  4. Enantioseparation of mandelic acid derivatives by high performance liquid chromatography with substituted β-cyclodextrin as chiral mobile phase additive and evaluation of inclusion complex formation

    PubMed Central

    Tong, Shengqiang; Zhang, Hu; Shen, Mangmang

    2014-01-01

    The enantioseparation of ten mandelic acid derivatives was performed by reverse phase high performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) or sulfobutyl ether-β-cyclodextrin (SBE-β-CD) as chiral mobile phase additives, in which inclusion complex formations between cyclodextrins and enantiomers were evaluated. The effects of various factors such as the composition of mobile phase, concentration of cyclodextrins and column temperature on retention and enantioselectivity were studied. The peak resolutions and retention time of the enantiomers were strongly affected by the pH, the organic modifier and the type of β-cyclodextrin in the mobile phase, while the concentration of buffer solution and temperature had a relatively low effect on resolutions. Enantioseparations were successfully achieved on a Shimpack CLC-ODS column (150×4.6 mm i.d., 5 μm). The mobile phase was a mixture of acetonitrile and 0.10 mol L-1 of phosphate buffer at pH 2.68 containing 20 mmol L-1 of HP-β-CD or SBE-β-CD. Semi-preparative enantioseparation of about 10 mg of α-cyclohexylmandelic acid and α-cyclopentylmandelic acid were established individually. Cyclodextrin-enantiomer complex stoichiometries as well as binding constants were investigated. Results showed that stoichiomertries for all the inclusion complex of cyclodextrin-enantiomers were 1:1. PMID:24893270

  5. Delayed cyanide poisoning following acetonitrile ingestion.

    PubMed Central

    Mueller, M.; Borland, C.

    1997-01-01

    Acetonitrile (methyl cyanide) is a common industrial organic solvent but is a rare cause of poisoning. We report the first recorded UK case. Acetonitrile is slowly converted to cyanide, resulting in delayed toxicity. We describe a case of deliberate self-poisoning by a 39-year-old woman resulting in cyanide poisoning 11 hours later which was successfully treated by repeated boluses of sodium nitrite and thiosulphate. The half-life of conversion of acetonitrile was 40 hours and harmful blood cyanide levels persisted for over 24 hours after ingestion. Departments treating or advising in cases of poisoning need to be aware of the delayed toxicity of acetonitrile. Monitoring in an intensive care unit of cases of acetonitrile poisoning should continue for 24-48 hours. PMID:9196706

  6. 77 FR 15369 - Mobility Fund Phase I Auction GIS Data of Potentially Eligible Census Blocks

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... COMMISSION Mobility Fund Phase I Auction GIS Data of Potentially Eligible Census Blocks AGENCY: Federal... information system (GIS) data for the census blocks potentially eligible for Mobility Fund Phase I support to...-0432 (TTY). SUPPLEMENTARY INFORMATION: This is a summary of the Mobility Fund Phase I Auction GIS...

  7. Comparison of an acetonitrile extraction/partitioning and "dispersive solid-phase extraction" method with classical multi-residue methods for the extraction of herbicide residues in barley samples.

    PubMed

    Díez, C; Traag, W A; Zommer, P; Marinero, P; Atienza, J

    2006-10-27

    An acetonitrile/partitioning extraction and "dispersive solid-phase extraction (SPE)" method that provides high quality results with a minimum number of steps and a low solvent and glassware consumption was published in 2003. This method, suitable for the analysis of multiple classes of pesticide residues in foods, has been given an acronymic name, QuEChERS, that reflects its major advantages (quick, easy, cheap, effective, rugged, safe). In this work, QuEChERS method, which was originally created for vegetable samples with a high amount of water, was modified to optimise the extraction of a wide range of herbicides in barley. Then, it was compared with known conventional multi-residue extraction procedures such as the Luke method, which was simplified and shortened by eliminating the Florisil clean-up (mini Luke) and the ethyl acetate extraction, which involves a subsequent clean-up by gel permeation chromatography (GPC) and which is the official extraction method used by some of European authorities. Finally, a simple acetone extraction was carried out to check the differences with the other three methods. Extracts were analysed by gas chromatography-time-of-flight mass spectrometry (GC-TOF/MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Mini Luke was significantly more effective for the extraction of non-polar and medium-polar compounds, but the best recoveries for polar compounds were achieved by QuEChERS and ethyl acetate methods. QuEChERS was the only method that provided an overall recovery value of 60-70% for non-, medium- and polar compounds, with some exceptions due to co-eluted matrix interferences. Clean-up by dispersive SPE was effective and did not differ so much with ethyl acetate extracts considering that QuEChERS clean-up step is much easier and less time-consuming. As a conclusion, it resulted to be the most universal extraction method by providing a well-defined phase separation without dilution and achieving acceptable

  8. Absolute negative mobility induced by potential phase modulation

    NASA Astrophysics Data System (ADS)

    Dandogbessi, Bruno S.; Kenfack, Anatole

    2015-12-01

    We investigate the transport properties of a particle subjected to a deterministic inertial rocking system, under a constant bias, for which the phase of the symmetric spatial potential used is time modulated. We show that this modulated phase, assisted by a periodic driving force, can lead to the occurrence of the so-called absolute negative mobility (ANM), the phenomenon in which the particle surprisingly moves against the bias. Furthermore, we discover that ANM predominantly originates from chaotic-periodic transitions. While a detailed mechanism of ANM remains unclear, we show that one can manipulate the control parameters, i.e., the amplitude and the frequency of the phase, in order to enforce the motion of the particle in a given direction. Finally, for this experimentally realizable system, we devise a two-parameter current plot which may be a good guide for controlling ANM.

  9. Considerations of digital phase modulation for narrowband satellite mobile communication

    NASA Technical Reports Server (NTRS)

    Grythe, Knut

    1990-01-01

    The Inmarsat-M system for mobile satellite communication is specified as a frequency division multiple access (FDMA) system, applying Offset Quadrature Phase Shift Keying (QPSK) for transmitting 8 kbit/sec in 10 kHz user channel bandwidth. We consider Digital Phase Modulation (DPM) as an alternative modulation format for INMARSAT-M. DPM is similar to Continuous Phase Modulation (CPM) except that DPM has a finite memory in the premodular filter with a continuous varying modulation index. It is shown that DPM with 64 states in the VA obtains a lower bit error rate (BER). Results for a 5 kHz system, with the same 8 kbit/sec transmitted bitstream, is also presented.

  10. Phased Arrays of Ground and Airborne Mobile Terminals for Satellite Communications

    NASA Technical Reports Server (NTRS)

    Huang, John

    1996-01-01

    Phased array antenna is beginning to play an important in the arena of mobile/satellite communications. Two examples of mobile terminal phased arrays will be shown. Their technical background, challenges, and cost drivers will be discussed. A possible solution to combat some of the deficiencies of the conventional phased array by exploiting the phased reflectarray technology will be briefly presented.

  11. Photochemistry of nitrate ion in acetonitrile

    NASA Astrophysics Data System (ADS)

    Meera, N.; Ramamurthy, P.

    1988-12-01

    The photochemistry of cobalt(II) nitrate in acetonitrile is investigated using steady-state and flash photolysis techniques. Formation of NO 3• radical has been observed as an intermediate by direct photolysis of nitrate ion and the reaction of the nitrate radical with the solvent is observed as a transient absorption around 600 nm in air-equilibrated acetonitrile. Nitrite ion forms as a product through a collision electron transfer complex intermediate.

  12. Dipolar ordering and relaxations in acetonitrile-β-hydroquinone clathrate

    NASA Astrophysics Data System (ADS)

    Rheinstädter, M. C.; Kityk, A. V.; Klöpperpieper, A.; Knorr, K.

    2002-08-01

    Single crystals of this clathrate have been studied by measurements of the frequency and temperature dependent dielectric permittivity as well as with polarization-electric field cycles and x-ray diffraction. The dipole moments of the acetonitrile guest molecules form Ising chains that are coupled by the electric dipole-dipole interaction and that are arranged in a triangular array. At 345 K a phase transition from a partially disordered antiferroelectric to a ferrielectric arrangement is observed.

  13. Detailed insights into the retention mechanism of caffeine metabolites on the amide stationary phase in hydrophilic interaction chromatography.

    PubMed

    Guo, Yong; Shah, Rajan

    2016-09-01

    The amide phase was investigated using a wide range of acetonitrile content in the mobile phase in both the HILIC and RPLC modes. Using caffeine metabolites as the model compounds, the retention, thermodynamic and kinetic data was obtained under various mobile phase conditions and supported the previous postulation that there might be a transition of the predominant retention mechanism in relation to the acetonitrile content in HILIC. On the amide phase, hydrophilic partitioning seemed to be the predominant retention mechanism below 85% acetonitrile; and a different retention mechanism (presumably surface adsorption) made more and more significant contributions to the overall retention when the acetonitrile content reached above 85%. This study also provided more direct evidences to explain the effect of salt concentration on the retention of non-charged solutes in HILIC. In addition, the retention, thermodynamic and kinetic data suggest that the amide phase behaved very differently from the conventional C18 phase in the RPLC mode. PMID:27522153

  14. Micellar versus hydro-organic mobile phases for retention-hydrophobicity relationship studies with ionizable diuretics and an anionic surfactant.

    PubMed

    Ruiz-Angel, M J; Carda-Broch, S; García-Alvarez-Coque, M C; Berthod, A

    2004-03-19

    Logarithm of retention factors (log k) of a group of 14 ionizable diuretics were correlated with the molecular (log P o/w) and apparent (log P(app)) octanol-water partition coefficients. The compounds were chromatographed using aqueous-organic (reversed-phase liquid chromatography, RPLC) and micellar-organic mobile phases (micellar liquid chromatography, MLC) with the anionic surfactant sodium dodecyl sulfate (SDS), in the pH range 3-7, and a conventional octadecylsilane column. Acetonitrile was used as the organic modifier in both modes. The quality of the correlations obtained for log P(app) at varying ionization degree confirms that this correction is required in the aqueous-organic mixtures. The correlation is less improved with SDS micellar media because the acid-base equilibriums are shifted towards higher pH values for acidic compounds. In micellar chromatography, an electrostatic interaction with charged solutes is added to hydrophobic forces; consequently, different correlations should be established for neutral and acidic compounds, and for basic compounds. Correlations between log k and the isocratic descriptors log k(w), log k(wm) (extrapolated retention to pure water in the aqueous-organic and micellar-organic systems, respectively), and psi0 (extrapolated mobile phase composition giving a k = 1 retention factor or twice the dead time), and between these descriptors and log P(app) were also satisfactory, although poorer than those between log k and log P(app) due to the extrapolation. The study shows that, in the particular case of the ionizable diuretics studied, classical RPLC gives better results than MLC with SDS in the retention hydrophobicity correlations. PMID:15043280

  15. Combined column-mobile phase mixture statistical design optimization of high-performance liquid chromatographic analysis of multicomponent systems.

    PubMed

    Breitkreitz, Márcia C; Jardim, Isabel C S F; Bruns, Roy E

    2009-02-27

    A statistical approach for the simultaneous optimization of the mobile and stationary phases used in reversed-phase liquid chromatography is presented. Mixture designs using aqueous mixtures of acetonitrile (ACN), methanol (MeOH) and tetrahydrofuran (THF) organic modifiers were performed simultaneously with column type optimization, according to a split-plot design, to achieve the best separation of compounds in two sample sets: one containing 10 neutral compounds with similar retention factors and another containing 11 pesticides. Combined models were obtained by multiplying a linear model for column type, C8 or C18, by quadratic or special cubic mixture models. Instead of using an objective response function, combined models were built for elementary chromatographic criteria (retention factors, resolution and relative retention) of each solute or pair of solutes and, after their validation, the global separation was accomplished by means of Derringer's desirability functions. For neutral compounds a 37:12:8:43 (v/v/v/v) percentage mixture of ACN:MeOH:THF:H2O with the C18 column and for pesticides a 15:15:70 (v/v/v) ACN:THF:H2O mixture with the C8 column provide excellent resolution of all peaks. PMID:19167715

  16. 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

  17. Adsorption interaction parameter of polyethers in ternary mobile phases: the critical adsorption line.

    PubMed

    Nguyen, V Cuong; Trathnigg, Bernd

    2010-04-01

    It is shown that in LC of polymers, the interaction parameter in ternary mobile phases can be described by a plane, which is determined by the dependencies in binary mobile phases. Instead of a critical adsorption point, critical conditions are observed along a straight line of composition between the two critical points in binary mobile phases. Consequently, a separation of block copolymers under critical conditions for one block by an adsorption mechanism for the other block can be achieved in ternary mobile phases of different compositions, which allows an adjustment of the retention of the adsorbing block. PMID:20222074

  18. Analysis of Phenacylester Derivatives of Fatty Acids from Human Skin Surface Sebum by Reversed-Phase HPLC: Chromatographic Mobility as a Function of Physico-Chemical Properties

    PubMed Central

    Bodoprost, Juliana; Rosemeyer, Helmut

    2007-01-01

    A set of 13 fatty acids was transformed into their phenacyl esters by reaction with phenacyl bromide in acetonitrile using 18-crown-6 as phase-transfer catalyst. Conditions for the RP-18 HPL chromatographic separation of most of the esters has been worked out. Using this standard the fatty acid spectra from skin surface sebum lipids of 17 test persons was taken after microwave-assisted hydrolysis, neutralization and extraction with n-hexane. Quantitative evaluation of the chromatograms exhibits that oleic acid predominates in the sebum of all test persons. In the second part of the work the chromatographic mobility (RE values) of fatty acid phenacyl esters is correlated with calculated physico-chemical parameters of the corresponding acids. The best linear correlation was found between the RE and the logP values. This is helpful for the structural elucidation of un-identified fatty acids in a chromatogram.

  19. Retention of functional polymers in liquid adsorption chromatography: effect of the end groups in PEGs and their methyl ethers in different mobile phases.

    PubMed

    Nguyen, V Cuong; Trathnigg, Bernd

    2010-04-01

    It is shown that the end group parameter, which describes the influence of the end group on retention, can be determined in RP chromatography from two chromatograms of a nonfunctional and a monofunctional sample, if a sufficient number of peaks with the same number of repeat units in each sample can be reasonably resolved and identified. The same procedure can also be applied for pairs of di- and monofunctional polymers. End group parameters have been determined in three different mobile phases: acetonitrile-water, acetone-water and methanol-water of different compositions. The temperature dependence of the interaction parameter of the repeat unit and the end group parameter has been found to be different, which allows a fine-tuning of retention. PMID:20187029

  20. Acetonitrile in the air over Europe

    SciTech Connect

    Hamm, S.; Helas, G.; Warneck, P.

    1989-06-01

    A gas chromatographic technique was developed to measure acetonitrile mixing ratios in air samples collected during three aircraft flights over Europe. Uniform mixing ratios were observed in the troposphere independent of altitude, with an average of 144+-26 pptv for the first two flights, and 194+-7 pptv for the third. /copyright/ American Geophysical Union 1989

  1. High resolution ion mobility measurements for gas phase proteins: correlation between solution phase and gas phase conformations

    NASA Astrophysics Data System (ADS)

    Hudgins, Robert R.; Woenckhaus, Jürgen; Jarrold, Martin F.

    1997-11-01

    Our high resolution ion mobility apparatus has been modified by attaching an electrospray source to perform measurements for biological molecules. While the greater resolving power permits the resolution of more conformations for BPTI and cytochrome c, the resolved features are generally much broader than expected for a single rigid conformation. A major advantage of the new experimental configuration is the much gentler introduction of ions into the drift tube, so that the observed gas phase conformations appear to more closely reflect those present in solution. For example, it is possible to distinguish between the native state of cytochrome c and the methanol-denatured form on the basis of the ion mobility measurements; the mass spectra alone are not sensitive enough to detect this change. Thus this approach may provide a quick and sensitive tool for probing the solution phase conformations of biological molecules.

  2. Ionic liquids as mobile phase additives for the high-performance liquid chromatographic analysis of fluoroquinolone antibiotics in water samples.

    PubMed

    Herrera-Herrera, Antonio V; Hernández-Borges, Javier; Rodríguez-Delgado, Miguel Angel

    2008-12-01

    In this work, four ionic liquids differing in the length of the alkyl chain on the imidazolium cation and one ionic liquid containing tetraethylammonium, all with the same counterion, (i.e. 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm-BF(4)), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF(4)), 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIm-BF(4)), 1-methyl-3-octylimidazolium tetrafluoroborate (MOIm-BF(4)), and tetraethylammonium tetrafluroborate (Et(4)N-BF(4))) were tested as mobile phase additives for HPLC separation of a group of seven basic fluoroquinolone (FQ) antibiotics for human and veterinary use (i.e. fleroxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin, and difloxacin) using a conventional reversed-phase Nova-Pak C(18) column. Fluorescence detection was used. Among the ionic liquids selected, use of BMIm-BF(4) enabled effective separation of these compounds with relatively low analysis time (14 min). The best separation was achieved by isocratic elution at 1 mL min(-1) with 5 mmol L(-1) BMIm-BF(4) and 10 mmol L(-1) ammonium acetate at pH 3.0 with 13% (v/v) acetonitrile. Limits of detection (LODs) for fluorescence detection were in the range 0.5-11 microg L(-1). The method was tested by analyzing several water samples after the optimization of a suitable solid-phase extraction (SPE) procedure using Oasis HLB cartridges. Mean recovery values were above 84% for all analytes with LODs in the range 1-29 ng L(-1). PMID:18854988

  3. Polarons and Mobile Impurities Near a Quantum Phase Transition

    NASA Astrophysics Data System (ADS)

    Shadkhoo, Shahriar

    This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which

  4. Diagnosis and misdiagnosis of poisoning with the cyanide precursor acetonitrile: nail polish remover or nail glue remover?

    PubMed

    Rainey, P M; Roberts, W L

    1993-03-01

    Accurate diagnosis of acetonitrile ingestion is critical to management. Often this involves differentiating nail polish remover (acetone) from nail glue remover (acetonitrile). Initial symptoms of acetonitrile ingestion are indistinguishable from those of acetone and common alcohols. However, acetonitrile is metabolized to cyanide, producing severe delayed toxicity. Acetonitrile produced increased serum osmolality and osmolal gap, but these findings are non-specific and normal values cannot rule out potentially fatal exposure. Acetone, but not acetonitrile, was detectable in urine or serum with Acetest tablets; both were unreactive with a ketone dipstick. Acetone and acetonitrile could be detected with routine gas chromatography methods for alcohols. Both substances had identical retention times on the widely used stationary phase, 5% Carbowax 20M on graphitized carbon, and with GasChrom 254. Three other systems afforded unique retention times, but acetonitrile was easily mistaken for ethanol in two. Physicians and laboratories must take care to avoid misdiagnosis of acetonitrile ingestion as exposure to acetone, ethanol or another alcohol. PMID:8476448

  5. Occurrence and behavior of system peaks in RP HPLC with solely aqueous mobile phases.

    PubMed

    Kalíková, Kveta; Hruska, Vlastimil; Svobodová, Jana; Chudoba, Richard; Gas, Bohuslav; Tesarová, Eva

    2009-09-01

    System peaks are important but often also disturbing phenomena occurring in separation systems. Behavior of system peaks was studied in reversed phase high performance liquid chromatography (RP HPLC) systems consisting of an RP Amide C16 column and aqueous solutions of organic acids with alkaline metal hydroxides as mobile phases. Binary mobile phases, composed of benzoic acid and lithium hydroxide (LiOH) or cesium hydroxide (CsOH), yielded two system peaks. The first peak was stationary and the second one moved with dilution of the mobile phase or with changes of the alkaline metal hydroxide concentration. The latter changes affected dissociation of the benzoic acid present in the mobile phase and thereby its retention. The presumption that the first system peak is not influenced by the type of alkaline metal cation and that it is related to the non-adsorbed component of the mobile phase was confirmed by a cyclic procedure. Three-component mobile phases composed of benzoic acid, tropic acid, and a hydroxide gave rise to three system peaks as expected. The first peak was again stationary and the two others shifted depending on the concentration variation of both acids. Resonance causing a zigzag peak, well described in capillary zone electrophoresis (CZE), was observed if 1-pentanol was injected into a chromatographic system with one-component mobile phase. PMID:19639550

  6. New method for the photo-chemiluminometric determination of benzoylurea insecticides based on acetonitrile chemiluminescence.

    PubMed

    Gil García, M D; Martínez Galera, M; Santiago Valverde, R

    2007-03-01

    The viability of tandem photochemical reaction-chemiluminescence detection has been studied for the determination of five benzoylurea insecticides, namely, diflubenzuron, triflumuron, hexaflumuron, lufenuron and flufenoxuron. The 'on-line' photochemical reaction of benzoylurea pesticides provides an enhanced chemiluminescence response of the pesticides during their oxidation by potassium hexacyanoferrate(III) and sodium hydroxide, whose signal increases with the percentage of acetonitrile in the reaction medium. The determination was performed using a photoreactor consisting of a PFA (perfluoroalkoxy) tube reactor coil (5 mx1.6-mm O.D. and 0.8-mm I.D.) and an 8-W xenon lamp. As the yield of the photoderivatization process and the chemiluminescent signals depend on the percentage of acetonitrile, the chromatographic column (a Gemini C18, Phenomenex 150 mmx4.6 mm, 5-microm particle size) was chosen with the aim of using high percentages of this organic solvent in the mobile phase. Previous studies showed that the rate of the chemiluminescent reaction was very fast. Therefore, a modification was carried out in the detector in order to mix the analytes and reactants as near as possible to the measure cell. The optimised method was validated with respect to linearity, precision, limits of detection and quantification accuracy. Under the optimised conditions, linear working range extends three orders of magnitude with the relative standard deviation of intra-day precision below 10% and detection limits between 0.012 and 0.18 microg mL-1, according to the compound. The proposed method has been successfully applied to the determination of benzoylureas in cucumber with good results. PMID:17205265

  7. Polarons and Mobile Impurities Near a Quantum Phase Transition

    NASA Astrophysics Data System (ADS)

    Shadkhoo, Shahriar

    This dissertation aims at improving the current understanding of the physics of mobile impurities in highly correlated liquid-like phases of matter. Impurity problems pose challenging and intricate questions in different realms of many-body physics. For instance, the problem of ''solvation'' of charged solutes in polar solvents, has been the subject of longstanding debates among chemical physicists. The significant role of quantum fluctuations of the solvent, as well as the break down of linear response theory, render the ordinary treatments intractable. Inspired by this complicated problem, we first attempt to understand the role of non-specific quantum fluctuations in the solvation process. To this end, we calculate the dynamic structure factor of a model polar liquid, using the classical Molecular Dynamics (MD) simulations. We verify the failure of linear response approximation in the vicinity of a hydrated electron, by comparing the outcomes of MD simulations with the predictions of linear response theory. This nonlinear behavior is associated with the pronounced peaks of the structure factor, which reflect the strong fluctuations of the local modes. A cavity picture is constructed based on heuristic arguments, which suggests that the electron, along with the surrounding polarization cloud, behave like a frozen sphere, for which the linear response theory is broken inside and valid outside. The inverse radius of the spherical region serves as a UV momentum cutoff for the linear response approximation to be applicable. The problem of mobile impurities in polar liquids can be also addressed in the framework of the ''polaron'' problem. Polaron is a quasiparticle that typically acquires an extended state at weak couplings, and crossovers to a self-trapped state at strong couplings. Using the analytical fits to the numerically obtained charge-charge structure factor, a phenomenological approach is proposed within the Leggett's influence functional formalism, which

  8. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... portable or mobile three-phase alternating current equipment; circuit breakers. 77.900 Section 77.900... mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage circuits supplying power to portable or mobile three-phase alternating current equipment shall be protected...

  9. 77 FR 73586 - Further Inquiry Into Issues Related to Mobility Fund Phase II

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-11

    ...The Wireless Telecommunications Bureau and Wireline Competition Bureau (collectively, the Bureaus) seek further comment on specific issues relating to the implementation of Phase II of the Mobility Fund. The Bureaus also seek to develop a more comprehensive record on certain issues relating to the award of ongoing support for advanced mobile...

  10. 77 FR 14012 - Eligible Telecommunications Carrier Designation for Participation in Mobility Fund Phase I

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-08

    ...In this document, the Commission's Wireless Telecommunications and Wireline Competition Bureaus describe the process and requirements for applicants seeking Eligible Telecommunications Carrier (ETC) Designation from the Commission for participation in Mobility Fund Phase I Auction...

  11. Liquid chromatography at critical conditions in ternary mobile phases: gradient elution along the critical line.

    PubMed

    Trathnigg, Bernd; Malik, Muhammad Imran; Pircher, Nicole; Hayden, Stephan

    2010-07-01

    In ternary mobile phases consisting of acetone, methanol, and water, the retention of PEG on reversed-phase columns is independent on molar mass at certain compositions of the mobile phase. Along this critical adsorption line, the retention of polypropylene glycol varies quite strongly, which can be utilized in the separation of block copolymers. Gradient elution along the critical line allows a baseline separation of all oligomers in polypropylene glycol up to approximately 25 propylene oxide units. The same resolution can be achieved in the separation of ethylene oxide-propylene oxide block copolymers, regardless of the length of the ethylene oxide block. PMID:20535754

  12. Acetone as a greener alternative to acetonitrile in liquid chromatographic fingerprinting.

    PubMed

    Funari, Cristiano Soleo; Carneiro, Renato Lajarim; Khandagale, Manish M; Cavalheiro, Alberto José; Hilder, Emily F

    2015-05-01

    A considerable amount of chemical waste from liquid chromatography analysis is generated worldwide. Acetonitrile is the most employed solvent in liquid chromatography analyses since it exhibits favorable physicochemical properties for separation and detection, but it is an unwelcome solvent from an environmental point of view. Acetone might be a much greener alternative to replace acetonitrile in reversed-phase liquid chromatography, since both share similar physicochemical properties, but its applicability with ultraviolet absorbance-based detectors is limited. In this work, a reference method using acetonitrile and high-performance liquid chromatography coupled to an ultraviolet photodiode array detector coupled to a corona charged aerosol detector system was developed to fingerprint a complex sample. The possibility of effectively substituting acetonitrile with acetone was investigated. Design of experiments was adopted to maximize the number of peaks acquired in both fingerprint developments. The methods with acetonitrile or acetone were successfully optimized and proved to be statistically similar when only the number of peaks or peak capacity was taken into consideration. However, the superiority of the latter was evidenced when parameters of separation and those related to greenness were heuristically combined. A green, comprehensive, time- and resource-saving approach is presented here, which is generic and applicable to other complex matrices. Furthermore, it is in line with environmental legislation and analytical trends. PMID:25708832

  13. Microfabricated refractive index gradient based detector for reversed-phase liquid chromatography with mobile phase gradient elution.

    PubMed

    McBrady, Adam D; Synovec, Robert E

    2006-02-10

    Typical refractive index (RI) detectors for liquid chromatography (LC) are not well suited to application with mobile phase gradient elution, due to the difficulty in correcting for the detected baseline shift during the gradient. We report a sensitive, highly reproducible, microfabricated refractive index gradient (micro-RIG) detector that performs well with mobile phase gradient elution LC. Since the micro-RIG signal remains on-scale throughout the mobile phase gradient, one can apply a baseline correction procedure. We demonstrate that by collecting two mobile phase gradient blanks and subtracting one of them from the other, a reproducible, flat baseline is achieved. Therefore, subtracting a blank from a separation provides a baseline corrected chromatogram with reasonably high signal-to-noise ratio for eluting analytes. The micro-RIG detector uses a collimated diode laser beam to optically probe a RIG formed perpendicular to the laminar flow direction within a microfabricated borosilicate glass chip. The chip-based design of the detector is suitable for either traditional bench-top or LC-on-a-chip technologies. We report reversed phase high performance liquid chromatography (RP-HPLC) separations of proteins and polymers, over mobile phase gradient conditions of 67% A:33% B to 3% A:97% B by volume, where A is 96% methanol:3.9% water:0.1% trifluoroacetic acid (TFA), and B is 3.9% methanol:96% water:0.1% TFA. The separations were performed on a Jupiter 5 mu C4 300 A 150 mm x 1.0 mm Phenomenex column at a flow rate of 20 microl/min. Viscosity changes during the mobile phase gradient separation are found to shift the on-chip merge position of the detected concentration gradient (i.e., RIG), in a reproducible fashion. However, this viscosity effect makes detection sensitivity vary throughout the mobile phase gradient, due to moving the optimized position of the probe beam in relation to the analyte concentration gradient being probed. None-the-less, consistent limits

  14. Pyrolysis and Combustion of Acetonitrile (CH{sub 3}CN)

    SciTech Connect

    Britt, P.F.

    2002-05-22

    Acetonitrile (CH{sub 3}CN) is formed from the thermal decomposition of a variety of cyclic, noncyclic, and polymeric nitrogen-containing compounds such as pyrrole and polyacrylonitrile. The pyrolysis and combustion of acetonitrile have been studied over the past 30 years to gain a more detailed understanding of the complex mechanisms involved in the release of nitrogen-containing compounds such as hydrogen cyanide (HCN) in fires and nitrogen oxides (NOx) in coal combustion. This report reviews the literature on the formation of HCN and NOx from the pyrolysis and combustion of acetonitrile and discusses the possible products found in an acetonitrile fire.

  15. The influence of mobile phase demixion on thin-layer chromatographic enantioseparation of ibuprofen and naproxen.

    PubMed

    Sajewicz, Mieczysław; Kaczmarski, Krzysztof; Gontarska, Monika; Kiszka, Sylwia; Kowalska, Teresa

    2007-09-01

    In our earlier article we presented the results of tracing the enantioseparation of the two test analytes (ibuprofen and naproxen) by means of video densitometry and scanning densitometry. In that way we demonstrated an excellent performance of this combined approach to the thin-layer chromatographic detection in the area of enantioseparation. In this paper we study an impact of the four different mobile phases on the enantioseparation of the scalemic mixtures of ibuprofen and naproxen on the silica gel layers impregnated with L-arginine as chiral selector. The main component of all the investigated mobile phases is 2-propanol. Mobile phase 1 consists of pure 2-propanol, while mobile phases 2-4 contain, respectively, ca. 0.66, 1.32, and 1.98 g/L of glacial acetic acid in 2-propanol. Acetic acid is used to protonate L-arginine, as the involved retention mechanism consists of the ion pair formation between L-arginine in the cationic form and the chiral 2-arylpropionic acids (2-APAs), ibuprofen and naproxen, in the anionic form. It is shown that in the absence of glacial acetic acid no enantioseparation can be obtained. Then with adding of 0.66 g/L glacial acetic acid partial enantioseparation of the naproxen and ibuprofen antimers is obtained, with a simultaneous effect of the mobile phase demixion. With the amount of acetic acid increasing, the effect of demixion becomes increasingly perceptible. In that case the displacement effect is observed (and mathematically modeled), which results in compressing of the antimer pairs by the second front of mobile phase. The obtained results allow a deeper insight into the mechanism of enantioseparation with the two test 2-APAs. A combined impact of the crystalline chirality of silica gel and the molecular chirality of L-arginine on the vertical and the horizontal enantioseparation of ibuprofen and naproxen is also discussed. PMID:18019559

  16. Dependence of negative-mode electrospray ionization response factors on mobile phase composition and molecular structure for newly-authenticated neutral acylsucrose metabolites.

    PubMed

    Ghosh, Banibrata; Jones, A Daniel

    2015-10-01

    Authentic standards of known concentrations serve as references for accurate absolute quantification of plant metabolites using liquid chromatography/mass spectrometry (LC/MS). However, often such standards are not commercially available or not amenable for custom syntheses. Despite the widespread use of electrospray ionization for metabolite analyses, the fundamentals needed for reliable prediction of molecular response factors have yet to be explored in detail for analytes that lack ionized functional groups. In order to lay a foundation for quantifying unknown neutral plant metabolites in absence of authentic standards, sub-milligram quantities of purified homologous acylsucrose metabolites were authenticated by subjecting each to basic hydrolysis and quantifying the sucrose product using stable-isotope dilution ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with multiple reaction monitoring (MRM). Once authenticated, molar response factors of [M + formate](-) ions for the acylsucrose metabolites were determined at different mobile phase compositions ranging from 40%-80% acetonitrile, and demonstrated relationships of response factors with mobile phase composition and metabolite structural features including nonpolar surface areas, the length of the longest acyl chain, and the number of hydroxyl groups. This approach was employed to calculate predicted response factors for three authenticated acylsucroses based on mean values for all isomers with a common number of total acyl carbon atoms. Absolute UHPLC-MS quantification was performed on these three metabolites in an extract from leaves of the wild tomato Solanum habrochaites LA1777, yielding deviations of 26%, 6.7%, and 7.3% from values established using compound-specific response factors. PMID:26331907

  17. 77 FR 9655 - Mobility Fund Phase I Auction Updated List of Potentially Eligible Census Blocks

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-17

    ..., 77 FR 7152, February 10, 2012, comments are due on or before February 24, 2012. Reply comments are... Public Notice, 77 FR 7152, February 10, 2012, all filings in response to the notice must refer to AU... program requirements in the Auction 901 (Mobility Fund Phase I) Comment Public Notice, 77 FR...

  18. 77 FR 38061 - Mobility Fund Phase I Auction Supplemental Short-Form Instructions and Other Information

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-26

    ... Notice, 77 FR 32092, May 31, 2012, the Bureaus provided general instructions for completing FCC Form 180... COMMISSION Mobility Fund Phase I Auction Supplemental Short-Form Instructions and Other Information AGENCY... provide other information regarding Auction 901. DATES: Short-Form applications are due prior to 6 p.m....

  19. Shift of the high-performance liquid chromatographic retention times of metabolites in relation to the original drug on an RP8 column with acidic mobile phase.

    PubMed

    Herre, S; Pragst, F

    1997-04-25

    The effect of the structural change in the metabolization of drugs on the HPLC retention time with an RP8 column with an acetonitrile-phosphate buffer (pH 2.3) as the mobile phase was investigated at model compound pairs of 29 functionalization reactions. A more or less typical region for T(M)=log(k'M/k'D) was found for each of these reactions (with k'M and k'D being the capacity factors of the metabolite and the drug, respectively), which can be explained by an increase or a decrease of the hydrophilic properties caused by the structural change. This effect is superimposed by an essential influence of the unchanged part of the molecule and in some cases by special intramolecular interactions like the hydrogen bond. Despite the more complicated structure of real drugs the results obtained at the model compound pairs were confirmed for most of the 55 metabolite/drug pairs. The practical use of the T(M) values as a support to distinguish between different metabolites in the HPLC-DAD analysis of intoxications is demonstrated with cases of poisoning with diphenhydramine, propafenone and methaqualone. PMID:9187390

  20. 78 FR 21355 - Tribal Mobility Fund Phase I Auction Scheduled for October 24, 2013; Comment Sought on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-10

    ..., 76 FR 73830, November 29, 2011 and 76 FR 81562, December 28, 2011. Auction 902 will award one-time... Mobility Fund Phase I, 77 FR 14012. Petitions for designation as an ETC should be filed in WC Docket No. 09... COMMISSION Tribal Mobility Fund Phase I Auction Scheduled for October 24, 2013; Comment Sought on...

  1. Thermodynamic studies of the solvent effects in chromatography on molecularly imprinted polymers. 3. Nature of the organic mobile phase

    SciTech Connect

    Kim, Hyunjung; Guiochon, Georges A

    2005-04-01

    Experimental isotherm data of the Fmoc-tryptophan (Fmoc-Trp) enantiomers were measured by frontal analysis on a Fmoc-L-Trp imprinted polymer, using different organic mobile phases, in a wide concentration range. The nonlinear regression of the data and the independent calculation of the affinity energy distributions of the two enantiomers allowed the selection of the isotherm model and the determination of the isotherm parameters. The organic solvents studied were acetonitrile (MeCN), methylene chloride, chloroform, and tetrahydrofuran (THF), all in the presence of the same concentration of acetic acid, used as an organic modifier. It was found that the highest overall affinity and enantiomeric selectivity were obtained in MeCN, which is also the solvent used in the polymerization. In the other solvents, the overall affinity decreases with increasing hydrogen-bonding ability of the solvents but not the enantiomer selectivity. In MeCN, three types of adsorption sites coexist for the two enantiomers on the MIP. The highest energy sites for Fmoc-L-Trp in MeCN are inactive in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF, and only two types of sites were identified in these solvents. Increasing the acetic acid concentration from 0.2 to 0.9 M causes a large decrease in the association constant of the highest energy sites in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF but not in MeCN. The overall affinity of Fmoc-L-trp in CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF is dominated by adsorption on the lowest energy sites, the most abundant ones. In contrast, in MeCN, the overall affinity of Fmoc-L-Trp is dominated by adsorption on the highest energy sites, the least abundant sites. In CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and THF, the number of each type of sites increases with decreasing hydrogen-bonding ability of the solvents while the association constant of the corresponding sites does not change significantly.

  2. Intermolecular forces in acetonitrile + ethanol binary liquid mixtures

    NASA Astrophysics Data System (ADS)

    Elangovan, A.; Shanmugam, R.; Arivazhagan, G.; Mahendraprabu, A.; Karthick, N. K.

    2015-10-01

    FTIR spectral measurements have been carried out on the binary mixtures of acetonitrile with ethanol at 1:0 (acetonitrile:ethanol), 1:1, 1:2, 1:3 and 0:1 at room temperature. DFT and isosurface calculations have been performed. The acetonitrile + ethanol binary mixtures consist of 1:1, 1:2, 1:3 and 1:4 complexes formed through both the red and blue shifting H-bonds. Inter as well as intra molecular forces are found to exist in 1:3 and 1:4 complexes.

  3. Trifluoroethanol-containing RP-HPLC mobile phases for the separation of transmembrane peptides human glycophorin-A, integrin alpha-1, and p24: analysis and prevention of potential side reactions due to formic acid.

    PubMed

    Hara, Toshiaki; Huang, Yue; Ito, Akihiro; Kawakami, Toru; Hojo, Hironobu; Murata, Michio

    2015-02-01

    Reversed-phase high-pressure liquid chromatography analysis and purification of three hydrophobic, aggregation-prone peptides, composed mainly of the transmembrane (TM) sequence, were performed using elution systems containing 2,2,2-trifluoroethanol (TFE). The addition of 10-16% TFE to a common mobile phase, such as a water/acetonitrile/propanol (PrOH) or a water/PrOH/formic acid system, markedly improved the chromatographic separation of these peptides. The superior performance of TFE-containing systems in separating peptides over water/PrOH/formic acid systems [Bollhagen R. et al., J. Chromatogr. A, 1995; 711: 181-186.] clearly demonstrated that adding TFE to the mobile phase is one of best methods for TM-peptide purification. Characterization of the potential side reactions using MALDI and ESI-LIT/Orbitrap mass spectrometry indicated that prolonged incubation of peptides in a mixture of TFE-formic acid possibly induces O-formylation of the Ser residue and N-formylation of the N-terminus of peptides. The conditions for selective removal of the formyl groups from TM peptides were also screened. We believe that these results will expand our ability to analyze and prepare hydrophobic, aggregation-prone TM peptides and proteins. PMID:25504594

  4. Investigation of retention on bare silica using reversed-phase mobile phases at elevated temperatures.

    PubMed

    Bidlingmeyer, Brian A; Henderson, John

    2004-12-10

    The use of unbonded silica as a stationary phase in reversed-phase HPLC is described as a useful alternative to bonded phase columns for polar, lipophilic amines. Using four lipophilic amines, the role of temperature is shown to favorably impact both efficiency and selectivity, which is not universally seen when using bonded phases. As temperature is raised, retention drops on the silica column. The temperature behavior appears to support the hypothesis that retention is dependant upon electrostatic and adsorptive forces. PMID:15628161

  5. The mobile phase in coals: Its nature and modes of release: Part 2, Efforts to better define the nature and magnitude of the mobile phase: Final report

    SciTech Connect

    Given, P.H.

    1987-04-01

    Several liquefaction conditions and many extracting solvents were used in attempts to set up conditions such that, as the conditions became more severe, progressively more hexane-solubles, analyzable by GC/MS, would be released. It was hoped to identify a threshold beyond which trapped mobile phase molecules would become evident. A set of 10 hexane-soluble fractions, all obtained under various conditions from the same coal (a sample of Herrin No. 6 seam, Illinois), were subjected to analysis by tandem mass spectrometry (MS/MS). Yields ranged from 0.6 to 16% of the organic matter in the coal. Prominent constituents of all of the fractions were homologous series of alkyl aromatic hydrocarbons, phenols and heterocycles, notably alkylacenaphthenes. Alkyl chains were either unbranched or lightly branched. There was a similarity in the spectra of all of the fractions irrespective of yield. The ease with which a certain homologous series can be released from a coal is highly variable. Thus the data are consistent with the concept of a mobile phase some components of which are trapped in cavities with entrances and exits of restricted size. Release of the various physically held species and the fragments from thermal breakdown of the structure will certainly present a very complex system for kinetic modeling. 30 refs., 10 tabs.

  6. Inhalation developmental toxicology studies: Acetonitrile in rats. Final report

    SciTech Connect

    Mast, T.J.; Weigel, R.J.; Westerberg, R.B.; Boyd, P.J.; Hayden, B.K.; Evanoff, J.J.; Rommereim, R.L.

    1994-02-01

    The potential for acetonitrile to cause developmental toxicity was assessed in Sprague-Dawley rats exposed to 0, 100, 400, or 1200 ppM acetonitrile, 6 hours/day, 7 days/week. Exposure of rats to these concentrations of acetonitrile resulted in mortality in the 1200 ppM group (2/33 pregnant females; 1/10 non-pregnant females). However, there were no treatment-related effects upon body weights or reproduction indices at any exposure level, nor was there a significant increase in the incidence of fetal malformations or variations. The only effect observed in the fetuses was a slight, but not statiscally significant, exposure-correlated increase in the incidence of supernumerary ribs. Determination of acetonitrile and cyanide concentrations in maternal rat blood showed that acetonitrile concentration in the blood increased with exposure concentration for all exposed maternal rats. Detectable amounts of cyanide in the blood were found only in the rats exposed to 1200 ppM acetonitrile ({approximately}2 {mu}g cyanide/g of blood).

  7. Fundamental studies of gas phase ionic reactions by ion mobility spectrometry

    NASA Technical Reports Server (NTRS)

    Giles, K.; Knighton, W. B.; Sahlstrom, K. E.; Grimsrud, E. P.

    1995-01-01

    Ion mobility spectrometry (IMS) provides a promising approach to the study of gas phase ionic reactions in buffer gases at unusually high pressures. This point is illustrated here by studies of the Sn2 nucleophilic displacement reaction, Cl(-) + CH3Br yields Br + CH3Br, using IMS at atmospheric pressure. The equilibrium clustering reaction, Cl(-)(CHCI3)(n - 1) + CHCI3 yields Cl(-)(CHCI3)(n), where n = 1 and 2, and the effect of clustering on the Sn2 reaction with CH3Br have also been characterized by this IMS-based kinetic method. Present problems and anticipated improvements in the application of ion mobility spectrometry to studies of other gas phase ionic processes are discussed.

  8. 78 FR 45071 - Annual Report for Mobility Fund Phase I Support and Record Retention

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-26

    .... 54.1008(d) and (e), 54.1009(a) through (c) and 54.1010, published at 76 FR 73830, November 29, 2011.... 10-208; FCC 11-161, 76 FR 73830 and FCC 12-52, 77 FR 30904, May 24, 2012. If you have any comments on.... 01-92, 96-45; WT Docket No. 10-208; FCC 11-161; FCC 12-52] Annual Report for Mobility Fund Phase...

  9. Mobile phone imaging module with extended depth of focus based on axial irradiance equalization phase coding

    NASA Astrophysics Data System (ADS)

    Sung, Hsin-Yueh; Chen, Po-Chang; Chang, Chuan-Chung; Chang, Chir-Weei; Yang, Sidney S.; Chang, Horng

    2011-01-01

    This paper presents a mobile phone imaging module with extended depth of focus (EDoF) by using axial irradiance equalization (AIE) phase coding. From radiation energy transfer along optical axis with constant irradiance, the focal depth enhancement solution is acquired. We introduce the axial irradiance equalization phase coding to design a two-element 2-megapixel mobile phone lens for trade off focus-like aberrations such as field curvature, astigmatism and longitudinal chromatic defocus. The design results produce modulation transfer functions (MTF) and phase transfer functions (PTF) with substantially similar characteristics at different field and defocus positions within Nyquist pass band. Besides, the measurement results are shown. Simultaneously, the design results and measurement results are compared. Next, for the EDoF mobile phone camera imaging system, we present a digital decoding design method and calculate a minimum mean square error (MMSE) filter. Then, the filter is applied to correct the substantially similar blur image. Last, the blur and de-blur images are demonstrated.

  10. Regularities of Anthocyanins Retention in RP HPLC for “Water–Acetonitrile–Phosphoric Acid” Mobile Phases

    PubMed Central

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

    2015-01-01

    The influence of exchange of HCOOH (System 2) by phosphoric acid (System 1) for acidification of the “acetonitrile–water” mobile phases for reversed-phase HPLC of anthocyanins was investigated in the framework of relative retention analysis. The differences and similarities of anthocyanins separation were revealed. It has been shown that some common features of the quantitative relationships may be used for preliminary anthocyanins structure differentiation, according to the number of OH-groups in anthocyanidin backbone as well as to a number of saccharide molecules in glycoside radicals in position 3 of the anthocyanin without MS detection. PMID:25692073

  11. Modulation of phase behaviors and charge carrier mobilities by linkage length in discotic liquid crystal dimers.

    PubMed

    Wang, Yi-Fei; Zhang, Chun-Xiu; Wu, Hao; Zhang, Ao; Wang, Jian-Chuang; Zhang, Shuai-Feng; Pu, Jia-Ling

    2015-01-28

    A clear structure-property relationship was revealed in a series of triphenylene-based dimers, which contained two triphenylene nuclei each bearing five β-OC4H9 substituents and are linked through a flexible O(CH2)nO polymethylene chain (n=6-12). Dimers with the linkage close to twice the length of the free side chains (n=8, 9) exhibited a single Colhp phase, while others with the linkage shorter (n=6, 7) or longer (n=10, 11, 12) showed multiphase behaviors with a transition from the Colhp phase to Colh phase; hole mobilities of Colhp phases reached 1.4×10(-2) cm2 V(-1) s(-1) in the dimer for which the linkage is exactly twice the length of the free side chains (n=8), and decreased regularly both with linkage length becoming shorter or longer. This modulation of phase behaviors and charge carrier mobilities was demonstrated to be generated by various steric perturbations introduced by linkages with different lengths, which result in different degrees of lateral fluctuations of discotic moieties in the columns. PMID:25467212

  12. Development and validation of a liquid chromatographic method for the stability study of a pharmaceutical formulation containing voriconazole using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector and polar organic mobile phases.

    PubMed

    Servais, Anne-Catherine; Moldovan, Radu; Farcas, Elena; Crommen, Jacques; Roland, Isabelle; Fillet, Marianne

    2014-10-10

    The ophthalmic solution of voriconazole, i.e. (2R,3S)-2-(2,4-difluorophenyl)-3-(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol, made from an injection formulation which also contains sulfobutylether-β-cyclodextrin sodium salt as an excipient (Vfend), is used for the treatment of fungal keratitis. A liquid chromatographic (LC) method using polar organic mobile phase and cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica as chiral stationary phase was successfully developed to evaluate the chiral stability of the ophthalmic solution. The percentage of methanol (MeOH) in the mobile phase containing acetonitrile (ACN) as the main solvent significantly influenced the retention and resolution of voriconazole and its enantiomer ((2S,3R)-2-(2,4-difluorophenyl)-3-(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-yl)butan-2-ol). The optimized mobile phase consisted of ACN/MeOH/diethylamine/trifluoroacetic acid (80/20/0.1/0.1; v/v/v/v). The method was found to be selective not only regarding the enantiomer of voriconazole but also regarding the specified impurities described in the monograph from the European Pharmacopoeia. The LC method was then fully validated applying the strategy based on total measurement error and accuracy profiles. Under the selected conditions, the determination of 0.1% of voriconazole enantiomer could be performed. Finally, a stability study of the ophthalmic solution was conducted using the validated LC method. PMID:25035235

  13. Degenerate mobilities in phase field models are insufficient to capture surface diffusion

    NASA Astrophysics Data System (ADS)

    Lee, Alpha A.; Münch, Andreas; Süli, Endre

    2015-08-01

    Phase field models frequently provide insight into phase transitions and are robust numerical tools to solve free boundary problems corresponding to the motion of interfaces. A body of prior literature suggests that interface motion via surface diffusion is the long-time, sharp interface limit of microscopic phase field models such as the Cahn-Hilliard equation with a degenerate mobility function. Contrary to this conventional wisdom, we show that the long-time behaviour of degenerate Cahn-Hilliard equation with a polynomial free energy undergoes coarsening, reflecting the presence of bulk diffusion, rather than pure surface diffusion. This reveals an important limitation of phase field models that are frequently used to model surface diffusion.

  14. Investigations into the separation behaviour of perfluorinated C8 and undecanoic acid modified silica hydride stationary phases.

    PubMed

    Kulsing, Chadin; Yang, Yuanzhong; Sepehrifar, Roshanak; Lim, Michael; Toppete, Joshua; Matyska, Maria T; Pesek, Joseph J; Boysen, Reinhard I; Hearn, Milton T W

    2016-04-15

    In this study, the surface charge properties of perfluorinated C8 (PerfluoroC8) and undecanoic acid (UDA) modified silica hydride stationary phases have been investigated. The zeta potential values of these stationary phases were measured in aqueous/acetonitrile mobile phases of different pH, buffer concentrations and acetonitrile contents. The retention behaviour of several basic, acidic and neutral compounds were then examined with these two stationary phases, with U-shaped retention dependencies evident with regard to the organic solvent content of the mobile phase. Plots of the logarithmic retention factor versus buffer concentration revealed slopes ≥ -0.41 for both stationary phases, indicating the involvement of mixed mode retention mechanisms with contributions from both ionic and non-ionic interactions. Using a linear solvation energy relationship approach, the origins of these interactions under different mobile phase conditions were differentiated and quantified. The PerfluoroC8 stationary phase exhibited stronger retention for basic compounds under high acetonitrile content mobile phase conditions, whilst stronger retention was observed for all compounds with the UDA stationary phase under high aqueous content mobile phase conditions. The more negative zeta potentials of the UDA stationary phase correlated with higher total charge density, surface charge density and charge density at the beta plane (the outer plane of the double layer) compared to the PerfluoroC8 stationary phase. With mobile phases of low buffer concentrations, more negative zeta potential values were unexpectedly observed for the PerfluoroC8 stationary phase with slight increases in the C descriptor value, reflecting also the greater accessibility of the analytes to the stationary phase surface. Comparison of the retention behaviours on these phases with other types of silica hydride stationary phases has revealed different patterns of selectivity. PMID:27016444

  15. STTR Phase 1 Final Technical Report for Project Entitled "Developing a Mobile Torrefaction Machine"

    SciTech Connect

    James, Joseph J.

    2014-03-11

    The goal of this project, sponsored by Agri-Tech Producers, LLC (ATP), the small business grantee, was to determine if the torrefaction technology, developed by North Carolina State University (NCSU), which ATP has licensed, could be feasibly deployed in a mobile unit. The study adds to the area investigated, by having ATP’s STTR Phase I team give thoughtful consideration to how to use NCSU’s technology in a mobile unit. The findings by ATP’s team were that NCSU’s technology would best perform in units 30’ by 80’ (See Spec Sheet for the Torre-Tech 5.0 Unit in the Appendix) and the technical effectiveness and economic feasibility investigation suggested that such units were not easily, efficiently or safely utilized in a forest or farm setting. (Note rendering of possible mobile system in the Appendix) Therefore, the findings by ATP’s team were that NCSU’s technology could not feasibly be deployed as a mobile unit.

  16. [Separation of bases, phenols and pharmaceuticals on ionic liquid-modified silica stationary phase with pure water as mobile phase].

    PubMed

    Wang, Xusheng; Qiu, Hongdeng; Liu, Xia; Jiang, Shengxiang

    2011-03-01

    N-methylimidazolium ionic liquid (IL) -modified silica was prepared with the reaction of 3-chloropropyl modified silica and N-methylimidazole using toluene as solvent. Based on the multiple interactions between N-methylimidazolium IL-modified silica and analytes such as hydrophobic interaction, electrostatic attraction, repulsion interaction, hydrogen-bonding, etc., the bases (cytosine, thymine, 2-aminopyrimidine and 6-chloroguanine), phenols (m-aminophenol, resorcinol and m-nitrophenol) and three pharmaceuticals (moroxydine hydrochloride, acyclovir and cephalexin hydrate) were separated successfully with only pure water as the mobile phase. These chromatographic separations are environmental friendly, economical and convenient, without any organic solvent or buffer additive. The retention mechanism of these samples on the stationary phase was also investigated. PMID:21657060

  17. Design and application of an expert system for mobile phase optimisation in reversed-phase liquid chromatography.

    PubMed

    Fell, A F; Bridge, T P; Williams, M H

    1988-01-01

    The selection of the optimum composition for the mobile phase in reversed-phase high-performance liquid chromatography (HPLC) is a complex task; conventional approaches require the expenditure of significant amounts of time by the analyst, particularly for complex mixtures of solutes of biological origin. Some of the existing strategies for the automated optimisation of mobile phase composition (e.g. Simplex), may fail if the elution order of the components changes; or they may require that standards be chromatographed in order to establish the retention behaviour of each component in a mixture (e.g. resolution mapping). These problems may be overcome if the retention behaviour of each individual solute can be established from the chromatogram of the mixture. In this regard, components can be tracked by exploiting the spectral information generated by a rapid scanning photodiode array detector. Unfortunately this information is often insufficiently detailed to allow an unambiguous model of retention behaviour to be constructed. The system developed by the Authors uses these spectral data as a basis for constructing one or more hypothetical retention models, each of which is refined or rejected as further information is obtained during the progress of the experiment. To improve the reliability of the retention models proposed by the system, the spectral data are utilised in a number of tests designed to assess the purity of each chromatographic peak. The information so generated may be used in conjunction with any previously acquired spectral data both to select an appropriate method for extracting spectra for each component from the matrix of (A, lambda, t) data and to establish reliability parameters for the resultant spectra. The development and philosophy of the expert system developed for eluent optimisation in reversed-phase HPLC is discussed. PMID:16867321

  18. The mobility of the amorphous phase in polyethylene as a determining factor for slow crack growth

    NASA Astrophysics Data System (ADS)

    Men, Y. F.; Rieger, J.; Enderle, H.-F.; Lilge, D.

    2004-12-01

    Polyethylene (PE) pipes generally exhibit a limited lifetime, which is considerably shorter than their chemical degradation period. Slow crack growth failure occurs when pipes are used in long-distance water or gas distribution though being exposed to a pressure lower than the corresponding yield stress. This slow crack growth failure is characterized by localized craze growth and craze fibril rupture. In the literature, the lifetime of PE pipes is often considered as being determined by the density of tie chains connecting adjacent crystalline lamellae. But this consideration cannot explain the excellent durability of the recent bimodal grade PE for pipe application. We show in this paper the importance of the craze fibril length as the determining factor for the pipe lifetime. The conclusions are drawn from stress analysis. It is found that longer craze fibrils sustain lower stress and are deformed to a lesser degree. The mobility of the amorphous phase is found to control the amount of material that can be “sucked” in by the craze fibrils and thus the length of the craze fibrils. The mobility of the amorphous phase can be monitored by dynamic mechanical analysis measurements. Excellent agreement between the mobility thus derived and lifetimes of PE materials as derived from FNCT (full notch creep test) is given, thus providing an effective means to estimate the lifetime of PE pipes by considering well-defined physical properties.

  19. The mobility of the amorphous phase in polyethylene as a determining factor for slow crack growth.

    PubMed

    Men, Y F; Rieger, J; Enderle, H-F; Lilge, D

    2004-12-01

    Polyethylene (PE) pipes generally exhibit a limited lifetime, which is considerably shorter than their chemical degradation period. Slow crack growth failure occurs when pipes are used in long-distance water or gas distribution though being exposed to a pressure lower than the corresponding yield stress. This slow crack growth failure is characterized by localized craze growth and craze fibril rupture. In the literature, the lifetime of PE pipes is often considered as being determined by the density of tie chains connecting adjacent crystalline lamellae. But this consideration cannot explain the excellent durability of the recent bimodal grade PE for pipe application. We show in this paper the importance of the craze fibril length as the determining factor for the pipe lifetime. The conclusions are drawn from stress analysis. It is found that longer craze fibrils sustain lower stress and are deformed to a lesser degree. The mobility of the amorphous phase is found to control the amount of material that can be "sucked" in by the craze fibrils and thus the length of the craze fibrils. The mobility of the amorphous phase can be monitored by dynamic mechanical analysis measurements. Excellent agreement between the mobility thus derived and lifetimes of PE materials as derived from FNCT (full notch creep test) is given, thus providing an effective means to estimate the lifetime of PE pipes by considering well-defined physical properties. PMID:15583973

  20. Gas-phase separation of drugs and metabolites using modifier-assisted differential ion mobility spectrometry hyphenated to liquid extraction surface analysis and mass spectrometry.

    PubMed

    Porta, Tiffany; Varesio, Emmanuel; Hopfgartner, Gérard

    2013-12-17

    The present work describes an alternative generic approach to LC-MS for the analysis of drugs of abuse as well as their metabolites in post-mortem tissue samples. The platform integrates liquid extraction surface analysis (LESA) for analytes tissue extraction followed by differential ion mobility spectrometry (DMS) mass spectrometry for analytes gas phase separation. Detection is performed on a triple quadrupole linear ion trap using the selected reaction monitoring mode for quantification as well as product ion scan mode for structural confirmatory analyses. The major advantages of the platform are that neither chromatographic separation nor extensive sample preparation are required. In DMS the combination of a high separation voltage (i.e., up to 4 kV) together with organic modifiers (e.g., alcohols, acetonitrile, acetone) added in the drift gas is required to achieve the separation of isomeric metabolites, such as the ones of cocaine and tramadol. DMS also separates morphine from its glucuronide metabolites, which allows for preventing the overestimation of morphine in case of fragmentation of the glucuronides in the atmospheric-to-vacuum interface of the mass spectrometer. Cocaine, opiates, opioids, amphetamines, benzodiazepines and several of their metabolites could be identified in post-mortem human kidney and muscle tissue based on simultaneous screening and confirmatory analysis in data-dependent acquisition mode using an analyte-dependent compensation voltage to selectively transmit ions through the DMS cell to the mass analyzer. Quantitative performance of the LESA-DMS-MS platform was evaluated for cocaine and two of its metabolites spotted onto a tissue section using deuterated internal standard. Analyte's responses were linear from 2 to 1000 pg on tissue corresponding to a limit of detection in the order of nanograms of analyte per gram of tissue. Accuracy and precision based on QC sample was found to be less than 10%. Replicate analyses of cocaine and

  1. Mobile terminal equipment design utilising split-loop phase-lock techniques

    NASA Technical Reports Server (NTRS)

    Kenington, P. B.; Mcgeehan, J. P.; Edwards, D. J.

    1990-01-01

    The design and resultant performance of the terminal equipment in a mobile satellite system is vitally important in respect to the overall cost/performance compromise of the whole system. Improvements in system performance which also result in a reduction of the equipment cost are rare. However, this paper details a significant advance in terminal design, utilizing a novel form of 'split-loop' phase locked receiver/downconverter system to enable an accurate, stable and wide coverage terminal to be realized at a reduced cost. The system has the capability of automatically locking onto any carrier within a complete transponder, and can cope with severe amplitude modulation and fading effects.

  2. Direct catalytic asymmetric addition of acetonitrile to N-thiophosphinoylimines.

    PubMed

    Kawato, Yuji; Kumagai, Naoya; Shibasaki, Masakatsu

    2013-12-11

    Direct catalytic addition of acetonitrile pronucleophiles to thiophosphinoylimines is described. Soft Lewis acid-hard Brønsted base cooperative catalysis is crucial to promote this elusive carbon-carbon bond-forming reaction in an enantioselective fashion. PMID:24158566

  3. Trying to detect gas-phase ions? Understanding Ion Mobility Spectrometry

    PubMed Central

    Cumeras, R.; Figueras, E.; Davis, C.E.; Baumbach, J.I.; Gràcia, I.

    2014-01-01

    Ion Mobility Spectrometry (IMS) is a widely used and ‘well-known’ technique of ion separation in gaseous phase based on the differences of ion mobilities under an electric field. This technique has received increased interest over the last several decades as evidenced by the pace and advances of new IMS devices available. In this review we explore the hyphenated techniques that are used with IMS, especially mass spectrometry as identification approach and multi-capillary column as pre-separation approach. Also, we will pay special attention to the key figures of merit of the ion mobility spectrum and how data is treated, and the influences of the experimental parameters in both a conventional drift time IMS (DTIMS) and a miniaturized IMS also known as high Field Asymmetric IMS (FAIMS) in the planar configuration. The current review article is preceded by a companion review article which details the current instrumentation and to the sections that configures both a conventional DTIMS and FAIMS devices. Those reviews will give the reader an insightful view of the main characteristics and aspects of the IMS technique. PMID:25465248

  4. Multiplicative effects model with internal standard in mobile phase for quantitative liquid chromatography-mass spectrometry.

    PubMed

    Song, Mi; Chen, Zeng-Ping; Chen, Yao; Jin, Jing-Wen

    2014-07-01

    Liquid chromatography-mass spectrometry assays suffer from signal instability caused by the gradual fouling of the ion source, vacuum instability, aging of the ion multiplier, etc. To address this issue, in this contribution, an internal standard was added into the mobile phase. The internal standard was therefore ionized and detected together with the analytes of interest by the mass spectrometer to ensure that variations in measurement conditions and/or instrument have similar effects on the signal contributions of both the analytes of interest and the internal standard. Subsequently, based on the unique strategy of adding internal standard in mobile phase, a multiplicative effects model was developed for quantitative LC-MS assays and tested on a proof of concept model system: the determination of amino acids in water by LC-MS. The experimental results demonstrated that the proposed method could efficiently mitigate the detrimental effects of continuous signal variation, and achieved quantitative results with average relative predictive error values in the range of 8.0-15.0%, which were much more accurate than the corresponding results of conventional internal standard method based on the peak height ratio and partial least squares method (their average relative predictive error values were as high as 66.3% and 64.8%, respectively). Therefore, it is expected that the proposed method can be developed and extended in quantitative LC-MS analysis of more complex systems. PMID:24840455

  5. Cryogenic Ion Mobility-Mass Spectrometry: Tracking Ion Structure from Solution to the Gas Phase.

    PubMed

    Servage, Kelly A; Silveira, Joshua A; Fort, Kyle L; Russell, David H

    2016-07-19

    Electrospray ionization (ESI) combined with ion mobility-mass spectrometry (IM-MS) is adding new dimensions, that is, structure and dynamics, to the field of biological mass spectrometry. There is increasing evidence that gas-phase ions produced by ESI can closely resemble their solution-phase structures, but correlating these structures can be complicated owing to the number of competing effects contributing to structural preferences, including both inter- and intramolecular interactions. Ions encounter unique hydration environments during the transition from solution to the gas phase that will likely affect their structure(s), but many of these structural changes will go undetected because ESI-IM-MS analysis is typically performed on solvent-free ions. Cryogenic ion mobility-mass spectrometry (cryo-IM-MS) takes advantage of the freeze-drying capabilities of ESI and a cryogenically cooled IM drift cell (80 K) to preserve extensively solvated ions of the type [M + xH](x+)(H2O)n, where n can vary from zero to several hundred. This affords an experimental approach for tracking the structural evolution of hydrated biomolecules en route to forming solvent-free gas-phase ions. The studies highlighted in this Account illustrate the varying extent to which dehydration can alter ion structure and the overall impact of cryo-IM-MS on structural studies of hydrated biomolecules. Studies of small ions, including protonated water clusters and alkyl diammonium cations, reveal structural transitions associated with the development of the H-bond network of water molecules surrounding the charge carrier(s). For peptide ions, results show that water networks are highly dependent on the charge-carrying species within the cluster. Specifically, hydrated peptide ions containing lysine display specific hydration behavior around the ammonium ion, that is, magic number clusters with enhanced stability, whereas peptides containing arginine do not display specific hydration around the

  6. A novel liquid/liquid extraction process composed of surfactant and acetonitrile for purification of polygalacturonase enzyme from Durio zibethinus.

    PubMed

    Amid, Mehrnoush; Manap, Yazid; Azmira, Farhana; Hussin, Muhaini; Sarker, Zaidul Islam

    2015-07-01

    Polygalacturonase is one of the important enzymes used in various industries such as food, detergent, pharmaceutical, textile, pulp and paper. A novel liquid/liquid extraction process composed of surfactant and acetonitrile was employed for the first time to purify polygalacturonase from Durio zibethinus. The influences of different parameters such as type and concentration of surfactants, concentrations of acetonitrile and composition of surfactant/acetonitrile on partitioning behavior and recovery of polygalacturonase was investigated. Moreover, the effect of pH of system and crude load on purification fold and yield of purified polygalacturonase were studied. The results of the experiment indicated the polygalacturonase was partitioned into surfactant top rich phase with impurities being partitioned into acetonitrile bottom rich phase in the novel method of liquid/liquid process composed of 23% (w/w) Triton X-100 and 19% (w/w) acetonitrile, at 55.6% of TLL (tie line length) crude load of 25% (w/w) at pH 6.0. Recovery and recycling of components also was measured in each successive step of liquid/liquid extraction process. The enzyme was successfully recovered by the method with a high purification factor of 14.3 and yield of 97.3% while phase components were also recovered and recycled above 95%. This study demonstrated that the novel method of liquid/liquid extraction process can be used as an efficient and economical extraction method rather than the traditional methods of extraction for the purification and recovery of the valuable enzyme. PMID:25973865

  7. Effects of twin boundary mobility on domain microstructure evolution in magnetic shape memory alloys: Phase field simulation

    SciTech Connect

    Jin, Yongmei M.

    2009-02-09

    Effects of twin boundary mobility on domain microstructure evolution during magnetic field-induced deformation in magnetic shape memory alloys are studied by phase field micromagnetic microelastic modeling. The simulations show that different twin boundary mobilities lead to drastically different domain microstructures and evolution pathways, yielding very different magnetization and strain responses, even with opposite signs. The study also reveals complex domain phenomena in magnetic shape memory alloys.

  8. Computational study of atomic mobility for the bcc phase of the U-Pu-Zr ternary system

    NASA Astrophysics Data System (ADS)

    Li, Weibang; Hu, Rui; Cui, Y.-W.; Zhong, Hong; Chang, Hui; Li, Jinshan; Zhou, Lian

    2010-12-01

    Experimental diffusion data in literature has been evaluated to assess the atomic mobility for the bcc phase in the U-Pu-Zr system by means of the DICTRA-type (Diffusion Controlled TRAnsformation) phenomenological treatment. The developed mobility database has been validated by comprehensive comparisons made between the experimental and calculated diffusion coefficients, as well as other interesting details resulting from interdiffusion, e.g. the concentration profile and the diffusion path of diffusion couples.

  9. Computational studies of coarsening rates for the Cahn-Hilliard equation with phase-dependent diffusion mobility

    NASA Astrophysics Data System (ADS)

    Dai, Shibin; Du, Qiang

    2016-04-01

    We study computationally coarsening rates of the Cahn-Hilliard equation with a smooth double-well potential, and with phase-dependent diffusion mobilities. The latter is a feature of many materials systems and makes accurate numerical simulations challenging. Our numerical simulations confirm earlier theoretical predictions on the coarsening dynamics based on asymptotic analysis. We demonstrate that the numerical solutions are consistent with the physical Gibbs-Thomson effect, even if the mobility is degenerate in one or both phases. For the two-sided degenerate mobility, we report computational results showing that the coarsening rate is on the order of l ∼ ct 1 / 4, independent of the volume fraction of each phase. For the one-sided degenerate mobility, that is non-degenerate in the positive phase but degenerate in the negative phase, we illustrate that the coarsening rate depends on the volume fraction of the positive phase. For large positive volume fractions, the coarsening rate is on the order of l ∼ ct 1 / 3 and for small positive volume fractions, the coarsening rate becomes l ∼ ct 1 / 4.

  10. Vertical Mobilization of a Residual Oil Phase in a Bead Pack Due to Flow of Discrete Gas Bubbles

    NASA Astrophysics Data System (ADS)

    Pakkala, Konark; Udell, Kent

    2007-11-01

    Mobilization of trapped oil ganglia is of interest in soil and groundwater clean-up and enhanced oil recovery applications. In this work, experiments with glass beads and various oil phase compositions were performed to determine the volumetric fraction of the non-aqueous phase liquid that may be mobilized with rising discrete gas bubbles. Experiments were performed using 6 mm and 2 mm beads. The oil phase liquids included dodecane, perchloroethene, and trichloroethene representing both spreading and non-spreading oil phases. It was found that bubbles were quite effective in mobilizing all three oils including those with densities greater than that of the suspending water. The effectiveness of the mobilization was greater in bead packs with larger beads than in packs comprised of small beads. Volumetric fractional flows of the oil phase were up to 10% of the bubble-droplet volumes, with volumetric fractions decreasing with decreasing oil phase saturations and bead size. The geometry of the oil ganglia/gas bubble combinatory body was also a function of the bead size with smaller beads producing larger, flatter gas bubbles, and the large beads producing bubbles and ganglia of similar size and geometries as the beads themselves.

  11. Determination of opiates and cocaine in urine by high pH mobile phase reversed phase UPLC-MS/MS.

    PubMed

    Berg, Thomas; Lundanes, Elsa; Christophersen, Asbjørg S; Strand, Dag Helge

    2009-02-01

    A fast and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the determination of opiates (morphine, codeine, 6-monoacetylmorphine (6-MAM), pholcodine, oxycodone, ethylmorphine), cocaine and benzoylecgonine in urine has been developed and validated. Sample preparation was performed by solid phase extraction (SPE) on a mixed mode cation exchange (MCX) cartridge. For optimized chromatographic performance with repeatable retention times, narrow and symmetrical peaks, and focusing of all analytes at the column inlet at gradient start, a basic mobile phase consisting of 5mM ammonium bicarbonate, pH 10.2, and methanol (MeOH) was chosen. Positive electrospray ionization (ESI(+)) MS/MS detection was performed with a minimum of two multiple reaction monitoring (MRM) transitions for each analyte. Deuterium labelled-internal standards were used for six of the analytes. Between-assay retention time repeatabilities (n=10 series, 225 injections in total) had relative standard deviation (RSD) values within 0.1-0.6%. Limit of detection (LOD) and limit of quantification (LOQ) values were in the range 0.003-0.05 microM (0.001-0.02 microg/mL) and 0.01-0.16 microM (0.003-0.06 microg/mL), respectively. The RSD values of the between-assay repeatabilities of concentrations were

  12. Photophysics of Diphenylbutadiynes in Water, Acetonitrile-Water, and Acetonitrile Solvent Systems: Application to Single Component White Light Emission.

    PubMed

    Pati, Avik Kumar; Jana, Rounak; Gharpure, Santosh J; Mishra, Ashok K

    2016-07-28

    Diacetylenes have been the subject of current research because of their interesting optoelectronic properties. Herein, we report that substituted diphenylbutadiynes exhibit locally excited (LE) and excimer emissions in water and multiple emissions from the LE, excimer, and intramolecular charge transfer (ICT) states in acetonitrile-water solvent systems. The LE, excimer, and ICT emissions are clearly distinguishable for a diphenylbutadiynyl derivative with push (-NMe2)-pull (-CN) substituents and those are closely overlapped for non-push-pull analogues. In neat acetonitrile, the excimer emission disappears and the LE and ICT emissions predominate. In the case of the push (-NMe2)-pull (-CN) diphenylbutadiyne, the intensity of the ICT emission increases with increasing the fluorophore concentration. This suggests that the ICT emission accompanies with intermolecular CT emission which is of exciplex type. As the LE and exciplex emissions of the push-pull diphenylbutadiyne together cover the visible region (400-700 nm) in acetonitrile, a control of the fluorophore concentration makes the relative intensities of the LE and exciplex emissions such that pure white light emission is achieved. The white light emission is not observed in those diphenylbutadiynyl analogues in which the peripheral substituents of the phenyl rings do not possess strong push-pull character. PMID:27379734

  13. Another glimpse over the salting-out assisted liquid-liquid extraction in acetonitrile/water mixtures.

    PubMed

    Valente, Inês Maria; Gonçalves, Luís Moreira; Rodrigues, José António

    2013-09-20

    The use of the salting-out effect in analytical chemistry is very diverse and can be applied to increase the volatility of the analytes in headspace extractions, to cause the precipitation of proteins in biological samples or to improve the recoveries in liquid-liquid extractions. In the latter, the salting-out process can be used to create a phase separation between water-miscible organic solvents and water. Salting-out assisted liquid-liquid extraction (SALLE) is an advantageous sample preparation technique aiming HPLC-UV analysis when developing analytical methodologies. In fact, some new extraction methodologies like QuEChERS include the SALLE concept. This manuscript discusses another point of view over SALLE with particular emphasis over acetonitrile-water mixtures for HPLC-UV analysis; the influence of the salting-out agents, their concentration and the water-acetonitrile volume ratios were the studied parameters. α-dicarbonyl compounds and beer were used as test analytes and test samples, respectively. The influence of the studied parameters was characterized by the obtained phase separation volume ratio and the fraction of α-dicarbonyls extracted to the acetonitrile phase. Results allowed the distribution of salts within three groups according to the phase separation and their extractability: (1) chlorides and acetates, (2) carbonates and sulfates and (3) magnesium sulfate; of all tested salts, sodium chloride had the highest influence on the α-dicarbonyls fraction extracted. PMID:23958692

  14. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry.

    PubMed

    Campbell, J Larry; Yang, Amy Meng-Ci; Melo, Luke R; Hopkins, W Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)-a probe of ion structure in mass spectrometry-actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS. Graphical Abstract ᅟ. PMID:27094827

  15. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-04-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  16. Ratchet Effects, Negative Mobility, and Phase Locking for Skyrmions on Periodic Substrates

    NASA Astrophysics Data System (ADS)

    Reichhardt, Charles; Ray, Dipanjan; Olson Reichhardt, Cynthia

    We examine the dynamics of skyrmions interacting with 1D and 2D periodic substrates in the presence of dc and ac drives. We find that the Magnus term strongly affects the skyrmion dynamics and that new kinds of phenomena can occur which are absent for overdamped ac and dc driven particles interacting with similar substrates. We show that it is possible to realize a Magnus induced ratchet for skyrmions interacting with an asymmetric potential, where the application of an ac drive can produce quantized dc motion of the skyrmions even when the ac force is perpendicular to the substrate asymmetry direction. For symmetric substrates it is also possible to achieve a negative mobility effect where the net skyrmion motion runs counter to an applied dc drive. Here, as a function of increasing dc drive, the velocity-force curves show a series of locking phases that have different features from the classic Shapiro steps found in overdamped systems. In the phase locking and ratcheting states, the skyrmions undergo intricate 2D orbits induced by the Magnus term.

  17. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  18. 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

  19. 77 FR 11115 - Mobility Fund Phase I Auction Limited Extension of Deadlines for Comments and Reply Comments on...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-24

    ... released the Auction 901 Comment Public Notice, 77 FR 7152, February 10, 2012, which seeks comment on... Commission in the USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562, December 28... COMMISSION Mobility Fund Phase I Auction Limited Extension of Deadlines for Comments and Reply Comments...

  20. 30 CFR 77.900 - Low- and medium-voltage circuits serving portable or mobile three-phase alternating current...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Low- and medium-voltage circuits serving... Medium-Voltage Alternating Current Circuits § 77.900 Low- and medium-voltage circuits serving portable or mobile three-phase alternating current equipment; circuit breakers. Low- and medium-voltage...

  1. 77 FR 32092 - Mobility Fund Phase I Auction Scheduled for September 27, 2012; Notice and Filing Requirements...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-31

    ... information system (GIS) data for the census blocks eligible for Mobility Fund Phase I support to be offered... through competitive bidding. The USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR... Public Notice, 77 FR 7152, February 10, 2012, which identified a preliminary list of census...

  2. Understanding gas phase modifier interactions in rapid analysis by Differential Mobility-Tandem Mass Spectrometry

    PubMed Central

    Kafle, Amol; Coy, Stephen L.; Wong, Bryan M.; Fornace, Albert J.; Glick, James J.; Vouros, Paul

    2014-01-01

    A systematic study involving the use and optimization of gas phase modifiers in quantitative differential mobility- mass spectrometry (DMS-MS) analysis is presented using mucleoside-adduct biomarkers of DNA damage as an important reference point for analysis in complex matrices. Commonly used polar protic and polar aprotic modifiers have been screened for use against two deoxyguanosine adducts of DNA: N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP) and N-(deoxyguanosin-8-y1)-2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (dG-C8-PhIP). Particular attention was paid to compensation voltage (CoV) shifts, peak shapes and product ion signal intensities while optimizing the DMS-MS conditions. The optimized parameters were then applied to rapid quantitation of the DNA adducts in calf thymus DNA. After a protein precipitation step, adduct levels corresponding to less than one modification in 106 normal DNA bases were detected using the DMS-MS platform. Based on DMS fundamentals and ab-initio thermochemical results we interpret the complexity of DMS modifier responses in terms of thermal activation and the development of solvent shells. At very high bulk gas temperature, modifier dipole moment may be the most important factor in cluster formation and cluster geometry in mobility differences, but at lower temperatures multi-neutral clusters are important and less predictable. This work provides a useful protocol for targeted DNA adduct quantitation and a basis for future work on DMS modifier effects. PMID:24452298

  3. Unexpected superoxide dismutase antioxidant activity of ferric chloride in acetonitrile.

    PubMed

    Foti, Mario C; Ingold, K U

    2003-11-14

    The azobis(isobutyronitrile)-initiated autoxidation of gamma-terpinene in acetonitrile at 50 degrees C yields only p-cymene and hydrogen peroxide (1:1) in a chain reaction carried by the hydroperoxyl radical, HOO. (Foti, M. C.; Ingold, K. U. J. Agric. Food Chem. 2003, 51, 2758-2765). This reaction is retarded by very low (microM) concentrations of FeCl(3) and CuCl(2). The kinetics of the FeCl(3)-inhibited autoxidation are consistent with chain-termination via the following: Fe(3+) + HOO. <==>[Fe(IV)-OOH](3+) and [Fe(IV)-OOH](3+) + HOO. --> Fe(3+) + H2O2 + O2. Thus, FeCl(3) in acetonitrile can be regarded as a very effective (and very simple) superoxide dismutase. The kinetics of the CuCl(2)-inhibited autoxidation indicate that chain transfer occurs and becomes more and more important as the reaction proceeds, i.e., the inhibition is replaced by autocatalysis. These kinetics are consistent withreduction of Cu2+ to Cu+ by HOO. and then the reoxidation of Cu+ to Cu2+ by both HOO.and the H2O2 product. The latter reaction yields HO. radicals which continue the chain. PMID:14604404

  4. Phases in development of an interactive mobile phone-based system to support self-management of hypertension.

    PubMed

    Hallberg, Inger; Taft, Charles; Ranerup, Agneta; Bengtsson, Ulrika; Hoffmann, Mikael; Höfer, Stefan; Kasperowski, Dick; Mäkitalo, Asa; Lundin, Mona; Ring, Lena; Rosenqvist, Ulf; Kjellgren, Karin

    2014-01-01

    Hypertension is a significant risk factor for heart disease and stroke worldwide. Effective treatment regimens exist; however, treatment adherence rates are poor (30%-50%). Improving self-management may be a way to increase adherence to treatment. The purpose of this paper is to describe the phases in the development and preliminary evaluation of an interactive mobile phone-based system aimed at supporting patients in self-managing their hypertension. A person-centered and participatory framework emphasizing patient involvement was used. An interdisciplinary group of researchers, patients with hypertension, and health care professionals who were specialized in hypertension care designed and developed a set of questions and motivational messages for use in an interactive mobile phone-based system. Guided by the US Food and Drug Administration framework for the development of patient-reported outcome measures, the development and evaluation process comprised three major development phases (1, defining; 2, adjusting; 3, confirming the conceptual framework and delivery system) and two evaluation and refinement phases (4, collecting, analyzing, interpreting data; 5, evaluating the self-management system in clinical practice). Evaluation of new mobile health systems in a structured manner is important to understand how various factors affect the development process from both a technical and human perspective. Forthcoming analyses will evaluate the effectiveness and utility of the mobile phone-based system in supporting the self-management of hypertension. PMID:24910510

  5. Phases in development of an interactive mobile phone-based system to support self-management of hypertension

    PubMed Central

    Hallberg, Inger; Taft, Charles; Ranerup, Agneta; Bengtsson, Ulrika; Hoffmann, Mikael; Höfer, Stefan; Kasperowski, Dick; Mäkitalo, Åsa; Lundin, Mona; Ring, Lena; Rosenqvist, Ulf; Kjellgren, Karin

    2014-01-01

    Hypertension is a significant risk factor for heart disease and stroke worldwide. Effective treatment regimens exist; however, treatment adherence rates are poor (30%–50%). Improving self-management may be a way to increase adherence to treatment. The purpose of this paper is to describe the phases in the development and preliminary evaluation of an interactive mobile phone-based system aimed at supporting patients in self-managing their hypertension. A person-centered and participatory framework emphasizing patient involvement was used. An interdisciplinary group of researchers, patients with hypertension, and health care professionals who were specialized in hypertension care designed and developed a set of questions and motivational messages for use in an interactive mobile phone-based system. Guided by the US Food and Drug Administration framework for the development of patient-reported outcome measures, the development and evaluation process comprised three major development phases (1, defining; 2, adjusting; 3, confirming the conceptual framework and delivery system) and two evaluation and refinement phases (4, collecting, analyzing, interpreting data; 5, evaluating the self-management system in clinical practice). Evaluation of new mobile health systems in a structured manner is important to understand how various factors affect the development process from both a technical and human perspective. Forthcoming analyses will evaluate the effectiveness and utility of the mobile phone-based system in supporting the self-management of hypertension. PMID:24910510

  6. Distribution of pesticides in n-hexane/water and n-hexane/acetonitrile systems and estimation of possibilities of their extraction isolation and preconcentration from various matrices.

    PubMed

    Zayats, M F; Leschev, S M; Petrashkevich, N V; Zayats, M A; Kadenczki, L; Szitás, R; Szemán Dobrik, H; Keresztény, N

    2013-04-24

    Distribution of 150 most widely used pesticides of different chemical classes (amides, anilinopirimidines, aromatics, benzenesulfonates, carbamates, dicarboximides, organophosphorus compounds, phenyl esters, phenylureas, pyrazoles, pyrethroids, pyrimidines, strobilurins, sulfamides, triazines, triazoles, etc.) in n-hexane/water and n-hexane/acetonitrile systems was investigated at 25°C. Distribution constants of pesticides (P) have been calculated as ratio of pesticide concentration in n-hexane to its concentration in water or acetonitrile phase. HPLC and GC methods were used for pesticides determination in phases. It was found that the overwhelming majority of pesticides are hydrophobic, i.e. in n-hexane/water system LgP≫0, and the difference in LgP values can reach 9.1 units. Replacement of water for acetonitrile leads to dramatic fall of LgP values reaching 9.5 units. The majority of LgP values in this case are negative and their differences is strongly leveled in comparison with a hexane/water system. Thus, maximal difference in pesticides LgP values for n-hexane/acetonitrile system is 3.2 units. It is shown that n-hexane can be used for selective and efficient extraction and preconcentration of pesticides from water matrices. On the other hand, acetonitrile is effective for the isolation and preconcentration of pesticides from hydrocarbon and vegetable oil matrices. The distribution constants described in the paper may be effectively used for the estimation of possibilities of extraction isolation, preconcentration and separation of pesticides. PMID:23567114

  7. Gas-Phase Dopant-Induced Conformational Changes Monitored with Transversal Modulation Ion Mobility Spectrometry.

    PubMed

    Meyer, Nicole Andrea; Root, Katharina; Zenobi, Renato; Vidal-de-Miguel, Guillermo

    2016-02-16

    The potential of a Transversal Modulation Ion Mobility Spectrometry (TMIMS) instrument for protein analysis applications has been evaluated. The Collision Cross Section (CCS) of cytochrome c measured with the TMIMS is in agreement with values reported in the literature. Additionally, it enables tandem IMS-IMS prefiltration in dry gas and in vapor doped gas. The chemical specificity of the different dopants enables interesting studies on the structure of proteins as CCS changed strongly depending on the specific dopant. Hexane produced an unexpectedly high CCS shift, which can be utilized to evaluate the exposure of hydrophobic parts of the protein. Alcohols produced higher shifts with a dual behavior: an increase in CCS due to vapor uptake at specific absorption sites, followed by a linear shift typical for unspecific and unstable vapor uptake. The molten globule +8 shows a very specific transition. Initially, its CCS follows the trend of the compact folded states, and then it rapidly increases to the levels of the unfolded states. This strong variation suggests that the +8 charge state undergoes a dopant-induced conformational change. Interestingly, more sterically demanding alcohols seem to unfold the protein more effectively also in the gas phase. This study shows the capabilities of the TMIMS device for protein analysis and how tandem IMS-IMS with dopants could provide better understanding of the conformational changes of proteins. PMID:26845079

  8. Evaluation of ternary mobile phases for the analysis of carbonyl compound derivatives using high-performance liquid chromatography.

    PubMed

    Ho, Duy Xuan; Kim, Ki-Hyun

    2011-01-01

    In this study, the feasibility of ternary mobile phases was examined in a high-performance liquid chromatography (HPLC)-based analysis of carbonyl compounds (CCs). To test the performance of different ternary phases, the liquid phase standards containing a 15 aldehyde/ketone-DNPH(o) mix were analyzed through a series of five-point calibration experiments. For this comparison, three types of ternary mobile phases were prepared initially by mixing water (W) with two of the following three organic solvents: isopropanol (I), methanol (M), and tetrahydrofuran (T). The resulting three types of ternary phases (named as WIM, WTM, and WIT) were tested and evaluated in relation to the water content or in terms of methanol-to-water ratio (M/W). The results derived by the three ternary phases revealed that the optimal resolution was attained near maximum water content, while those of WIT consistently suffered from poor resolution problems. The relative performances of WIM and WTM phases, if assessed by three key operating parameters (sensitivity, retention time, and resolution), were found to be reliable for most selected CCs with the decreasing M/W ratio. PMID:21218260

  9. Quinolones control in milk and eggs samples by liquid chromatography using a surfactant-mediated mobile phase.

    PubMed

    Rambla-Alegre, M; Collado-Sánchez, M A; Esteve-Romero, J; Carda-Broch, S

    2011-05-01

    Four quinolones (danofloxacin, difloxacin, flumequine and marbofloxacin) were determined in milk and egg samples by a simplified high-performance liquid chromatographic procedure using a micellar mobile phase. No extraction was needed to precipitate the proteins from the matrices since they were solubilised in micelles. The only pretreatment steps required were homogenisation, dilution and filtration before injecting the sample into the chromatographic system. An adequate resolution of the quinolones was achieved by a chemometrics approach where retention was modelled as a first step using the retention factors in only five mobile phases. Afterwards, an optimisation criterion was applied to consider the position and shape of the chromatographic peaks. Analytical separation involved a C18 reversed-phase column, a hybrid micellar mobile phase of 0.05 M sodium dodecyl sulphate, 10% (v/v) butanol and 0.5% (v/v) triethylamine buffered at pH 3 and fluorimetric detection. Quinolones were eluted in less than 15 min without the protein band or other endogenous compounds from the food matrices interfering. The calculated relevant validation parameters, e.g., decision limit (CC(α)), detection capability (CC(β)), repeatability, within-laboratory reproducibility, recoveries and robustness, were acceptable and complied with European Commission Decision 2002/657/EC. Finally, the proposed method was successfully employed in quantifying the four quinolones in spiked egg and milk samples. PMID:21085936

  10. Conversion of Dinitrogen into Acetonitrile under Ambient Conditions.

    PubMed

    Klopsch, Isabel; Kinauer, Markus; Finger, Markus; Würtele, Christian; Schneider, Sven

    2016-04-01

    About 20% of the ammonia production is used as the chemical feedstock for nitrogen-containing chemicals. However, while synthetic nitrogen fixation at ambient conditions has had some groundbreaking contributions in recent years, progress for the direct conversion of N2 into organic products remains limited and catalytic reactions are unknown. Herein, the rhenium-mediated synthesis of acetonitrile using dinitrogen and ethyl triflate is presented. A synthetic cycle in three reaction steps with high individual isolated yields and recovery of the rhenium pincer starting complex is shown. The cycle comprises alkylation of a nitride that arises from N2 splitting and subsequent imido ligand centered oxidation to nitrile via a 1-azavinylidene (ketimido) intermediate. Different synthetic strategies for intra- and intermolecular imido ligand oxidation and associated metal reduction were evaluated that rely on simple proton, electron, and hydrogen-atom transfer steps. PMID:26948973

  11. Ultrafast vibrational energy flow in water monomers in acetonitrile

    NASA Astrophysics Data System (ADS)

    Dahms, Fabian; Costard, Rene; Nibbering, Erik T. J.; Elsaesser, Thomas

    2016-05-01

    Vibrational relaxation of the OH stretching and bending modes of water monomers in acetonitrile is studied by two-color pump-probe experiments in a frequency range from 1400 to 3800 cm-1. Measurements with resonant infrared excitation reveal vibrational lifetimes of 6.4 ± 1.0 ps of the OH stretching modes and 4.0 ± 0.5 ps of the OH bending mode. After OH stretching excitation, the OH bending mode shows an instantaneous response, a hallmark of the anharmonic coupling of stretching and bending modes, and a delayed population buildup by relaxation of the stretching via the bending mode. The relaxation steps are discussed within the framework of current theoretical pictures of water's vibrational relaxation.

  12. Capacitance of edge plane of pyrolytic graphite in acetonitrile solutions

    SciTech Connect

    Minick, S.K.; Ishida, Takanobu.

    1991-05-01

    The capacitance of the edge plane of pyrolytic graphite electrodes, in acetonitrile solutions, is measured by recording the current response to an applied triangular voltage sweep; TVS, and then fitting the current response with an appropriate function, (via a set of adjustable parameters). The pretreatment of the electrodes, the supporting electrolyte concentration used, and the frequency of the input TVS, were all found to affect the measured capacitance. In these experiments, a background current was also seen and the shape of the current output for the TVS; the charging/discharging curve, is shown to correlate with the magnitude of this background current. In addition, the size of the background current was found to have some dependence on the type of electrode pretreatment procedure used. 60 refs., 49 figs., 3 tabs.

  13. Electrolyte Solvation and Ionic Association. VI. Acetonitrile-Lithium Salt Mixtures. Highly Associated Salts Revisited

    SciTech Connect

    Borodin, Oleg; Han, Sang D.; Daubert, James S.; Seo, D. M.; Yun, Sung-Hyun; Henderson, Wesley A.

    2015-01-14

    Molecular dynamics (MD) simulations of acetonitrile (AN) mixtures with LiBF4, LiCF3SO3 and LiCF3CO2 provide extensive details about the molecular- and mesoscale-level solution interactions and thus explanations as to why these electrolytes have very different thermal phase behavior and electrochemical/physicochemical properties. The simulation results are in full accord with a previous experimental study of these (AN)n-LiX electrolytes. This computational study reveals how the structure of the anions strongly influences the ionic association tendency of the ions, the manner in which the aggregate solvates assemble in solution and the length of time in which the anions remain coordinated to the Li+ cations in the solvates which result in dramatic variations in the transport properties of the electrolytes.

  14. Use of micellar mobile phases and microbore column switching for the assay of drugs in physiological fluids.

    PubMed

    Koenigbauer, M J; Curtis, M A

    1988-06-01

    The feasibility of directly assaying drugs in physiological fluids using on-line preconcentration and microbore high-performance liquid chromatography has been demonstrated. The untreated sample is injected onto a hydrophobic pre-column, using micellar sodium dodecyl sulfate (SDS) in the case of serum or phosphate buffer in the case of urine, as the load mobile phase. This traps the components of interest which are then backflushed onto a microbore analytical column using a stronger mobile phase. This procedure was then applied to diazepam in serum and phenobarbital in urine. Recovery was linear and quantitative over the range 30-3000 ng/ml for diazepam in serum and 2-200 micrograms/ml for phenobarbital in urine. The diazepam method was specific against caffeine and the three major metabolites of diazepam: oxazepam, temazepam, and nordiazepam. The effects of varying pre-column dimensions, pre-column loading time, and SDS concentration volume were evaluated. PMID:3410911

  15. Improved size exclusion chromatography of coal derived materials using N-methyl-2-pyrolidinone as mobile phase

    SciTech Connect

    Johnson, B.R.; Bartle, K.D.; Mitchell, S.C.

    1995-12-31

    A detailed knowledge of the molecular mass distribution (MMD) in coal and its derived products is essential for a fundamental understanding of coal structure, and of the processes occurring during pyrolyis, liquefaction and combustion. In size exclusion chromatography (SEC) tetrahydrofuran (THF) is commonly employed as the mobile phase. However, THF has limited solvating power and consequently a significant proportion of such materials goes undetected. By comparison, N-methyl-2-pyrolidinone is capable of solvating more of the coal sample and therefore gives the opportunity to determine an improved MMD. In this contribution the extended capabilities of NRP as the mobile phase are demonstrated by analysis of the solutions from solvent fractionation of a coal tar pitch, by SEC using UV/V is absorption, fluorescence and differential refractive index detection. Further application to other coal derived materials appears to indicate that separation is by a substantially size-dependent mechanism.

  16. Understanding Gas Phase Modifier Interactions in Rapid Analysis by Differential Mobility-Tandem Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Kafle, Amol; Coy, Stephen L.; Wong, Bryan M.; Fornace, Albert J.; Glick, James J.; Vouros, Paul

    2014-07-01

    A systematic study involving the use and optimization of gas-phase modifiers in quantitative differential mobility-mass spectrometry (DMS-MS) analysis is presented using nucleoside-adduct biomarkers of DNA damage as an important reference point for analysis in complex matrices. Commonly used polar protic and polar aprotic modifiers have been screened for use against two deoxyguanosine adducts of DNA: N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP) and N-(deoxyguanosin-8-y1)-2-amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (dG-C8-PhIP). Particular attention was paid to compensation voltage (CoV) shifts, peak shapes, and product ion signal intensities while optimizing the DMS-MS conditions. The optimized parameters were then applied to rapid quantitation of the DNA adducts in calf thymus DNA. After a protein precipitation step, adduct levels corresponding to less than one modification in 106 normal DNA bases were detected using the DMS-MS platform. Based on DMS fundamentals and ab initio thermochemical results, we interpret the complexity of DMS modifier responses in terms of thermal activation and the development of solvent shells. At very high bulk gas temperature, modifier dipole moment may be the most important factor in cluster formation and cluster geometry, but at lower temperatures, multi-neutral clusters are important and less predictable. This work provides a useful protocol for targeted DNA adduct quantitation and a basis for future work on DMS modifier effects.

  17. The effect of spontaneous gas expansion and mobilization on the aqueous-phase concentrations above a dense non-aqueous phase liquid pool

    NASA Astrophysics Data System (ADS)

    Mumford, Kevin G.; Smith, James E.; Dickson, Sarah E.

    2010-04-01

    The spontaneous expansion and mobilization of discontinuous gas above dense non-aqueous-phase liquid (DNAPL) pools can affect the aqueous-phase concentrations of the DNAPL constituents above the pool. The results of an intermediate-scale, two-dimensional flow cell experiment showed that the discontinuous gas flow produced by spontaneous expansion, driven by the partitioning of 1,1,1-TCA from the surface of a DNAPL pool, resulted in detectable aqueous-phase concentrations of 1,1,1-TCA well above the pool surface. In comparison to a conventional model for DNAPL pool dissolution in the absence of a discontinuous gas phase, these concentrations were greater than expected, and were present at greater than expected elevations. Additionally, this study showed that the discontinuous gas flow produced transient behavior in the aqueous-phase concentrations, where the elevated concentrations occurred as short-term, pulse-like events. These results suggest that the spontaneous expansion and mobilization of discontinuous gas in DNAPL source zones could lead to the misdiagnosis of source zone architecture using aqueous concentration data, and that the transient nature of the elevated concentrations could further complicate the difficult task of source zone characterization.

  18. Bioconversion of cyanide and acetonitrile by a municipal-sewage-derived anaerobic consortium

    SciTech Connect

    Nagle, N.J.; Rivard, C.J.; Mohagheghi, A.; Philippidis, G.

    1995-12-31

    In this study, an anaerobic consortium was examined for its ability to adapt to and degrade the representative organonitriles, cyanide and acetonitrile. Adaptation to cyanide and acetonitrile was achieved by adding increasing levels of cyanide and acetonitrile to the anaerobic consortium, followed by extensive incubation over a 90-day period. The anaerobic consortium adapted most rapidly to the lower concentrations of each substrate and resulted in reductions of 85% and 83% of the cyanide and acetonitrile, respectively, at the 50 mg/L addition level. Increasing the concentration of both cyanide and acetonitrile resulted in reduced bioconversion. Two continuously stirred tank reactors (CSTR) were set up to examine the potential for continuous bioconversion of organonitriles. The anaerobic consortium was adapted to continuous infusion of acetonitrile at an initial concentration of 10 mg/L{center_dot}day in phosphate buffer.

  19. 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.

  20. Acetonitrile and benzene in the breath of smokers and non-smokers investigated by proton transfer reaction mass spectrometry (PTR-MS)

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Hansel, A.; Holzinger, R.; Lindinger, W.

    1995-09-01

    Benzene and acetonitrile are both present in greater concentrations in the breath of smokers than in non-smokers. The concentrations of these neutrals can be readily detected in the gas phase by their proton transfer reactions with H3O+. The concentration of benzene in the breath of smokers rapidly decreases with the time since the last cigarette was smoked, declining to values similar to those of non-smokers within an hour. In contrast, the concentration of acetonitrile in the breath of smokers takes nearly a week to decrease to that of non-somokers, once smoking stops. Thus the analysis of acetonitrile in the breath is a most suitable indicator of whether a given subject is or is not a smoker.

  1. Improved size exclusion chromatography of coal derived materials using N-methyl-2-pyrrolidinone as mobile phase

    SciTech Connect

    Johnson, B.R.; Bartle, K.D.; Herod, A.A.; Kandiyoti, R.

    1995-12-31

    A detailed knowledge of the molecular mass distribution (MMD) in coal and its derived products is essential for a fundamental understanding of coal structure, and of the processes occurring during pyrolysis, liquefaction and combustion. Indeed with increased economic and environmental pressure to use natural resources more effectively such knowledge can be applied to gaining more from finite coal reserves. Of the methods available for determining MMDs size exclusion chromatography (SEC) is perhaps the most routinely employed. In SEC tetrahydrofuran (THF) is the most commonly employed mobile phase. However THF has limited solvating power for coal derived materials and consequently a significant proportion of such materials goes undetected. In addition the interpretation of chromatograms with reference to calibration of the column with polystyrene standards is flawed. By comparison, N-methyl-2-pyrrolidinone (NMP) is capable of solvating more of the coal sample and therefore gives the opportunity to determine an improved MMD. In this contribution the extended capabilities of NMP as the mobile phase are demonstrated primarily through the analysis of a coal tar pitch. Both NMP and THF are used as mobile phases for SEC using a number of detection techniques, allowing comparison and evaluation of different chromatographic systems to the analysis of coal derived materials.

  2. Comparison of the adsorption mechanisms of pyridine in hydrophilic interaction chromatography and in reversed-phase aqueous liquid chromatography.

    PubMed

    Gritti, Fabrice; Pereira, Alberto dos Santos; Sandra, Pat; Guiochon, Georges

    2009-11-27

    The adsorption isotherms of pyridine were measured by frontal analysis (FA) on a column packed with shell particles of neat porous silica (Halo), using water-acetonitrile mixtures as the mobile phase at 295K. The isotherm data were measured for pyridine concentrations covering a dynamic range of four millions. The degree of heterogeneity of the surface was characterized by the adsorption energy distribution (AED) function calculated from the raw adsorption data, using the expectation-maximization (EM) procedure. The results showed that two different retention mechanisms dominate in Per aqueous liquid chromatography (PALC) at low acetonitrile concentrations and in hydrophilic interaction chromatography (HILIC) at high acetonitrile concentrations. In the PALC mode, the adsorption mechanism of pyridine on the silica surface is controlled by hydrophobic interactions that take place on very few and ultra-active adsorption sites, which might be pores on the irregular and rugose surface of the porous silica particles. The surface is seriously heterogeneous, with up to five distinct adsorption sites and five different energy peaks on the AED of the packing material. In contrast, in the HILIC mode, the adsorption behavior is quasi-homogeneous and pyridine retention is governed by its adsorption onto free silanol groups. For intermediate mobile phase compositions, the siloxane and the silanol groups are both significantly saturated with acetonitrile and water, respectively, causing a minimum of the retention factor of pyridine on the Halo column. PMID:19853257

  3. Electron Transport in a High Mobility Free-Standing GaN Substrate Grown by Hydride Vapor Phase Epitaxy

    NASA Astrophysics Data System (ADS)

    Farina, L.; Kurdak, C.; Yun, F.; Morkoc, H.; Rode, D. L.; Tsen, K. T.; Park, S. S.; Lee, K. Y.

    2001-03-01

    We studied electron transport properties in a high quality free-standing GaN grown by hydride vapor phase epitaxy. The GaN, with a thickness of more than 200 μm, was lifted off the sapphire substrate and mechanically polished. At room temperature the carrier density is 1.3x10^16cm-3 and the Hall mobility is 1200 cm^2/V-s, which is the highest reported electron mobility for GaN with a wurtzite structure. Transport properties are studied using a van der Pauw geometry in a temperature range of 20 to 300 K and in magnetic fields up to 8 Tesla. Electron mobility is found to increase at lower temperatures with a peak mobility of 7400 cm^2/V-s at 48 K. The carrier density decreases exponentially at temperatures below 80 K with an activation energy of 28 meV. The electron transport measurements were used to examine the contributions of different scattering mechanisms. Numerical solution of the Boltzmann transport equation was carried out, including non-parabolic conduction bands and wavefunction admixture, along with lattice scattering and ionized-impurity scattering. LO and TO phonon energies were determined by Raman spectroscopy.

  4. Comparison of different types of stationary phases for the analysis of soy isoflavones by HPLC.

    PubMed

    Manchón, N; D'Arrigo, M; García-Lafuente, A; Guillamón, E; Villares, A; Martínez, J A; Ramos, A; Rostagno, M A

    2011-05-01

    Nowadays, there are new technologies in high-performance liquid chromatography columns available enabling faster and more efficient separations. In this work, we compared three different types of columns for the analysis of main soy isoflavones. The evaluated columns were a conventional reverse phase particle column, a fused-core particle column, and a monolithic column. The comparison was in terms of chromatographic parameters such as resolution, asymmetry, number of theoretical plates, variability of retention time, and peak width. The lower column pressure was provided by the monolithic column, although lower chromatographic performance was achieved. Conventional and fused-core particle columns presented similar pressure. Results also indicate that direct transfer between particle and monolithic columns is not possible requiring adjustment of conditions and a different method optimization strategy. The best chromatographic performance and separation speed were observed for the fused-core particle column. Also, the effect of sample solvent on the separation and peak shape was evaluated and indicated that monolithic column is the most affected especially when using higher concentrations of acetonitrile or ethanol. Sample solvent that showed the lowest effect on the chromatographic performance of the columns was methanol. Overall evaluation of methanol and acetonitrile as mobile phase for the separation of isoflavones indicated higher chromatographic performance of acetonitrile, although methanol may be an attractive alternative. Using acetonitrile as mobile phase resulted in faster, higher resolution, narrower, and more symmetric peaks than methanol with all columns. It also generated the lower column pressure and flatter pressure profile due to mobile phase changes, and therefore, it presents a higher potential to be explored for the development of faster separation methods. PMID:21274519

  5. Description of Gas-Phase Ion/Neutral Interactions in Differential Ion Mobility Spectrometry: CV Prediction Using Calibration Runs

    NASA Astrophysics Data System (ADS)

    Auerbach, David; Aspenleiter, Julia; Volmer, Dietrich A.

    2014-09-01

    Differential ion mobility spectrometry (DMS) coupled to mass spectrometry is increasingly used in both quantitative analyses of biological samples and as a means of removing background interferences for enhanced selectivity and improved quality of mass spectra. However, DMS separation efficiency using dry inert gases often lacks the required selectivity to achieve baseline separation. Polar gas-phase modifiers such as alcohols are therefore frequently employed to improve selectivity via clustering/declustering processes. The choice of an optimal modifier currently relies on trial and error experiments, making method development a tedious activity. It was the goal of this study to establish a means of CV prediction for compounds using a homologous series of alcohols as gas-phase modifiers. This prediction was based on linear regression of compensation voltages of two calibration runs for the alcohols with the lowest and the highest molecular weights and readily available descriptors such as proton affinity and gas phase acidity of the modifier molecules. All experiments were performed on a commercial quadrupole linear ion trap mass spectrometer equipped with a DMS device between electrospray ionization source and entrance quadrupole lens. We evaluated our approach using a homologous series of 4-alkylbenzoic acids and a selection of 23 small molecules of high chemical diversity. Predicted CV values typically deviated from the experimentally determined values by less than 0.5 V. Several test compounds changed their ion mobility behavior for the investigated gas phase modifiers (e.g., from type B to type A) and thus could thus not be evaluated.

  6. Bromidotris(triphenyl­phosphane)silver acetonitrile monosolvate monohydrate

    PubMed Central

    Owczarzak, Anita M.; Kyros, Loukas; Hadjikakou, Sotiris K.; Kubicki, Maciej

    2011-01-01

    In the title compound, [AgBr(C18H15P)3]·C2H3N·H2O, the coordination of the Ag atom is close to ideal tetra­hedral, with the three Ag—P bond lengths almost equal [2.5441 (10), 2.5523 (9) and 2.5647 (10) ° A] and the Ag—Br bond slightly longer [2.7242 (5) Å]. The coordination tetra­hedron is slightly flattened, the Ag atom is closer to the PPP plane; the P—Ag—P angles are wider than the Br—Ag—P angles. The voids in the crystal structure are filled with ordered acetonitrile solvent mol­ecules. The remaining electron density was inter­preted as a water mol­ecule, disordered over three alternative positions. Neither of the solvent mol­ecules is connected by any directional specific inter­actions with the complex. PMID:22219758

  7. Bromidotris(triphenyl-phosphane)silver acetonitrile monosolvate monohydrate.

    PubMed

    Owczarzak, Anita M; Kyros, Loukas; Hadjikakou, Sotiris K; Kubicki, Maciej

    2011-11-01

    In the title compound, [AgBr(C(18)H(15)P)(3)]·C(2)H(3)N·H(2)O, the coordination of the Ag atom is close to ideal tetra-hedral, with the three Ag-P bond lengths almost equal [2.5441 (10), 2.5523 (9) and 2.5647 (10) ° A] and the Ag-Br bond slightly longer [2.7242 (5) Å]. The coordination tetra-hedron is slightly flattened, the Ag atom is closer to the PPP plane; the P-Ag-P angles are wider than the Br-Ag-P angles. The voids in the crystal structure are filled with ordered acetonitrile solvent mol-ecules. The remaining electron density was inter-preted as a water mol-ecule, disordered over three alternative positions. Neither of the solvent mol-ecules is connected by any directional specific inter-actions with the complex. PMID:22219758

  8. Lithium solvation in dimethyl sulfoxide-acetonitrile mixtures.

    PubMed

    Semino, Rocío; Zaldívar, Gervasio; Calvo, Ernesto J; Laria, Daniel

    2014-12-01

    We present molecular dynamics simulation results pertaining to the solvation of Li(+) in dimethyl sulfoxide-acetonitrile binary mixtures. The results are potentially relevant in the design of Li-air batteries that rely on aprotic mixtures as solvent media. To analyze effects derived from differences in ionic size and charge sign, the solvation of Li(+) is compared to the ones observed for infinitely diluted K(+) and Cl(-) species, in similar solutions. At all compositions, the cations are preferentially solvated by dimethyl sulfoxide. Contrasting, the first solvation shell of Cl(-) shows a gradual modification in its composition, which varies linearly with the global concentrations of the two solvents in the mixtures. Moreover, the energetics of the solvation, described in terms of the corresponding solute-solvent coupling, presents a clear non-ideal concentration dependence. Similar nonlinear trends were found for the stabilization of different ionic species in solution, compared to the ones exhibited by their electrically neutral counterparts. These tendencies account for the characteristics of the free energy associated to the stabilization of Li(+)Cl(-), contact-ion-pairs in these solutions. Ionic transport is also analyzed. Dynamical results show concentration trends similar to those recently obtained from direct experimental measurements. PMID:25481154

  9. Lithium solvation in dimethyl sulfoxide-acetonitrile mixtures

    SciTech Connect

    Semino, Rocío; Zaldívar, Gervasio; Calvo, Ernesto J.; Laria, Daniel

    2014-12-07

    We present molecular dynamics simulation results pertaining to the solvation of Li{sup +} in dimethyl sulfoxide-acetonitrile binary mixtures. The results are potentially relevant in the design of Li-air batteries that rely on aprotic mixtures as solvent media. To analyze effects derived from differences in ionic size and charge sign, the solvation of Li{sup +} is compared to the ones observed for infinitely diluted K{sup +} and Cl{sup −} species, in similar solutions. At all compositions, the cations are preferentially solvated by dimethyl sulfoxide. Contrasting, the first solvation shell of Cl{sup −} shows a gradual modification in its composition, which varies linearly with the global concentrations of the two solvents in the mixtures. Moreover, the energetics of the solvation, described in terms of the corresponding solute-solvent coupling, presents a clear non-ideal concentration dependence. Similar nonlinear trends were found for the stabilization of different ionic species in solution, compared to the ones exhibited by their electrically neutral counterparts. These tendencies account for the characteristics of the free energy associated to the stabilization of Li{sup +}Cl{sup −}, contact-ion-pairs in these solutions. Ionic transport is also analyzed. Dynamical results show concentration trends similar to those recently obtained from direct experimental measurements.

  10. Lithium solvation in dimethyl sulfoxide-acetonitrile mixtures

    NASA Astrophysics Data System (ADS)

    Semino, Rocío; Zaldívar, Gervasio; Calvo, Ernesto J.; Laria, Daniel

    2014-12-01

    We present molecular dynamics simulation results pertaining to the solvation of Li+ in dimethyl sulfoxide-acetonitrile binary mixtures. The results are potentially relevant in the design of Li-air batteries that rely on aprotic mixtures as solvent media. To analyze effects derived from differences in ionic size and charge sign, the solvation of Li+ is compared to the ones observed for infinitely diluted K+ and Cl- species, in similar solutions. At all compositions, the cations are preferentially solvated by dimethyl sulfoxide. Contrasting, the first solvation shell of Cl- shows a gradual modification in its composition, which varies linearly with the global concentrations of the two solvents in the mixtures. Moreover, the energetics of the solvation, described in terms of the corresponding solute-solvent coupling, presents a clear non-ideal concentration dependence. Similar nonlinear trends were found for the stabilization of different ionic species in solution, compared to the ones exhibited by their electrically neutral counterparts. These tendencies account for the characteristics of the free energy associated to the stabilization of Li+Cl-, contact-ion-pairs in these solutions. Ionic transport is also analyzed. Dynamical results show concentration trends similar to those recently obtained from direct experimental measurements.

  11. Gas phase studies on terpenes by ion mobility spectrometry using different atmospheric pressure chemical ionization techniques

    NASA Astrophysics Data System (ADS)

    Borsdorf, H.; Stone, J. A.; Eiceman, G. A.

    2005-11-01

    The ionization pathways and drift behavior were determined for sets of constitutional isomeric and stereoisomeric non-polar hydrocarbons (unsaturated monocyclic terpenes, unsaturated and saturated bicyclic terpenes) using ion mobility spectrometry (IMS) with different techniques of atmospheric pressure chemical ionization (APCI) to assess how structural and stereochemical differences influence ion formation. Depending on the structural features, different ions were observed for constitutional isomers using ion mobility spectrometry with photoionization (PI) and corona discharge (CD) ionization. Photoionization provides ion mobility spectra containing one major peak for saturated compounds while at two peaks were observed for unsaturated compounds, which can be assigned to product ions related to monomer and dimer ions. However, differences in relative abundance of product ions were found depending on the position of the double bond. Although IMS using corona discharge ionization permits the most sensitive detection of non-polar hydrocarbons, the spectra are complex and differ from those obtained using photoionization. Additional cluster ions and fragment ions were detected. Only small differences in ion mobility spectra were observed for the diastereomers while the enantiomers provide identical spectra. The structure of the product ions formed was checked by investigations using the coupling of ion mobility spectrometry with mass spectrometry (IMS-MS).

  12. ENHANCED MOBILITY OF DENSE NONAQUEOUS-PHASE LIQUIDS (DNAPLs) USING DISSOLVED HUMIC ACIDS

    SciTech Connect

    EDWIN S. OLSON; JOHN R. GALLAGHER; MARC D. KURZ

    1998-10-01

    The specific objectives of this subtask are as follows: � Evaluate the suitability of using humic acids to enhance the solubility and mobility of DNAPL contaminants sorbed to soils. � Evaluate the toxicity and bioavailablity of the DNAPLs to biodegrading microorganisms. To meet the first objective, the Energy & Environmental Research Center (EERC) evaluated a set of humic acids (two) with different chemical compositions and polarities for the following: � Ability of the humates to mobilize/solubilize selected (three) DNAPLs � Mobilization/solubilization in batch soil�water experiments (one soil) � Removal rate via biotreatment with a well-established active microbial culture. The second objective was met by evaluating the inhibiting effects of a leonardite-derived humic acid on active microbial populations.

  13. Influence of sample and mobile phase composition on peptide retention behaviour and sensitivity in reversed-phase liquid chromatography/mass spectrometry.

    PubMed

    Houbart, V; Rozet, E; Matagne, A; Crommen, J; Servais, A-C; Fillet, M

    2013-11-01

    Because the chromatographic behaviour of peptides is totally different from that of small molecules, a good understanding of the mechanisms that occur from injection to detection in reversed-phase LC-MS is strongly recommended to successfully develop not only qualitative but also quantitative methods. In this study, design of experiments was used in order to investigate the influence of the experimental parameters, i.e. sample and mobile phase composition, on a peptide mixture covering a wide range of molecular weights, isoelectric points and hydropathies. First, a screening design was developed to identify the significant factors concerning mobile phase (ion-pairing reagent nature and concentration) and sample composition (organic modifier proportion and ion-pairing reagent nature) on retention and response intensity (sensitivity). Then, after having selected the experimental domain and the significant factors, a full factorial design was used to further investigate the role of the considered factors and their interactions. Interestingly, ion-pairing reagent nature present in the sample had a tremendous effect on retention and response intensity. Optimal conditions leading to good sensitivity and adequate peptide retention without band splitting were selected and could be used as starting point for rapid method development using classical solvents and ion-pairing reagents. PMID:24070623

  14. A convenient pathway to Sm(II)-mediated chemistry in acetonitrile.

    PubMed

    Maisano, Todd; Tempest, Kevin E; Sadasivam, Dhandapani V; Flowers, Robert A

    2011-03-21

    In this communication we show that the instability of samarium diiodide (SmI(2)) in acetonitrile is a consequence of ionization of the reductant in this solvent. Samarium triflate (Sm(OTf)(2)) is exceptionally stable in acetonitrile for periods over six months and can be used with appropriate additives to initiate a ketyl-olefin coupling reaction in high yield. PMID:21321772

  15. Reversed-phase high-performance liquid chromatography of the stereoisomers of some sweetener peptides with a helical nickel(II) chelate in the mobile phase.

    PubMed

    Bazylak, G

    1994-05-13

    The use of a chiral mobile phase additive in the form of the helically distorted, square-planar, chiral nickel(II) chelate dl-[4,4'-(1-methyl-2-propylethane-1,2-diyldiimino)bis(pent-3 -en-2- onato)]nickel(II) was investigated for the resolution of optical isomers of dipeptide-type sweeteners, viz., aspartame, alitame and antiaspartame, and some of their decomposition products, e.g., diketopiperazines. The chiral discrimination mechanism for the solutes was elucidated. The proposed chiral RP-HPLC system was applied to the stereoselective determination of aspartame impurities in samples of its commercial dietetic and pharmaceutical formulations. PMID:8032495

  16. Electrolyte Solvation and Ionic Association. V. Acetonitrile-Lithium Bis(fluorosulfonyl)imide (LiFSI) Mixtures

    SciTech Connect

    Han, Sang D.; Borodin, Oleg; Seo, D. M.; Zhou, Zhi B.; Henderson, Wesley A.

    2014-09-30

    Electrolytes with the salt lithium bis(fluorosulfonyl)imide (LiFSI) have been evaluated relative to comparable electrolytes with other lithium salts. Acetonitrile (AN) has been used as a model electrolyte solvent. The information obtained from the thermal phase behavior, solvation/ionic association interactions, quantum chemical (QC) calculations and molecular dynamics (MD) simulations (with an APPLE&P many-body polarizable force field for the LiFSI salt) of the (AN)n-LiFSI mixtures provides detailed insight into the coordination interactions of the FSI- anions and the wide variability noted in the electrolyte transport property (i.e., viscosity and ionic conductivity).

  17. Isomerization and fragmentation of acetonitrile upon interaction with N(4S) atoms: the chemistry of nitrogen in dense molecular clouds

    NASA Astrophysics Data System (ADS)

    Mencos, Alejandro; Krim, Lahouari

    2016-08-01

    We experimentally show that the reaction between ground state nitrogen atoms N(4S) and acetonitrile CH3CN can lead to two distinct chemical pathways that are both thermally activated at very low temperatures. First is CH3CN isomerization which produces CH3NC and H2CCNH. Second is CH3CN decomposition which produces HNC and CH3CNH+CN- fragments, with the possible release of H2. Our results reveal that the mobility of N(4S)-atoms is stimulated in the 3-11 K temperature range, and that its subsequent encounter with one acetonitrile molecule is sufficient for the aforementioned reactions to occur without the need for additional energy to be supplied to the CH3CN + N(4S) system. These findings shed more light on the nitrogen chemistry that can possibly take place in dense molecular clouds, which until now was thought to only involve high-energy processes and therefore be unlikely to occur in such cold and dark interstellar regions. The reaction pathways we propose in this study have very important astrochemical implications, as it was shown recently that the atomic nitrogen might be more abundant, in many interstellar icy grain mantles, than previously thought. Also, these reaction pathways can now be considered within dense molecular clouds, and possibly affect the branching ratios for N-bearing molecules computed in astrochemical modelling.

  18. The use of phase sequence image sets to reconstruct the total volume occupied by a mobile lung tumor

    SciTech Connect

    Gagne, Isabelle M.; Robinson, Don M.; Halperin, Ross; Roa, Wilson

    2005-07-15

    The use of phase sequence image (PSI) sets to reveal the total volume occupied by a mobile target is presented. Isocontrast composite clinical target volumes (CCTVs) may be constructed from PSI sets in order to reveal the total volume occupied by a mobile target during the course of its travel. The ability of the CCTV technique to properly account for target motion is demonstrated by comparison to contours of the true total volume occupied (TVO) for a number of experimental phantom geometries. Finally, using real patient data, the clinical utility of the CCTV technique to properly account for internal tumor motion while minimizing the volume of healthy lung tissue irradiated is assessed by comparison to the standard approach of applying safety margins. Results of the phantom study reveal that CCTV cross sections constructed at the 20% isocontrast level yield good agreement with the total cross sections (TXO) of mobile targets. These CCTVs conform well to the TVOs of the moving targets examined whereby the addition of small uniform margins ensures complete circumscription of the TVO with the inclusion of minimal amounts of surrounding external volumes. The CCTV technique is seen to be clearly superior to the common practice of the addition of safety margins to individual CTV contours in order to account for internal target motion. Margins required with the CCTV technique are eight to ten times smaller than those required with individual CTVs.

  19. Trellis coding with Continuous Phase Modulation (CPM) for satellite-based land-mobile communications

    NASA Technical Reports Server (NTRS)

    1989-01-01

    This volume of the final report summarizes the results of our studies on the satellite-based mobile communications project. It includes: a detailed analysis, design, and simulations of trellis coded, full/partial response CPM signals with/without interleaving over various Rician fading channels; analysis and simulation of computational cutoff rates for coherent, noncoherent, and differential detection of CPM signals; optimization of the complete transmission system; analysis and simulation of power spectrum of the CPM signals; design and development of a class of Doppler frequency shift estimators; design and development of a symbol timing recovery circuit; and breadboard implementation of the transmission system. Studies prove the suitability of the CPM system for mobile communications.

  20. Syntheses, phase behavior, supramolecular chirality, and field-effect carrier mobility of asymmetrically end-capped mesogenic oligothiophenes.

    PubMed

    Meng, Qingwei; Sun, Xiao-Hua; Lu, Zhengyu; Xia, Ping-Fang; Shi, Zehua; Chen, Dongzhong; Wong, Man Shing; Wakim, Salem; Lu, Jianping; Baribeau, Jean-Marc; Tao, Ye

    2009-01-01

    phase of the single end-capped oligothiophenes can be utilized to improve field-effect charge mobility. C(10)O-Ar-OT(4)-H showed a hole mobility of 0.07 cm(2) V(-1) s(-1) when deposited on octyltrichlorosilane-treated substrates at 140 degrees C and the on/off current ratios reached 5 x 10(5); on the other hand, its mobility was only 8 x 10(-3) cm(2) V(-1) s(-1) on the same substrate when deposited at room temperature. PMID:19219863

  1. Automated screening of reversed-phase stationary phases for small-molecule separations using liquid chromatography with mass spectrometry.

    PubMed

    Appulage, Dananjaya K; Wang, Evelyn H; Carroll, Frances; Schug, Kevin A

    2016-05-01

    There are various reversed-phase stationary phases that offer significant differences in selectivity and retention. To investigate different reversed-phase stationary phases (aqueous stable C18 , biphenyl, pentafluorophenyl propyl, and polar-embedded alkyl) in an automated fashion, commercial software and associated hardware for mobile phase and column selection were used in conjunction with liquid chromatography and a triple quadrupole mass spectrometer detector. A model analyte mixture was prepared using a combination of standards from varying classes of analytes (including drugs, drugs of abuse, amino acids, nicotine, and nicotine-like compounds). Chromatographic results revealed diverse variations in selectivity and peak shape. Differences in the elution order of analytes on the polar-embedded alkyl phase for several analytes showed distinct selectivity differences compared to the aqueous C18 phase. The electron-rich pentafluorophenyl propyl phase showed unique selectivity toward protonated amines. The biphenyl phase provided further changes in selectivity relative to C18 with a methanolic phase, but it behaved very similarly to a C18 when an acetonitrile-based mobile phase was evaluated. This study shows the value of rapid column screening as an alternative to excessive mobile phase variation to obtain suitable chromatographic settings for analyte separation. PMID:26959840

  2. Influence of crystallization-induced amorphous phase confinement on α- and β-relaxation molecular mobility in parylene F

    NASA Astrophysics Data System (ADS)

    Diaham, S.; Bechara, M.; Locatelli, M.-L.; Lebey, T.

    2011-09-01

    The molecular mobility of cooperative segmental (α-process) and local (β-process) motions in semicrystalline fluorinated parylene (PA-F) films has been studied using broadband dielectric spectroscopy in a wide temperature range. Particularly, the α-relaxation is, for the first time in a semicrystalline polymer, probed well above the glass transition temperature (˜10Tg) based on the PA-F strong difference between Tg and the crystallization temperature (Tc ˜ 16Tg). The influence of the amorphous phase confinement on the chain dynamics, induced by increasing crystallinity, is also explored. Thus, in the range of Tg, the α-relaxation is described by two crossover Vogel-Fulcher-Tamman characteristics, and the high temperature one presents an exacerbated low fragility. The space confinement of the amorphous regions, as characterized by x-ray diffraction, shows an important mobility restriction of both the α- and β-relaxations. The β-process, which has been related to CF2 group local motions, does not present a modification of its activation energy (Ea ˜ 30.8 kJ mol-1) with confinement, showing that it happens in the pure amorphous regions. The dielectric strength analysis of each process, through the Onsager-Kirkwood-Fröhlich (OKF) theory, has demonstrated that a rigid amorphous phase is strongly involved in the very high temperature range well above Tg. In the range around Tg, a peculiar behavior of the low temperature α-relaxation dielectric strength is reported, in agreement with the OKF temperature decreasing dependency that has been related to cooperative rearranging regions in the pure amorphous phase. The disappearance of the α-relaxation with the amorphous phase confinement leads to a transformation from 2D to 3D crystallite arrangements of the PA-F chains in correlation with the formation of spherulitic structures.

  3. Task 1.16 - Enhanced Mobility of Dense Nonaqueoius-Phase Liquids (DNAPLs) Using Dissolved Humic Acids

    SciTech Connect

    Marc D. Kurz

    1997-08-01

    Chlorinated solvent contamination is widespread across the U.S. Department of Energy (DOE) complex and other industrial facilities. Because of the physical properties of dense nonaqueous-phase liquids (DNAPLs), current treatment technologies are generally incapable of completely removing contamination from the source area. Incomplete removal means that the residual DNAPL will persist as a long-term source of groundwater contamination. When DNALPs occur in the subsurface, they resist remediation, owing to low water volubility, high viscosity and interracial tension, and microbial recalcitrance. Because of their high density and polarity, they are usually found sorbed to aquifer solids or in pools on impermeable materials. Surfactants have been used with some success to reduce interracial tension between the aqueous and organic phases and improve volubility of DNAPLs. However, surfactants are expensive and toxic and exhibit an oxygen demand. An alternative is the use of dissolved humic acids in improving DNAPL mobilization and solubilization. Humic acids, a. natural form of organic carbon, are abundant, inexpensive, and nontoxic; biodegrade slowly (low oxygen demand); and have excellent mobilization properties. The present work is to establish the feasibility of using humates for enhancing DNAPL remediation.

  4. Task 1.16 - Enhanced Mobility of Dense Nonaqueous-Phase Liquids (DNAPLs) Using Dissolved Humic Acids

    SciTech Connect

    Edwin S. Olson; Marc D. Kurz

    1998-02-01

    Chlorinated solvent contamination is widespread across the U.S. Department of Energy (DOE) complex and other industrial facilities. Because of the physical properties of dense nonaqueous-phase liquids (DNAPLs), current treatment technologies are generally incapable of completely removing contamination from the source area. Incomplete removal means that the residual DNAPL WN persist as a long-term source of groundwater contamination. When DNALPs occur in the subsurface, they resist remediation, owing to low water volubility, high viscosity and interracial tension, and microbial recalcitrance. Because of their high density and polarity, they are usually found sorbed to aquifer solids or in pools on impermeable materials. Surfactants have been used with some success to reduce interracial tension between the aqueous and organic phases and improve volubility of DNAPLs. However, surfactants are expensive and toxic and exhibit an oxygen demand. An alternative is the use of dissolved humic acids in improving DNAPL mobilization and solubilization. Humic acids, a natural form of organic carbon, are abundant, inexpensive, and nontoxic; biodegrade slowly (low oxygen demand); and have excellent mobilization properties. The present work is to establish the feasibility of using hurnates for enhancing DNAPL remediation.

  5. Laboratory investigations of irradiated acetonitrile-containing ices on an interstellar dust analog

    SciTech Connect

    Abdulgalil, Ali G. M.; Marchione, Demian; Rosu-Finsen, Alexander; Collings, Mark P.; McCoustra, Martin R. S.

    2012-07-15

    Reflection-absorption infrared spectroscopy is used to study the impact of low-energy electron irradiation of acetonitrile-containing ices, under conditions close to those in the dense star-forming regions in the interstellar medium. Both the incident electron energy and the surface coverage were varied. The experiments reveal that solid acetonitrile is desorbed from its ultrathin solid films with a cross section of the order of 10{sup -17} cm{sup 2}. Evidence is presented for a significantly larger desorption cross section for acetonitrile molecules at the water-ice interface, similar to that previously observed for the benzene-water system.

  6. Phase boundary mobility in naturally deformed, high-grade quartzofeldspathic rocks: evidence for diffusional creep

    NASA Astrophysics Data System (ADS)

    Gower, Robert J. W.; Simpson, Carol

    1992-03-01

    Grain shape fabrics and optical microstructures of some quartzofeldspathic rocks deformed under upper amphibolite facies conditions in the southwestern Grenville Province, Ontario, Canada, suggest that quartz and feldspar have accommodated intracrystalline plastic strains by both diffusional and dislocation creep. In these rocks, quartz and feldspar form polycrystalline domains separated by gently curved and locally cuspate phase boundaries whose morphology is similar in certain respects to the phase boundary morphology of rocks annealed experimentally under hydrostatic stress conditions. In the naturally deformed rocks, however, phase boundary cusps consistently point along the foliation and parallel to the mineral fibre lineation (i.e. in directions of inferred finite extension) which implies that phase boundary motion and cusp formation occurred during deformation. Optical microstructures in feldspar and crystallographic preferred orientations in quartz are consistent with the accommodation of some intracrystalline plastic strains by dislocation creep. However, the morphology of quartz-feldspar phase boundaries cannot be explained by either dislocation creep or static annealing alone. We propose that phase boundary motion resulted from a diffusion-assisted process involving dissolution at foliation-parallel quartz-feldspar phase boundaries, mass transfer over length scales of the order of feldspar domain size (≈200 μm or greater) and precipitation at quartz-feldspar phase boundary cusps. This study extends the range of natural deformation conditions under which diffusional creep has been identified in quartzofeldspathic rocks. It also has important implications for the natural rheological behavior of the mid- and lower-continental crust.

  7. 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. PMID:25595534

  8. 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.

  9. Ionic liquid as a mobile phase additive in high-performance liquid chromatography for the simultaneous determination of eleven fluorescent whitening agents in paper materials.

    PubMed

    Wang, Qing; Chen, Xianbo; Qiu, Bin; Zhou, Liang; Zhang, Hui; Xie, Juan; Luo, Yan; Wang, Bin

    2016-04-01

    In the present study, 11 4,4'-diaminostilbene-2,2'-disulfonic acid based fluorescent whitening agents with different numbers of sulfonic acid groups were separated by using an ionic liquid as a mobile phase additive in high-performance liquid chromatography with fluorescence detection. The effects of ionic liquid concentration, pH of mobile phase B, and composition of mobile phase A on the separation of fluorescent whitening agents were systematically investigated. The ionic liquid tetrabutylammonium tetrafluoroborate is superior to tetrabutylammomnium bromide for the separation of the fluorescent whitening agents. The optimal separation conditions were an ionic liquid concentration at 8 mM and the pH of mobile phase B at 8.5 with methanol as mobile phase A. The established method exhibited low limits of detection (0.04-0.07 ng/mL) and wide linearity ranges (0.30-20 ng/mL) with high linear correlation coefficients from 0.9994 to 0.9998. The optimized procedure was applied to analyze target analytes in paper samples with satisfactory results. Eleven target analytes were quantified, and the recoveries of spiked paper samples were in the range of 85-105% with the relative standard deviations from 2.1 to 5.1%. The obtained results indicated that the method was efficient for detection of 11 fluorescent whitening agents. PMID:26843408

  10. EVALUATION OF MUTAGENIC AND CARCINOGENIC PROPERTIES OF BROMINATED AND CHLORINATED ACETONITRILES: BY-PRODUCTS OF CHLORINATION

    EPA Science Inventory

    The present study was undertaken to determine if chlorinated and brominated acetonitriles formed during the chlorination of drinking water possess mutagenic and/or carcinogenic properties. Chloroacetonitrile (CAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), bromoc...

  11. Facilitated Diffusion of Acetonitrile Revealed by Quantitative Breath Analysis Using Extractive Electrospray Ionization Mass Spectrometry

    PubMed Central

    Li, Ming; Ding, Jianhua; Gu, Haiwei; Zhang, Yan; Pan, Susu; Xu, Ning; Chen, Huanwen; Li, Hongmei

    2013-01-01

    By using silver cations (Ag+) as the ionic reagent in reactive extractive electrospray ionization mass spectrometry (EESI-MS), the concentrations of acetonitrile in exhaled breath samples from the volunteers including active smokers, passive smokers, and non-smokers were quantitatively measured in vivo, without any sample pretreatment. A limit of detection (LOD) and relative standard deviation (RSD) were 0.16 ng/L and 3.5% (n = 8), respectively, for the acetonitrile signals in MS/MS experiments. Interestingly, the concentrations of acetonitrile in human breath continuously increased for 1–4 hours after the smoker finished smoking and then slowly decreased to the background level in 7 days. The experimental data of a large number of (> 165) samples indicated that the inhaled acetonitrile is excreted most likely by facilitated diffusion, instead of simple diffusion reported previously for other volatile compounds. PMID:23386969

  12. Peak shapes of acids and bases under overloaded conditions in reversed-phase liquid chromatography, with weakly buffered mobile phases of various pH: A thermodynamic interpretation

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2009-01-01

    We measured overloaded band profiles for a series of nine compounds (phenol, caffeine, 3-phenyl 1-propanol, 2-phenylbutyric acid, amphetamine, aniline, benzylamine, p-toluidine, and procainamidium chloride) on columns packed with four different C{sub 18}-bonded packing materials: XTerra-C{sub 18}, Gemini-C{sub 18}, Luna-C{sub 18}(2), and Halo-C{sub 18}, using buffered methanol-water mobile phases. The {sub W}{sup S}pH of the mobile phase was increased from 2.6 to 11.3. The buffer concentration (either phosphate, acetate, or carbonate buffers) was set constant at values below the maximum concentration of the sample in the band. The influence of the surface chemistry of the packing material on the retention and the shape of the peaks was investigated. Adsorbents having a hybrid inorganic/organic structure tend to give peaks exhibiting moderate or little tailing. The retention and the shape of the band profiles can easily be interpreted at {sub W}{sup S}pHs that are well above or well below the {sub W}{sup S}pK{sub a} of the compound studied. In contrast, the peak shapes in the intermediary pH range (i.e., close to the compound {sub W}{sup S}pK{sub a}) have rarely been studied. These shapes reveal the complexity of the competitive adsorption behavior of couples of acido-basic conjugated compounds at {sub W}{sup S}pHs that are close to their {sub W}{sup S}pK{sub a}. They also reveal the role of the buffer capacity on the resulting peak shape. With increasing {sub W}{sup S}pH, the overloaded profiles are first langmuirian (isotherm type I) at low {sub W}{sup S}pHs, they become S-shaped (isotherm type II), then anti-langmuirian (isotherm type III), S-shaped again at intermediate {sub W}{sup S}pHs, and finally return to a langmuirian shape at high {sub W}{sup S}pHs. A new general adsorption isotherm model that takes into account the dissociation equilibrium of conjugated acidic and basic species in the bulk mobile phase accounts for these transient band shapes. An

  13. Towards the Development of a Mobile Phonopneumogram: Automatic Breath-Phase Classification Using Smartphones.

    PubMed

    Reyes, Bersain A; Reljin, Natasa; Kong, Youngsun; Nam, Yunyoung; Ha, Sangho; Chon, Ki H

    2016-09-01

    Correct labeling of breath phases is useful in the automatic analysis of respiratory sounds, where airflow or volume signals are commonly used as temporal reference. However, such signals are not always available. The development of a smartphone-based respiratory sound analysis system has received increased attention. In this study, we propose an optical approach that takes advantage of a smartphone's camera and provides a chest movement signal useful for classification of the breath phases when simultaneously recording tracheal sounds. Spirometer and smartphone-based signals were acquired from N = 13 healthy volunteers breathing at different frequencies, airflow and volume levels. We found that the smartphone-acquired chest movement signal was highly correlated with reference volume (ρ = 0.960 ± 0.025, mean ± SD). A simple linear regression on the chest signal was used to label the breath phases according to the slope between consecutive onsets. 100% accuracy was found for the classification of the analyzed breath phases. We found that the proposed classification scheme can be used to correctly classify breath phases in more challenging breathing patterns, such as those that include non-breath events like swallowing, talking, and coughing, and alternating or irregular breathing. These results show the feasibility of developing a portable and inexpensive phonopneumogram for the analysis of respiratory sounds based on smartphones. PMID:26847825

  14. Changes in mobile phase ion distribution when combining pressurized flow and electric field.

    PubMed

    Eriksson, Björn O; Dahl, Magnus; Andersson, Magnus B O; Blomberg, Lars G

    2004-10-01

    The distribution of ions in a capillary with both pressurized flow and an electric field has been studied. We have earlier reported that the overall concentration of ions increase in a capillary with high electric field and a pressurized flow. Now we describe how the ions are distributed in the capillary both along the capillary length and in the radial direction as a result of the parabolic flow profile. We have combined current measurements with finite element techniques in order to get better understanding of the system. We have found that the concentration of the ions that because of the electric mobility moves towards the flow primarily increases at the beginning of the electric field and close to the capillary wall. In view of the results we have proposed an alterative explanation of earlier published results concerning voltage-induced variation in capacity factors. PMID:15472979

  15. Combined carbon and nitrogen removal from acetonitrile using algal-bacterial bioreactors.

    PubMed

    Muñoz, Raul; Jacinto, Marco; Guieysse, Benoit; Mattiasson, Bo

    2005-06-01

    When compared with Chlorella vulgaris, Scenedesmus obliquus and Selenastrum capricornutum, C. sorokiniana presented the highest tolerance to acetonitrile and the highest O(2) production capacity. It also supported the fastest acetonitrile biodegradation when mixed with a suitable acetonitrile-degrading bacterial consortium. Consequently, this microalga was tested in symbiosis with the bacterial culture for the continuous biodegradation of acetonitrile at 2 g l(-1) in a stirred tank photobioreactor and in a column photobioreactor under continuous illumination (250 microE m(-2) s(-1)). Acetonitrile removal rates of up to 2.3 g l(-1) day(-1) and 1.9 g l(-1) day(-1) were achieved in the column photobioreactor and the stirred-tank photobioreactor, respectively, when operated at the shortest retention times tested (0.4 days, 0.6 days, respectively). In addition, when the stirred-tank photobioreactor was operated with a retention time of 3.5 days, the microbial culture was capable of assimilating up to 71% and nitrifying up to 12% of the NH(4) (+) theoretically released through the biodegradation of acetonitrile, thus reducing the need for subsequent nitrogen removal. This study suggests that complete removal of N-organics can be combined with a significant removal of nitrogen by using algal-bacterial systems and that further residual biomass digestion could pay-back part of the operation costs of the treatment plant. PMID:15666149

  16. [Transfer possibilities of the mobile phases between different liquid chromatographic techniques for the analysis and isolation of compounds of biological matrices].

    PubMed

    Nyiredy, S

    1999-01-01

    After the survey and characterisation of the solid/liquid chromatographic methods, the author summarized the features of overpressure layer chromatography; the disturbing zone and the multi-front effect as well as the elimination of their influence. In light of these effects, the strategy of the mobile phase transfer possibilities is demonstrated between the various analytical and preparative liquid chromatographic methods, with the OPLC playing a central role. The main point of this strategy is that the examination of biological matrices is always begun with unsaturated TLC chamber, in which the compounds to be separated are placed between the Rf values of 0.3 and 0.8. The optimized TLC mobile phase is transferred without changes to the OPLC technique where a prerun is applied. For separation of nonpolar compounds, the prerun can be performed with hexane; for separation of polar substances the prerun can be performed with any component of the mobile phase in which the components are unable to migrate. The selection of this solvent might be considered during optimization of the mobile phase. Using HPTLC chromatoplate and analytical OPLC technique, highly effective separation can be achieved. The scaling-up for the various preparative chromatographic systems can be performed on basis of the applied chromatographic circumstances. The dry-filled preparative (FC, LPLC, MPLC) columns can be equilibrated with the solvent used for the prerun in analytical OPLC, while in case of filling with slurry technique, the slurry has to be prepared using the same solvent as was used for the prerun of OPLC. The air bubbles can be eliminated in both cases by pumping over the appropriate quantity of the solvent used for prerun, afterwards the preparative separation can be started with the optimized unsaturated TLC mobile phase. The author deals separately with the mobile phase transfer possibilities between the different analytical and preparative planar (OPLC and RPC with various

  17. 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

  18. The effects of molecular collisions between the mobile phase and the solute in gas-solid chromatography.

    PubMed

    Zhang, Dali; Ke, Jiajun; Lu, Lizhu

    2015-10-01

    In chromatographic processes, molecular collisions between the mobile phase and the solute result in the transfer of kinetic energy. Based on these interactions, the relationship between the gauge pressure of the carrier gas at the column inlet and the partition frequency of the solute is derived; consequently, the relationship between the column temperature and partition frequency can be obtained. These relationships have been experimentally validated. The change in the peak shape described herein has been successfully explained using this relationship: the partition frequency was calculated from the theoretical plate number of a tailing peak. We propose a new mechanism for peak tailing using plate theory, which states that as the number of plates increases, the symmetry of the peak increases. PMID:26227076

  19. Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2

    NASA Astrophysics Data System (ADS)

    Neupane, M.; Xu, S.-Y.; Sankar, R.; Alidoust, N.; Bian, G.; Liu, Chang; Belopolski, I.; Chang, T.-R.; Jeng, H.-T.; Lin, H.; Bansil, A.; Chou, Fangcheng; Hasan, M. Z.

    2014-03-01

    Experimental identification of three-dimensional (3D) Dirac semimetals in solid state systems is critical for realizing exotic topological phenomena and quantum transport. Using high-resolution angle-resolved photoemission spectroscopy, we performed systematic electronic structure studies on well-known compound Cd3As2. For the first time, we observe a highly linear bulk Dirac cone located at the Brillouin zone center projected onto the (001) surface, which is consistent with a 3D Dirac semimetal phase in Cd3As2. Remarkably, an unusually high Dirac Fermion velocity is seen in samples where the mobility far exceeds 20,000 cm2/V.s suggesting that Cd3As2 can be a promising candidate as a hypercone analog of graphene in many device-applications, which can also incorporate topological quantum phenomena in a large gap setting. This work is primarily supported by U.S. DOE and Princeton University.

  20. Chemical systems for improved oil recovery: Phase behavior, oil recovery, and mobility control studies

    SciTech Connect

    Llave, F.; Gall, B.; Gao, H., Scott, L., Cook, I.

    1995-09-01

    Selected surfactant systems containing a series of ethoxylated nonionic surfactants in combination with an anionic surfactant system have been studied to evaluate phase behavior as well as oil recovery potential. These experiments were conducted to evaluate possible improved phase behavior and overall oil recovery potential of mixed surfactant systems over a broad range of conditions. Both polyacrylamide polymers and Xanthan biopolymers were evaluated. Studies were initiated to use a chemical flooding simulation program, UTCHEM, to simulate oil recovery for laboratory and field applications and evaluate its use to simulate oil saturation distributions obtained in CT-monitoring of oil recovery experiments. The phase behavior studies focused on evaluating the effect of anionic-nonionic surfactant proportion on overall phase behavior. Two distinct transition behaviors were observed, depending on the dominant surfactant in the overall system. The first type of transition corresponded to more conventional behavior attributed to nonionic-dominant surfactant systems. This behavior is manifested by an oil-water-surfactant system that inverts from a water-external (highly conducting) microemulsion to an oil-external (nonconducting) one, as a function of temperature. The latter type which inverts in an opposite manner can be attributed to the separation of the anionic-nonionic mixtures into water- and oil-soluble surfactants. Both types of transition behavior can still be used to identify relative proximity to optimal areas. Determining these transition ranges provided more insight on how the behavior of these surfactant mixtures was affected by altering component proportions. Efforts to optimize the chemical system for oil displacement experiments were also undertaken. Phase behavior studies with systems formulated with biopolymer in solution were conducted.

  1. Membrane-based continuous remover of trifluoroacetic acid in mobile phase for LC-ESI-MS analysis of small molecules and proteins.

    PubMed

    Zhou, Zhigui; Zhang, Jialing; Xing, Jiawei; Bai, Yu; Liao, Yiping; Liu, Huwei

    2012-07-01

    We developed a "continuous" trifluoroacetic acid (TFA) remover based on electrodialysis with bipolar membrane for online coupling of liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI-MS) using TFA containing mobile phase. With the TFA remover as an interface, the TFA anion in the mobile phase was removed based on electrodialysis mechanism, and meanwhile, the anion exchange membrane was self-regenerated by the hydroxide ions produced by the bipolar membrane. So the remover could continuously work without any additional regeneration process. The established LC-TFA remover-MS system has been successfully applied for the qualitative and quantitative analysis of small molecules as well as proteins. PMID:22528206

  2. Membrane-Based Continuous Remover of Trifluoroacetic Acid in Mobile Phase for LC-ESI-MS Analysis of Small Molecules and Proteins

    NASA Astrophysics Data System (ADS)

    Zhou, Zhigui; Zhang, Jialing; Xing, Jiawei; Bai, Yu; Liao, Yiping; Liu, Huwei

    2012-07-01

    We developed a "continuous" trifluoroacetic acid (TFA) remover based on electrodialysis with bipolar membrane for online coupling of liquid chromatography (LC) and electrospray ionization mass spectrometry (ESI-MS) using TFA containing mobile phase. With the TFA remover as an interface, the TFA anion in the mobile phase was removed based on electrodialysis mechanism, and meanwhile, the anion exchange membrane was self-regenerated by the hydroxide ions produced by the bipolar membrane. So the remover could continuously work without any additional regeneration process. The established LC-TFA remover-MS system has been successfully applied for the qualitative and quantitative analysis of small molecules as well as proteins.

  3. The Use of Mobile, Electrochemical Sensor Nodes for the Measurement of Personal Exposure to Gas-Phase Air Pollutants

    NASA Astrophysics Data System (ADS)

    Stewart, G.; Popoola, O. A.; Mead, M. I.; McKeating, S. J.; Calleja, M.; Hayes, M.; Baron, R. P.; Saffell, J.; Jones, R.

    2012-12-01

    , and thus also the potential insufficiency at quantifying the risks to health in the surrounding area. Recent campaigns with mobile sensor nodes have included attempts to probe the differences in personal exposure to gas-phase air pollutants at different heights of breathing zone and between different methods of transport.

  4. Gas phase ion chemistry of an ion mobility spectrometry based explosive trace detector elucidated by tandem mass spectrometry.

    PubMed

    Kozole, Joseph; Levine, Lauren A; Tomlinson-Phillips, Jill; Stairs, Jason R

    2015-08-01

    The gas phase ion chemistry for an ion mobility spectrometer (IMS) based explosive detector has been elucidated using tandem mass spectrometry. The IMS system, which is operated with hexachloroethane and isobutyramide reagent gases and an ion shutter type gating scheme, is connected to the atmospheric pressure interface of a triple quadrupole mass spectrometer (MS/MS). Product ion masses, daughter ion masses, and reduced mobility values for a collection of nitro, nitrate, and peroxide explosives measured with the IMS/MS/MS instrument are reported. The mass and mobility data together with targeted isotopic labeling experiments and information about sample composition and reaction environment are leveraged to propose molecular formulas, structures, and ionization pathways for the various product ions. The major product ions are identified as [DNT-H](-) for DNT, [TNT-H](-) for TNT, [RDX+Cl](-) and [RDX+NO2](-) for RDX, [HMX+Cl](-) and [HMX+NO2](-) for HMX, [NO3](-) for EGDN, [NG+Cl](-) and [NG+NO3](-) for NG, [PETN+Cl](-) and [PETN+NO3](-) for PETN, [HNO3+NO3](-) for NH4NO3, [NO2](-) for DMNB, [HMTD-NC3H6O3+H+Cl](-) and [HMTD+H-CH2O-H2O2](+) for HMTD, and [(CH3)3CO2](+) for TATP. In general, the product ions identified for the IMS system studied here are consistent with the product ions reported previously for an ion trap mobility spectrometer (ITMS) based explosive trace detector, which is operated with dichloromethane and ammonia reagent gases and an ion trap type gating scheme. Differences between the explosive trace detectors include the [NG+Cl](-) and [PETN+Cl](-) product ions being major ions in the IMS system compared to minor ions in the ITMS system as well as the major product ion for TATP being [(CH3)3CO2](+) for the IMS system and [(CH3)2CNH2](+) for the ITMS system. PMID:26048817

  5. Wireless Roadside Inspection Phase II Tennessee Commercial Mobile Radio Services Pilot Test Final Report

    SciTech Connect

    Franzese, Oscar; Lascurain, Mary Beth; Capps, Gary J; Siekmann, Adam

    2011-05-01

    The Federal Motor Carrier Safety Administration (FMCSA) Wireless Roadside Inspection (WRI) Program is researching the feasibility and value of electronically assessing truck and bus driver and vehicle safety at least 25 times more often than is possible using only roadside physical inspections. The WRI program is evaluating the potential benefits to both the motor carrier industry and to government. These potential benefits include reduction in accidents, fatalities and injuries on our highways and keeping safe and legal drivers and vehicles moving on the highways. WRI Pilot tests were conducted to prototype, test and demonstrate the feasibility and benefits of electronically collecting safety data message sets from in-service commercial vehicles and performing wireless roadside inspections using three different communication methods. This report summarizes the design, conduct and results of the Tennessee CMRS WRI Pilot Test. The purpose of this Pilot test was to demonstrate the implementation of commercial mobile radio services to electronically request and collect safety data message sets from a limited number of commercial vehicles operating in Tennessee. The results of this test have been used in conjunction with the results of the complimentary pilot tests to support an overall assessment of the feasibility and benefits of WRI in enhancing motor carrier safety (reduction in accidents) due to increased compliance (change in motor carrier and driver behavior) caused by conducting frequent safety inspections electronically, at highway speeds, without delay or need to divert into a weigh station

  6. Environmental mobility of cobalt-Influence of solid phase characteristics and groundwater chemistry.

    PubMed

    Payne, T E; Itakura, T; Comarmond, M J; Harrison, J J

    2009-01-01

    The adsorption of cobalt on samples from a potential waste repository site in an arid region was investigated in batch experiments, as a function of various solution phase parameters including the pH and ionic strength. The samples were characterized using a range of techniques, including BET surface area measurements, total clay content and quantitative X-ray diffraction. The statistical relationships between the measured cobalt distribution coefficients (K(d) values) and the solid and liquid phase characteristics were assessed. The sorption of cobalt increased with the pH of the aqueous phase. In experiments with a fixed pH value, the measured K(d) values were strongly correlated to the BET surface area, but not to the amount of individual clay minerals (illite, kaolinite or smectite). A further set of sorption experiments was undertaken with two samples of distinctive mineralogy and surface area, and consequently different sorption properties. A simple surface complexation model (SCM) that conceptualized the surface sites as having equivalent sorption properties to amorphous Fe-oxide was moderately successful in explaining the pH dependence of the sorption data on these samples. Two different methods of quantifying the input parameters for the SCM were assessed. While a full SCM for cobalt sorption on these complex environmental substrates is not yet possible, the basic applicability and predictive capability of this type of modeling is demonstrated. A principal requirement to further develop the modeling approach is adequate models for cobalt sorption on component mineral phases of complex environmental sorbents. PMID:19299159

  7. Chiral stationary phase covalently bound with a chiral pseudo-18-crown-6 ether for enantiomer separation of amino compounds using a normal mobile phase.

    PubMed

    Hirose, Keiji; Yongzhu, Jin; Nakamura, Takashi; Nishioka, Ryota; Ueshige, Tetsuro; Tobe, Yoshito

    2005-03-01

    In order to apply the excellent chiral recognition ability of chiral pseudo-18-crown-6 ethers that we developed to chiral separation, we prepared a chiral stationary phase (CSP) by immobilizing a chiral pseudo-18-crown-6-type host on 3-aminopropyl silica gel. A chiral column was prepared by the slurry-packing method in a stainless steel HPLC column. A liquid chromatography system using this CSP combined with the detection by mass spectrometry was used for enantiomer separation of amino compounds. A normal mobile phase can be used on this CSP as opposed to conventional dynamic coating-type CSPs. Enantiomers of 18 common natural amino acids were efficiently separated. The chiral separation observed for amino acid methyl esters, amino alcohols, and lipophilic amines was fair using this HPLC system. In view of the correlation between the enantiomer selectivity observed in chromatography and the complexion in solution, the chiral recognition in host-guest interactions might contribute to this enantiomer separation. PMID:15704196

  8. The stereochemical resolution of the enantiomers of aspartame on an immobilized alpha-chymotrypsin HPLC chiral stationary phase: the effect of mobile-phase composition and enzyme activity.

    PubMed

    Jadaud, P; Wainer, I W

    1990-01-01

    The enantioselective and diastereoselective resolutions of the stereoisomers of N alpha-aspartyl-phenylalanine 1-methyl ester (APME) have been accomplished on an HPLC chiral stationary phase based upon alpha-chymotrypsin (the ACHT-CSP) with observed enantioselectivities (alpha 1) for the DL-/LD-enantiomer of as high as 29.17 and for the DD-/LL-enantiomers of as high as 28.97. In addition, the effect on the chromatographic retention of the APME stereoisomers of the activity of the ACHT and the composition of the mobile phase--structure of the anionic component, molarity, and pH--have been studied. The results of this study suggest that the aspartyl moiety and/or the aspartyl-phenylalanine amide linkage play key roles in the observed enantioselectivity; the APME stereoisomers containing L-phenylalanine, i.e., DL- and LL-APME, bind at a different site in the ACHT molecule (the L-Phe site) than the APME stereoisomers containing D-phenylalanine (the D-Phe site); and the observed enantioselectivity is a measure of the difference in the binding affinities at the two sites rather than the consequence of differential affinities at a single site. PMID:2400637

  9. Interaction of acetonitrile with the surfaces of amorphous and crystalline ice

    SciTech Connect

    Schaff, J.E.; Roberts, J.T.

    1999-10-12

    The adsorption of acetonitrile (CH{sub 3}CN) on ultrathin films of ice under ultrahigh vacuum was investigated with temperature-programmed desorption ass spectrometry (TPD) and Fourier transform infrared reflection absorption spectroscopy (FTIRAS). Two types of film were studied, amorphous and crystalline. On the amorphous films, two sates of adsorbed acetonitrile were observed by TPD and FTIRAS. One of the states is attributed to acetonitrile that is hydrogen bonded to agree OH group at the ice surface; the other state is assigned to acetonitrile that is purely physiorbed. Evidence for the hydrogen-bonded state is two-fold. First, there is a large kinetic isotope effect for desorption from H{sub 2}O-and D{sub 2}O-ice: the desorption temperatures from ice-h{sub 2} and ice-d{sub 2} are {approximately}161 and {approximately}176 K, respectively. Second, the C{triple{underscore}bond}N stretching frequency (2,265 cm{sup {minus}1}) is 16 cm{sup {minus}1} is greater than that of physisorbed acetonitrile, and it is roughly equal to that of acetonitrile which is hydrogen bonded to an OH group at the air-liquid water interface. On the crystalline films, there is no evidence for a hydrogen-bonded state in the TPD spectra. The FTIRAS spectra do show that some hydrogen-bonded acetonitrile is present but at a maximum coverage that is roughly one-sixth of that on the amorphous surface. The difference between the amorphous and crystalline surfaces cannot be attributed to a difference n surface areas. Rather, this work provides additional evidence that the surface chemical properties of amorphous ice are different from those of crystalline ice.

  10. Comparison of the performance of non-ionic and anionic surfactants as mobile phase additives in the RPLC analysis of basic drugs.

    PubMed

    Ruiz-Ángel, María J; García-Álvarez-Coque, María C

    2011-03-01

    Surfactants added to the mobile phases in reversed-phase liquid chromatography (RPLC) give rise to a modified stationary phase, due to the adsorption of surfactant monomers. Depending on the surfactant nature (ionic or non-ionic), the coated stationary phase can exhibit a positive net charge, or just change its polarity remaining neutral. Also, micelles in the mobile phase introduce new sites for solute interaction. This affects the chromatographic behavior, especially in the case of basic compounds. Two surfactants of different nature, the non-ionic Brij-35 and the anionic sodium dodecyl sulfate (SDS) added to water or aqueous-organic mixtures, are here compared in the separation of basic compounds (β-blockers and tricyclic antidepressants). The reversible/irreversible adsorption of the monomers of both surfactants on the stationary phase was examined. The changes in the nature of the chromatographic system using different columns and chromatographic conditions were followed based on the changes in retention and peak shape. The study revealed that Brij-35 is suitable for analyzing basic compounds of intermediate polarity, using "green chemistry", since the addition of an organic solvent is not needed and Brij-35 is a biodegradable surfactant. In contrast, RPLC with hydro-organic mixtures or mobile phases containing SDS required high concentrations of organic solvents. PMID:21328695

  11. Chromatographic behavior of small organic compounds in low-temperature high-performance liquid chromatography using liquid carbon dioxide as the mobile phase.

    PubMed

    Motono, Tomohiro; Nagai, Takashi; Kitagawa, Shinya; Ohtani, Hajime

    2015-07-01

    Low-temperature high-performance liquid chromatography, in which a loop injector, column, and detection cell were refrigerated at -35ºC, using liquid carbon dioxide as the mobile phase was developed. Small organic compounds (polyaromatic hydrocarbons, alkylbenzenes, and quinones) were separated by low-temperature high-performance liquid chromatography at temperatures from -35 to -5ºC. The combination of liquid carbon dioxide mobile phase with an octadecyl-silica (C18 ) column provided reversed phase mode separation, and a bare silica-gel column resulted in normal phase mode separation. In both the cases, nonlinear behavior at approximately -15ºC was found in the relationship between the temperature and the retention factors of the analytes (van't Hoff plots). In contrast to general trends in high-performance liquid chromatography, the decrease in temperature enhanced the separation efficiency of both the columns. PMID:25917311

  12. Tensor-based classification of an auditory mobile BCI without a subject-specific calibration phase

    NASA Astrophysics Data System (ADS)

    Zink, Rob; Hunyadi, Borbála; Van Huffel, Sabine; De Vos, Maarten

    2016-04-01

    Objective. One of the major drawbacks in EEG brain-computer interfaces (BCI) is the need for subject-specific training of the classifier. By removing the need for a supervised calibration phase, new users could potentially explore a BCI faster. In this work we aim to remove this subject-specific calibration phase and allow direct classification. Approach. We explore canonical polyadic decompositions and block term decompositions of the EEG. These methods exploit structure in higher dimensional data arrays called tensors. The BCI tensors are constructed by concatenating ERP templates from other subjects to a target and non-target trial and the inherent structure guides a decomposition that allows accurate classification. We illustrate the new method on data from a three-class auditory oddball paradigm. Main results. The presented approach leads to a fast and intuitive classification with accuracies competitive with a supervised and cross-validated LDA approach. Significance. The described methods are a promising new way of classifying BCI data with a forthright link to the original P300 ERP signal over the conventional and widely used supervised approaches.

  13. [Effect of Acetonitrile and n-hexane on the Immunoassay of Environmental Representative Pollutants].

    PubMed

    Lou, Xue-ning; Zhou, Li-ping; Song, Dan; Yang, Rong; Long, Feng

    2016-01-15

    Based on indirect competitive immunoassay mechanism, bisphenol A (BPA) was detected by the evanescent wave all-fiber immunosensor previously developed with the detection limit of 0.2 microg x L(-1) and the linear detection range of 0.3-33.4 microg x L(-1). The effects of two commonly used organic solvents, including acetonitrile and n-hexane, on the immunosensing assay of BPA were investigated. The influence mechanism of organic solvents on immunosensing assay was discussed. The experimental results showed that the effect of n-hexane on immunosensing assay was negligible even at a high concentration of up to 10%, whereas the effect of acetonitrile on the immunosensing assay was relatively great. BPA could be detected in solutions containing a low concentration of acetonitrile. However, the specific binding reaction between antibody and antigen in homogeneous solution was completely inhibited by high concentrations of acetonitrile, and the quantitative analysis of BPA was not achieved. This might result from the changes of antibody conformation or binding capability between antibody and antigen because acetonitrile replaced a part of the water molecules on the antibody surface. PMID:27078982

  14. Characterization of acetonitrile-tolerant marine bacterium Exiguobacterium sp. SBH81 and its tolerance mechanism.

    PubMed

    Kongpol, Ajiraporn; Kato, Junichi; Tajima, Takahisa; Vangnai, Alisa S

    2012-01-01

    A Gram-positive marine bacterium, Exiguobacterium sp. SBH81, was isolated as a hydrophilic organic-solvent tolerant bacterium, and exhibited high tolerance to various types of toxic hydrophilic organic solvents, including acetonitrile, at relatively high concentrations (up to 6% [v/v]) under the growing conditions. Investigation of its tolerance mechanisms illustrated that it does not rely on solvent inactivation processes or modification of cell surface characteristics, but rather, increase of the cell size lowers solvent partitioning into cells and the extrusion of solvents through the efflux system. A test using efflux pump inhibitors suggested that secondary transporters, i.e. resistance nodulation cell division (RND) and the multidrug and toxic compound extrusion (MATE) family, are involved in acetonitrile tolerance in this strain. In addition, its acetonitrile tolerance ability could be stably and significantly enhanced by repetitive growth in the presence of toxic acetonitrile. The marked acetonitrile tolerance of Exiguobacterium sp. SBH81 indicates its potential use as a host for biotechnological fermentation processes as well as bioremediation. PMID:21971080

  15. Use of basic mobile phase to improve chromatography and boost sensitivity for quantifying tetrahydrocurcumin in human plasma by LC-MS/MS.

    PubMed

    Tan, Aimin; Wu, Yanxin; Wong, Molly; Licollari, Albert; Bolger, Gordon; Fanaras, John C; Shopp, George; Helson, Lawrence

    2016-08-15

    Tetrahydrocurcumin (THC), a major metabolite of curcumin, is often quantified by LC-MS or LC-MS/MS using acidic mobile phases due to the concern of its instability in a basic medium. However, acidic mobile phases often lead to poor chromatography (e.g. split or double peaks) and reduced detection sensitivity in the commonly used negative ionization mode. To overcome these shortcomings, a basic mobile phase was used for the first time in the LC-MS/MS quantification of THC. In comparison with the acidic mobile phases, a single symmetrical chromatographic peak was obtained and the sensitivity increased by 7-fold or more under the equivalent conditions. The new LC-MS/MS method using the basic mobile phase has been successfully validated for the quantification of THC in human EDTA plasma over the concentration range of 5-2500ng/ml. The within-batch accuracy (% nominal concentration) was between 88.7 and 104.9 and the between-batch accuracy ranged from 96.7 to 108.6. The CVs for within- and between-batch precisions were equal to or less than 5.5% and 9.1%, respectively. No significant matrix interference or matrix effect was observed from normal or lipemic and hemolytic plasma matrices. In addition, the common stabilities with adequate durations were established, including up to 5days of post-preparative stability. Furthermore, when the validated method was applied to a clinical study, the passing rate of ISR samples was 83%, indicating the good reproducibility of the method. The success of the unconventional approach presented in this article demonstrates that a mobile phase could be selected based mainly on its merits to facilitate LC separation and/or MS detection. There is no need for excessive concern about the stability of the compound(s) of interest in the selected mobile phase because the run time of modern LC-MS or LC-MS/MS methods is typically only a few minutes. PMID:27327398

  16. 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.

  17. Applicability of the Remote Mobile Emplacement Package (RMEP) design as a mobility aid for proposed post-84 Mars missions, phase O

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The results of study to determine the applicability of the Remote Mobile Emplacement Package (RMEP) design concept as a mobility aid for the proposed post-'84 Mars missions are presented. The RMEP wheel and mobility subsystem parameters: wheel tire size, weight, stowed volume, and environmental effects; obstacle negotiation; reliability and wear; motor and drive train; and electrical power demand were reviewed. Results indicated that: (1) the basic RMEP wheel design would be satisfactory, with additional attention to heating, side loading, tread wear and ultraviolet radiation protection; (2) motor and drive train power requirements on Mars would be less than on Earth; and (3) the mobility electrical power requirements would be small enough to offer the option of operating the Mars mini rover untethered. Payload power required for certain sampling functions would preclude the use of battery power for these missions. Hazard avoidance and reverse direction maneuvers are discussed. Limited examination of vehicle payload integration and thermal design was made, pending establishment of a baseline vehicle/payload design.

  18. Extensive database of liquid phase diffusion coefficients of some frequently used test molecules in reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography.

    PubMed

    Song, Huiying; Vanderheyden, Yoachim; Adams, Erwin; Desmet, Gert; Cabooter, Deirdre

    2016-07-15

    Diffusion plays an important role in all aspects of band broadening in chromatography. An accurate knowledge of molecular diffusion coefficients in different mobile phases is therefore crucial in fundamental column performance studies. Correlations available in literature, such as the Wilke-Chang equation, can provide good approximations of molecular diffusion under reversed-phase conditions. However, these correlations have been demonstrated to be less accurate for mobile phases containing a large percentage of acetonitrile, as is the case in hydrophilic interaction liquid chromatography. A database of experimentally measured molecular diffusion coefficients of some 45 polar and apolar compounds that are frequently used as test molecules under hydrophilic interaction liquid chromatography and reversed-phase conditions is therefore presented. Special attention is given to diffusion coefficients of polar compounds obtained in large percentages of acetonitrile (>90%). The effect of the buffer concentration (5-10mM ammonium acetate) on the obtained diffusion coefficients is investigated and is demonstrated to mainly influence the molecular diffusion of charged molecules. Diffusion coefficients are measured using the Taylor-Aris method and hence deduced from the peak broadening of a solute when flowing through a long open tube. The validity of the set-up employed for the measurement of the diffusion coefficients is demonstrated by ruling out the occurrence of longitudinal diffusion, secondary flow interactions and extra-column effects, while it is also shown that radial equilibration in the 15m long capillary is effective. PMID:27240944

  19. Simultaneous Determination of Diosmin and Hesperidin in Pharmaceuticals by RPLC using Ionic Liquids as Mobile Phase Modifiers

    PubMed Central

    Szymański, Marcin; Młynarek, Daria; Szymański, Arkadiusz; Matławska, Irena

    2016-01-01

    Diosmin and hesperidin are natural flavonoid glycosides found in various plant materials, mainly in citrus fruits in different concentrations. Diosmin for pharmaceutical use is obtained mainly semi-synthetically from hesperidin. Hesperidin often accompanies diosmin as a natural impurity in different pharmaceutical formulations; therefore, a simple, fast and precise method for the simultaneous assay of diosmin and hesperidin in pharmaceutical formulations has been developed to control their contents. Chromatographic resolution was performed using a column with C-18 packing and the following mobile phase: methanol/water (45:55, v/v) with 0.025% added didecyldimethylammonium lactate, which significantly affects retention, shortening analysis time and having a positive impact on the symmetry of resulting chromatographic peaks. The method shows linearity between 2.5 and 100 μg/mL, high repeatability (0.39 and 0.42% for diosmin and hesperidin, respectively) and accuracy of 96 to 102% for both the assayed compounds. Intraday and interday precision of the new method were less than RSD% 1, 2. The limit of detection of the assayed compounds is 2.5 and 1.2 μg/mL for diosmin and hesperidin, respectively. The method was tested on several pharmaceutical products available in Poland. PMID:27610154

  20. Simultaneous Determination of Diosmin and Hesperidin in Pharmaceuticals by RPLC using Ionic Liquids as Mobile Phase Modifiers.

    PubMed

    Szymański, Marcin; Młynarek, Daria; Szymański, Arkadiusz; Matławska, Irena

    2016-01-01

    Diosmin and hesperidin are natural flavonoid glycosides found in various plant materials, mainly in citrus fruits in different concentrations. Diosmin for pharmaceutical use is obtained mainly semi-synthetically from hesperidin. Hesperidin often accompanies diosmin as a natural impurity in different pharmaceutical formulations; therefore, a simple, fast and precise method for the simultaneous assay of diosmin and hesperidin in pharmaceutical formulations has been developed to control their contents. Chromatographic resolution was performed using a column with C-18 packing and the following mobile phase: methanol/water (45:55, v/v) with 0.025% added didecyldimethylammonium lactate, which significantly affects retention, shortening analysis time and having a positive impact on the symmetry of resulting chromatographic peaks. The method shows linearity between 2.5 and 100 μg/mL, high repeatability (0.39 and 0.42% for diosmin and hesperidin, respectively) and accuracy of 96 to 102% for both the assayed compounds. Intraday and interday precision of the new method were less than RSD% 1, 2. The limit of detection of the assayed compounds is 2.5 and 1.2 μg/mL for diosmin and hesperidin, respectively. The method was tested on several pharmaceutical products available in Poland. PMID:27610154

  1. Solvent viscosity mismatch between the solute plug and the mobile phase: Considerations in the applications of two-dimensional HPLC

    SciTech Connect

    Shalliker, R. Andrew; Guiochon, Georges A

    2010-01-01

    Understanding the nature of viscosity contrast induced flow instabilities is an important aspect in the design of two-dimensional HPLC separations. When the viscosity contrast between the sample plug and the mobile phase is sufficiently large, the phenomenon known as viscous fingering can be induced. Viscous fingering is a flow instability phenomenon that occurs at the interface between two fluids with different viscosities. In liquid chromatography, viscous fingering results in the solute band undergoing a change in form as it enters into the chromatography column. Moreover, even in the absence of viscous fingering, band shapes change shape at low viscosity contrasts. These changes can result in a noticeable change in separation performance, with the result depending on whether the solvent pushing the solute plug has a higher or lower viscosity than the solute plug. These viscosity induced changes become more important as the solute injection volume increases and hence understanding the process becomes critical in the implementation of multidimensional HPLC techniques, since in these techniques the sample injection plug into the second dimension is an order of magnitude greater than in one-dimensional HPLC. This review article assesses the current understanding of the viscosity contrast induced processes as they relate to liquid chromatographic separation behaviour.

  2. Fourier transform infrared assay of membrane lipids immobilized to silica: leaching and stability of immobilized artificial membrane-bonded phases.

    PubMed

    Markovich, R J; Stevens, J M; Pidgeon, C

    1989-11-01

    A nondestructive, sensitive assay to monitor the hydrocarbon content of silica-based chromatography particles has been developed. The assay requires a microscope accessory interfaced with a Fourier transform infrared (FTIR) spectrometer. For determining hydrocarbon content, undiluted alkyl-silica-bonded phases were pressed into a thin wafer. Hydrocarbon content was quantitated using the integrated hydrocarbon band intensity between 2995 and 2825 cm-1 [i.e., band area C-H] and the integrated silica oxide band intensity between 1945 and 1780 cm-1 [i.e., band area Si-O]. Plotting the [band area C-H]/[band area Si-O] ratio vs the carbon content determined by elemental analysis gave a correlation coefficient of r = 0.997. The FTIR assay was validated on 5-, 7-, and 12-microns silica particles using three different immobilized artificial membrane (IAM) silica-bonded phases. The utility of the FTIR assay in determining hydrocarbon content was demonstrated by evaluating hydrocarbon leaching from IAM phases exposed to mobile-phase solvents. The ability of organic solvents to leach hydrocarbon from IAM phases containing phosphatidylcholine (PC) as the immobilized ligand was chloroform greater than ethanol approximately methanol greater than ethyl acetate greater than methylene chloride greater than acetonitrile greater than acetone. Acetone and acetonitrile cause very little hydrocarbon leaching from HPLC-IAM.PC columns. When challenged with different mobile phases, IAM.PC columns perfused with mobile phase are more stable than IAM.PC-bonded phases stirred in mobile phases. IAM.PC contains lecithin linked to silica by amide bonds.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2558589

  3. Effect of hypochlorite oxidation on cholinesterase-inhibition assay of acetonitrile extracts from fruits and vegetables for monitoring traces of organophosphate pesticides.

    PubMed

    Kitamura, Kentaro; Maruyama, Kaori; Hamano, Sachiko; Kishi, Tomohiro; Kawakami, Tsuyoshi; Takahashi, Yasuo; Onodera, Sukeo

    2014-02-01

    A reproducible method for monitoring traces of cholinesterase (ChE) inhibitors in acetonitrile extracts from fruits and vegetables is described. The method is based on hypochlorite oxidation and ChE inhibition assay. Four common representative samples of produce were selected from a supermarket to investigate the effect of different matrices on pesticides recoveries and assay precision. The samples were extracted with acetonitrile to prepare them for ChE inhibition assays: if necessary, clean-up was performed using dispersive solid-phase extraction for gas chromatography-mass spectrometry (GC/MS) analyses. Chlorine was tested as an oxidising reagent for the conversion of thiophosphorus pesticides (P=S compounds) into their P=O analogues, which have high ChE-inhibiting activity. Chlorine consumption of individual acetonitrile extracts was determined and was strongly dependent on the individual types of fruits and vegetables. After treating the acetonitrile extracts with an excess hypochlorite at 25°C for 15 min, the ChE-inhibiting activities and detection limits for each chlorine-treated pesticide solution were determined. Matrix composition did not interfere significantly with the determination of the pesticides. Enhanced anti-ChE activities leading to low detection limits (ppb levels) were observed for the chlorine-treated extracts that were spiked with chlorpyrifos, diazinon, fenitrothion, and isoxathion. This combination of oxidative derivatisation and ChE inhibition assays was used successfully to monitor and perform semi-quantitative determination of ChE inhibitors in apple, tomato, cucumber, and strawberry samples. PMID:24418711

  4. The adsorption and reaction of Acetonitrile on clean and oxygen covered Ag(110) surfaces

    NASA Astrophysics Data System (ADS)

    Capote, Armand J.; Hamza, Alex V.; Canning, Nicholas D. S.; Madix, Robert J.

    1986-10-01

    The adsorption and reaction of acetonitrile (CH 3CN) on clean and oxygen covered Ag(110) surfaces has been studied using temperature programmed reaction spectroscopy (TPRS), isotope exchange, chemical displacement reactions and high resolution electron energy loss spectroscopy (EELS). On the clean Ag(110) surface, CH 3CN was reversibly adsorbed, desorbing with an activation energy of 10 kcal mol -1 at 166 K from a monolayer state and at 158 K from a multilayer state. Vibrational spectra of multilayer, monolayer and sub-monolayer CH 3CN were in excellent agreement with that of gas phase CH 3CN indicating that CH 3CN is only weakly bonded to the clean Ag(110) surface. On the partially oxidized surface CH 3CN reacts with atomic oxygen to form adsorbed CH 2CN, OH and H 2O in addition to forming another molecular adsorption state with a desorption peak at 240 K. This molecular state shows a CN stretching frequency of 1840 cm -1, which is indicative of substantial rehybridization of the CN bond and is associated with side-on coordination via the π system. The CH 2CN species is stable up to 430 K, where C-H bond breaking and reformation begins, leading to the formation of CH 3CN at 480 K and HCN at 510 K and leaving only carbon on the surface. In the presence of excess oxygen atoms C-H bond breaking and reformation is more facile leading to additional desorption peaks for CH 3CN and H 2O at 420 K. This destabilizing effect of O (a) on Ch 2CN (a) is explained in terms of an anionic (CH 2CN -1) species. Comparison of the vibrational spectra from CH 2CN (a) and CD 2CN (a) supports the following assignment for the modes of adsorbed CH 2CN: ν(Ag-C) 215: δ(CCN) 545; ϱ t(CH 2) 695; ϱ w(CH 2) 850; ν(C-C) 960; ϱ r(CH 2) 1060; δ(CH 2) 1375; ν(CN) 2075; and ν(CH 2) 2940 cm -1. These results serve to further indicate the wide applicability of the acid-base reaction concept for reactions between gas phase Brönsted acids and adsorbed oxygen atoms on solver surfaces.

  5. Structural and energetic properties of acetonitrile-Group IV (A & B) halide complexes.

    PubMed

    Helminiak, Heather M; Knauf, Robin R; Danforth, Samuel J; Phillips, James A

    2014-06-19

    We have conducted an extensive computational study of the structural and energetic properties of select acetonitrile-Group IV (A & B) tetrahalide complexes, both CH3CN-MX4 and (CH3CN)2-MX4 (M = Si, Ge, Ti; X = F, Cl). We have also examined the reactivity of CH3CN with SiF4, SiCl4, GeCl4, and TiCl4, and measured low-temperature IR spectra of thin films containing CH3CN with SiF4, GeCl4, or TiCl4. The six 1:1 complexes fall into two general structural classes. CH3CN-TiCl4, CH3CN-TiF4, and CH3CN-GeF4, exhibit relatively short M-N bonds (~2.3 Å), an intermediate degree of distortion in the MX4 subunit, and binding energies ranging from 11.0 to 13.0 kcal/mol. Conversely, CH3CN-GeCl4, CH3CN-SiF4, and CH3CN-SiCl4, are weakly bonded systems, with long M-N distances (>3.0 Å), little distortion in the MX4 subunit, and binding energies ranging from 3.0 to 4.4 kcal/mol. The structural features of analogous 2:1 systems resemble those of their 1:1 counterparts, whereas the binding energies (relative to three isolated fragments) are roughly twice as large. Calculated M-N potential curves in the gas phase and bulk, dielectric media are reported for all 1:1 complexes, and for two systems, CH3CN-GeF4 and CH3CN-SiF4, these data predict significant condensed-phase structural changes. The effect on the CH3CN-SiF4 potential is extreme; the curve becomes quite flat over a broad range in dielectric media, and at higher ε values, the global minimum shifts inward by about 1.0 Å. In bulk reactivity experiments, no reaction was observed between CH3CN and SiF4, SiCl4, or GeCl4, whereas CH3CN and TiCl4 were found to react immediately upon contact. Also, thin-film IR spectra indicate a strong interaction between CH3CN and TiCl4, yet only weak interactions between CH3CN and GeCl4 or SiF4 in the solid state. PMID:24852185

  6. DEVELOPMENTAL TOXICITY OF HALOGENATED ACETONITRILES: DRINKING WATER BY-PRODUCTS OF CHLORINE DISINFECTION

    EPA Science Inventory

    The developmental toxicity of acetonitrile and five halogenated derivatives was examined with an in vivo teratology screen adapted for use in the Long Evans rat. The screen was extended to an evaluation of growth till postnatal days 41-42, and weight of several organs at sacrific...

  7. Stacking and separation of coproporphyrin isomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography.

    PubMed

    So, T S; Jia, L; Huie, C W

    2001-07-01

    The effectiveness of the addition of salt and acetonitrile in the sample matrix to induce narrowing of the analyte zones is demonstrated for the first time in micellar electrokinetic chromatography (MEKC). Using coproporphyrin (CP) I and III isomers as test compounds, the use of sodium cholate (SC) as the micelle in the separation buffer and a high concentration of sodium chloride in the aqueous sample solution (without the presence of an organic solvent) were found to provide enhancement in peak heights for both CP I and III, but yielded very poor resolution of these two positional isomers at sample size of 10% capillary volume or larger. With the addition of acetonitrile as the organic solvent in the aqueous sample solution (acetonitrile-salt mixtures), baseline/partial resolution of CP I and III was obtained even at large injection volumes, along with significant increase in peak heights for both isomers. Possible mechanisms responsible for the narrowing of analyte zones are briefly discussed. The effects of experimental parameters, such as concentrations of salt and acetonitrile, on peak heights and resolution of the test compounds were studied. Importantly, the usefulness of the present method was demonstrated for the MEKC determination of endogenous CP I and III present in normal urine samples with good separation and detection performances. PMID:11504047

  8. Why a diaminopyrrolic tripodal receptor binds mannosides in acetonitrile but not in water?

    PubMed Central

    Vila-Viçosa, Diogo; Francesconi, Oscar

    2014-01-01

    Summary Intermolecular interactions involving carbohydrates and their natural receptors play important roles in several biological processes. The development of synthetic receptors is very useful to study these recognition processes. Recently, it was synthetized a diaminopyrrolic tripodal receptor that is selective for mannosides, which are obtained from mannose, a sugar with significant relevance in living systems. However, this receptor is significantly more active in acetonitrile than in water. In this work, we performed several molecular dynamics and constant-pH molecular dynamics simulations in acetonitrile and water to evaluate the conformational space of the receptor and to understand the molecular detail of the receptor–mannoside interaction. The protonation states sampled by the receptor show that the positive charges are always as distant as possible in order to avoid large intramolecular repulsions. Moreover, the conformational space of the receptor is very similar in water above pH 4.0 and in acetonitrile. From the simulations with the mannoside, we observe that the interactions are more specific in acetonitrile (mainly hydrogen bonds) than in water (mainly hydrophobic). Our results suggest that the readiness of the receptor to bind mannoside is not significantly affected in water (above pH 4.0). Probably, the hydrogen bond network that is formed in acetonitrile (which is weaker in water) is the main reason for the higher activity in this solvent. This work also presents a new implementation of the stochastic titration constant-pH molecular dynamics method to a synthetic receptor of sugars and attests its ability to describe the protonation/conformation coupling in these molecules. PMID:25161708

  9. 77 FR 7152 - Mobility Fund Phase I Auction Scheduled for September 27, 2012; Comment Sought on Competitive...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-10

    ... the Commission in the USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562... current- and next-generation mobile networks in areas where these networks are unavailable. This support... current or next generation mobile networks, the USF/ICC Transformation Order provides that the...

  10. Enantiomeric separation of dansyl amino acids using macrocyclic antibiotics as chiral mobile phase additives by narrow-bore high-performance liquid chromatography.

    PubMed

    Sharp, V Scott; Letts, Maureen N; Risley, Donald S; Rose, John P

    2004-03-01

    Seven macrocyclic antibiotics were evaluated as chiral selectors for the enantiomeric separation of 11 dansyl amino acids using narrow-bore high-performance liquid chromatography (HPLC). The macrocyclic antibiotics were incorporated as mobile phase additives to determine the enantioselective effects on the chiral analytes. The resolution and capacity factor (k') of each analyte were assessed while varying the structure of macrocyclic antibiotic and the mobile phase buffer pH. The selectivity of the chiral selectors was measured as a function of changes in these parameters. All 11 dansyl amino acids were separated by at least one of the chiral selectors. Three-dimensional computer modeling of the more effective chiral selectors illustrated the importance of macrocyclic antibiotic structure concerning stereospecific analyte interaction. PMID:14770411

  11. Defect-mediated relaxation in the random tiling phase of a binary mixture: Birth, death and mobility of an atomic zipper

    NASA Astrophysics Data System (ADS)

    Tondl, Elisabeth; Ramsay, Malcolm; Harrowell, Peter; Widmer-Cooper, Asaph

    2014-03-01

    This paper describes the mechanism of defect-mediated relaxation in a dodecagonal square-triangle random tiling phase exhibited by a simulated binary mixture of soft discs in 2D. We examine the internal transitions within the elementary mobile defect (christened the "zipper") that allow it to move, as well as the mechanisms by which the zipper is created and annihilated. The structural relaxation of the random tiling phase is quantified and we show that this relaxation is well described by a model based on the distribution of waiting times for each atom to be visited by the diffusing zipper. This system, representing one of the few instances where a well defined mobile defect is capable of structural relaxation, can provide a valuable test case for general theories of relaxation in complex and disordered materials.

  12. Defect-mediated relaxation in the random tiling phase of a binary mixture: Birth, death and mobility of an atomic zipper

    SciTech Connect

    Tondl, Elisabeth; Ramsay, Malcolm; Harrowell, Peter; Widmer-Cooper, Asaph

    2014-03-14

    This paper describes the mechanism of defect-mediated relaxation in a dodecagonal square-triangle random tiling phase exhibited by a simulated binary mixture of soft discs in 2D. We examine the internal transitions within the elementary mobile defect (christened the “zipper”) that allow it to move, as well as the mechanisms by which the zipper is created and annihilated. The structural relaxation of the random tiling phase is quantified and we show that this relaxation is well described by a model based on the distribution of waiting times for each atom to be visited by the diffusing zipper. This system, representing one of the few instances where a well defined mobile defect is capable of structural relaxation, can provide a valuable test case for general theories of relaxation in complex and disordered materials.

  13. [The resolution of racemic sec-phenethyl alcohol on cellulose tribenzoate-based CSP: influence of different alcohols in the mobile phase].

    PubMed

    Wang, L; Lü, S; Gao, P; Li, S

    1999-07-01

    Several primary and secondary alcohols (ethanol, 1-propanol, 2-propanol, 1-butanol) were used as the mobile phase components separately, to investigate their effects on the capacity factor and stereoselectivity of sec-phenethyl alcohol enantiomers on cellulose tribenzoate-based CSP. The chiral recognition mechanism for the enantiomeric aromatic alcohols studied may involve: (1) the aromatic portion of the solute may insert into a chiral cavity of the CSP through a hydrogen bonding interaction between the solute's alcoholic hydrogen and the ester carbonyl group on the CSP; (2) the mobile phase modifiers (various alcohols) compete with the solutes for chiral, as well as achiral, binding sites on the CSP; (3) the structure of the modifier has some effect on stereoselectivity through an alteration of the steric environment of the chiral cavity. PMID:12552849

  14. Formation of Iron Complexes from Trifluoroacetic Acid Based Liquid Chromatography Mobile Phases as Interference Ions in LC-ESI-MS Analysis

    PubMed Central

    Shukla, Anil; Zhang, Rui; Orton, Daniel; Zhao, Rui; Clauss, Therese; Moore, Ronald; Smith, Richard

    2011-01-01

    Two unexpected singly charged ions at m/z 1103 and 944 have been observed in mass spectra obtained from electrospray ionization-mass spectrometric analysis of liquid chromatography effluents with mobile phases containing trifluoroacetic acid that severely interfered with sample analysis. Accurate mass measurement and tandem mass spectrometry studies revealed that these two ions are composed of three components; clusters of trifluoroacetic acid, clusters of mass 159 and iron. Formation of these ions is inhibited by removing trifluoroacetic acid from the mobile phases and using formic acid in its place, replacing the stainless steel union with a titanium union or by adding a small blank fused silica capillary column between the chromatography column and the electrospray tip via a stainless steel union without any adverse effects to chromatographic separation, peak broadening or peptide identifications. PMID:21504012

  15. Palladium-catalyzed oxidative arylalkylation of activated alkenes: dual C-H bond cleavage of an arene and acetonitrile.

    PubMed

    Wu, Tao; Mu, Xin; Liu, Guosheng

    2011-12-23

    Not one but two: The title reaction proceeds through the dual C-H bond cleavage of both aniline and acetonitrile. The reaction affords a variety of cyano-bearing indolinones in excellent yield. Mechanistic studies demonstrate that this reaction involves a fast arylation of the olefin and a rate-determining C-H activation of the acetonitrile. PMID:22076660

  16. High mobility of flap endonuclease 1 and DNA polymerase eta associated with replication foci in mammalian S-phase nucleus.

    PubMed

    Solovjeva, Lioudmila; Svetlova, Maria; Sasina, Lioudmila; Tanaka, Kyoji; Saijo, Masafumi; Nazarov, Igor; Bradbury, Morton; Tomilin, Nikolai

    2005-05-01

    Originally detected in fixed cells, DNA replication foci (RFi) were later visualized in living cells by using green fluorescent protein (GFP)-tagged proliferating cell nuclear antigen (PCNA) and DNA ligase I. It was shown using fluorescence redistribution after photobleaching (FRAP) assay that focal GFP-PCNA slowly exchanged, suggesting the existence of a stable replication holocomplex. Here, we used the FRAP assay to study the dynamics of the GFP-tagged PCNA-binding proteins: Flap endonuclease 1 (Fen1) and DNA polymerase eta (Pol eta). We also used the GFP-Cockayne syndrome group A (CSA) protein, which does associate with transcription foci after DNA damage. In normal cells, GFP-Pol eta and GFP-Fen1 are mobile with residence times at RFi (t(m)) approximately 2 and approximately 0.8 s, respectively. GFP-CSA is also mobile but does not concentrate at discrete foci. After methyl methanesulfonate (MMS) damage, the mobile fraction of focal GFP-Fen1 decreased and t(m) increased, but it then recovered. The mobilities of focal GFP-Pol eta and GFP-PCNA did not change after MMS. The mobility of GFP-CSA did not change after UV-irradiation. These data indicate that the normal replication complex contains at least two mobile subunits. The decrease of the mobile fraction of focal GFP-Fen1 after DNA damage suggests that Fen1 exchange depends on the rate of movement of replication forks. PMID:15758026

  17. 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

  18. Simultaneous determination of fangchinoline and tetrandrine in Stephania tetrandra S. Moore by using 1-alkyl-3-methylimidazolium-based ionic liquids as the RP-HPLC mobile phase additives.

    PubMed

    Tang, Yan; Sun, Ailing; Liu, Renmin; Zhang, Yongqing

    2013-03-12

    A reversed phase high performance liquid chromatography (RP-HPLC) method for simultaneous determination of fangchinoline (FAN) and tetrandrine (TET) in Stephania tetrandra S. Moore was established by using 1-hexyl-3-methylimidazolium tetrafluoroborate as the mobile phase additives in this paper. Four types of 1-alkyl-3-methylimidazolium-based ionic liquids (ILs) were used as additives of the mobile phase to separate FAN and TET by RP-HPLC. The effects of the length of the alkyl group on the imidazolium ring and its counterion, the concentrations of IL and the pH of the mobile phase, which influenced the chromatographic behaviors of FAN and TET, were investigated in detail. The linearity, sensitivity, accuracy and repeatability of the proposed method were also investigated. The probable mechanism of the separation with ILs as the mobile phase additives was explored and discussed. PMID:23452799

  19. Photoinduced ultrafast dynamics of the triphenylamine-based organic sensitizer D35 on TiO2, ZrO2 and in acetonitrile.

    PubMed

    Oum, Kawon; Lohse, Peter W; Klein, Johannes R; Flender, Oliver; Scholz, Mirko; Hagfeldt, Anders; Boschloo, Gerrit; Lenzer, Thomas

    2013-03-21

    The relaxation dynamics of the dye D35 has been characterized by transient absorption spectroscopy in acetonitrile and on TiO(2) and ZrO(2) thin films. In acetonitrile, upon photoexcitation of the dye via the S(0) → S(1) transition, we observed ultrafast solvation dynamics with subpicosecond time constants. Subsequent decay of the S(1) excited state absorption (ESA) band with a 7.1 ps time constant is tentatively assigned to structural relaxation in the excited state, and a spectral decay with 203 ps time constant results from internal conversion (IC) back to S(0). On TiO(2), we observed fast (<90 fs) electron injection from the S(1) state of D35 into the TiO(2) conduction band, followed by a biphasic dynamics arising from changes in a transient Stark field at the interface, with time constants of 0.8 and 12 ps, resulting in a characteristic blue-shift of the S(0) → S(1) absorption band. Several processes can contribute to this spectral shift: (i) photoexcitation induces immediate formation of D35˙(+) radical cations, which initially form electron-cation complexes; (ii) dissociation of these complexes generates mobile electrons, and when they start diffusing in the mesoporous TiO(2), the local electrostatic field may change; (iii) this may trigger the reorientation of D35 molecules in the changing electric field. A slower spectral decay on a nanosecond timescale is interpreted as a reduction of the local Stark field, as mobile electrons move deeper into TiO(2) and are progressively screened. Multiexponential electron-cation recombination occurs on much longer timescales, with time constants of 30 μs, 170 μs and 1.4 ms. For D35 adsorbed on ZrO(2), there is no clear evidence for a transient Stark shift, which suggests that initially formed cation-electron (trap state) complexes do not dissociate to form mobile conduction band electrons. Multiexponential decay with time constants of 4, 35, and 550 ps is assigned to recombination between cations and trapped

  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. Electrosynthesis and characterization of oligophenylene deriving from 4-(methoxyphenyl)acetonitrile

    NASA Astrophysics Data System (ADS)

    Amor, Sarra Ben; Said, Ayoub Haj; Chemek, Mourad; Ayachi, Sahbi; Massuyeau, Florian; Wéry, Jany; Alimi, Kamel; Roudesli, Sadok

    2013-01-01

    An oligophenylene deriving from the 4-(methoxyphenyl)acetonitrile (MPA), was electrosynthesized by direct anodic oxidation at a constant potential in acetonitrile on a platinium electrode. This oligomer (OMPA) showed a good solubility in common organic solvents. The results of osmometry and gel permeation chromatography analyzes indicated that the average chain length for OMPA was about 5 units. Its chemical structure was elucidated by 1H and 13C NMR, FTIR and UV spectroscopy. A thermal study carried out by thermogravimetric analysis and Differential Scanning Calorimetry showed that the oligomer was stable up to 268 °C. In addition, the photoluminescent properties of OMPA were investigated. In solution, an emission was recorded in the indigo-blue region, however, in solid state this emission was shifted to the orange-red zone. Finally a mechanism for the electro-oligomerization was evoked in the light of the electronic structures of the MPA and its radical cation obtained by DFT calculation.

  2. Copper(I) halide adducts with acetonitrile: an infrared and Raman investigation

    NASA Astrophysics Data System (ADS)

    Zarembowitch, J.; Maleki, R.

    Infrared (4000-200 cm -1) and Raman (4000-15 cm -1) spectra are reported for polycrystalline samples of aN . CuCl and aN . CuBr (aN = acetonitrile). Comparison with the spectral data obtained for liquid acetonitrile leads to a thorough assignment of the bands. The frequency shifts of the stretching modes νCN, νCCN and νCH upon coordination is discussed. The loosening observed for the CH bonds and the fact that the νCN frequency increases only slightly (20 cm -1) upon coordination are accounted for by the existence of a significant π back-bonding from copper(I) to nitrogen. The stretching fundamentals νCuN and νCuX can be identified unambiguously.

  3. The lipophilicity of artificial and natural sweeteners estimated by reversed-phase thin-layer chromatography and computed by various methods.

    PubMed

    Briciu, Rodica Domnica; Kot-Wasik, Agata; Wasik, Andrzej; Namieśnik, Jacek; Sârbu, Costel

    2010-06-01

    The chromatographic behavior of some artificial and natural sweeteners was established by reverse phase high performance thin-layer chromatography (RP-HPTLC) on RP-18, RP-18W, RP-8, CN and NH(2) stationary phases. The mobile phases were mixtures of acetonitrile-water in different proportions of volume, chosen to create a suitable migration during the chromatographic process. The lipophilicity was described through different chromatographic descriptors such as R(M0), mean of R(M) (mR(M)), and scores of R(M) values corresponding to the first principal component (PC1/R(M)). In addition, scores and loadings resulting from covariance matrix of retention data enable new information about similarity and differences of investigated compounds and between both the stationary and mobile phases. The experimental lipophilicity indices estimated from retention data are directly correlated with the computed values, via computer software and internet module, at a high significant statistical level. PMID:20430396

  4. Copper-mediated direct C2-cyanation of indoles using acetonitrile as the cyanide source.

    PubMed

    Pan, Changduo; Jin, Hongming; Xu, Pan; Liu, Xu; Cheng, Yixiang; Zhu, Chengjian

    2013-09-20

    A copper-mediated C2-cyanation of indoles using cheap and commercially available acetonitrile as the "nonmetallic" cyanide source was achieved through sequential C-C and C-H bond cleavages. The installation of a removable pyrimidyl group on the indole nitrogen atom is the key for this C2 selectivity. This approach provides a novel and alternative route leading to indole-2-carbonitrile. PMID:23957858

  5. Photochemistry of rose bengal in water and acetonitrile: a comprehensive kinetic analysis.

    PubMed

    Ludvíková, Lucie; Friš, Pavel; Heger, Dominik; Šebej, Peter; Wirz, Jakob; Klán, Petr

    2016-06-28

    The photophysical and photochemical properties of rose bengal (RB) in degassed aqueous and acetonitrile solutions were studied using steady-state and transient absorption spectroscopies. This comprehensive investigation provides detailed information about the kinetics and the optical properties of all intermediates involved: the triplet excited state and the oxidized and reduced forms of RB. A full kinetic description is used to control the concentrations of these intermediates by changing the initial experimental conditions. PMID:27253480

  6. Advantages of the AlGaN spacer in InAlN high-electron-mobility transistors grown using metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Yamada, Atsushi; Ishiguro, Tetsuro; Kotani, Junji; Tomabechi, Shuichi; Nakamura, Norikazu; Watanabe, Keiji

    2016-05-01

    We demonstrate the advantages of an AlGaN spacer layer in an InAlN high-electron-mobility transistor (HEMT). We investigated the effects of the growth parameters of the spacer layer on electron mobility in InAlN HEMTs grown by metalorganic vapor phase epitaxy, focusing on the surface roughness of the spacer layer and sharpness of the interface with the GaN channel layer. The electron mobility degraded, as evidenced by the formation of a graded AlGaN layer at the top of the GaN channel layer and the surface roughness of the AlN spacer layer. We believe that the short migration length of aluminum atoms is responsible for the observed degradation. An AlGaN spacer layer was employed to suppress the formation of the graded AlGaN layer and improve surface morphology. A high electron mobility of 1550 cm2 V‑1 s‑1 and a low sheet resistance of 211 Ω/sq were achieved for an InAlN HEMT with an AlGaN spacer layer.

  7. Accessing structure and dynamics of mobile phase in organic solids by real-time T1C filter PISEMA NMR spectroscopy.

    PubMed

    Zhang, Rongchun; Chen, Yuzhu; Chen, Tiehong; Sun, Pingchuan; Li, Baohui; Ding, Datong

    2012-01-26

    The structure and dynamic behavior of mobile components play a significant role in determining properties of solid materials. Herein, we propose a novel real-time spectrum-editing method to extract signals of mobile components in organic solids on the basis of the polarization inversion spin exchange at magic angle (PISEMA) pulse sequence and the difference in (13)C T(1) values of rigid and mobile components. From the dipolar splitting spectrum sliced along the heteronuclear dipolar coupling dimension of the 2D spectrum, the structural and dynamic information can be obtained, such as the distances between atoms, the dipolar coupling strength, the order parameter of the polymer backbone chain, and so on. Furthermore, our proposed method can be used to achieve the separation of overlapped NMR signals of mobile and rigid phases in the PISEMA experiment. The high efficacy of this 2D NMR method is demonstrated on organic solids, including crystalline L-alanine, semicrystalline polyamide-6, and the natural abundant silk fibroin. PMID:22185485

  8. Simulation of elution profiles in liquid chromatography-I: Gradient elution conditions, and with mismatched injection and mobile phase solvents.

    PubMed

    Jeong, Lena N; Sajulga, Ray; Forte, Steven G; Stoll, Dwight R; Rutan, Sarah C

    2016-07-29

    High-performance liquid chromatography (HPLC) simulators are effective method development tools. The goal of the present work was to design and implement a simple algorithm for simulation of liquid chromatographic separations that allows for characterization of the effect of injection solvent mismatch and injection solvent volume overload. The simulations yield full analyte profiles during solute migration and at elution, which enable a thorough physical understanding of the effects of method variables on chromatographic performance. The Craig counter-current distribution model (the plate model) is used as the basis for simulation, where a local retention factor is assigned for each spatial and temporal element within the simulation. The algorithm, which is an adaptation of an approach originally described by Czok and Guiochon (Ref. [10]), is sufficiently flexible to allow the use of either linear (e.g., Linear Solvent Strength Theory) or non-linear models of solute retention (e.g., Neue-Kuss (Ref. [36])). In this study, both types of models were used, one for simulating separations of a homologous series of alkylbenzenes, and the other for separations of selected amphetamines. The simulation program was validated first by comparison of simulated retention times and peak widths for five amphetamines to predictions obtained using linear solvent strength (LSS) theory, and to results from experimental separations of these compounds. The simulated retention times for the amphetamines agreed within 0.02% and 2.5% compared to theory and experiment, respectively. Secondly, the program was evaluated for simulating the case where there is a compositional mismatch between the mobile phase at the column inlet and the injection solvent (i.e., the sample matrix). This work involved alkylbenzenes, and retention time and peak width predictions from simulations were within 1.5 and 6.0% of experimental values, respectively, even without correction for extra-column dispersion. The

  9. Complex formation of Am(III) and Am(IV) with phosphate ions in acetonitrile solutions

    SciTech Connect

    Perevalov, S.A.; Lebedev, I.A.; Myasoedov, B.F.

    1988-05-01

    The first dissociation constant of H/sub 3/PO/sub 4/ in acetonitrile solution (K/sub 1//sup 0/ = 1.75/centered dot/10/sup /minus/13/) and the constant of formation of H(H/sub 2/PO/sub 4/)/sub 2//sup /minus// dimers (K/sub d//sup 0/ = 8/centered dot/10/sup 2/) were determined by the method of pH-potentiometry. The complex formation of Am(III) in acetonitrile solutions containing 0.05-2.0 M H/sub 3/PO/sub 4/ was investigated by a spectrophotometric method; the stability constants of the complexes AmH/sub 2/PO/sub 4//sup 2+/ (/beta//sub 1//sup III/ = 1.0/centered dot/10/sup 12/) and Am(H/sub 2/PO/sub 4/)/sub 2//sup +/ (/beta//sub 2//sup III/ = 4.3/centered dot/10/sup 24/) were determined. The formal potentials of the couple Am/sup (IV)//Am/sup (III)/ in 0.3-1.9 M solutions of H/sub 3/PO/sub 4/ in acetonitrile were measured, and the stability constant of the phosphate complex of tetravalent americium Am(H/sub 2/PO/sub 4/)/sub 3//sup +/ (/beta//sub 3//sup IV/ = 2.5/centered dot/10/sup 46/) was calculated according to the value of the shift of the potential relative to the standard.

  10. Understanding the importance of the viscosity contrast between the sample solvent plug and the mobile phase and its potential consequences in two-dimensional high-performance liquid chromatography

    SciTech Connect

    Shalliker, R. Andrew; Guiochon, Georges A

    2009-01-01

    The effect of solvent viscosity mismatch on elution performance in reversed-phase HPLC was studied using moment analysis. Two conditions were tested: (1) the mobile phase viscosity was less than the injection plug viscosity, and (2) the mobile phase viscosity was greater than the injection plug viscosity. Under the first condition, retention time and elution performance decreased as the viscosity contrast between the mobile phase and injection plug increased. The effect on performance was more marked as the injection volume increased. A decrease in performance of 12% for compounds with retention factors up to 2.8 was apparent even when the viscosity contrast was only 0.165 cP. In the second set of conditions, elution performance was actually observed to increase, by as much as 25% for a 40 {micro}L injection, as the viscosity contrast between the mobile phase and the solute plug increased. No change in the retention factor was observed. This behaviour was attributed to the shape of an injection plug as it enters into the column, whereby a low viscosity plug permeates away from the wall when the column contains a higher viscosity mobile phase, and vice a versa for a high viscosity plug entering a low viscosity mobile phase. At no stage was either a band splitting or shoulders observed with viscosity contrasts up to 1.283 cP, as could have been expected.

  11. Liquid phase separation of proteins based on electrophoretic effects in an electrospray setup during sample introduction into a gas-phase electrophoretic mobility molecular analyzer (CE–GEMMA/CE–ES–DMA)

    PubMed Central

    Weiss, Victor U.; Kerul, Lukas; Kallinger, Peter; Szymanski, Wladyslaw W.; Marchetti-Deschmann, Martina; Allmaier, Günter

    2014-01-01

    Nanoparticle characterization is gaining importance in food technology, biotechnology, medicine, and pharmaceutical industry. An instrument to determine particle electrophoretic mobility (EM) diameters in the single-digit to double-digit nanometer range receiving increased attention is the gas-phase electrophoretic mobility molecular analyzer (GEMMA) separating electrophoretically single charged analytes in the gas-phase at ambient pressure. A fused-silica capillary is used for analyte transfer to the gas-phase by means of a nano electrospray (ES) unit. The potential of this capillary to separate analytes electrophoretically in the liquid phase due to different mobilities is, at measurement conditions recommended by the manufacturer, eliminated due to elevated pressure applied for sample introduction. Measurements are carried out upon constant feeding of analytes to the system. Under these conditions, aggregate formation is observed for samples including high amounts of non-volatile components or complex samples. This makes the EM determination of individual species sometimes difficult, if not impossible. With the current study we demonstrate that liquid phase electrophoretic separation of proteins (as exemplary analytes) occurs in the capillary (capillary zone electrophoresis, CE) of the nano ES unit of the GEMMA. This finding was consecutively applied for on-line desalting allowing EM diameter determination of analytes despite a high salt concentration within samples. The present study is to our knowledge the first report on the use of the GEMMA to determine EM diameters of analytes solubilized in the ES incompatible electrolyte solutions by the intended use of electrophoresis (in the liquid phase) during sample delivery. Results demonstrate the proof of concept of such an approach and additionally illustrate the high potential of a future on-line coupling of a capillary electrophoresis to a GEMMA instrument. PMID:25109866

  12. The hydrophilicity vs. ion interaction selectivity plot revisited: The effect of mobile phase pH and buffer concentration on hydrophilic interaction liquid chromatography selectivity behavior.

    PubMed

    Iverson, Chad D; Gu, Xinyun; Lucy, Charles A

    2016-08-01

    This work systematically investigates the selectivity changes on many HILIC phases from w(w)pH 3.7-6.8, at 5 and 25mM buffer concentrations. Hydrophilicity (kcytosine/kuracil) vs. ion interaction (kBTMA/kuracil) selectivity plots developed by Ibrahim et al. (J. Chromatogr. A 1260 (2012) 126-131) are used to investigate the effect of mobile phase changes on the selectivity of 18 HILIC columns from various classes. "Selectivity change plots" focus on the change in hydrophilicity and ion interaction that the columns exhibit upon changing mobile phase conditions. In general, the selectivity behavior of most HILIC columns is dominated by silanol activity. Minimal changes in selectivity are observed upon changing pH between w(w)pH 5 and 6.8. However, a reduction in ionic interaction is observed when the buffer concentration is increased at w(w)pH≥5.0 due to ionic shielding. Reduction of the w(w)pH to<5.0 results in decreasing cation exchange activity due to silanol protonation. Under all eluent conditions, the majority of phases show little change in their hydrophilicity. PMID:27388658

  13. Comparison of methanol and acetonitrile eluents for the quantitation of chelators specific to soft-metal ions by HPLC.

    PubMed

    Ogawa, Shinya; Yoshimura, Etsuro

    2012-11-15

    HPLC eluent systems employing acetonitrile and methanol were evaluated for the quantitation of glutathione (GSH) and phytochelatin (PC(n)), a family of peptides implicated in heavy-metal detoxification in higher plants. The detection system is based on the dequenching of copper(I)-bathocuproine disulfonate and is specific for soft-metal chelators. Although both elution systems yielded comparable analytical performance for each PC(n), the acetonitrile system had a lower sensitivity for GSH and a steadily increasing baseline. The inferior properties of the acetonitrile system may be due to complex formation between acetonitrile and Cu(I) ions. Both methods were applied to measure peptide levels in the primitive red alga Cyanidioschyzon merolae. Coefficients of variation (CVs) were less than 5%, except for GSH and PC(4) determinations in the acetonitrile system, in cases when CV values were found to be 8.8% and 6.3%, respectively. Recoveries were greater than 96%, except for GSH determination in the acetonitrile system, with a recovery of 84.4%; however, the concentration measured in the acetonitrile system did not differ from that measured in the methanol system at a significance level of 0.05. PMID:23153641

  14. Convenient treatment of acetonitrile-containing wastes using the tandem combination of nitrile hydratase and amidase-producing microorganisms.

    PubMed

    Kohyama, Erina; Yoshimura, Akihiro; Aoshima, Daisuke; Yoshida, Toyokazu; Kawamoto, Hiroyoshi; Nagasawa, Toru

    2006-09-01

    This study aimed to construct an acetonitrile-containing waste treatment process by using nitrile-degrading microorganisms. To degrade high concentrations of acetonitrile, the microorganisms were newly acquired from soil and water samples. Although no nitrilase-producing microorganisms were found to be capable of degrading high concentrations of acetonitrile, the resting cells of Rhodococcus pyridinivorans S85-2 containing nitrile hydratase could degrade acetonitrile at concentrations as high as 6 M. In addition, an amidase-producing bacterium, Brevundimonas diminuta AM10-C-1, of which the resting cells degraded 6 M acetamide, was isolated. The combination of R. pyridinivorans S85-2 and B. diminuta AM10-C-1 was tested for the conversion of acetonitrile into acetic acid. The resting cells of B. diminuta AM10-C-1 were added after the first conversion involving R. pyridinivorans S85-2. Through this tandem process, 6 M acetonitrile was converted to acetic acid at a conversion rate of >90% in 10 h. This concise procedure will be suitable for practical use in the treatment of acetonitrile-containing wastes on-site. PMID:16402166

  15. Portable Solid Phase Micro-Extraction Coupled with Ion Mobility Spectrometry System for On-Site Analysis of Chemical Warfare Agents and Simulants in Water Samples

    PubMed Central

    Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

    2014-01-01

    On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples. PMID:25384006

  16. Portable solid phase micro-extraction coupled with ion mobility spectrometry system for on-site analysis of chemical warfare agents and simulants in water samples.

    PubMed

    Yang, Liu; Han, Qiang; Cao, Shuya; Yang, Jie; Yang, Junchao; Ding, Mingyu

    2014-01-01

    On-site analysis is an efficient approach to facilitate analysis at the location of the system under investigation as it can result in more accurate, more precise and quickly available analytical data. In our work, a novel self-made thermal desorption based interface was fabricated to couple solid-phase microextraction with ion mobility spectrometry for on-site water analysis. The portable interface can be connected with the front-end of an ion mobility spectrometer directly without other modifications. The analytical performance was evaluated via the extraction of chemical warfare agents and simulants in water samples. Several parameters including ionic strength and extraction time have been investigated in detail. The application of the developed method afforded satisfactory recoveries ranging from 72.9% to 114.4% when applied to the analysis of real water samples. PMID:25384006

  17. Structure of aldehyde cluster ions in the gas phase, according to data from ion mobility spectrometry and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Lantsuzskaya (Krisilova), E. V.; Krisilov, A. V.; Levina, A. M.

    2015-09-01

    Ion-mobility spectra of a set of aliphatic linear aldehydes with the number of carbon atoms from 3 to 7 are obtained. Values of the mobility corresponding to two most intense peaks, considered to be those of a monomer and dimer, are determined according the spectra. Based on mobility, collision cross sections are calculated using the Mason-Schamp equation. The linear increase in the collision cross sections upon an increase in molecular weight is determined. According to the experimental results, the contribution to the cross section that has no dependence on molecular weight diminishes with the formation of dimers. It is established using quantum chemical calculations that this is associated with a reduction in the dipole moment upon the formation of dimers.

  18. Electronic structure calculations of mercury mobilization from mineral phases and photocatalytic removal from water and the atmosphere.

    PubMed

    Da Pieve, Fabiana; Stankowski, Martin; Hogan, Conor

    2014-09-15

    Mercury is a hazardous environmental pollutant mobilized from natural sources, and anthropogenically contaminated and disturbed areas. Current methods to assess mobility and environmental impact are mainly based on field measurements, soil monitoring, and kinetic modelling. In order to understand in detail the extent to which different mineral sources can give rise to mercury release it is necessary to investigate the complexity at the microscopic level and the possible degradation/dissolution processes. In this work, we investigated the potential for mobilization of mercury structurally trapped in three relevant minerals occurring in hot spring environments and mining areas, namely, cinnabar (α-HgS), corderoite (α-Hg3S2Cl2), and mercuric chloride (HgCl2). Quantum chemical methods based on density functional theory as well as more sophisticated approaches are used to assess the possibility of a) direct photoreduction and formation of elemental Hg at the surface of the minerals, providing a path for ready release in the environment; and b) reductive dissolution of the minerals in the presence of solutions containing halogens. Furthermore, we study the use of TiO2 as a potential photocatalyst for decontamination of polluted waters (mainly Hg(2+)-containing species) and air (atmospheric Hg(0)). Our results partially explain the observed pathways of Hg mobilization from relevant minerals and the microscopic mechanisms behind photocatalytic removal of Hg-based pollutants. Possible sources of disagreement with observations are discussed and further improvements to our approach are suggested. PMID:24982025

  19. 78 FR 56875 - Tribal Mobility Fund Phase I Auction Rescheduled for December 19, 2013; Notice and Filing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-16

    ... service support through reverse competitive bidding. The USF/ICC Transformation Order, 76 FR 73830, November 29, 2011 and 76 FR 81562, December 28, 2011, established the Mobility Fund as a universal service... program details. On March 29, 2013, the Bureaus released the Auction 902 Comment Public Notice, 78...

  20. Socio-Technical Dimensions of an Outdoor Mobile Learning Environment: A Three-Phase Design-Based Research Investigation

    ERIC Educational Resources Information Center

    Land, Susan M.; Zimmerman, Heather Toomey

    2015-01-01

    This design-based research project examines three iterations of Tree Investigators, a learning environment designed to support science learning outdoors at an arboretum and nature center using mobile devices (iPads). Researchers coded videorecords and artifacts created by children and parents (n = 53) to understand how both social and…

  1. Semiconducting tin and lead iodide perovskites with organic cations: phase transitions, high mobilities, and near-infrared photoluminescent properties.

    PubMed

    Stoumpos, Constantinos C; Malliakas, Christos D; Kanatzidis, Mercouri G

    2013-08-01

    A broad organic-inorganic series of hybrid metal iodide perovskites with the general formulation AMI3, where A is the methylammonium (CH3NH3(+)) or formamidinium (HC(NH2)2(+)) cation and M is Sn (1 and 2) or Pb (3 and 4) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of 1-4 classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100-400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that 1-4 behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25-1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700-1000 nm range (1.1-1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH3NH3Sn(1-x)Pb(x)I3 (5). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as p- or n-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are n-type; p

  2. Immobilization of Rhodococcus rhodochrous BX2 (an acetonitrile-degrading bacterium) with biofilm-forming bacteria for wastewater treatment.

    PubMed

    Li, Chunyan; Li, Yue; Cheng, Xiaosong; Feng, Liping; Xi, Chuanwu; Zhang, Ying

    2013-03-01

    In this study, a unique biofilm consisting of three bacterial strains with high biofilm-forming capability (Bacillus subtilis E2, E3, and N4) and an acetonitrile-degrading bacterium (Rhodococcus rhodochrous BX2) was established for acetonitrile-containing wastewater treatment. The results indicated that this biofilm exhibited strong resistance to acetonitrile loading shock and displayed a typical spatial and structural heterogeneity and completely depleted the initial concentration of acetonitrile (800mgL(-1)) within 24h in a moving-bed-biofilm reactor (MBBR) after operation for 30days. The immobilization of BX2 cells in the biofilm was confirmed by PCR-DGGE. It has been demonstrated that biofilm-forming bacteria can promote the immobilization of contaminant-degrading bacteria in the biofilms and can subsequently improve the degradation of contaminants in wastewater. This approach offers a novel strategy for enhancing biological oxidation of toxic pollutants in wastewater. PMID:23376196

  3. Spectroscopic studies and molecular orbital calculations of charge transfer complexation between 3,5-dimethylpyrazole with DDQ in acetonitrile

    NASA Astrophysics Data System (ADS)

    Habeeb, Moustafa M.; Al-Attas, Amirah S.; Al-Raimi, Doaa S.

    2015-05-01

    Charge transfer (CT) interaction between 3,5-dimethylpyrazole (DMP) with the π-acceptor 2,3-dichloro-5,6-dicyano-p-benzoquinon (DDQ) has been investigated spectrophotometrically in acetonitrile (AN). Simultaneous reddish brown color has been observed upon mixing donor with acceptor solutions attributing to CT complex formation. The electronic spectra of the formed complex exhibited multi-charge transfer bands at 429, 447, 506, 542 and 589 nm, respectively. Job's method of continuous variations and spectrophotometric titration methods confirmed the formation of the studied complex in 1:2 ratio between DMP and DDQ. Benesi-Hildebrand equation has been applied to calculate the stability constant of the formed complex where it recorded high value supporting formation of stable complex. Molecular orbital calculations using MM2 method and GAMESS (General Atomic and Molecular Electronic Structure System) interface computations as a package of ChemBio3D Ultra12 software were carried out for more analysis of the formed complex in the gas phase. The computational analysis included energy minimisation, stabilisation energy, molecular geometry, Mullikan charges, molecular electrostatic potential (MEP) surfaces of reactants and complex as well as characterization of the higher occupied molecular orbitals (HOMO) and lower unoccupied molecular orbitals (LUMO) surfaces of the complex. A good consistency between experimental and theoretical results has been recorded.

  4. Determination of individual homologues and total content of benzalkonium chloride by reversed-phase high-performance liquid chromatography using a short butyl column.

    PubMed

    Liu, Fangzhu; Xiao, Kang Ping; Rustum, Abu M

    2009-01-01

    Benzalkonium chloride (a mixture of alkylbenzyldimethylammonium chlorides that usually contains C-10, C-12, C-14, and C-16 homologues), commonly known as BKC, is used as a bacteriostatic agent in many household, food, and drug products. In this paper, we report a simple, rapid, robust, and stability-indicating reversed-phase HPLC method using a short butyl (C4) column for the simultaneous determination of each individual homologue content, as well as the total concentration of individual homologues in commercial bulk raw material batches of BKC samples. The chromatographic separation was performed on a 5 cm ACE C4 column with mobile phase consisting of water, acetonitrile, and potassium chloride. Even though using a short column can potentially cause some challenges to resolving certain critical pairs of peaks, we have successfully separated all of the analyte peaks (including those from stressed, degraded products) on a short column using an optimal mobile phase. PMID:20166581

  5. Aminoglycoside analysis in food of animal origin with a zwitterionic stationary phase and liquid chromatography-tandem mass spectrometry.

    PubMed

    Díez, Cristina; Guillarme, Davy; Staub Spörri, Aline; Cognard, Emmanuelle; Ortelli, Didier; Edder, Patrick; Rudaz, Serge

    2015-07-01

    In this study, fourteen highly polar aminoglycoside (AGs) antibiotics were selected. Various stationary phases were tested, including Obelisc R, ZIC-HILIC, BEH amide and aminopropyl. The nature of the stationary phase, mobile phase (water or buffer solutions and acetonitrile), pH (percentage of formic acid), gradient conditions and injection solvents were systematically studied as relevant parameters for tuning retention selectivity and detectability of AGs in liquid chromatography electrospray tandem mass spectrometry (LC-(ESI)-MS/MS). Only the two zwitterionic phases (Obelisc R and ZIC-HILIC) achieved a proper chromatographic separation considering interferences due to the crosstalk effect in low resolution mass spectrometers. The water/acetonitrile mobile phase containing 1% formic acid used with Obelisc R provided more sensitivity than the highly concentrated buffered mobile phases required for ZIC-HILIC. A solid phase extraction (SPE) clean-up procedure with polymeric weak cation exchange (WCX) cartridges was optimized for honey, milk and liver samples. Different brands of cartridges and elution solvents were tested, and the Taurus WCX offered the best recovery rate with a buffer elution at pH 3. The final optimized method was validated in these matrices according to Decision 2002/657/EC. A monitoring campaign for sixty honey, milk and liver samples was carried out at the Food Authority Control in Geneva. The concentration of dihydrostreptomycin (DSTP) found in one ovine liver exceeded the established maximum residue levels (MRLs) within the European and Swiss legislations but it was compliant taking into account the validation data. PMID:26043099

  6. Strategies for the Hyperpolarization of Acetonitrile and Related Ligands by SABRE

    PubMed Central

    2014-01-01

    We report on a strategy for using SABRE (signal amplification by reversible exchange) for polarizing 1H and 13C nuclei of weakly interacting ligands which possess biologically relevant and nonaromatic motifs. We first demonstrate this via the polarization of acetonitrile, using Ir(IMes)(COD)Cl as the catalyst precursor, and confirm that the route to hyperpolarization transfer is via the J-coupling network. We extend this work to the polarization of propionitrile, benzylnitrile, benzonitrile, and trans-3-hexenedinitrile in order to assess its generality. In the 1H NMR spectrum, the signal for acetonitrile is enhanced 8-fold over its thermal counterpart when [Ir(H)2(IMes)(MeCN)3]+ is the catalyst. Upon addition of pyridine or pyridine-d5, the active catalyst changes to [Ir(H)2(IMes)(py)2(MeCN)]+ and the resulting acetonitrile 1H signal enhancement increases to 20- and 60-fold, respectively. In 13C NMR studies, polarization transfers optimally to the quaternary 13C nucleus of MeCN while the methyl 13C is hardly polarized. Transfer to 13C is shown to occur first via the 1H–1H coupling between the hydrides and the methyl protons and then via either the 2J or 1J couplings to the respective 13Cs, of which the 2J route is more efficient. These experimental results are rationalized through a theoretical treatment which shows excellent agreement with experiment. In the case of MeCN, longitudinal two-spin orders between pairs of 1H nuclei in the three-spin methyl group are created. Two-spin order states, between the 1H and 13C nuclei, are also created, and their existence is confirmed for Me13CN in both the 1H and 13C NMR spectra using the Only Parahydrogen Spectroscopy protocol. PMID:25539423

  7. Acetonitrile and N-Chloroacetamide Formation from the Reaction of Acetaldehyde and Monochloramine.

    PubMed

    Kimura, Susana Y; Vu, Trang Nha; Komaki, Yukako; Plewa, Michael J; Mariñas, Benito J

    2015-08-18

    Nitriles and amides are two classes of nitrogenous disinfection byproducts (DBPs) associated with chloramination that are more cytotoxic and genotoxic than regulated DBPs. Monochloramine reacts with acetaldehyde, a common ozone and free chlorine disinfection byproduct, to form 1-(chloroamino)ethanol. Equilibrium (K1) and forward and reverse rate (k1,k-1) constants for the reaction between initial reactants and 1-(chloroamino)ethanol were determined between 2 and 30 °C. Activation energies for k1 and k-1 were 3.04 and 45.2 kJ·mol(-1), respectively, and enthalpy change for K1 was -42.1 kJ·mol(-1). In parallel reactions, 1-(chloroamino)ethanol (1) slowly dehydrated (k2) to (chloroimino)ethane that further decomposed to acetonitrile and (2) was oxidized (k3) by monochloramine to produce N-chloroacetamide. Both reactions were acid/base catalyzed, and rate constants were characterized at 10, 18, and 25 °C. Modeling for drinking water distribution system conditions showed that N-chloroacetamide and acetonitrile concentrations were 5-9 times higher at pH 9.0 compared to 7.8. Furthermore, acetonitrile concentration was found to form 7-10 times higher than N-chloroacetamide under typical monochloramine and acetaldehyde concentrations. N-chloroacetamide cytotoxicity (LC50 = 1.78 × 10(-3) M) was comparable to dichloroacetamide and trichloroacetamide, but less potent than N,2-dichloroacetamide and chloroacetamide. While N-chloroacetamide was not found to be genotoxic, N,2-dichloroacetamide genotoxic potency (5.19 × 10(-3) M) was on the same order of magnitude as chloroacetamide and trichloroacetamide. PMID:26167888

  8. Tropospheric light alcohols, carbonyls, and acetonitrile: Concentrations in the southwestern United States and Henry's Law data

    NASA Astrophysics Data System (ADS)

    Snider, Jefferson R.; Dawson, G. A.

    1985-04-01

    Aliphatic alcohols (C1 - C4), aldehydes (C1 - C2) and ketones (C3 - C4) have been determined at Tucson, Arizona, and at two rural sites about 40 km distant. Acetonitrile was also measured at the rural sites. The method involved condensation sampling, condensate preconcentration, and gas chromatography. Henry's law coefficients were required for all components and were determined. Mean concentrations in Tucson were higher than those in the rural areas by factors typically between 2 and 8; urban formaldehyde was only slightly elevated. Mean alcohol concentrations ranged from 7.9 ppb (C1) to 0.12 ppb (C4) within the city and from 2.6 ppb (C1) to 0.06 ppb (C4) at the rural sites. Acetone was found at 12 ppb in the city and 2.8 ppb at the rural sites. Concentrations of butanone were a factor of 5 lower. Acetaldehyde, at 23 ppb (city) and 6.9 ppb (rural), far exceeded formaldehyde concentrations (1.8 ppb in the city, and 1.5 ppb at the rural sites). Acetonitrile was found at the rural sites at a mean concentration of 60 ppt. A dimensionless Henry's law coefficient (mol L-1 of liquid/mol L-1 of vapor) was suprisingly similar for the alcohols at 0°C, ranging between 2×104 and 3.4×104 (900-1500 mol L-1 atm-1) the ketones were a factor of 10 lower. For acetaldehyde the coefficient was 1.7×103 (76 mol L-1 atm-1) and for acetonitrile 3.7×103 (165 mol L-1 atm-1). Concentrations of oxygenated organics in the condensates and in precipitation were compared; it was tentatively concluded that concentration differences of the carbonyls were consistent with these species being produced within the cloud, for example, by aqueous photochemistry.

  9. Ion Mobility-Mass Spectrometry Analysis of Cross-Linked Intact Multiprotein Complexes: Enhanced Gas-Phase Stabilities and Altered Dissociation Pathways.

    PubMed

    Samulak, Billy M; Niu, Shuai; Andrews, Philip C; Ruotolo, Brandon T

    2016-05-17

    Analysis of protein complexes by ion mobility-mass spectrometry is a valuable method for the rapid assessment of complex composition, binding stoichiometries, and structures. However, capturing labile, unknown protein assemblies directly from cells remains a challenge for the technology. Furthermore, ion mobility-mass spectrometry measurements of complexes, subcomplexes, and subunits are necessary to build complete models of intact assemblies, and such data can be difficult to acquire in a comprehensive fashion. Here, we present the use of novel mass spectrometry cleavable cross-linkers and tags to stabilize intact protein complexes for ion mobility-mass spectrometry. Our data reveal that tags and linkers bearing permanent charges are superior stabilizers relative to neutral cross-linkers, especially in the context of retaining compact forms of the assembly under a wide array of activating conditions. In addition, when cross-linked protein complexes are collisionally activated in the gas phase, a larger proportion of the product ions produced are often more compact and reflect native protein subcomplexes when compared with unmodified complexes activated in the same fashion, greatly enabling applications in structural biology. PMID:27078797

  10. Modelling the transition between fixed and mobile bed conditions in two-phase free-surface flows: The Composite Riemann Problem and its numerical solution

    NASA Astrophysics Data System (ADS)

    Rosatti, Giorgio; Zugliani, Daniel

    2015-03-01

    In a two-phase free-surface flow, the transition from a mobile-bed condition to a fixed-bed one (and vice versa) occurs at a sharp interface across which the relevant system of partial differential equations changes abruptly. This leads to the possibility of conceiving a new type of Riemann Problem (RP), which we have called Composite Riemann Problem (CRP), where not only the initial constant values of the variables but also the system of equations change from left to right of a discontinuity. In this paper, we present a strategy for solving a CRP by reducing it to a standard RP of a single, composite system of equations. This can be obtained by combining the two original systems by means of a suitable weighting function, namely the erodibility variable, and the introduction of an appropriate differential equation for this quantity. In this way, the CRP problem can be analyzed theoretically with standard methods, and the features of the solutions can be clearly identified. In particular, a stationary contact wave is able to correctly describe the sharp transition between mobile- and fixed-bed conditions. A finite volume scheme based on the Multiple Averages Generalized Roe approach (Rosatti and Begnudelli (2013) [22]) was used to numerically solve the fixed-mobile CRP. Several test cases demonstrate the effectiveness, exact well balanceness and high accuracy of the scheme when applied to problems that fall within the physical range of applicability of the relevant mathematical model.

  11. Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: A new luminescent uranyl benzoate specie

    NASA Astrophysics Data System (ADS)

    Kumar, Satendra; Maji, S.; Joseph, M.; Sankaran, K.

    2015-03-01

    Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3]- which is highly luminescent. In particular, three sharp bands at 431, 443, 461 nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68 μs which is much more compared to the lifetime of uncomplexed uranyl (20 μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3]- specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed.

  12. Ligand sensitized luminescence of uranyl by benzoic acid in acetonitrile medium: a new luminescent uranyl benzoate specie.

    PubMed

    Kumar, Satendra; Maji, S; Joseph, M; Sankaran, K

    2015-03-01

    Benzoic acid (BA) is shown to sensitize and enhance the luminescence of uranyl ion in acetonitrile medium. Luminescence spectra and especially UV-Vis spectroscopy studies reveal the formation of tri benzoate complex of uranyl i.e. [UO2(C6H5COO)3](-) which is highly luminescent. In particular, three sharp bands at 431, 443, 461nm of absorption spectra provides evidence for tri benzoate specie of uranyl in acetonitrile medium. The luminescence lifetime of uranyl in this complex is 68μs which is much more compared to the lifetime of uncomplexed uranyl (20μs) in acetonitrile medium. In contrary to aqueous medium where uranyl benzoate forms 1:1 and 1:2 species, spectroscopic data reveal formation of 1:3 complex in acetonitrile medium. Addition of water to acetonitrile results in decrease of luminescence intensity of this specie and the luminescence features implode at 20% (v/v) of water content. For the first time, to the best of our knowledge, the existence of [UO2(C6H5COO)3](-) specie in acetonitrile is reported. Mechanism of luminescence enhancement is discussed. PMID:25528510

  13. Density Functional Studies on the Complexation and Spectroscopy of Uranyl Ligated with Acetonitrile and Acetone Derivatives

    SciTech Connect

    Schoendorff, George E.; Windus, Theresa L.; De Jong, Wibe A.

    2009-12-12

    The coordination of nitrile (acetonitrile, propionitrile, and benzonitrile) and carbonyl (formaldehyde, ethanal, and acetone) ligands to the uranyl dication (UO22+) has been examined using density functional theory (DFT) utilizing relativistic effective core potentials (RECPs). Complexes containing up to six ligands have been modeled for all ligands except formaldehyde, for which no minimum could be found. A comparison of relative binding energies indicates that five coordinate complexes are predominant while a six coordinate complex involving propionitrile ligands might be possible. Additionally, the relative binding energy and the weakening of the uranyl bond is related to the size of the ligand and, in general, nitriles bind more strongly to uranyl than carbonyls.

  14. Elemental step thermodynamics of various analogues of indazolium alkaloids to obtaining hydride in acetonitrile.

    PubMed

    Lei, Nan-Ping; Fu, Yan-Hua; Zhu, Xiao-Qing

    2015-12-21

    A series of analogues of indazolium alkaloids were designed and synthesized. The thermodynamic driving forces of the 6 elemental steps for the analogues of indazolium alkaloids to obtain hydride in acetonitrile were determined using an isothermal titration calorimeter (ITC) and electrochemical methods, respectively. The effects of molecular structure and substituents on the thermodynamic driving forces of the 6 steps were examined. Meanwhile, the oxidation mechanism of NADH coenzyme by indazolium alkaloids was examined using the chemical mimic method. The result shows that the oxidation of NADH coenzyme by indazolium alkaloids in vivo takes place by one-step concerted hydride transfer mechanism. PMID:26451708

  15. Possible stabilization of the tetravalent oxidation state of berkelium and californium in acetonitrile with triphenylarsine oxide

    SciTech Connect

    Payne, G.F.; Peterson, J.R.

    1987-01-01

    It appears that we may have prepared Bk(IV) nitrate.nTPAs0 and Bk(IV) perchlorate.nTPAs0 complexes which formed the corresponding Cf(IV) complexes through the beta decay of Bk-249. Definitive proof should come from similar experiments with quantities of Bk-249 large enough to allow spectrophotometric detection of the characteristic f..-->..f transitions in these berkelium and californium species. It is clear, however, that TPAs0 and acetonitrile can play a pivotal role in the stabilization of lanact(IV) species.

  16. Atmospheric pressure ionization and gas phase ion mobility studies of isomeric dihalogenated benzenes using different ionization techniques

    NASA Astrophysics Data System (ADS)

    Borsdorf, H.; Nazarov, E. G.; Eiceman, G. A.

    2004-03-01

    Ion mobility spectrometry (IMS) featuring different ionization techniques was used to analyze isomeric ortho-, meta- and para-dihalogenated benzenes in order to assess how structural features affect ion formation and drift behavior. The structure of the product ions formed was investigated by atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and IMS-MS coupling. Photoionization provided [M]+ ions for chlorinated and fluorinated compounds while bromine was cleaved from isomers of dibromobenzene and bromofluorobenzene. This ionization technique does not permit the different isomers to be distinguished. Comparable ions and additional clustered ions were obtained using 63Ni ionization. Depending on the chemical constitution, different clustered ions were observed in ion mobility spectra for the separate isomers of dichlorobenzene and dibromobenzene. Corona discharge ionization permits the most sensitive detection of dihalogenated compounds. Only clustered product ions were obtained. Corona discharge ionization enables the classification of different structural isomers of dichlorobenzene, dibromobenzene and bromofluorobenzene.

  17. Solid phase epitaxial growth of high mobility La:BaSnO3 thin films co-doped with interstitial hydrogen

    NASA Astrophysics Data System (ADS)

    Niedermeier, Christian A.; Rhode, Sneha; Fearn, Sarah; Ide, Keisuke; Moram, Michelle A.; Hiramatsu, Hidenori; Hosono, Hideo; Kamiya, Toshio

    2016-04-01

    This work presents the solid phase epitaxial growth of high mobility La:BaSnO3 thin films on SrTiO3 single crystal substrates by crystallization through thermal annealing of nanocrystalline thin films prepared by pulsed laser deposition at room temperature. The La:BaSnO3 thin films show high epitaxial quality and Hall mobilities up to 26 ± 1 cm2/Vs. Secondary ion mass spectroscopy is used to determine the La concentration profile in the La:BaSnO3 thin films, and a 9%-16% La doping activation efficiency is obtained. An investigation of H doping to BaSnO3 thin films is presented employing H plasma treatment at room temperature. Carrier concentrations in previously insulating BaSnO3 thin films were increased to 3 × 1019 cm-3 and in La:BaSnO3 thin films from 6 × 1019 cm-3 to 1.5 × 1020 cm-3, supporting a theoretical prediction that interstitial H serves as an excellent n-type dopant. An analysis of the free electron absorption by infrared spectroscopy yields a small (H,La):BaSnO3 electron effective mass of 0.27 ± 0.05 m0 and an optical mobility of 26 ± 7 cm2/Vs. As compared to La:BaSnO3 single crystals, the smaller electron mobility in epitaxial thin films grown on SrTiO3 substrates is ascribed to threading dislocations as observed in high resolution transmission electron micrographs.

  18. Characterizing the gas phase ion chemistry of an ion trap mobility spectrometry based explosive trace detector using a tandem mass spectrometer.

    PubMed

    Kozole, Joseph; Tomlinson-Phillips, Jill; Stairs, Jason R; Harper, Jason D; Lukow, Stefan R; Lareau, Richard T; Boudries, Hacene; Lai, Hanh; Brauer, Carolyn S

    2012-09-15

    A commercial-off-the-shelf (COTS) ion trap mobility spectrometry (ITMS) based explosive trace detector (ETD) has been interfaced to a triple quadrupole mass spectrometer (MS/MS) for the purpose of characterizing the gas phase ion chemistry intrinsic to the ITMS instrument. The overall objective of the research is to develop a fundamental understanding of the gas phase ionization processes in the ITMS based ETD to facilitate the advancement of its operational effectiveness as well as guide the development of next generation ETDs. Product ion masses, daughter ion masses, and reduced mobility values measured by the ITMS/MS/MS configuration for a suite of nitro, nitrate, and peroxide containing explosives are reported. Molecular formulas, molecular structures, and ionization pathways for the various product ions are inferred using the mass and mobility data in conjunction with density functional theory. The predominant product ions are identified as follows: [TNT-H](-) for trinitrotoluene (TNT), [RDX+Cl](-) for cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX), [NO(3)](-) for ethylene glycol dinitrate (EGDN), [NG+NO(3)](-) for nitroglycerine (NG), [PETN+NO(3)](-) for pentaerythritol tetranitrate (PETN), [HNO(3)+NO(3)](-) for ammonium nitrate (NH(4)NO(3)), [HMTD-NC(3)H(6)O(3)+H+Cl](-) for hexamethylene triperoxide diamine (HMTD), and [(CH(3))(2)CNH(2)](+) for triacetone triperoxide (TATP). The predominant ionization pathways for the formation of the various product ions are determined to include proton abstraction, ion-molecule attachment, autoionization, first-order and multi-order thermolysis, and nucleophilic substitution. The ion trapping scheme in the reaction region of the ITMS instrument is shown to increase predominant ion intensities relative to the secondary ion intensities when compared to non-ion trap operation. PMID:22967626

  19. Injury Risk Assessment of Extravehicular Mobility Unit (EMU) Phase VI and Series 4000 Gloves During Extravehicular Activity (EVA) Hand Manipulation Tasks

    NASA Technical Reports Server (NTRS)

    Kilby, Melissa

    2015-01-01

    Functional Extravehicular Mobility Units (EMUs) with high precision gloves are essential for the success of Extravehicular Activity (EVA). Previous research done at NASA has shown that total strength capabilities and performance are reduced when wearing a pressurized EMU. The goal of this project was to characterize the human-space suit glove interaction and assess the risk of injury during common EVA hand manipulation tasks, including pushing, pinching and gripping objects. A custom third generation sensor garment was designed to incorporate a combination of sensors, including force sensitive resistors, strain gauge sensors, and shear force sensors. The combination of sensors was used to measure the forces acting on the finger nails, finger pads, finger tips, as well as the knuckle joints. In addition to measuring the forces, data was collected on the temperature, humidity, skin conductance, and blood perfusion of the hands. Testing compared both the Phase VI and Series 4000 glove against an ungloved condition. The ungloved test was performed wearing the sensor garment only. The project outcomes identified critical landmarks that experienced higher workloads and are more likely to suffer injuries. These critical landmarks varied as a function of space suit glove and task performed. The results showed that less forces were acting on the hands while wearing the Phase VI glove as compared to wearing the Series 4000 glove. Based on our findings, the engineering division can utilize these methods for optimizing the current space suit glove and designing next generation gloves to prevent injuries and optimize hand mobility and comfort.

  20. Ultra high performance supercritical fluid chromatography coupled with tandem mass spectrometry for screening of doping agents. I: Investigation of mobile phase and MS conditions.

    PubMed

    Nováková, Lucie; Grand-Guillaume Perrenoud, Alexandre; Nicoli, Raul; Saugy, Martial; Veuthey, Jean-Luc; Guillarme, Davy

    2015-01-01

    The conditions for the analysis of selected doping substances by UHPSFC-MS/MS were optimized to ensure suitable peak shapes and maximized MS responses. A representative mixture of 31 acidic and basic doping agents was analyzed, in both ESI+ and ESI- modes. The best compromise for all compounds in terms of MS sensitivity and chromatographic performance was obtained when adding 2% water and 10mM ammonium formate in the CO2/MeOH mobile phase. Beside mobile phase, the nature of the make-up solvent added for interfacing UHPSFC with MS was also evaluated. Ethanol was found to be the best candidate as it was able to compensate for the negative effect of 2% water addition in ESI- mode and provided a suitable MS response for all doping agents. Sensitivity of the optimized UHPSFC-MS/MS method was finally assessed and compared to the results obtained in conventional UHPLC-MS/MS. Sensitivity was improved by 5-100-fold in UHPSFC-MS/MS vs. UHPLC-MS/MS for 56% of compounds, while only one compound (bumetanide) offered a significantly higher MS response (4-fold) under UHPLC-MS/MS conditions. In the second paper of this series, the optimal conditions for UHPSFC-MS/MS analysis will be employed to screen >100 doping agents in urine matrix and results will be compared to those obtained by conventional UHPLC-MS/MS. PMID:25467513

  1. Conformational ordering of biomolecules in the gas phase: nitrogen collision cross sections measured on a prototype high resolution drift tube ion mobility-mass spectrometer.

    PubMed

    May, Jody C; Goodwin, Cody R; Lareau, Nichole M; Leaptrot, Katrina L; Morris, Caleb B; Kurulugama, Ruwan T; Mordehai, Alex; Klein, Christian; Barry, William; Darland, Ed; Overney, Gregor; Imatani, Kenneth; Stafford, George C; Fjeldsted, John C; McLean, John A

    2014-02-18

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid "omni-omic" characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  2. Conformational Ordering of Biomolecules in the Gas Phase: Nitrogen Collision Cross Sections Measured on a Prototype High Resolution Drift Tube Ion Mobility-Mass Spectrometer

    PubMed Central

    2014-01-01

    Ion mobility-mass spectrometry measurements which describe the gas-phase scaling of molecular size and mass are of both fundamental and pragmatic utility. Fundamentally, such measurements expand our understanding of intrinsic intramolecular folding forces in the absence of solvent. Practically, reproducible transport properties, such as gas-phase collision cross-section (CCS), are analytically useful metrics for identification and characterization purposes. Here, we report 594 CCS values obtained in nitrogen drift gas on an electrostatic drift tube ion mobility-mass spectrometry (IM-MS) instrument. The instrument platform is a newly developed prototype incorporating a uniform-field drift tube bracketed by electrodynamic ion funnels and coupled to a high resolution quadrupole time-of-flight mass spectrometer. The CCS values reported here are of high experimental precision (±0.5% or better) and represent four chemically distinct classes of molecules (quaternary ammonium salts, lipids, peptides, and carbohydrates), which enables structural comparisons to be made between molecules of different chemical compositions for the rapid “omni-omic” characterization of complex biological samples. Comparisons made between helium and nitrogen-derived CCS measurements demonstrate that nitrogen CCS values are systematically larger than helium values; however, general separation trends between chemical classes are retained regardless of the drift gas. These results underscore that, for the highest CCS accuracy, care must be exercised when utilizing helium-derived CCS values to calibrate measurements obtained in nitrogen, as is the common practice in the field. PMID:24446877

  3. Vibrational Relaxation of the Aqueous Proton in Acetonitrile: Ultrafast Cluster Cooling and Vibrational Predissociation.

    PubMed

    Ottosson, N; Liu, L; Bakker, H J

    2016-07-28

    We study the ultrafast O-H stretch vibrational relaxation dynamics of protonated water clusters embedded in a matrix of deuterated acetonitrile, using polarization-resolved mid-IR femtosecond spectroscopy. The clusters are produced by mixing triflic (trifluoromethanesulfonic) acid and H2O in molar ratios of 1:1, 1:2, and 1:3, thus varying the degree of hydration of the proton. At all hydration levels the excited O-H stretch vibration of the hydrated proton shows an ultrafast vibrational relaxation with a time constant T1 < 100 fs, leading to an ultrafast local heating of the protonated water cluster. This excess thermal energy, initially highly localized to the region of the excited proton, first re-distributes over the aqueous cluster and then dissipates into the surrounding acetonitrile matrix. For clusters with a triflic acid to H2O ratio of 1:3 these processes occur with time constants of 320 ± 20 fs and 1.4 ± 0.1 ps, respectively. The cooling of the clusters reveals a long-living, underlying transient absorption change with high anisotropy. We argue that this feature stems from the vibrational predissociation of a small fraction of the proton hydration structures, directly following the ultrafast infrared excitation. PMID:27333302

  4. Pediatric cyanide intoxication and death from an acetonitrile-containing cosmetic

    SciTech Connect

    Caravati, E.M.; Litovitz, T.L. )

    1988-12-16

    Two cases of pediatric accidental ingestion of an acetonitrile-containing cosmetic are reported. One of the children, a 16-month-old boy, was found dead in bed the morning after ingesting the product. No therapy had been undertaken, as the product was mistakenly assumed to be an acetone-containing nail polish remover. The second child, a 2-year-old boy, experienced signs of severe cyanide poisoning, but survived with vigorous supportive care. Both children had blood cyanide levels in the potentially lethal range. The observed delayed onset of severe toxic reactions supports the proposed mechanism of acetonitrile conversion to inorganic cyanide via hepatic microsomal enzymes. Physicians and poison centers should be alerted to the existence of this highly toxic product, sold for removal of sculptured nails and likely to be confused with the less toxic acetone-containing nail polish removers. The authors urge regulatory agencies to reconsider the wisdom of marketing a cosmetic that poses such an extreme health hazard.

  5. Pediatric cyanide intoxication and death from an acetonitrile-containing cosmetic.

    PubMed

    Caravati, E M; Litovitz, T L

    1988-12-16

    Two cases of pediatric accidental ingestion of an acetonitrile-containing cosmetic are reported. One of the children, a 16-month-old boy, was found dead in bed the morning after ingesting the product. No therapy had been undertaken, as the product was mistakenly assumed to be an acetone-containing nail polish remover. The second child, a 2-year-old boy, experienced signs of severe cyanide poisoning, but survived with vigorous supportive care. Both children had blood cyanide levels in the potentially lethal range. The observed delayed onset of severe toxic reactions supports the proposed mechanism of acetonitrile conversion to inorganic cyanide via hepatic microsomal enzymes. Physicians and poison centers should be alerted to the existence of this highly toxic product, sold for removal of sculptured nails and likely to be confused with the less toxic acetone-containing nail polish removers. We urge regulatory agencies to reconsider the wisdom of marketing a cosmetic that poses such an extreme health hazard. PMID:3062198

  6. A tetranuclear cadmium(II) complex based on the 2-(quinolin-8-yloxy)acetonitrile ligand.

    PubMed

    Liu, Ming-Liang; Ye, Qiong

    2013-01-01

    The hydrothermal reaction of 2-(quinolin-8-yloxy)acetonitrile and Cd(ClO(4))(2) yielded the noncentrosymmetric coordination complex tetrakis[μ-2-(quinolin-8-yloxy)acetato]tetrakis[μ-2-(quinolin-8-yloxy)acetonitrile]tetracadmium tetrakis(perchlorate) dihydrate, [Cd(4)(C(11)H(8)NO(3))(4)(C(11)H(8)N(2)O)(4)](ClO(4))(4)·2H(2)O. The local coordination environment around the Cd(II) cation can be best described as a capped octahedron defined by two N atoms and five O atoms from three ligands. The Cd(II) cations are linked by the ligands with Cd-O-Cd and Cd-O-C-C-O-Cd bridges, forming tetranuclear units, there being two independent tertranuclear units in the structure. The fourfold rotoinversion centre sits at the centre of each Cd(4) core. The two perchlorate anions in the asymmetric unit are linked by the water molecule through O-H...O hydrogen bonds. PMID:23282905

  7. Health Services Mobility Study. First Progress Report for Phase Four for the Period April 1, 1972 to March 15, 1973.

    ERIC Educational Resources Information Center

    City Univ. of New York, NY.

    This report describes the overall work of the project and the first 10 months of its current demonstration phase, Phase IV. It presents an overview of the project's history and objectives, a description of the methodologies involved, the steps taken in applying the methodologies in task analysis and curriculum design, the approach to…

  8. Analysis of a Common Cold Virus and Its Subviral Particles by Gas-Phase Electrophoretic Mobility Molecular Analysis and Native Mass Spectrometry

    PubMed Central

    2015-01-01

    Gas-phase electrophoretic mobility molecular analysis (GEMMA) separates nanometer-sized, single-charged particles according to their electrophoretic mobility (EM) diameter after transition to the gas-phase via a nano electrospray process. Electrospraying as a soft desorption/ionization technique preserves noncovalent biospecific interactions. GEMMA is therefore well suited for the analysis of intact viruses and subviral particles targeting questions related to particle size, bioaffinity, and purity of preparations. By correlating the EM diameter to the molecular mass (Mr) of standards, the Mr of analytes can be determined. Here, we demonstrate (i) the use of GEMMA in purity assessment of a preparation of a common cold virus (human rhinovirus serotype 2, HRV-A2) and (ii) the analysis of subviral HRV-A2 particles derived from such a preparation. (iii) Likewise, native mass spectrometry was employed to obtain spectra of intact HRV-A2 virions and empty viral capsids (B-particles). Charge state resolution for the latter allowed its Mr determination. (iv) Cumulatively, the data measured and published earlier were used to establish a correlation between the Mr and EM diameter for a range of globular proteins and the intact virions. Although a good correlation resulted from this analysis, we noticed a discrepancy especially for the empty and subviral particles. This demonstrates the influence of genome encapsulation (preventing analytes from shrinking upon transition into the gas-phase) on the measured analyte EM diameter. To conclude, GEMMA is useful for the determination of the Mr of intact viruses but needs to be employed with caution when subviral particles or even empty viral capsids are targeted. The latter could be analyzed by native MS. PMID:26221912

  9. The interhemispheric distribution and the budget of acetonitrile in the troposphere

    NASA Astrophysics Data System (ADS)

    Hamm, Stephan; Warneck, Peter

    1990-11-01

    Gas chromatography in conjunction with a thermionic nitrogen-specific detector was used to determine mixing ratios of acetonitrile in air samples collected in Europe and over the Atlantic Ocean. In the city of Mainz, values of the order of 340 pptv were observed with large variations indicating the vicinity of sources. In the rural community of Deuselbach the average mixing ratio was 147±28 pptv; over the North Sea the range was 65-196 pptv depending on wind direction, with the lowest values occurring for northerly winds from the open ocean. The distribution of CH3 CN with geographic latitude over the Atlantic Ocean was explored between 30°S and 50°N on board R/V Polarstern during the cruise ANT V/5 in March-April 1987. Over the open ocean, maximum mixing ratios were observed near 4°S with values of 175 pptv. At latitudes near 30°S the mixing ratio averaged 90.4 pptv, whereas at 30°N the average was 52.1 pptv. The lowest mixing ratios of 21 pptv were found near 50°N. The tropical maximum is attributed to the advection with the trade winds of continental air from Africa, enriched with acetonitrile from biomass burning. The mixing ratios north and south of the maximum correlate well with the surface temperature of seawater, indicating a gas-liquid equilibrium for CH3 CN dissolved in seawater. From the observations and with the further assumption that CH3 CN is vertically well mixed, its total mass content in the troposphere was estimated as 0.37-0.57 Tg. Global emission rates for various sources were estimated as follows: automobiles 0.27 Tg/year, oil-fired power stations 0.0035 Tg/year, and biomass burning 0.80 Tg/year. The total estimated source strength is 1.1±0.5 Tg/year. The tropospheric residence time of acetonitrile was calculated from these data as 0.23-0.90 year with a probable value of 0.45 year. Wet precipitation and reaction with OH radicals are known sinks for tropospheric CH3 CN, but they can take up only 30% of the global emission rate. We

  10. CsSnI3: Semiconductor or metal? High electrical conductivity and strong near-infrared photoluminescence from a single material. High hole mobility and phase-transitions.

    PubMed

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D; Li, Hao; Freeman, Arthur J; Kenney, John T; Kanatzidis, Mercouri G

    2012-05-23

    CsSnI(3) is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI(3) have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI(3), coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI(3). The black orthorhombic form of CsSnI(3) demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI(3) indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of ∼ 10(17) cm(-3) and a hole mobility of ∼585 cm(2) V(-1) s(-1). The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from Sn defects in the crystal structure, which arise

  11. Use of a Novel Sub-2 µm Silica Hydride Vancomycin Stationary Phase in Nano-Liquid Chromatography. II. Separation of Derivatized Amino Acid Enantiomers.

    PubMed

    Rocchi, Silvia; Fanali, Chiara; Fanali, Salvatore

    2015-11-01

    A novel vancomycin silica hydride stationary phase was synthesized and the particles of 1.8 µm were packed into fused silica capillaries of 75 µm internal diameter (I.D.). The chiral stationary phase (CSP) was tested for the separation of some derivatized amino acid enantiomers by using nano-liquid chromatography (nano-LC). Some experimental parameters such as the type and the content of organic modifier, the pH, and the concentration of the buffer added to the mobile phase were modified and the effect on enantioselectivity, retention time, and enantioresolution factor was studied. The separation of selected dansyl amino acids (Dns-AAs), e.g., Asp, Glu, Leu, and Phe in their enantiomers was initially achieved utilizing a mobile phase containing 85% (v/v) methanol (MeOH) and formate buffer measuring the enantioresolution factor and enantioselectivity in the range 1.74-4.17 and 1.39-1.59, respectively. Better results were obtained employing a more polar organic solvent as acetonitrile (ACN) in the mobile phase. Optimum results (Rs 1.41-6.09 and α 1.28-2.36) were obtained using a mobile phase containing formate buffer pH 2.5/water/MeOH/ACN 6:19:12.5:62.5 (v/v/v/v) in isocratic elution mode at flow rate of 130 nL/min. PMID:26335144

  12. Analysis of testosterone in human urine using molecularly imprinted solid-phase extraction and corona discharge ion mobility spectrometry.

    PubMed

    Mirmahdieh, Shiva; Mardihallaj, Azam; Hashemian, Zahra; Razavizadeh, Jalal; Ghaziaskar, Hassan; Khayamian, Taghi

    2011-01-01

    Analysis of testosterone was accomplished using corona discharge ion mobility spectrometry. Molecular imprinted polymer was used for the extraction and pre-concentration of testosterone. Analytical parameters including precision, dynamic range and detection limit were obtained. The linear dynamic range was from 10 to 250 ng/mL and the limit of detection was 0.9 ng/mL. The proposed method was used for analysis of testosterone in urine samples. A urine sample from a 3-year-old girl was used as the blank. The RSD was below 10%. The obtained results from the method were also compared with the standard method for analysis of testosterone using SPE-HPLC analysis. The results demonstrate the accuracy of the method. PMID:21171183

  13. On the reactions of perfluoroisobutene with some anions in the gas phase: studies in an ion mobility spectrometer

    NASA Astrophysics Data System (ADS)

    Bell, A. J.; Hayhurst, C. J.; Mayhew, C. A.; Watts, P.

    1994-12-01

    An ion mobility spectrometer (IMS), operating in air in the negative ion mode, has been shown to have potential for detecting and monitoring perfluoroisobutene (PFIB), a toxic perfluorocarbon and potential industrial hazard. Complex spectra with a variety of product ions are observed. Most of these ions result from reactions of PFIB with the negative reactant ions although some important product ions (particularly at high PFIB concentrations) are attributed to reactions with reactive transient species (including electrons) in the ionization region of the IMS system. The ions have been identified using mass spectrometry and a wide variety of isotopic tracers. The results of our parallel studies using a selected ion flow tube have been included where appropriate.

  14. Phase impact factor: a novel parameter for determining optimal CT phase in 4D radiation therapy treatment planning for mobile lung cancer

    NASA Astrophysics Data System (ADS)

    Song, Yulin; Huang, Xiaolei; Mueller, Boris; Mychalczak, Borys

    2008-03-01

    Due to respiratory motion, lung tumor can move up to several centimeters. If respiratory motion is not carefully considered during the radiation treatment planning, the highly conformal dose distribution with steep gradients could miss the target. To address this issue, the common strategy is to add a population-derived safety margin to the gross tumor volume (GTV). However, during a free breathing CT simulation, the images could be acquired at any phase of a breathing cycle. With such a generalized uniform margin, the planning target volume (PTV) may either include more normal lung tissue than required or miss the GTV at certain phases of a breathing cycle. Recently, respiration correlated CT (4DCT) has been developed and implemented. With 4DCT, it is now possible to trace the tumor 3D trajectories during a breathing cycle and to define the tumor volume as the union of these 3D trajectories. The tumor volume defined in this way is called the internal target volume (ITV). In this study, we introduced a novel parameter, the phase impact factor (PIF), to determine the optimal CT phase for intensity modulated radiation therapy (IMRT) treatment planning for lung cancer. A minimum PIF yields a minimum probability for the GTV to move out of the ITV during the course of an IMRT treatment, providing a minimum probability of a geometric miss. Once the CT images with the optimal phase were determined, an IMRT plan with three to five co-planner beams was computed and optimized using the inverse treatment planning technique.

  15. Development of an achiral supercritical fluid chromatography method with ultraviolet absorbance and mass spectrometric detection for impurity profiling of drug candidates. Part I: Optimization of mobile phase composition.

    PubMed

    Lemasson, Elise; Bertin, Sophie; Hennig, Philippe; Boiteux, Hélène; Lesellier, Eric; West, Caroline

    2015-08-21

    Supercritical fluid chromatography (SFC) is a very useful tool in the purpose of impurity profiling of drug candidates, as an adequate selection of stationary phases can provide orthogonal separations so as to maximize the chances to see all impurities. The purpose of the present work is to develop a method for chemical purity assessment. The first part, presented here, focuses on mobile phase selection to ensure adequate elution and detection of drug-like molecules, while the second part focuses on stationary phase selection for optimal separation and orthogonality. The use of additives in the carbon dioxide - solvent mobile phase in SFC is now commonplace, and enables in particular to increase the number of eluted compounds and to improve peak shapes. The objective of this first part was to test different additives (acids, bases, salts and water) for their chromatographic performance assessed in gradient elution with a diode-array detector, but also for the mass responses obtained with a single-quadrupole mass detector, equipped with an electrospray ionization source (Waters ACQUITY QDa). In this project, we used a selection of one hundred and sixty compounds issued from Servier Research Laboratories to screen a set of columns and additives in SFC with a Waters ACQUITY UPC(2) system. The selected columns were all high-performance columns (1.7-1.8μm with totally porous particles or 2.6-2.7μm with superficially porous particles) with a variety of stationary phase chemistries. Initially, eight additives dissolved in the methanol co-solvent were tested on a UPC(2) ACQUITY UPC(2) HSS C18 SB column. A Derringer desirability function was used to classify the additives according to selected criteria: elution capability, peak shapes, UV baseline drift, and UV and mass responses (signal-to-noise ratios). Following these tests, the two best additives (ammonium acetate and ammonium hydroxide) were tested on a larger number of columns (10) where the two additives appeared

  16. An Analysis of the Rotational Spectrum of Acetonitrile (CH_3CN) in Excited Vibrational States

    NASA Astrophysics Data System (ADS)

    Neese, Christopher F.; McMillan, James; Fortman, Sarah; De Lucia, Frank C.

    2014-06-01

    Acetonitrile (CH_3CN) is a well-known interstellar molecule whose vibrationally excited states need to be accounted for in searches for new molecules in the interstellar medium. To help catalog such `weed' molecules, we have developed a technique that involves recording complete spectra over a range of astrophysically significant temperatures. With such a data set, we can experimentally measure the line strengths and lower state energies of unassigned lines in the spectrum. In this talk we will present the ongoing analysis of complete temperature resolved spectra in the 215-265 GHz and 570-650 GHz regions. We have been able to assign many vibrationally hot lines from this data and a room temperature data set spanning 165-700 GHz. To date, we have assigned lines from most of the vibrational states below ν_6 at 1448 wn.

  17. Photon emission via surface state at the gold/acetonitrile solution interface

    SciTech Connect

    Uosaki, Kohei; Murakoshi, Kei; Kita, Hideaki )

    1991-01-24

    The emission of light caused by an electron-transfer reaction at a gold electrode in acetonitrile solution containing one of three redox species (benzophenone, trans-stilbene, and benzonitrile) with different redox potentials was studied. The high-energy threshold of the spectrum decreases linearly as the potential of the gold electrode becomes more negative. The peak position with respect to the high-energy threshold of the spectrum varies with electrode potential and is not affected by the redox potential of the electron injection species at the same electrode potential. The emission efficiency also depends on the potential. From these results, the authors proposed that the emission is due to a charge-transfer reaction inverse photoemission (CTRIP) process that takes place via a surface state.

  18. Isolation and identification of (3-methoxyphenyl)acetonitrile as a phytotoxin from meadowfoam (Limnanthes alba) seedmeal.

    PubMed

    Vaughn, S F; Boydston, R A; Mallory-Smith, C A

    1996-10-01

    Ethyl ether, ethanol, and water extracts of meadowfoam (Limnanthes alba Hartweg ex. Benth.) seedmeal were prepared and bioassayed against velvetleaf (Abutilon theophrasti Medicus) and wheat (Triticum aestivum L. "Cardinal"). Both the ethyl ether and ethanol fractions, but not the water extract, inhibited velvetleaf and wheat radicle elongation. Fractionation of the extracts indicated that (3-methoxyphenyl)acetonitrile (3-MPAN) was the active compound from both extracts, comprising >97% of the active ethanol fraction. 3-Methoxybenzyl isothiocyanate, which had been previously shown to be the major breakdown product of glucolimnanthin, the majorL. alba glucosinolate, was not detected in either extract. Radicle elongation of velvetleaf and wheat were inhibited by 3-MPAN with I50 (the concentration required to inhibit growth by 50%) values of approximately 4 × 10(-4) M (velvetleaf) and 7×10(-4) M (wheat). PMID:24227117

  19. The biochemical pathway for the breakdown of methyl cyanide (acetonitrile) in bacteria.

    PubMed Central

    Firmin, J L; Gray, D O

    1976-01-01

    [2-14C]Methyl cyanide (acetonitrile) is metabolized to citrate, succinate, fumarate, malate, glutamate, pyrrolidonecarboxylic acid and aspartate. Non-radioactive acetamide and acetate compete with 14C from methyl cyanide, and [2-14C]acetate and [2-14C]methyl cyanide are metabolized at similar rates, giving identical products. This evidence, combined with the inhibitory effect of fluoroacetate and arsenite on methyl cyanide metabolism, indicates that the pathway is: methyl cyanide leads to acetamide leads to acetate leads to tricarboxylic acid-cycle intermediates. The pathway was investigated in a species of Pseudomonas (group III; N.C.I.B. 10477), but comparison of labelling patterns suggests that it also exists in several higher plants. PMID:985423

  20. The response of Paracoccus sp. SKG to acetonitrile-induced oxidative stress.

    PubMed

    Kirankumar, B; Guruprasad, B Kulkarni; Santoshkumar, M; Anand, S Nayak; Karegoudar, T B

    2013-11-01

    Organic solvents enhance intracellular oxidative stress and induce various physiological responses in bacteria. The study shows the morphological changes in Paracoccus sp. SKG when exposed to higher concentrations of acetonitrile, which alter the composition of the membrane fatty acid that accompanies the increase in K(+) efflux. This enhances the oxidative stress with greater activities of catalase and super oxide dismutase (SOD). The increased oxidative stress results in the generation of free radicals, which was confirmed by electron paramagnetic resonance (EPR) studies. The free radical scavenging activities were measured by ABTS and DPPH to understand the non-enzymatic defensive system during oxidative stress. The studies demonstrate the increase in free radicals in association with enzymatic and non-enzymatic defense systems under solvent stress. PMID:24092001

  1. On-site quantitation of arsenic in drinking water by disk solid-phase extraction/mobile X-ray fluorescence spectrometry.

    PubMed

    Hagiwara, Kenta; Koike, Yuya; Aizawa, Mamoru; Nakamura, Toshihiro

    2015-11-01

    A rapid and simple method was developed for As determination in drinking water by solid-phase extraction (SPE)/mobile X-ray fluorescence (XRF) spectrometry. A 50 mL aqueous sample was adjusted to pH 3 with dilute hydrochloric acid, and then passed through a Ti and Zr-loaded carbon disk (TiZr-CD) to pre-concentrate the As. The SPE disk was adhered to an acrylic plate with cellophane tape, and then examined by mobile XRF spectrometry. The TiZr-CD adsorbed inorganic As (as As(III) and As(V)) and organic As (as methyl, phenyl and aromatic arsenic compounds) from water. The As calibration curve had good linearity over the range of 0.5-5 μg, and the limit of detection was 0.10 μg (2.0 μgL(-1) in As concentration). The concentrations of As in well water samples were determined using the proposed method were similar to results obtained from atomic absorption spectrometry. The proposed method did not require a power supply or a toxic solution and/or gas in any analytical step, therefore it is suitable for the on-site determination of As in drinking water. PMID:26452891

  2. Energetics and structural characterization of isomers using ion mobility and gas-phase H/D exchange: Learning from lasso peptides.

    PubMed

    Hanozin, Emeline; Morsa, Denis; De Pauw, Edwin

    2015-08-01

    State-of-the-art characterization of proteins using MS namely relies on fragmentation methods that allow exploring featured dissociative reaction pathways. These pathways are often initiated by a series of potentially informative mass-constant conformational changes that are nonetheless frequently overlooked by lack of adequate investigation techniques. In the present study, we propose a methodology to readily address both structural and energetic aspects of stereoisomerization reactions using ion mobility coupled with MS. To this end, a commercial spectrometer was used as a reactor comprising an energy resolved collisional activation step intended at promoting controlled conformational changes and a structural assignment step dedicated to the identification of the generated isomers. This identification relies on ion mobility and other on-line coupled techniques, namely an originally designed gas-phase H/D exchange experiment. We here apply this methodology to characterize the isomerization kinetics of capistruin, a 19-residue long lasso-folded peptide. We expect this approach to bring insights into the physical origin of global dissociation thresholds monitored in MS/MS experiments and to set a promising basis for quantitative investigations of the stability of different molecular folds. PMID:25821205

  3. Standard Reduction Potentials for Oxygen and Carbon Dioxide Couples in Acetonitrile and N,N-Dimethylformamide

    SciTech Connect

    Pegis, Michael L.; Roberts, John A.; Wasylenko, Derek J.; Mader, Elizabeth A.; Appel, Aaron M.; Mayer, James M.

    2015-12-21

    A variety of energy processes utilize the electrochemical interconversions of dioxygen and water, the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Reported here are the first estimates of the equilibrium reduction potential of the O2 + 4e– + 4H+ 2H2O couple in organic solvents. The values are +1.21 V in acetonitrile (MeCN) and +0.60 V in dimethylformamide (DMF), each versus the ferrocenium/ferrocene couple (Fc+/0) in the respective solvent (as are all the potentials reported here). The potentials have been determined using a thermochemical cycle that combines the free energy for transferring water from aqueous solution to organic solvent, -0.43 kcal mol-1 for MeCN and -1.47 kcal mol-1 for DMF, and the potential of the H+/H2 couple, –0.028 V in MeCN and –0.662 V in DMF. The H+/H2 couple in DMF has been directly measured electrochemically, using the previously reported procedure for the MeCN value. The thermochemical approach used for the O2/H2O couple can also be extended to the CO2/CO and CO2/CH4 couples to give values of -0.12 V and +0.15 V in MeCN, and -0.73 V and -0.48 V in DMF. Extensions to other reduction potentials are discussed. Additionally, the free energy for transfer of protons from water to organic solvent is roughly estimated as +14 kcal mol-1 for acetonitrile and +0.6 kcal mol-1 for dimethylformamide. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

  4. Standard Reduction Potentials for Oxygen and Carbon Dioxide Couples in Acetonitrile and N,N-Dimethylformamide.

    PubMed

    Pegis, Michael L; Roberts, John A S; Wasylenko, Derek J; Mader, Elizabeth A; Appel, Aaron M; Mayer, James M

    2015-12-21

    A variety of next-generation energy processes utilize the electrochemical interconversions of dioxygen and water as the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Reported here are the first estimates of the standard reduction potential of the O2 + 4e(-) + 4H(+) ⇋ 2H2O couple in organic solvents. The values are +1.21 V in acetonitrile (MeCN) and +0.60 V in N,N-dimethylformamide (DMF), each versus the ferrocenium/ferrocene couple (Fc(+/0)) in the respective solvent (as are all of the potentials reported here). The potentials have been determined using a thermochemical cycle that combines the free energy for transferring water from aqueous solution to organic solvent, -0.43 kcal mol(-1) for MeCN and -1.47 kcal mol(-1) for DMF, and the potential of the H(+)/H2 couple, - 0.028 V in MeCN and -0.662 V in DMF. The H(+)/H2 couple in DMF has been directly measured electrochemically using the previously reported procedure for the MeCN value. The thermochemical approach used for the O2/H2O couple has been extended to the CO2/CO and CO2/CH4 couples to give values of -0.12 and +0.15 V in MeCN and -0.73 and -0.48 V in DMF, respectively. Extensions to other reduction potentials are discussed. Additionally, the free energy for transfer of protons from water to organic solvent is estimated as +14 kcal mol(-1) for acetonitrile and +0.6 kcal mol(-1) for DMF. PMID:26640971

  5. Ion mobility, conductivity, structure, and phase transitions in K0.7M0.3SbF4 compounds with M=Rb, NH4

    NASA Astrophysics Data System (ADS)

    Kavun, V. Ya.; Gerasimenko, A. V.; Uvarov, N. F.; Polyantsev, M. M.; Zemnukhova, L. A.

    2016-09-01

    Ion mobility, phase transitions, structure, and conductivity in the K0.7M0.3SbF4 (M=Rb, NH4) compounds were studied by NMR spectroscopy, DSC, X-ray, and conductivity measurements. The predominant form in the ion motions resulting from the phase transition of high modification was diffusion of fluoride and ammonium ions above 450 K. The high-temperature phases of K0.7M0.3SbF4 (M=Rb, NH4) are superionic, while their conductivity attains the values of ~10-2-10-4 S/cm at 450-500 K. The structures of α- and β-modifications of the K0.7Rb0.3SbF4 are monoclinic (space group P21/m). The main structural units in them are statistically substituting each other K+ and Rb+ cations and complex ∞1[ SbF4]- anions linked into zigzag-like chains by bridge fluorine atoms. The nearest surrounding of each antimony atom contains five fluorine atoms, so that the antimony coordination polyhedron can be described, taking into account the lone electron pair, as a distorted SbF5E octahedron (ψ-octahedron).

  6. Effects of capillary pressure and use of polymer solutions on dense, non-aqueous-phase liquid retention and mobilization in a rough-walled fracture

    SciTech Connect

    Longino, B.L.; Kueper, B.H. . Dept. of Civil Engineering)

    1999-07-15

    In this laboratory study, perchloroethylene (PCE) was permitted to migrate through a horizontal rough-walled limestone fracture under controlled conditions to assess fracture retention capacity. Retention of immiscible-phase PCE in the absence of an applied wetting-phase hydraulic gradient varied between 11% and 26% of the fracture volume. A portion of this residual could be removed through water flooding; however, even at the maximum applied hydraulic gradient of 1.0, residual PCE remained in the fracture. The observed correlation of reduced residual saturation with capillary number (N[sub c]) demonstrated that this rough-walled fracture exhibited behavior similar to that of a porous medium under water-flooding conditions. For a given hydraulic gradient, polymer-enhanced floods (using xanthan gum) were not as successful as conventional water flooding at removing residual from the fracture. The traditional form of the capillary number became an increasingly poor predictor of mobilization behavior as the viscosity of the displacing phase was increased. Incorporation of ([mu][sub w]/[mu][sub nw])[sup [minus]0.5] into the traditional capillary number provided a more appropriate dimensionless group with which to correlate residual PCE saturation in the fracture as [mu][sub w] increased.

  7. A kinetic study on the bioremediation of sodium cyanide and acetonitrile by free and immobilized cells of pseudomonas putida

    SciTech Connect

    Chapatwala, K.D.; Babu, G.R.V.; Armstead, E.R.

    1995-12-31

    Pseudomonas putida capable of utilizing organic nitrile (acetonitrile) and inorganic cyanide (sodium cyanide) as the sole source of carbon and nitrogen was isolated from contaminated industrial sites and waste water. The bacterium possesses nitrile aminohydrolase (EC 3.5.5.1) and amidase (EC 3.5.1.4), which are involved in the transformation of cyanides and nitrites into ammonia and CO{sub 2} through the formation of amide as an intermediate. Both of the enzymes have a high selectivity and affinity toward the {sup -}CN group. The rate of degradation of acetonitrile and sodium cyanide to ammonia and CO{sub 2} by the calcium-alginate immobilized cells of P. putida was studied. The rate of reaction during the biodegradation of acetonitrile and sodium cyanide, and the substrate- and product-dependent kinetics of these toxic compounds were studied using free and immobilized cells of P. putida and modeled using a simple Michaelis-Menten equation.

  8. The origin of halide melt phases in layered intrusions, and their significance to platinum-group element mobility

    NASA Astrophysics Data System (ADS)

    Hanley, J. J.

    2007-12-01

    Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles became increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids, and the partitioning behavior of Cl in fluid-melt systems. Previously unreported, the latest stage volatiles in the layered intrusions were halide melts (slightly hydrous molten salts) of relatively simply composition (NaCl with minor KCl or CaCl2) with salinities in excess of 90 wt% eq. NaCl or CaCl2. These volatiles were trapped at minimum temperatures of 760-800°C, near the eutectic temperature for water-saturated granitic liquid at moderate crustal pressures. Trace element analysis of the salt melt inclusions by laser ablation ICP-MS (ETH Zürich) show that they contain no detectable concentrations of ore and accessory metals. This is in contrast to the earlier, lower salinity volatiles which contain ppm-concentrations of Pt, Pd, As, Bi, Sb as well as abundant S and base metals. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic or felsic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H2O ratios for the parental silicate liquid (> 9 for a granitic residue). Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show

  9. Reverse phase liquid chromatographic determination of sulfathiazole residues in honey.

    PubMed

    Barry, C P; MacEachern, G M

    1983-01-01

    Sulfathiazole residues were extracted from honey by homogenizing samples in acetone, filtering, and then evaporating the acetone under nitrogen at 40 degrees C. The remaining extract was transferred to a separatory funnel with 1N HCl and ethyl ether. An aliquot of the retained acid layer was screened by using the Bratton-Marshall reaction. If the test was positive, the remaining portion was analyzed directly through a mu Bondapak phenyl column monitored by a UV detector at 254 nm. The mobile phase was potassium phosphate monobasic in 10% acetonitrile adjusted to pH 3.0. Time for elution was 13 min. Average recoveries were 78% at the 0.1 ppm spiking level and 68% at the 1.0 ppm level. The minimum detectable amount was 0.06 ppm based on a spiked sample extract. PMID:6826511

  10. Intelligent mobile sensor system for drum inspection and monitoring: Phase 1. Topical report, October 1, 1992--June 8, 1993

    SciTech Connect

    Not Available

    1993-06-01

    The objective of this project was to develop an operational system for monitoring and inspection activities for waste storage facility operations at several DOE sites. Specifically, the product of this effort is a robotic device with enhanced intelligence and maneuverability capable of conducting routine inspection of stored waste drums. The device is capable of operating in narrow aisles and interpolating the free aisle space between rows of stacked drums. The system has an integrated sensor suite for leak detection, and is interfaced with a site database both for inspection planning and for data correlation, updating, and report generation. The system is capable of departing on an assigned mission, collecting required data, recording which positions of its mission had to be aborted or modified due to environmental constraints, and reporting back when the mission is complete. Successful identification of more than 90% of all drum defects has been demonstrated in a high fidelity waste storage facility mockup. Identified anomalies included rust spots, rust streaks, areas of corrosion, dents, and tilted drums. All drums were positively identified and correlated with the site database. This development effort is separated into three phases of which phase one is now complete. The first phase has demonstrated an integrated system for monitoring and inspection activities for waste storage facility operations. This demonstration system was quickly fielded and evaluated by leveraging technologies developed from previous NASA and DARPA contracts and internal research. The second phase will demonstrate a prototype system appropriate for operational use in an actual storage facility. The prototype provides an integrated design that considers operational requirements, hardware costs, maintenance, safety, and robustness. The final phase will demonstrate commercial viability using the prototype vehicle in a pilot waste operations and inspection project.

  11. Comprehensive size-determination of whole virus vaccine particles using gas-phase electrophoretic mobility macromolecular analyzer, atomic force microscopy, and transmission electron microscopy.

    PubMed

    Havlik, Marlene; Marchetti-Deschmann, Martina; Friedbacher, Gernot; Winkler, Wolfgang; Messner, Paul; Perez-Burgos, Laura; Tauer, Christa; Allmaier, Günter

    2015-09-01

    Biophysical properties including particle size distribution, integrity, and shape of whole virus vaccine particles at different stages in tick-borne encephalitis (TBE) vaccines formulation were analyzed by a new set of methods. Size-exclusion chromatography (SEC) was used as a conservative sample preparation for vaccine particle fractionation and gas-phase electrophoretic mobility macromolecular analyzer (GEMMA) for analyzing electrophoretic mobility diameters of isolated TBE virions. The derived particle diameter was then correlated with molecular weight. The diameter of the TBE virions determined after SEC by GEMMA instrumentation was 46.8 ± 1.1 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were implemented for comparison purposes and to gain morphological information on the virion particle. Western blotting (Dot Blot) as an immunological method confirmed biological activity of the particles at various stages of the developed analytical strategy. AFM and TEM measurements revealed higher diameters with much higher SD for a limited number of virions, 60.4 ± 8.5 and 53.5 ± 5.3 nm, respectively. GEMMA instrumentation was also used for fractionation of virions with specifically selected diameters in the gas-phase, which were finally collected by means of an electrostatic sampler. At that point (i.e., after particle collection), AFM and TEM showed that the sampled virions were still intact, exhibiting a narrow size distribution (i.e., 59.8 ± 7.8 nm for AFM and 47.5 ± 5.2 nm for TEM images), and most importantly, dot blotting confirmed immunological activity of the collected samples. Furthermore dimers and virion artifacts were detected, too. PMID:26266988

  12. Evaluation of mobile phase composition for enhancing sensitivity of targeted quantification of oligonucleotides using ultra-high performance liquid chromatography and mass spectrometry: application to phosphorothioate deoxyribonucleic acid.

    PubMed

    Chen, Buyun; Bartlett, Michael G

    2013-05-01

    LC-MS based assays are a promising approach for the bioanalysis of oligonucleotide therapeutics due to their selectivity and structure identification capabilities. However, the lack of sensitivity and complicated sample preparation procedures remain a barrier for application of LC-MS based assays to preclinical and clinical studies. Numerous studies have shown that the mobile phase composition, especially organic solvent type, has a significant impact on the MS sensitivity of oligonucleotides. In this study, we systematically investigated the type of organic solvents and concentration of organic modifiers for their effect on electrospray desorption efficiency, chromatographic separation and LC-MS signal intensity and provide mechanisms for these effects. 25mM HFIP, 15mM DIEA and the use of ethanol as an organic solvent were observed to achieve a two order of magnitude increase in LC-MS signal intensity when compared to the most commonly used LC-MS mobile phase composition. Phenol-chloroform LLE in combination with ethanol precipitation was demonstrated to be effective for quantitative bioanalysis of therapeutic oligonucleotides. Various conditions for ethanol precipitation were evaluated and >75% absolute recovery was achieved using an optimized extraction procedure. No increase in column pressure or deterioration of separation was observed for >500 injections of biological samples. The method run time was 5min and the LOQ was 2.5ng/ml. The accuracy (% error) and precision (%RSD) are <5.09% and <10.56%, respectively, over a dynamic range of 2.5-1000ng/ml. The assay was applied to a proof of concept animal study and similar PK parameters to previous studies were obtained. PMID:23528868

  13. Comprehensive Size-Determination of Whole Virus Vaccine Particles Using Gas-Phase Electrophoretic Mobility Macromolecular Analyzer, Atomic Force Microscopy, and Transmission Electron Microscopy

    PubMed Central

    Havlik, Marlene; Marchetti-Deschmann, Martina; Friedbacher, Gernot; Winkler, Wolfgang; Messner, Paul; Perez-Burgos, Laura; Tauer, Christa; Allmaier, Günter

    2015-01-01

    Biophysical properties including particle size distribution, integrity, and shape of whole virus vaccine particles at different stages in tick-borne encephalitis (TBE) vaccines formulation were analyzed by a new set of methods. Size-exclusion chromatography (SEC) was used as a conservative sample preparation for vaccine particle fractionation and gas-phase electrophoretic mobility macromolecular analyzer (GEMMA) for analyzing electrophoretic mobility diameters of isolated TBE virions. The derived particle diameter was then correlated with molecular weight. The diameter of the TBE virions determined after SEC by GEMMA instrumentation was 46.8 ± 1.1 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were implemented for comparison purposes and to gain morphological information on the virion particle. Western blotting (Dot Blot) as an immunological method confirmed biological activity of the particles at various stages of the developed analytical strategy. AFM and TEM measurements revealed higher diameters with much higher SD for a limited number of virions, 60.4 ± 8.5 and 53.5 ± 5.3 nm, respectively. GEMMA instrumentation was also used for fractionation of virions with specifically selected diameters in the gas-phase, which were finally collected by means of an electrostatic sampler. At that point (i.e., after particle collection), AFM and TEM showed that the sampled virions were still intact, exhibiting a narrow size distribution (i.e., 59.8 ± 7.8 nm for AFM and 47.5 ± 5.2 nm for TEM images), and most importantly, dot blotting confirmed immunological activity of the collected samples. Furthermore dimers and virion artifacts were detected, too. PMID:26266988

  14. [Influences of ion-suppressors on retention behaviors of nine food additives in reversed-phase high performance liquid chromatographic separation].

    PubMed

    Zhao, Yonggang; Chen, Xiaohong; Li, Xiaoping; Yao, Shanshan; Jin, Micong

    2011-10-01

    The influences of ion-suppressors on retention behaviors of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in reversed-phase high performance liquid chromatographic (RP-HPLC) separation were investigated. The organic modification effects of acids, i. e. , trifluoroacetic acid (TFA) and buffer salts, i. e. , TFA-ammonium acetate (AmAc) were studied emphatically. The relationships between retention factors of solutes and volume percentages of ion-suppressors in the mobile phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, separately. The separation of nine food additives was completed by a gradient elution with acetonitrile-TFA (0.01%, v/v)-AmAc (2. 5 mmol/L) aqueous solution as the mobile phases. An RP-HPLC method was established for the simultaneous determination of nine food additives in red wine. In the range of 10. 0 - 100. 0 mg/L, nine food additives showed good linearity with the correlation coefficients ( r2 ) larger than 0. 999 1. The limits of detection (LODs) were in the range of 0. 33 - 2. 36 mg/L and the limits of quantification (LOQs) were in the range of 1. 11 - 7. 80 mg/L. The spiked recoveries were between 87. 61% and 108. 4% with the relative standard deviations (RSDs) of 2. 2% -9. 4%. These results are of referential significance for the rapid establishment and accu- rate optimization of RP-HPLC separation for the simultaneous determination of food additives in other foods. PMID:22268355

  15. A radial differential mobility analyzer for the size-classification of gas-phase synthesized nanoparticles at low pressures

    NASA Astrophysics Data System (ADS)

    Nanda, K. K.; Kruis, F. E.

    2014-07-01

    Differential mobility analyzers (DMAs) are commonly used to generate monodisperse nanoparticle aerosols. Commercial DMAs operate at quasi-atmospheric pressures and are therefore not designed to be vacuum-tight. In certain particle synthesis methods, the use of a vacuum-compatible DMA is a requirement as a process step for producing high-purity metallic particles. A vacuum-tight radial DMA (RDMA) has been developed and tested at low pressures. Its performance has been evaluated by using a commercial NANO-DMA as the reference. The performance of this low-pressure RDMA (LP-RDMA) in terms of the width of its transfer function is found to be comparable with that of other NANO-DMAs at atmospheric pressure and is almost independent of the pressure down to 30 mbar. It is shown that LP-RDMA can be used for the classification of nanometer-sized particles (5-20 nm) under low pressure condition (30 mbar) and has been successfully applied to nanoparticles produced by ablating FeNi at low pressures.

  16. Performance of the Extravehicular Mobility Unit (EMU): Airlock Coolant Loop Recovery (A/L CLR) Hardware - Phase II

    NASA Technical Reports Server (NTRS)

    Steele, John; Rector, tony; Gazda, Daniel; Lewis, John

    2009-01-01

    An EMU water processing kit (Airlock Coolant Loop Recovery A/L CLR) was developed as a corrective action to Extravehicular Mobility Unit (EMU) coolant flow disruptions experienced on the International Space Station (ISS) in May of 2004 and thereafter. Conservative schedules for A/L CLR use and component life were initially developed and implemented based on prior analysis results and analytical modeling. The examination of postflight samples and EMU hardware in November of 2006 indicated that the A/L CLR kits were functioning well and had excess capacity that would allow a relaxation of the initially conservative schedules of use and component life. A relaxed use schedule and list of component lives was implemented thereafter. Since the adoption of the relaxed A/L CLR schedules of use and component lives, several A/L CLR kit components, transport loop water samples and sensitive EMU transport loop components have been examined to gage the impact of the relaxed requirements. The intent of this paper is to summarize the findings of that evaluation, and to outline updated schedules for A/L CLR use and component life.

  17. Mobile satellite service for Canada

    NASA Technical Reports Server (NTRS)

    Sward, David

    1988-01-01

    The Mobile Satellite (MSAT) system and a special program designed to provide interim mobile satellite services (IMSS) during the construction phase of MSAT are described. A mobile satellite system is a key element in extending voice and and data telecommunications to all Canadians.

  18. 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

  19. Mobile Learning Using Mobile Phones

    ERIC Educational Resources Information Center

    Vicente, Paula

    2013-01-01

    The participation in mobile learning programs is conditioned by having/using mobile communication technology. Those who do not have or use such technology cannot participate in mobile learning programs. This study evaluates who are the most likely participants of mobile learning programs by examining the demographic profile and mobile phone usage…

  20. Kinetic behaviour in supercritical fluid chromatography with modified mobile phase for 5 μm particle size and varied flow rates.

    PubMed

    Lesellier, E; Fougere, L; Poe, Donald P

    2011-04-15

    After much development of stationary phase chemistry, in recent years the focus of many studies in HPLC has shifted to increase the efficiency and analysis speed. Ultra high pressure liquid chromatography (UHPLC) using sub-2 μm particles, and high temperature liquid chromatography (HTLC), using temperatures above 100°C have received much attention. These new approaches allow the use of flow rates higher than those classically used in HPLC, reducing the analysis duration. Due to the low viscosity of supercritical fluids, high velocities, i.e. high flow rates, can be achieved with classical pumping systems typically used in supercritical fluid chromatography (SFC). The effects of the flow rate increase with CO(2)/methanol mobile phase was studied on the inlet pressure, t(0), the retention factor of the compounds, and on the efficiency. Simple comparisons of efficiencies obtained at varied temperature between SFC and HPLC, with a packed column containing 5 μm particles, show the greater kinetic performances achieved with the CO(2)/methanol fluid, and underline specific behaviours of SFC, occurring for high flow rates and sub-ambient temperature. Some values (N/t(0)) are also compared to UHPLC data, showing that good performance can be achieved in SFC without applying drastic analytical conditions. Finally, simple kinetic plots (t(0) vs N) at constant column length are used to select combinations of temperature and flow rate necessary to achieve a required theoretical plate number. PMID:21232748

  1. Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS].

    PubMed

    Steiner, Wes E; Harden, Charles S; Hong, Feng; Klopsch, Steve J; Hill, Herbert H; McHugh, Vincent M

    2006-02-01

    The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined. Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified reference materials (CRM) of CWA degradation products for the detection of Schedule 1, 2, or 3 toxic chemicals or their precursors as defined by the chemical warfare convention (CWC) treaty verification were used in this study. A mixture of six G-series nerve related CWA degradation products (EMPA, IMPA, EHEP, IHEP, CHMPA, and PMPA) and their related collision induced dissociation (CID) fragment ions (MPA and EPA) were found in each case to be clearly resolved and detected using the IM(tof)MS instrument in negative ion monitoring mode. Corresponding ions, masses, drift times, K(o) values, and signal intensities for each of the CWA degradation products are reported. PMID:16413205

  2. Effects of Select Anions from the Hofmeister Series on the Gas-Phase Conformations of Protein Ions Measured with Traveling-Wave Ion Mobility Spectrometry/Mass Spectrometry

    PubMed Central

    Merenbloom, Samuel I.; Flick, Tawnya G.; Daly, Michael P.; Williams, Evan R.

    2011-01-01

    The gas-phase conformations of ubiquitin, cytochrome c, lysozyme, and ↦-lactalbumin ions, formed by electrospray ionization (ESI) from aqueous solutions containing 5 mM ammonium perchlorate, ammonium iodide, ammonium sulfate, ammonium chloride, ammonium thiocyanate, or guanidinium chloride, are examined using traveling-wave ion mobility spectrometry (TWIMS) coupled to time-of-flight (TOF) mass spectrometry (MS). For ubiquitin, cytochrome c, and ↦-lactalbumin, adduction of multiple acid molecules results in no significant conformational changes to the highest and lowest charge states formed from aqueous solutions, whereas the intermediate charge states become more compact. The transition to more compact conformers for the intermediate charge states occurs with fewer bound H2SO4 molecules than HClO4 or HI molecules, suggesting ion-ion or salt-bridge interactions are stabilizing more compact forms of the gaseous protein. However, the drift time distributions for protein ions of the same net charge with the highest levels of adduction of each acid are comparable, indicating that these protein ions all adopt similarly compact conformations or families of conformers. No change in conformation is observed upon the adduction of multiple acid molecules to charge states of lysozyme. These results show that the attachment of HClO4, HI, or H2SO4 to multiply protonated proteins can induce compact conformations in the resulting gas-phase protein ions. In contrast, differing Hofmeister effects are observed for the corresponding anions in solution at higher concentrations. PMID:21952780

  3. Simultaneous determination of 5-hydroxymethylfurfural and patulin in apple juice by reversed-phase liquid chromatography.

    PubMed

    Gökmen, V; Acar, J

    1999-06-25

    A rapid, simple and economical method was described for the simultaneous determination of 5-hydroxymethylfurfural (HMF) and patulin in apple juice. The sample was extracted with ethyl acetate and the extract was then cleaned up by extraction with a sodium carbonate solution. Then HMF and patulin were determined by reversed-phase liquid chromatography using a C18 column and a photodiode array detector. HMF and patulin could be completely resolved by using the mixture water-acetonitrile (99:1, v/v) as the mobile phase with a flow rate of 1.0 ml/min. Mean recoveries of HMF ranged from 86% to 100% with an overall mean of 94%, that of patulin ranged from 94% to 125% with an overall mean of 103%, for different spiking levels. The limits of detection for HMF and patulin in apple juice were found to be < 0.01 mg/l and < 5 micrograms/l, respectively. PMID:10431352

  4. Rapid reversed-phase liquid chromatographic determination of patulin in apple juice.

    PubMed

    Gökmen, V; Acar, J

    1996-04-12

    A rapid, simple and economical method using a limited amount of organic solvent is described for the determination of patulin in apple juice. The sample was extracted with ethyl acetate and the extract was cleaned up by extraction with sodium carbonate solution. Patulin was then determined by reversed-phase liquid chromatography using a MicroPack C18 column and a variable-wavelength UV-Vis detector set at 276 nm. Patulin and 5-hydroxymethylfurfural were completely resolved by using water-acetonitrile (99:1, v/v) as the mobile phase at a flow-rate of 1.0 ml/min. The detection limit was < 5 micrograms/l and the recovery was 98%. PMID:8680596

  5. 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

  6. Evaluation of mobile phase characteristics on three zwitterionic columns in hydrophilic interaction liquid chromatography mode for liquid chromatography-high resolution mass spectrometry based untargeted metabolite profiling of Leishmania parasites.

    PubMed

    Zhang, Rong; Watson, David G; Wang, Lijie; Westrop, Gareth D; Coombs, Graham H; Zhang, Tong

    2014-10-01

    It has been reported that HILIC column chemistry has a great effect on the number of detected metabolites in LC-HRMS-based untargeted metabolite profiling studies. However, no systematic investigation has been carried out with regard to the optimisation of mobile phase characteristics. In this study using 223 metabolite standards, we explored the retention mechanisms on three zwitterionic columns with varied mobile phase composition, demonstrated the interference from poor chromatographic peak shapes on the output of data extraction, and assessed the quality of chromatographic signals and the separation of isomers under each LC condition. As expected, on the ZIC-cHILIC column the acidic metabolites showed improved chromatographic performance at low pH which can be attributed to the opposite arrangement of the permanently charged groups on this column in comparison with the ZIC-HILIC column. Using extracts from the protozoan parasite Leishmania, we compared the numbers of repeatedly detected LC-HRMS features under different LC conditions with putative identification of metabolites not amongst the standards being based on accurate mass (±3ppm). Besides column chemistry, the pH of the mobile phase plays a key role in not only determining the retention mechanisms of solutes but also the output of the LC-HRMS data processing. Fast evaporation of ammonium carbonate produced less ion suppression in ESI source and consequently improved the detectability of the metabolites in low abundance in comparison with other ammonium salts. Our results show that the combination of a ZIC-pHILIC column with an ammonium carbonate mobile phase, pH 9.2, at 20mM in the aqueous phase or 10mM in both aqueous and organic mobile phase components, provided the most suitable LC conditions for LC-HRMS-based untargeted metabolite profiling of Leishmania parasite extracts. The signal reliability of the mass spectrometer used in this study (Exactive Orbitrap) was also investigated. PMID:25160959

  7. Decay dynamics of nascent acetonitrile and nitromethane dipole-bound anions produced by intracluster charge-transfer

    SciTech Connect

    Yandell, Margaret A.; King, Sarah B.; Neumark, Daniel M.

    2014-05-14

    Decay dynamics of nascent dipole bound states of acetonitrile and nitromethane are examined using time-resolved photoelectron imaging of iodide-acetonitrile (I{sup −}·CH{sub 3}CN) and iodide-nitromethane (I{sup −}·CH{sub 3}NO{sub 2}) complexes. Dipole-bound anions are created by UV-initiated electron transfer to the molecule of interest from the associated iodide ion at energies just below the vertical detachment energy of the halide-molecule complex. The acetonitrile anion is observed to decay biexponentially with time constants in the range of 4–900 ps. In contrast, the dipole bound state of nitromethane decays rapidly over 400 fs to form the valence bound anion. The nitromethane valence anion species then decays biexponentially with time constants of 2 ps and 1200 ps. The biexponential decay dynamics in acetonitrile are interpreted as iodine atom loss and autodetachment from the excited dipole-bound anion, followed by slower autodetachment of the relaxed metastable ion, while the dynamics of the nitromethane system suggest that a dipole-bound anion to valence anion transition proceeds via intramolecular vibrational energy redistribution to nitro group modes in the vicinity of the iodine atom.

  8. Theoretical analysis of co-solvent effect on the proton transfer reaction of glycine in a water–acetonitrile mixture

    SciTech Connect

    Kasai, Yukako; Yoshida, Norio Nakano, Haruyuki

    2015-05-28

    The co-solvent effect on the proton transfer reaction of glycine in a water–acetonitrile mixture was examined using the reference interaction-site model self-consistent field theory. The free energy profiles of the proton transfer reaction of glycine between the carboxyl oxygen and amino nitrogen were computed in a water–acetonitrile mixture solvent at various molar fractions. Two types of reactions, the intramolecular proton transfer and water-mediated proton transfer, were considered. In both types of the reactions, a similar tendency was observed. In the pure water solvent, the zwitterionic form, where the carboxyl oxygen is deprotonated while the amino nitrogen is protonated, is more stable than the neutral form. The reaction free energy is −10.6 kcal mol{sup −1}. On the other hand, in the pure acetonitrile solvent, glycine takes only the neutral form. The reaction free energy from the neutral to zwitterionic form gradually increases with increasing acetonitrile concentration, and in an equally mixed solvent, the zwitterionic and neutral forms are almost isoenergetic, with a difference of only 0.3 kcal mol{sup −1}. The free energy component analysis based on the thermodynamic cycle of the reaction also revealed that the free energy change of the neutral form is insensitive to the change of solvent environment but the zwitterionic form shows drastic changes. In particular, the excess chemical potential, one of the components of the solvation free energy, is dominant and contributes to the stabilization of the zwitterionic form.

  9. Effect of the physicochemical parameters of benzimidazole molecules on their retention by a nonpolar sorbent from an aqueous acetonitrile solution

    NASA Astrophysics Data System (ADS)

    Shafigulin, R. V.; Safonova, I. A.; Bulanova, A. V.

    2015-09-01

    The effect of the structure of benzimidazoles on their chromatographic retention on octadecyl silica gel from an aqueous acetonitrile eluent was studied. One- and many-parameter correlation equations were obtained by linear regression analysis, and their prognostic potential in determining the retention factors of benzimidazoles under study was analyzed.

  10. Theoretical analysis of co-solvent effect on the proton transfer reaction of glycine in a water-acetonitrile mixture

    NASA Astrophysics Data System (ADS)

    Kasai, Yukako; Yoshida, Norio; Nakano, Haruyuki

    2015-05-01

    The co-solvent effect on the proton transfer reaction of glycine in a water-acetonitrile mixture was examined using the reference interaction-site model self-consistent field theory. The free energy profiles of the proton transfer reaction of glycine between the carboxyl oxygen and amino nitrogen were computed in a water-acetonitrile mixture solvent at various molar fractions. Two types of reactions, the intramolecular proton transfer and water-mediated proton transfer, were considered. In both types of the reactions, a similar tendency was observed. In the pure water solvent, the zwitterionic form, where the carboxyl oxygen is deprotonated while the amino nitrogen is protonated, is more stable than the neutral form. The reaction free energy is -10.6 kcal mol-1. On the other hand, in the pure acetonitrile solvent, glycine takes only the neutral form. The reaction free energy from the neutral to zwitterionic form gradually increases with increasing acetonitrile concentration, and in an equally mixed solvent, the zwitterionic and neutral forms are almost isoenergetic, with a difference of only 0.3 kcal mol-1. The free energy component analysis based on the thermodynamic cycle of the reaction also revealed that the free energy change of the neutral form is insensitive to the change of solvent environment but the zwitterionic form shows drastic changes. In particular, the excess chemical potential, one of the components of the solvation free energy, is dominant and contributes to the stabilization of the zwitterionic form.

  11. Effect of solvent strength and temperature on retention for a polar-endcapped, octadecylsiloxane-bonded silica stationary phase with methanol-water mobile phases.

    PubMed

    Kiridena, Waruna; Poole, Colin F; Koziol, Wladyslaw W

    2004-12-10

    Synergi Hydro-RP is a new type of polar-endcapped, octadecylsiloxane-bonded silica packing for reversed-phase liquid chromatography. Its retention properties as a function of solvent strength and temperature are evaluated from the change in retention factors over the composition range (0-70% v/v methanol) and temperature range (25-65 degrees C) using the solvation parameter model and response surface methodologies. The main factors that affect retention are solute size and hydrogen-bond basicity, with minor contributions from solute hydrogen-bond acidity, dipole-type and electron lone pair interactions. Within the easily accessible range for both temperature and solvent strength, the ability to change selectivity is much greater for solvent strength than temperature. Also, a significant portion of the effect of increasing temperature is to reduce retention without changing selectivity. Response surfaces for the system constants are smooth and non-linear, except for cavity formation and dispersion interactions (v system constant), which is linear. Modeling of the response surfaces suggests that solvent strength and temperature are not independent factors for the b, s and e system constants and for the model intercept (c term). PMID:15628160

  12. Arsenic removal from contaminated brackish sea water by sorption onto Al hydroxides and Fe phases mobilized by land-use.

    PubMed

    Yu, Changxun; Peltola, Pasi; Nystrand, Miriam I; Virtasalo, Joonas J; Österholm, Peter; Ojala, Antti E K; Hogmalm, Johan K; Åström, Mats E

    2016-01-15

    This study examines the spatial and temporal distribution patterns of arsenic (As) in solid and aqueous materials along the mixing zone of an estuary, located in the south-eastern part of the Bothnian Bay and fed by a creek running through an acid sulfate (AS) soil landscape. The concentrations of As in solution form (<1 kDa) increase steadily from the creek mouth to the outer estuary, suggesting that inflowing seawater, rather than AS soil, is the major As source in the estuary. In sediments at the outer estuary, As was accumulated and diagenetically cycled in the surficial layers, as throughout much of the Bothnian Bay. In contrast, in sediments in the inner estuary, As concentrations and accumulation rates showed systematical peaks at greater depths. These peaks were overall consistent with the temporal trend of past As discharges from the Rönnskär smelter and the accompanied As concentrations in past sea-water of the Bothnian Bay, pointing to a connection between the historical smelter activities and the sediment-bound As in the inner estuary. However, the concentrations and accumulation rates of As peaked at depths where the smelter activities had already declined, but a large increase in the deposition of Al hydroxides and Fe phases occurred in response to intensified land-use in the mid 1960's and early 1970's. This correspondence suggests that, apart from the inflowing As-contaminated seawater, capture by Al hydroxides, Fe hydroxides and Fe-organic complexes is another important factor for As deposition in the inner estuary. After accumulating in the sediment, the solid-phase As was partly remobilized, as reflected by increased pore-water As concentrations, a process favored by As(V) reduction and high concentrations of dissolved organic matter. PMID:26558848

  13. 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.

  14. Gas-Phase Structure of Amyloid-β (12 - 28) Peptide Investigated by Infrared Spectroscopy, Electron Capture Dissociation and Ion Mobility Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Le, Thi Nga; Poully, Jean Christophe; Lecomte, Frédéric; Nieuwjaer, Nicolas; Manil, Bruno; Desfrançois, Charles; Chirot, Fabien; Lemoine, Jerome; Dugourd, Philippe; van der Rest, Guillaume; Grégoire, Gilles

    2013-12-01

    The gas-phase structures of doubly and triply protonated Amyloid-β12-28 peptides have been investigated through the combination of ion mobility (IM), electron capture dissociation (ECD) mass spectrometry, and infrared multi-photon dissociation (IRMPD) spectroscopy together with theoretical modeling. Replica-exchange molecular dynamics simulations were conducted to explore the conformational space of these protonated peptides, from which several classes of structures were found. Among the low-lying conformers, those with predicted diffusion cross-sections consistent with the ion mobility experiment were further selected and their IR spectra simulated using a hybrid quantum mechanical/semiempirical method at the ONIOM DFT/B3LYP/6-31 g(d)/AM1 level. In ECD mass spectrometry, the c/z product ion abundance (PIA) has been analyzed for the two charge states and revealed drastic differences. For the doubly protonated species, N - Cα bond cleavage occurs only on the N and C terminal parts, while a periodic distribution of PIA is clearly observed for the triply charged peptides. These PIA distributions have been rationalized by comparison with the inverse of the distances from the protonated sites to the carbonyl oxygens for the conformations suggested from IR and IM experiments. Structural assignment for the amyloid peptide is then made possible by the combination of these three experimental techniques that provide complementary information on the possible secondary structure adopted by peptides. Although globular conformations are favored for the doubly protonated peptide, incrementing the charge state leads to a conformational transition towards extended structures with 310- and α-helix motifs.

  15. Toward a Rational Design of Highly Folded Peptide Cation Conformations. 3D Gas-Phase Ion Structures and Ion Mobility Characterization

    NASA Astrophysics Data System (ADS)

    Pepin, Robert; Laszlo, Kenneth J.; Marek, Aleš; Peng, Bo; Bush, Matthew F.; Lavanant, Helène; Afonso, Carlos; Tureček, František

    2016-07-01

    Heptapeptide ions containing combinations of polar Lys, Arg, and Asp residues with non-polar Leu, Pro, Ala, and Gly residues were designed to study polar effects on gas-phase ion conformations. Doubly and triply charged ions were studied by ion mobility mass spectrometry and electron structure theory using correlated ab initio and density functional theory methods and found to exhibit tightly folded 3D structures in the gas phase. Manipulation of the basic residue positions in LKGPADR, LRGPADK, KLGPADR, and RLGPADK resulted in only minor changes in the ion collision cross sections in helium. Replacement of the Pro residue with Leu resulted in only marginally larger collision cross sections for the doubly and triply charged ions. Disruption of zwitterionic interactions in doubly charged ions was performed by converting the C-terminal and Asp carboxyl groups to methyl esters. This resulted in very minor changes in the collision cross sections of doubly charged ions and even slightly diminished collision cross sections in most triply charged ions. The experimental collision cross sections were related to those calculated for structures of lowest free energy ion conformers that were obtained by extensive search of the conformational space and fully optimized by density functional theory calculations. The predominant factors that affected ion structures and collision cross sections were due to attractive hydrogen bonding interactions and internal solvation of the charged groups that overcompensated their Coulomb repulsion. Structure features typically assigned to the Pro residue and zwitterionic COO-charged group interactions were only secondary in affecting the structures and collision cross sections of these gas-phase peptide ions.

  16. Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions

    DOE PAGESBeta

    Zheng, Haiyan; Li, Kuo; Cody, George D.; Tulk, Christopher A.; Dong, Xiao; Gao, Guoying; Molaison, Jamie J.; Liu, Zhenxian; Feygenson, Mikhail; Yang, Wenge; et al

    2016-08-25

    Acetonitrile (CH3CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. In this study, it is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH···N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp2 and sp3more » bonded carbon. Lastly, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst.« less

  17. Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions.

    PubMed

    Zheng, Haiyan; Li, Kuo; Cody, George D; Tulk, Christopher A; Dong, Xiao; Gao, Guoying; Molaison, Jamie J; Liu, Zhenxian; Feygenson, Mikhail; Yang, Wenge; Ivanov, Ilia N; Basile, Leonardo; Idrobo, Juan-Carlos; Guthrie, Malcolm; Mao, Ho-Kwang

    2016-09-19

    Acetonitrile (CH3 CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH⋅⋅⋅N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp(2) and sp(3) bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst. PMID:27561179

  18. Quantitative determination of aflatoxin B1 concentration in acetonitrile by chemometric methods using terahertz spectroscopy.

    PubMed

    Ge, Hongyi; Jiang, Yuying; Lian, Feiyu; Zhang, Yuan; Xia, Shanhong

    2016-10-15

    Aflatoxins contaminate and colonize agricultural products, such as grain, and thereby potentially cause human liver carcinoma. Detection via conventional methods has proven to be time-consuming and complex. In this paper, the terahertz (THz) spectra of aflatoxin B1 in acetonitrile solutions with concentration ranges of 1-50μg/ml and 1-50μg/l are obtained and analyzed for the frequency range of 0.4-1.6THz. Linear and nonlinear regression models are constructed to relate the absorption spectra and the concentrations of 160 samples using the partial least squares (PLS), principal component regression (PCR), support vector machine (SVM), and PCA-SVM methods. Our results indicate that PLS and PCR models are more accurate for the concentration range of 1-50μg/ml, whereas SVM and PCA-SVM are more accurate for the concentration range of 1-50μg/l. Furthermore, ten unknown concentration samples extracted from mildewed maize are analyzed quantitatively using these methods. PMID:27173565

  19. DFT simulation, quantum chemical electronic structure, spectroscopic and structure-activity investigations of 2-benzothiazole acetonitrile.

    PubMed

    Arjunan, V; Thillai Govindaraja, S; Jose, Sujin P; Mohan, S

    2014-07-15

    The Fourier transform infrared and FT-Raman spectra of 2-benzothiazole acetonitrile (BTAN) have been recorded in the range 4000-450 and 4000-100 cm(-1) respectively. The conformational analysis of the compound has been carried out to obtain the stable geometry of the compound. The complete vibrational assignment and analysis of the fundamental modes of the compound are carried out using the experimental FTIR and FT-Raman data and quantum chemical studies. The experimental vibrational frequencies are compared with the wavenumbers derived theoretically by B3LYP gradient calculations employing the standard 6-31G(**), high level 6-311++G(**) and cc-pVTZ basis sets. The structural parameters, thermodynamic properties and vibrational frequencies of the normal modes obtained from the B3LYP methods are in good agreement with the experimental data. The (1)H (400 MHz; CDCl3) and (13)C (100 MHz;CDCl3) nuclear magnetic resonance (NMR) spectra are also recorded. The electronic properties, the energies of the highest occupied and lowest unoccupied molecular orbitals are measured by DFT approach. The kinetic stability of the molecule has been determined from the frontier molecular orbital energy gap. The charges of the atoms and the structure-chemical reactivity relations of the compound are determined by its chemical potential, global hardness, global softness, electronegativity, electrophilicity and local reactivity descriptors by conceptual DFT methods. The non-linear optical properties of the compound have been discussed by measuring the polarisability and hyperpolarisability tensors. PMID:24662754

  20. Surprisingly Long-Lived Ascorbyl Radicals in Acetonitrile: Concerted Proton-Electron Transfer Reactions and Thermochemistry

    PubMed Central

    Warren, Jeffrey J.; Mayer, James M.

    2008-01-01

    Proton-coupled electron transfer (PCET) reactions and thermochemistry of 5,6-isopropylidene ascorbate (iAscH−) have been examined in acetonitrile solvent.iAscH− is oxidized by 2,4,6-tBu3C6H2O• and by excess TEMPO• to give the corresponding 5,6-isopropylidene ascorbyl radical anion (iAsc•−), which persists for hours at 298 K in dry MeCN solution. The stability of iAsc•− is surprising in light of the transience of the ascorbyl radical in aqueous solutions, and is due to the lack of the protons needed for radical disproportionation. A concerted proton-electron transfer (CPET) mechanism is indicated for the reactions of iAscH−. Redox potential, pKa and equilibrium measurements define the thermochemical landscape for 5,6-isopropylidene ascorbic acid and its derivatives in MeCN. These measurements give an O–H bond dissociation free energy (BDFE) for iAscH−of 65.4 ± 1.5 kcal mol−1 in MeCN. Similar studies on underivatized ascorbate indicate a BDFE of 67.8 ± 1.2 kcal mol−1. These values are much lower than the aqueous BDFE for ascorbate of 74.0 ± 1.5 kcal mol−1 derived from reported data. PMID:18505256

  1. Surprisingly long-lived ascorbyl radicals in acetonitrile: concerted proton-electron transfer reactions and thermochemistry.

    PubMed

    Warren, Jeffrey J; Mayer, James M

    2008-06-18

    Proton-coupled electron transfer (PCET) reactions and thermochemistry of 5,6-isopropylidene ascorbate (iAscH-) have been examined in acetonitrile solvent. iAscH- is oxidized by 2,4,6-tBu3C6H2O. and by excess TEMPO. to give the corresponding 5,6-isopropylidene ascorbyl radical anion (iAsc.-), which persists for hours at 298 K in dry MeCN solution. The stability of iAsc.- is surprising in light of the transience of the ascorbyl radical in aqueous solutions and is due to the lack of the protons needed for radical disproportionation. A concerted proton-electron transfer (CPET) mechanism is indicated for the reactions of iAscH-. Redox potential, pKa and equilibrium measurements define the thermochemical landscape for 5,6-isopropylidene ascorbic acid and its derivatives in MeCN. These measurements give an O-H bond dissociation free energy (BDFE) for iAscH- of 65.4 +/- 1.5 kcal mol-1 in MeCN. Similar studies on underivatized ascorbate indicate a BDFE of 67.8 +/- 1.2 kcal mol-1. These values are much lower than the aqueous BDFE for ascorbate of 74.0 +/- 1.5 kcal mol-1 derived from reported data. PMID:18505256

  2. ALMA Spectroscopy of Titan's Atmosphere: First Detections of Vinyl Cyanide and Acetonitrile Isotopologues

    NASA Astrophysics Data System (ADS)

    Cordiner, Martin; Y Palmer, Maureen; Nixon, Conor A.; Charnley, Steven B.; Mumma, Michael J.; Irwin, Pat G. J.; Teanby, Nick A.; Kisiel, Zbigniew; Serigano, Joseph

    2015-11-01

    Studies of Titan's atmospheric chemistry provide a unique opportunity to explore the origin and evolution of complex organic matter in primitive planetary atmospheres. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new telescope, well suited to the study of molecular emission from Titan's stratosphere and mesosphere. Here we present early results from our ongoing study to exploit the large volume of Titan data taken using ALMA in Early Science Mode (during the period 2012-2014). Combining data from multiple ALMA Band 6 observations, we obtained high-resolution mm-wave spectra with unprecedented sensitivity, enabling the first detection of vinyl cyanide (C2H3CN) in Titan's atmosphere. Initial estimates indicate a mesospheric abundance ratio with respect to ethyl cyanide (C2H5CN) of [C2H3CN]/[C2H5CN] = 0.31. In addition, we report the first detections on Titan of the 13C and 15N-substituted isotopologues of acetonitrile (13CH3CN and CH3C15N). Radiative transfer models and possible chemical formation pathways for these molecules will be discussed.

  3. Mineralogical and solid phase physical and geochemical controls on U mobility in the sediments from Rifle, CO

    NASA Astrophysics Data System (ADS)

    Qafoku, N.; Gartman, B.; Murray, C.; Arey, B.; Kukkadapu, R. K.; Resch, C.; Ward, A. L.; Draper, K.; Williams, K.; Long, P.

    2011-12-01

    An understanding of the subsurface mineralogical, physical and solid phase geochemical controls on contaminant U behavior and fate is of primordial importance in designing remediation strategies. Systematic studies using a variety of techniques, such as XRD, μ-XRD, Mössbauer spectroscopy, SEM/EDS, SEM/FIB, TEM/SAED, EMPA, XRF, EXAFS, and XANES were conducted with a variety of subsurface sediments from the Integrated Field Research Challenge site at Rifle, CO, to study U interaction with different subsurface minerals. The cores represented a cross section of sediment conditions that ranged from typical aquifer sediment (minimally reduced) to highly naturally bioreduced sediment from the saturated zone. Some of the subsurface minerals are unique, e.g., the framboidal pyrites of the naturally reduced zone (NRZ) of the Winchester gallery, or the sulfide minerals of different elements and co-contaminants (e.g., ZnS framboids) that were present in the NRZ of the La Quinta experimental plot. All these and other more common minerals, such as Fe oxides and phyllosilicate minerals have a pronounced effect on U fate and behavior in the Rifle subsurface. The solid phase physical and geochemical properties revealed a number of interesting trends. All particle size frequency distributions of the sediments from well CD-08 of the Plot C experimental plot were polymodal, implying complex pore size distribution and water retention functions. Surface area analysis suggests the presence of significant surface area in Rifle IFRC sediment, even on fine-gravel sediment. The wet chemical extractions and microwave digestion analyses showed that substantial amounts of co-contaminants, such as V, Zn, As, Se and Cu (some of them are redox sensitive elements which may compete for the available electrons), were present in the subsurface sediments. NRZs contain elevated concentrations of natural organic matter, Fe(II) and reduced inorganic sulfides. All of these constituents can scavenge

  4. Minimizing ultraviolet noise due to mis-matches between detector flow cell and post column mobile phase temperatures in supercritical fluid chromatography: effect of flow cell design.

    PubMed

    Berger, Terry A

    2014-10-17

    A mis-match between the post-column mobile phase temperature and the UV detector flow cell temperature can cause significant UV noise in supercritical fluid chromatography (SFC). Deviations as little as 5 °C can increase noise as much as 5 times, making the detector unsuited for trace analysis. Two approaches were used to minimize this noise. When a flow cell was in direct thermal contact (metal on metal) with the detector optical bench, the mobile phase temperature was actively controlled to the measured flow cell temperature, by using one of the heat exchangers (HX) in the column compartment. However, with some older, but still widely used flow cell designs, this required repeated, hourly monitoring of the flow cell temperature and repeated manual adjustment of the heat exchanger temperature, due to thermal drift. Flow cell design had a strong influence on susceptibility to this thermally induced noise. Thermally insulating the flow cell from the optical bench made some cells much less susceptible to such thermally induced noise. Five different flow cells, some insulated, some un-insulated, were evaluated. Most had a truncated conical flow path, but one had a cylindrical flow path. Using either approach, the ASTM noise, with a 10mm, 13 μL conical flow cell, could be optimized to ≈0.007 mAU at 2.5 Hz, in SFC, which is very near the 0.006 mAU manufacturer's specification for HPLC. The insulated version of this flow cell required far less optimization, compared to the un-insulated version. At 150 bar, an experimental 3mm, 2 μL flow cell, with only one side insulated, yielded noise slightly too high (≈0.16-0.18 mAU) for trace analysis, at 80 Hz. However, at 200 bar, noise at 80 Hz was <0.06 mAU, which should allow quantification of a 1 mAU tall trace component with a signal to noise ratio (S/N) >10. Even partially un-insulated, this flow cell design was much less susceptible to thermally induced noise. Further insulating this flow cell design failed to improve

  5. Fluoroquinolone antibiotic determination in bovine, ovine and caprine milk using solid-phase extraction and high-performance liquid chromatography-fluorescence detection with ionic liquids as mobile phase additives.

    PubMed

    Herrera-Herrera, Antonio V; Hernández-Borges, Javier; Rodríguez-Delgado, Miguel Angel

    2009-10-23

    This paper describes the use of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm-BF(4)) as mobile phase additive for the analysis by high-performance liquid chromatography with fluorescence detection of a group of seven basic fluoroquinolone antibiotics (i.e. fleroxacin, ciprofloxacin, lomefloxacin, danofloxacin, enrofloxacin, sarafloxacin and difloxacin) in different milk samples. EMIm-BF(4) was found superior to 1-butyl-3-methylimidazolium tetrafluoroborate for the separation of the analytes from chromatographic interferences of the sample matrix. The optimized method was applied to the analysis of ovine, caprine and bovine milk, in the last case in either skimmed, semi-skimmed and full-cream milk after suitable acidic deproteination followed by a solid-phase extraction procedure. Recovery values between 73% and 113% were obtained for the three types of bovine milk samples, as well as for ovine and caprine milk (RSDs below 16% in all cases), which clearly demonstrates the applicability of the method to the three types of milk irrespective of the fat content of the samples. Limits of detection were in the range of 0.5-8.1 microg/L (approximately 0.5-25.9 microg/kg), well below the maximum residue limits established for these compounds by the current European legislation. A screening study of 24 different milk samples was also developed. In none of the samples, residues of the selected antibiotics were found. PMID:19268960

  6. Analysis of nine food additives in red wine by ion-suppression reversed-phase high-performance liquid chromatography using trifluoroacetic acid and ammonium acetate as ion-suppressors.

    PubMed

    Zhao, Yong-Gang; Chen, Xiao-Hong; Yao, Shan-Shan; Pan, Sheng-Dong; Li, Xiao-Ping; Jin, Mi-Cong

    2012-01-01

    A reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed for the simultaneous determination of nine food additives, i.e., acesulfame, saccharin, caffeine, aspartame, benzoic acid, sorbic acid, stevioside, dehydroacetic acid and neotame in red wine. The effects of ion-suppressors, i.e., trifluoroacetic acid (TFA) and ammonium acetate (AmAc) on retention behavior of nine food additives in RP-HPLC separation were discussed in detail. The relationships between retention factors of solutes and volume percent of ion-suppressors in the mobile-phase systems of acetonitrile-TFA aqueous solution and acetonitrile-TFA-AmAc aqueous solution were quantitatively established, respectively. The results showed that the ion suppressors had not only an ion suppression effect, but also an organic modification effect on the acidic analytes. The baseline separation of nine food additives was completed by a gradient elution with acetonitrile-TFA(0.01%, v/v)-AmAc(2.5 mmol L(-1)) aqueous solution as the mobile phase. The recoveries were between 80.2 - 99.5% for all analytes with RSDs in the range of 1.5 - 8.9%. The linearities were in the range of 0.2 - 100.0 mg L(-1) with determination coefficients (r(2)) higher than 0.9991 for all analytes. The limits of quantification (LOQs) were between 0.53 - 0.99 mg L(-1). The applicability of the proposed method to detect and quantify food additives has been demonstrated in the analysis of 30 real samples. PMID:23059992

  7. Soil phosphorus mobility and solid-to-solution phase resupply studied by diffusive gradients in thin films: background soil properties driving their variation

    NASA Astrophysics Data System (ADS)

    Menezes-Blackburn, Daniel; Zhang, Hao; Giles, Courtney; George, Timothy; Shand, Charlie; Lumsdon, David; Cooper, Patricia; Wendler, Renate; Brown, Lawrie; Stutter, Marc; Blackwell, Martin; Darch, Tegan; Wearing, Catherine; Philip, Haygarth

    2015-04-01

    The mobility and resupply of inorganic phosphorus (P) from the solid phase was studied in 32 representative soils from the UK. The objective was to identify the background soil properties driving the variation of soil inorganic P desorption kinetics across different soil types. Diffusive gradients in thin films (DGT), diffusive equilibration in thin films (DET) and the DGT-induced fluxes in sediments model (DIFS) were used as tools for exploring solid-to-solution desorption kinetics. Previously characterized physicochemical properties of the same soils were used for correlation analysis. On average and across soil types, the inorganic P maximum distance of depletion was 0.42±0.10 cm, the equilibration time (Tc) was 3.63 h, the desorption rate constant (k-1) was 0.0046 h-1, and the desorption rate was 4.71 nmol l-1 s-1. The correlation between P in Olsen extractcs (POlsen) with PDGT, PDET and phosphorus effective concentration (PE) was enhanced when similar soils were isolated and used in the comparison, clearly showing that these parameters are affected differently by soil types. The PE was better correlated to Ptot, POlsen, PFeO, and PNaOH/EDTA than PDGT. This may indicate that PE is a better representation of P availability across soil types than PDGT. While the relative DGT-induced inorganic P flux in the first hour is mainly a function of soil wetting properties and % Corg, at longer times it is a function of the resupply capacity (R-Rdiff) of the soil solid phase. In general, resupply of P from the solid phase was less than that for other chemical elements, as shown by high Tc and low k-1 values. Desorption rates and resupply from the solid phase were fundamentally influenced by P saturation status, as reflected by their strong correlation with P concentration in water, FeO strips, Olsen and NaOH-EDTA extracts. Soil pH and particle size distribution had little or no effect on the evaluated parameters. The DGT and DET techniques, along with the DIFS model

  8. Influence of the charge distribution on the stationary phases zeta potential.

    PubMed

    Bocian, Szymon; Dziubakiewicz, Ewelina; Buszewski, Bogusław

    2015-08-01

    A set of seven home-made silica based bonded phases with different functional groups was investigated. Their zeta potential data in methanol and acetonitrile as well as in methanol/water and acetonitrile/water solution were obtained by using a Zetasizer. The influence of polar functional groups on a zeta potential was investigated. The results show that the amines incorporated in the structure of chemically bonded phases of reversed-phase materials are protonated during chromatographic analysis, resulting in changes of the zeta potential from negative to positive values. Acetonitrile causes more negative values and methanol provides positive (or less negative) values of the zeta potential. PMID:26011770

  9. Aqueous phase oligomerization of α,β-unsaturated carbonyls and acids investigated using ion mobility spectrometry coupled to mass spectrometry (IMS-MS)

    NASA Astrophysics Data System (ADS)

    Renard, Pascal; Tlili, Sabrine; Ravier, Sylvain; Quivet, Etienne; Monod, Anne

    2016-04-01

    One of the current essential issues to unravel our ability to forecast future climate change and air quality, implies a better understanding of natural processes leading to secondary organic aerosol (SOA) formation, and in particular the formation and fate of oligomers. The difficulty in characterizing macromolecules is to discern between large oxygenated molecules from series of oligomers containing repeated small monomers of diverse structures. In the present study, taking advantage from previously established radical vinyl oligomerization of methyl vinylketone (MVK) in the aqueous phase, where relatively simple oligomers containing up to 14 monomers were observed, we have investigated the same reactivity on several other unsaturated water soluble organic compounds (UWSOCs) and on a few mixtures of these precursor compounds. The technique used to characterize the formed oligomers was a traveling wave ion mobility spectrometry coupled to a hybrid quadrupole - time of flight mass spectrometer (IMS-MS) fitted with an electrospray source and ultra-high performance liquid chromatography (UPLC). The technique allows for an additional separation, especially for large ions, containing long carbon chains. We have shown the efficiency of the IMS-mass spectrometry technique to detect oligomers derived from MVK photooxidation in the aqueous phase. The results were then compared to other oligomers, derived from ten other individual biogenic UWSOCs. The technique allowed distinguishing between different oligomers arising from different precursors. It also clearly showed that compounds bearing a non-conjugated unsaturation did not provide oligomerization. Finally, it was shown that the IMS-mass spectrometry technique, applied to mixtures of unsaturated conjugated precursors, exhibited the ability of these precursors to co-oligomerize, i.e. forming only one complex oligomer system bearing monomers of different structures. The results are discussed in terms of atmospheric

  10. Carbon nanotubes@silicon dioxide nanohybrids coating for solid-phase microextraction of organophosphorus pesticides followed by gas chromatography-corona discharge ion mobility spectrometric detection.

    PubMed

    Saraji, Mohammad; Jafari, Mohammad Taghi; Mossaddegh, Mehdi

    2016-01-15

    A high efficiency solid-phase microextraction (SPME) fiber coated with porous carbon nanotubes-silicon dioxide (CNTs-SiO2) nanohybrids was synthesized and applied for the determination of some organophosphorus pesticides (OPPs) in vegetables, fruits and water samples. Gas chromatography-corona discharge ion mobility spectrometry was used as the detection system. Glucose, as a biocompatible compound, was used for connecting CNT and SiO2 during a hydrothermal process. The electrospinning technique was also applied for the fiber preparation. The parameters affecting the efficiency of extraction, including stirring rate, salt effect, extraction temperature, extraction time, desorption temperature and desorption time, were investigated and optimized. The developed CNTs@SiO2 fiber presented better extraction efficiency than the commercial SPME fibers (PA, PDMS, and PDMS-DVB). The intra- and inter-day relative standard deviations were found to be lower than 6.2 and 9.0%, respectively. For water samples, the limits of detection were in the range of 0.005-0.020 μg L(-1) and the limits of quantification were between 0.010 and 0.050 μg L(-1). The results showed a good linearity in the range of 0.01-3.0 μg L(-1) for the analytes. The spiking recoveries ranged from 79 (± 9) to 99 (± 8). The method was successfully applied for the determination of OPPs in real samples. PMID:26709024

  11. High Sensitivity Method to Estimate Distribution of Hyaluronan Molecular Sizes in Small Biological Samples Using Gas-Phase Electrophoretic Mobility Molecular Analysis

    PubMed Central

    Do, Lan; Dahl, Christen P.; Kerje, Susanne; Hansell, Peter; Mörner, Stellan; Lindqvist, Ulla; Engström-Laurent, Anna; Larsson, Göran; Hellman, Urban

    2015-01-01

    Hyaluronan is a negatively charged polydisperse polysaccharide where both its size and tissue concentration play an important role in many physiological and pathological processes. The various functions of hyaluronan depend on its molecular size. Up to now, it has been difficult to study the role of hyaluronan in diseases with pathological changes in the extracellular matrix where availability is low or tissue samples are small. Difficulty to obtain large enough biopsies from human diseased tissue or tissue from animal models has also restricted the study of hyaluronan. In this paper, we demonstrate that gas-phase electrophoretic molecular mobility analyzer (GEMMA) can be used to estimate the distribution of hyaluronan molecular sizes in biological samples with a limited amount of hyaluronan. The low detection level of the GEMMA method allows for estimation of hyaluronan molecular sizes from different parts of small organs. Hence, the GEMMA method opens opportunity to attain a profile over the distribution of hyaluronan molecular sizes and estimate changes caused by disease or experimental conditions that has not been possible to obtain before. PMID:26448761

  12. Detection of piperonal emitted from polymer controlled odor mimic permeation systems utilizing Canis familiaris and solid phase microextraction-ion mobility spectrometry.

    PubMed

    Macias, Michael S; Guerra-Diaz, Patricia; Almirall, José R; Furton, Kenneth G

    2010-02-25

    Currently, in the field of odor detection, there is generally a wider variation in limit of detections (LODs) for canines than instruments. The study presented in this paper introduces an improved protocol for the creation of controlled odor mimic permeation system (COMPS) devices for use as standards in canine training and discusses the canine detection thresholds of piperonal, a starting material for the illicit drug 3,4-methylenedioxymethamphetamine (MDMA), when exposed to these devices. Additionally, this paper describes the first-ever reported direct comparison of solid phase microextraction-ion mobility spectrometry (SPME-IMS) to canine detection for the MDMA odorant, piperonal. The research presented shows the reliability of COMPS devices as low cost field calibrants providing a wide range of odorant concentrations for biological and instrumental detectors. The canine LOD of piperonal emanating from the 100 ng s(-1) COMPS was found to be 1 ng as compared to the SPME-IMS LOD of piperonal in a static, closed system at 2 ng, with a linear dynamic range from 2 ng to 11 ng. The utilization of the COMPS devices would allow for training that will reduce the detection variability between canines and maintain improved consistency for training purposes. Since both SPME and IMS are field portable technologies, it is expected that this coupled method will be useful as a complement to canine detection for the field detection of MDMA. PMID:20044224

  13. Improved isoelectric focusing chromatography on strong anion exchange media via a new model that custom designs mobile phases using simple buffers.

    PubMed

    Choy, Derek Y C; Creagh, A Louise; Haynes, Charles

    2014-03-01

    Isoelectric chromatofocusing (ICF), a mode of chromatography by which proteins are separated based on changes in their charge state with pH, is widely used at analytical scales and finding increasing interest in biologics manufacturing due to its exceptional resolving power. Here, a method is described for using simple monoprotic and diprotic buffers to create stable mobile phases for sample loading on a strong anion exchange column and for achieving an elution pH gradient of desired shape covering any pH range from pH 10.0 to 3. The buffers used are selected to satisfy cost constraints, and to permit facile detection of eluted biologics by UV spectroscopy and mass spectrometry. The method exploits a new model described here that combines multiple-chemical and adsorption-equilibria theory to enable in silico tailoring of elution pH profiles using mixtures of these simple buffers. It is shown to provide a versatile platform for optimizing and conducting ICF of protein mixtures on strong anion exchange media. PMID:24166014

  14. Polypyrrole nanowire as an excellent solid phase microextraction fiber for bisphenol A analysis in food samples followed by ion mobility spectrometry.

    PubMed

    Kamalabadi, Mahdie; Mohammadi, Abdorreza; Alizadeh, Naader

    2016-08-15

    A polypyrrole nanowire coated fiber was prepared and used in head-space solid phase microextraction coupled with ion mobility spectrometry (HS-SPME-IMS) to the analysis of bisphenol A (BPA) in canned food samples, for the first time. This fiber was synthesized by electrochemical oxidation of the monomer in aqueous solution. The fiber characterization by scanning electron microscopy (SEM) revealed that the new fiber exhibited two-dimensional structures with a nanowire morphology. The effects of important extraction parameters on the efficiency of HS-SPME were investigated and optimized. Under the optimum conditions, the linearity of 10-150ngg(-1) and limit of detection (based on S/N=3) of 1ngg(-1) were obtained in BPA analysis. The repeatability (n=5) expressed as the relative standard deviation (RSD%) was 5.8%. At the end, the proposed method was successfully applied to determine BPA in various canned food samples (peas, corns, beans). Relative recoveries were obtained 93-96%. Method validation was conducted by comparing our results with those obtained through HPLC with fluorescence detection (FLD). Compatible results indicate that the proposed method can be successfully used in BPA analysis. This method is simple and cheaper than chromatographic methods, with no need of extra organic solvent consumption and derivatization prior to sample introduction. PMID:27260447

  15. Determination of furfural and hydroxymethylfurfural from baby formula using headspace solid phase microextraction based on nanostructured polypyrrole fiber coupled with ion mobility spectrometry.

    PubMed

    Kamalabadi, Mahdie; Ghaemi, Elham; Mohammadi, Abdorreza; Alizadeh, Naader

    2015-08-15

    Furfural (Fu) and hydroxymethylfurfural (HMFu) are extracted using a dodecylbenzenesulfonate-doped polypyrrole coating as a fiber for headspace solid phase microextraction (HS-SPME) method in baby formula samples and detected using ion mobility spectrometry (IMS). Sample pH, salt effect, extraction time and temperature were investigated and optimized as effective parameters in HS-SPME. The calibration curves were linear in the range of 20-300 ng g(-1) (R(2)>0.99). Limits of detection for Fu and HMFu were 6 ng g(-1) and 5 ng g(-1), respectively. The RSD% of Fu and HMFu for five analyses was 4.4 and 4.9, respectively. The proposed method was successfully applied to determine of Fu and HMFu in the different baby formula samples with satisfactory result. The results were in agreement with those obtained using HPLC analysis. The HS-SPME-IMS is precise, selective and sensitive analytical method for determination of Fu and HMFu in baby formula samples, without any derivatization process. PMID:25794723

  16. HPLC/APCI Mass Spectrometry of Saturated and Unsaturated Hydrocarbons by Using Hydrocarbon Solvents as the APCI Reagent and HPLC Mobile Phase

    NASA Astrophysics Data System (ADS)

    Gao, Jinshan; Owen, Benjamin C.; Borton, David J.; Jin, Zhicheng; Kenttämaa, Hilkka I.

    2012-05-01

    Saturated and unsaturated, linear, branched, and cyclic hydrocarbons, as well as polyaromatic and heteroaromatic hydrocarbons, were successfully ionized by atmospheric pressure chemical ionization (APCI) using small hydrocarbons as reagents in a linear quadrupole ion trap (LQIT) mass spectrometer. Pentane was proved to be the best reagent among the hydrocarbon reagents studied. This ionization method generated different types of abundant ions (i.e., [M + H]+, M+•, [M - H]+ and [M - 2H]+ •), with little or no fragmentation. The radical cations can be differentiated from the even-electron ions by using dimethyl disulfide, thus facilitating molecular weight (MW) determination. While some steroids and lignin monomer model compounds, such as androsterone and 4-hydroxy-3-methoxybenzaldehyde, also formed abundant M+• and [M + H]+ ions, this was not true for all of them. Analysis of two known mixtures as well as a base oil sample demonstrated that each component of the known mixtures could be observed and that a correct MW distribution was obtained for the base oil. The feasibility of using this ionization method on the chromatographic time scale was demonstrated by using high-performance liquid chromatography (HPLC) with hexane as the mobile phase (and APCI reagent) to separate an artificial mixture prior to mass spectrometric analysis.

  17. The solvation of ions in acetonitrile and acetone. II. Monte Carlo simulations using polarizable solvent models

    NASA Astrophysics Data System (ADS)

    Fischer, R.; Richardi, J.; Fries, P. H.; Krienke, H.

    2002-11-01

    Structural properties and energies of solvation are simulated for alkali and halide ions. The solvation structure is discussed in terms of various site-site distribution functions, of solvation numbers, and of orientational correlation functions of the solvent molecules around the ions. The solvent polarizability has notable effects which cannot be intuitively predicted. In particular, it is necessary to reproduce the experimental solvation numbers of small ions. The changes of solvation properties are investigated along the alkali and halide series. By comparing the solvation of ions in acetone to that in acetonitrile, it is shown that the spatial correlations among the solvent molecules around an ion result in a strong screening of the ion-solvent direct intermolecular potential and are essential to understand the changes in the solvation structures and energies between different solvents. The solvation properties derived from the simulations are compared to earlier predictions of the hypernetted chain (HNC) approximation of the molecular Ornstein-Zernike (MOZ) theory [J. Richardi, P. H. Fries, and H. Krienke, J. Chem. Phys. 108, 4079 (1998)]. The MOZ(HNC) formalism gives an overall qualitatively correct picture of the solvation and its various unexpected findings are corroborated. For the larger ions, its predictions become quantitative. The MOZ approach allows to calculate solvent-solvent and ion-solvent potentials of mean force, which shed light on the 3D labile molecular and ionic architectures in the solution. These potentials of mean force convey a unique information which is necessary to fully interpret the angle-averaged structural functions computed from the simulations. Finally, simulations of solutions at finite concentrations show that the solvent-solvent and ion-solvent spatial correlations at infinite dilution are marginally altered by the introduction of fair amounts of ions.

  18. Iron(II) catalysis in oxidation of hydrocarbons with ozone in acetonitrile

    DOE PAGESBeta

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2015-02-11

    Oxidation of alcohols, ethers, and sulfoxides by ozone in acetonitrile is catalyzed by submillimolar concentrations of Fe(CH3CN)62+. The catalyst provides both rate acceleration and greater selectivity toward the less oxidized products. For example, Fe(CH3CN)62+-catalyzed oxidation of benzyl alcohol yields benzaldehyde almost exclusively (>95%), whereas the uncatalyzed reaction generates a 1:1 mixture of benzaldehyde and benzoic acid. Similarly, aliphatic alcohols are oxidized to aldehydes/ketones, cyclobutanol to cyclobutanone, and diethyl ether to a 1:1 mixture of ethanol and acetaldehyde. The kinetics of oxidation of alcohols and diethyl ether are first-order in [Fe(CH3CN)62+] and [O3] and independent of [substrate] at concentrations greater thanmore » ~5 mM. In this regime, the rate constant for all of the alcohols is approximately the same, kcat = (8 ± 1) × 104 M–1 s–1, and that for (C2H5)2O is (5 ± 0.5) × 104 M–1 s–1. In the absence of substrate, Fe(CH3CN)62+ reacts with O3 with kFe = (9.3 ± 0.3) × 104 M–1 s–1. The similarity between the rate constants kFe and kcat strongly argues for Fe(CH3CN)62+/O3 reaction as rate-determining in catalytic oxidation. The active oxidant produced in Fe(CH3CN)62+/O3 reaction is suggested to be an Fe(IV) species in analogy with a related intermediate in aqueous solutions. As a result, this assignment is supported by the similarity in kinetic isotope effects and relative reactivities of the two species toward substrates.« less

  19. Liquid chromatographic resolution of amino acid esters of acyclovir including racemic valacyclovir on crown ether-based chiral stationary phases.

    PubMed

    Ahn, Seong Ae; Hyun, Myung Ho

    2015-03-01

    Valacyclovir, a potential prodrug for the treatment of patients with herpes simplex and herpes zoster, and its analogs were resolved on two chiral stationary phases (CSPs) based on (3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 covalently bonded to silica gel. In order to find out an appropriate mobile phase condition, various mobile phases consisting of various organic modifiers in water containing various acidic modifiers were applied to the resolution of valacyclovir and its analogs. When 30% acetonitrile in water containing any of 0.05 M, 0.10 M, or 0.15 M perchloric acid was used as a mobile phase, valacyclovir and its analogs were resolved quite well on the two CSPs with the separation factors (α) in the range of 2.49 ~ 6.35 and resolutions (RS ) in the range of 2.95 ~ 12.21. Between the two CSPs, the CSP containing residual silanol protecting n-octyl groups on the silica surface was found to be better than the CSP containing residual silanol groups. PMID:25626672

  20. Kinetics and mechanism of monomolecular heterolysis of framework compounds. VI. Dehydrobromination of 2-bromo-2-methyladamantane in acetonitrile

    SciTech Connect

    Ponomareva, E.A.; Vasil'kevich, A.I.; Tarsenko, P.V.; Dvorko, G.F.

    1988-08-10

    The kinetics of dehydrobromination of 2-bromo-2-methyladamantane in acetonitrile were studied in the presence of triphenylverdazyl as internal indicator; k/sub 25/ = 8.57 /times/ 10/sup /minus/5/ sec/sup /minus/1/, /Delta/H/sup /ne// 79 kJ/mole, /Delta/S/sup /ne// /minus/58 kJ/mole /times/ deg. Additions of water, phenols, lithium perchlorate, and bromides increase the reaction rate, and additions of nitrates and picrates reduce it. A similar pattern is observed in the dehydrobromination of tert-butyl bromide in acetonitrile. In the presence of tetraethylammonium chloride the heterolysis rate of 2-bromo-2-methyladamantane decreases, while that of tert-butyl bromide increases. The positive salt effect is explained by stabilization of the transition state by the salt, and the negative salt effect is explained by the reaction of the anion with the sterically separated or solvent-separated ion pair of the substrate.

  1. Fluorescence of excited charge-transfer complexes and absolute dynamics of radical-ion pairs in acetonitrile

    SciTech Connect

    Gould, I.R.; Farid, S.

    1992-09-17

    An analysis of the dynamics of the radical-ion pairs of a series of 2,6,9,10-tetracyanoanthracene acceptor/alkylbenzene donor systems in acetonitrile is described in this paper. This analysis is carried out by using a combination of time-resolved emission and absorption spectroscopies and measurements of {Phi} {sub ions} from the contact radical-ion pair (CRIP) and the solvent-separated radical-ion pair (SSRIP).

  2. Complexation dynamics of CH3SCN and Li(+) in acetonitrile studied by two-dimensional infrared spectroscopy.

    PubMed

    Kwon, YoungAh; Park, Sungnam

    2015-10-01

    Ion-molecule complexation dynamics were studied with CH3SCN and Li(+) in acetonitrile by vibrationally probing the nitrile stretching vibration of CH3SCN. The nitrile stretching vibration of CH3SCN has a long lifetime (T1 = ∼90 ps) and its frequency is significantly blue-shifted when CH3SCN is bound with Li(+) ions to form a CH3SCNLi(+) complex in acetonitrile. Such spectral properties enable us to distinguish free CH3SCN and the CH3SCNLi(+) complex in solutions and measure their dynamics occurring on hundred picosecond timescales. For the complexation between CH3SCN and Li(+) in acetonitrile, the change in enthalpy (ΔH = -7.17 kJ mol(-1)) and the change in entropy (ΔS = -34.4 J K(-1) mol(-1)) were determined by temperature-dependent FTIR experiments. Polarization-controlled infrared pump-probe (IR PP) spectroscopy was used to measure the population decay and orientational dynamics of free CH3SCN and the CH3SCNLi(+) complex. Especially, the orientational relaxation of the CH3SCNLi(+) complex was found to be almost 3 times slower than those of free CH3SCN because Li(+) ions strongly interact with the neighboring solvents. Most importantly, the complexation dynamics of CH3SCN and Li(+) in acetonitrile were successfully measured in real time by 2DIR spectroscopy for the first time and the dissociation and association time constants were directly determined by using the two-species exchange kinetic model. Our experimental results provide a comprehensive overview of the ion-molecule complexation dynamics in solutions occurring under thermal equilibrium conditions. PMID:26323322

  3. Iron(II) catalysis in oxidation of hydrocarbons with ozone in acetonitrile

    SciTech Connect

    Bataineh, Hajem; Pestovsky, Oleg; Bakac, Andreja

    2015-02-11

    Oxidation of alcohols, ethers, and sulfoxides by ozone in acetonitrile is catalyzed by submillimolar concentrations of Fe(CH3CN)62+. The catalyst provides both rate acceleration and greater selectivity toward the less oxidized products. For example, Fe(CH3CN)62+-catalyzed oxidation of benzyl alcohol yields benzaldehyde almost exclusively (>95%), whereas the uncatalyzed reaction generates a 1:1 mixture of benzaldehyde and benzoic acid. Similarly, aliphatic alcohols are oxidized to aldehydes/ketones, cyclobutanol to cyclobutanone, and diethyl ether to a 1:1 mixture of ethanol and acetaldehyde. The kinetics of oxidation of alcohols and diethyl ether are first-order in [Fe(CH3CN)62+] and [O3] and independent of [substrate] at concentrations greater than ~5 mM. In this regime, the rate constant for all of the alcohols is approximately the same, kcat = (8 ± 1) × 104 M–1 s–1, and that for (C2H5)2O is (5 ± 0.5) × 104 M–1 s–1. In the absence of substrate, Fe(CH3CN)62+ reacts with O3 with kFe = (9.3 ± 0.3) × 104 M–1 s–1. The similarity between the rate constants kFe and kcat strongly argues for Fe(CH3CN)62+/O3 reaction as rate-determining in catalytic oxidation. The active oxidant produced in Fe(CH3CN)62+/O3 reaction is suggested to be an Fe(IV) species in analogy with a related intermediate in aqueous solutions. As a result, this assignment is supported by the similarity in kinetic isotope effects and relative reactivities of the two species toward substrates.

  4. Determination of Sudan dyes in chili pepper powder by online solid-phase extraction with a butyl methacrylate monolithic column coupled to liquid chromatography with tandem mass spectrometry.

    PubMed

    Liu, Yao; Wang, Man-Man; Ai, Lian-Feng; Zhang, Chang-Kun; Li, Xin; Wang, Xue-Sheng

    2014-07-01

    A poly(butyl methacrylate-co-ethylene dimethacrylate) monolithic column was fabricated and used as a novel sorbent for online solid-phase extraction coupled to liquid chromatography with tandem mass spectrometry for the simultaneous determination of Sudan I-IV in chili pepper powder. The prepared columns were characterized by scanning electron microscopy, nitrogen adsorption-desorption, and pressure drop measurements. Online solid-phase extraction was performed on the synthesized monolithic column using 10 mM ammonium acetate solution as the loading solution with the aid of an online cleanup chromatography system. The desorption of Sudan I-IV was achieved with acetonitrile as the eluting solution at the flow rate of 0.5 mL/min. The extracted analytes were subsequently eluted into a C18 analytical column for chromatographic separation using a mixture of 10% acetonitrile/90% formic acid (0.5%) solution as the mobile phase. Under the optimized conditions, the developed method had linear range of 1.0-50 μg/kg, a detection limit of 0.3 μg/kg, and a quantification limit of 1.0 μg/kg for each analyte. The intraday and interday recoveries of Sudan I-IV in chili pepper powder samples ranged from 94.8 to 100.9% and 94.9 to 99.4%, respectively. The intraday and interday precision were between 3.37-7.01% and 5.01-7.68%, respectively. PMID:24723310

  5. N-MOSFETs Formed on Solid Phase Epitaxially Grown GeSn Film with Passivation by Oxygen Plasma Featuring High Mobility.

    PubMed

    Fang, Yung-Chin; Chen, Kuen-Yi; Hsieh, Ching-Heng; Su, Chang-Chia; Wu, Yung-Hsien

    2015-12-01

    Solid phase epitaxially grown GeSn was employed as the platform to assess the eligibility of direct O2 plasma treatment on GeSn surface for passivation of GeSn N-MOSFETs. It has been confirmed that O2 plasma treatment forms a GeSnO(x) film on the surface and the GeSnO(x) topped by in situ Al2O3 constitutes the gate stack of GeSn MOS devices. The capability of the surface passivation was evidenced by the low interface trap density (D(it)) of 1.62 × 10(11) cm(-2) eV(-1), which is primarily due to the formation of Ge-O and Sn-O bonds at the surface by high density/reactivity oxygen radicals that effectively suppress dangling bonds and decrease gap states. The good D(it) not only makes tiny frequency dispersion in the characterization of GeSn MOS capacitors, but results in GeSn N-MOSFETs with outstanding peak electron mobility as high as 518 cm(2)/(V s) which outperforms other devices reported in the literature due to reduced undesirable carrier scattering. In addition, the GeSn N-MOSFETs also exhibit promising characteristics in terms of acceptable subthreshold swing of 156 mV/dec and relatively large I(ON)/I(OFF) ratio more than 4 orders. Moreover, the robust reliability in terms small V(t) variation against high field stress attests the feasibility of using the O2 plasma-treated passivation to advanced GeSn technology. PMID:26579560

  6. Halloysite nanotubes-titanium dioxide as a solid-phase microextraction coating combined with negative corona discharge-ion mobility spectrometry for the determination of parathion.

    PubMed

    Saraji, Mohammad; Jafari, Mohammad Taghi; Mossaddegh, Mehdi

    2016-07-01

    Halloysite nanotubes-titanium dioxide (HNTs-TiO2) as a biocompatible environmentally friendly solid-phase microextraction (SPME) fiber coating was prepared. HNTs-TiO2 was chemically coated on the surface of a fused-silica fiber using a sol-gel process. Parathion as an organophosphorus pesticide was selected as a model compound to investigate the extraction efficiency of the fiber. The extracted analyte was detected by negative corona discharge-ion mobility spectrometer (NCD-IMS). The effective parameters on the extraction efficiency, such as salt effect, extraction temperature and extraction time were investigated and optimized. The extraction efficiency of HNTs-TiO2 fiber was compared with bare-silica (sol-gel based coating without HNTs-TiO2), HNTs, carbon nanotubes and commercial SPME fibers (PA, PDMS, and PDMS-DVB). The HNTs-TiO2 fiber showed highest extraction efficiency among the studied fibers. The intra- and inter-day relative standard deviations were found to be 4.3 and 6.3%, respectively. The limit of detection and limit of quantification values were 0.03 and 0.1 μg L(-1), respectively. The dynamic range of the method was in the range of 0.1-25 μg L(-1). The spiking recoveries were between 85 (±9) and 97 (±6). The SPME-HNTs-TiO2 combined with NCD-IMS was successfully applied for the determination of parathion in apple, strawberry, celery and water samples. PMID:27216393

  7. Thermodynamics and mass transfer kinetics of phenol in reversed phase liquid chromatography

    SciTech Connect

    Kaczmarski, Krzysztof; Gritti, Fabrice; Guiochon, Georges A

    2006-05-01

    The thermodynamics and the mass transfer kinetics of the chromatographic system made of phenol, in a water-acetonitrile mobile phase, on a C18 RPLC column, were studied in the temperature range from 21 to 77 C and the interstitial velocity range of 0.021 to 1.27 cm/s. The equilibrium isotherm was accurately approximated by a multilayer model assuming lateral interactions between adsorbed molecules. The parameters of the kinetics of the phenol mass transfer in this column were measured by the method of moments. These data were analyzed using the available models and correlations. It was proven that the parameters of the mass transfer kinetics measured under linear conditions could be successfully used for the prediction of the concentration profiles obtained under overloaded conditions.

  8. HPLC-MS/MS enantioseparation of triazole fungicides using polysaccharide-based stationary phases.

    PubMed

    Zhang, Hu; Qian, Mingrong; Wang, Xinquan; Wang, Xiangyun; Xu, Hao; Wang, Qiang; Wang, Minghua

    2012-04-01

    The enantiomeric separation of 21 triazole fungicides was carried out on four polysaccharide-derived chiral stationary phases in the reversed phase separation mode using high performance liquid chromatography coupled with tandem mass spectrometry. All fungicides were detected in electrospray ionization (ESI) positive mode with selected reaction monitoring (SRM). Complete enantioseparation was achieved for 21 fungicides except for difenoconazole based on cellulose tris (3,5-dimethylphenylcarbamate) and cellulose tris (3-chloro-4-methylphenyl carbamate) columns by optimizing experimental conditions including mobile phase and column temperature. Mobile phase was 0.1% formic acid aqueous solution mixed with methanol or acetonitrile in different proportions. Among all the fungicides, 15 with two enantiomers and three with four stereoisomers (bitertanol, bromuconazole, and cyproconazole) were successfully separated at 25°C. Enantioseparation for the other three fungicides (propiconazole, triadimenol, and difenoconazole) with four stereoisomers could be achieved by changing the column temperature from 10 to 40°C. Propiconazole and triadimenol were enantioseparated on baseline at 40 and at 35°C, respectively, and difenoconazole was enantioseparated partially with the R(s) > 1.1 at 25°C. Moreover, linearities and limits of detection (LODs) of 21 fungicides except for difenoconazole were studied, showing coefficients of determination (R(2)) higher than 0.99 and LODs lower than 2.5 μg/L. PMID:22532344

  9. Development and validation of a reversed phase liquid chromatographic method for analysis of oxytetracycline and related impurities.

    PubMed

    Kahsay, Getu; Shraim, Fairouz; Villatte, Philippe; Rotger, Jacques; Cassus-Coussère, Céline; Van Schepdael, Ann; Hoogmartens, Jos; Adams, Erwin

    2013-03-01

    A simple, robust and fast high-performance liquid chromatographic method is described for the analysis of oxytetracycline and its related impurities. The principal peak and impurities are all baseline separated in 20 min using an Inertsil C₈ (150 mm × 4.6 mm, 5 μm) column kept at 50 °C. The mobile phase consists of a gradient mixture of mobile phases A (0.05% trifluoroacetic acid in water) and B (acetonitrile-methanol-tetrahydrofuran, 80:15:5, v/v/v) pumped at a flow rate of 1.3 ml/min. UV detection was performed at 254 nm. The developed method was validated for its robustness, sensitivity, precision and linearity in the range from limit of quantification (LOQ) to 120%. The limits of detection (LOD) and LOQ were found to be 0.08 μg/ml and 0.32 μg/ml, respectively. This method allows the separation of oxytetracycline from all known and 5 unknown impurities, which is better than previously reported in the literature. Moreover, the simple mobile phase composition devoid of non-volatile buffers made the method suitable to interface with mass spectrometry for further characterization of unknown impurities. The developed method has been applied for determination of related substances in oxytetracycline bulk samples available from four manufacturers. The validation results demonstrate that the method is reliable for quantification of oxytetracycline and its impurities. PMID:23277151

  10. The effects of mobile ATM switches on PNNI peer group operation

    SciTech Connect

    Martinez, L.; Sholander, P.; Tolendino, L.

    1997-04-01

    This contribution discusses why, and how, mobile networks and mobile switches might be discussed during Phase 1 of the WATM standards process. Next, it reviews mobile routers within Mobile IP. That IP mobility architecture may not apply to the proposed mobile ATM switches. Finally, it discusses problems with PNNI peer group formation and operation when mobile ATM switches are present.

  11. Poly(L-lactic acid)-modified silica stationary phase for reversed-phase and hydrophilic interaction liquid chromatography.

    PubMed

    Ohyama, Kaname; Takasago, Shizuka; Kishikawa, Naoya; Kuroda, Naotaka

    2015-03-01

    Poly(L-lactic acid) is a linear aliphatic thermoplastic polyester that can be produced from renewable resources. A poly(L-lactic acid)-modified silica stationary phase was newly prepared by amide bond reaction between amino groups on aminopropyl silica and carboxylic acid groups at the end of the poly(L-lactic acid) chain. The poly(L-lactic acid)-silica column was characterized in reversed-phase liquid chromatography and hydrophilic interaction liquid chromatography with the use of different mobile phase compositions. The poly(L-lactic acid)-silica column was found to work in both modes, and the retention of test compounds depending on acetonitrile content exhibited "U-shaped" curves, which was an indicator of reversed-phase liquid chromatography/hydrophilic interaction liquid chromatography mixed-mode retention behavior. In addition, carbonyl groups included into the poly(L-lactic acid) backbone work as an electron-accepting group toward a polycyclic aromatic hydrocarbon and provide π-π interactions. PMID:25546473

  12. Pyrazolylamidino ligands from coupling of acetonitrile and pyrazoles: a systematic study.

    PubMed

    Gómez-Iglesias, Patricia; Arroyo, Marta; Bajo, Sonia; Strohmann, Carsten; Miguel, Daniel; Villafañe, Fernando

    2014-12-01

    Mixed pyrazole-acetonitrile complexes, both neutral fac-[ReBr(CO)3(NCMe)(pz*H)] (pz*H = pzH, pyrazole; dmpzH, 3,5-dimethylpyrazole; or indzH, indazole) and cationic fac-[Re(CO)3(NCMe)(pz*H)2]A (A = BF4, ClO4, or OTf), are described. Their role as the only starting products to obtain final pyrazolylamidino complexes fac-[ReBr(CO)3(NH═C(Me)pz*-κ(2)N,N)] and fac-[Re(CO)3(pz*H)(NH═C(Me)pz*-κ(2)N,N)]A, respectively, is examined. Other products involved in the processes, such as fac-[ReBr(CO)3(pz*H)2], fac-[Re(CO)3(NCMe)(NH═C(Me)pz*-κ(2)N,N)]A, and fac-[Re(CO)3(pz*H)2(OTf)] are also described. Warming CD3CN solutions of fac-[Re(CO)3(NCMe)(pz*H)2]A at 40 °C gives cleanly the pyrazolylamidino complexes [Re(CO)3(pz*H)(NH═C(Me)pz*-κ(2)N,N)]A as the only products, pointing to an intramolecular process. This is confirmed by carrying out reactions in the presence of one equivalent of a pyrazole different from that coordinated, which affords complexes where the pyrazolylamidino ligand contains only the pyrazole previously coordinated. When the reactions lead to an equilibrium mixture of the final and starting products, the reverse reaction gives the same equilibrium mixture, which indicates that the coupling reaction of pyrazoles and nitriles to obtain pyrazolylamidino ligands is a reversible intramolecular process. A systematic study of the possible factors which may affect the reaction gives the following results: (a) the yields of the direct reactions are higher for lower temperatures; (b) the tendency of the pyrazoles to give pyrazolylamidino complexes follows the sequence indzH > pzH > dmpzH; and (c) the reaction rates do not depend on the nature of the anion even when a large excess is added. The presence of a small amount of aqueous solution of NaOH catalyzes the reaction. Thus, addition of 0.5-1% of NaOH (aq) to solutions of fac-[ReBr(CO)3(NCMe)(pz*H)] (in CD3CN) or fac-[Re(CO)3(NCMe)(pz*H)2]A (in CD3CN, CD3NO2 or (CD3)2CO) allowed the syntheses of the

  13. An Unexpected Observation Concerning the Effect of Anionic Additives on the Retention Behavior of Basic Drugs and Peptides in Reversed-Phase Liquid Chromatography

    PubMed Central

    Wang, Xiaoli; Carr, Peter W.

    2011-01-01

    Anionic species with ion pair forming ability are commonly used to enhance the retention and efficiency of basic analytes in RPLC separations. However, little is known about the interactions between organic mobile phase modifiers and such ion pairing anions. In this work, we measured the magnitude of the retention increase of basic drugs and peptides upon addition of strong inorganic ion pairing anions (e.g. perchlorate) as a function of the volume fraction of modifier in acidic water-acetonitrile mobile phases on two different stationary phases. We found that the increase in retention upon addition of various salts depended strongly on the eluent strength. In general, larger retention increases upon addition of the anion were observed at higher organic fractions. Regression of retention against the volume fraction of organic modifier indicated that the ion pair forming anions substantially decreased S values while only slightly changing ln k’w values. The decrease in S is the major cause of the retention increase of basic drugs and peptides when such anions are added to the mobile phase. PMID:17448482

  14. Terahertz Frequency-Domain Spectroscopy of Low-Pressure Acetonitrile Gas by a Photomixing Terahertz Synthesizer Referenced to Dual Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hsieh, Yi-Da; Kimura, Hiroto; Hayashi, Kenta; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Yasui, Takeshi

    2016-05-01

    A terahertz (THz) frequency synthesizer based on photomixing of two near-infrared lasers with a sub-THz to THz frequency offset is a powerful tool for spectroscopy of polar gas molecules due to its broad spectral coverage; however, its frequency accuracy and resolution are relatively low. To tune the output frequency continuously and widely while maintaining its traceability to a frequency standard, we developed a photomixing THz synthesizer phase-locked to dual optical frequency combs (OFCs). While the phase-locking to dual OFCs ensured continuous tuning within a spectral range of 120 GHz, in addition to the traceability to the frequency standard, use of a broadband uni-traveling carrier photodiode for photomixing enabled the generation of CW-THz radiation within a frequency range from 0.2 to 1.5 THz. We demonstrated THz frequency-domain spectroscopy of gas-phase acetonitrile CH3CN and its isotope CH3 13CN in the frequency range of 0.600-0.720 THz using this THz synthesizer. Their rotational transitions were assigned with a frequency accuracy of 8.42 × 10-8 and a frequency resolution of 520 kHz. Furthermore, the concentration of the CH3CN gas at 20 Pa was determined to be (5.41 ± 0.05) × 1014 molecules/cm3 by curve fitting analysis of the measured absorbance spectrum, and the mixture ratio of the mixed CH3CN/CH3 13CN gas was determined to be 1:2.26 with a gas concentration of 1014-1015 molecules/cm3. The developed THz synthesizer is highly promising for high-precision THz-FDS of low-pressure molecular gases and will enable the qualitative and quantitative analyses of multiple gases.

  15. Terahertz Frequency-Domain Spectroscopy of Low-Pressure Acetonitrile Gas by a Photomixing Terahertz Synthesizer Referenced to Dual Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Hsieh, Yi-Da; Kimura, Hiroto; Hayashi, Kenta; Minamikawa, Takeo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Iwata, Tetsuo; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Yasui, Takeshi

    2016-09-01

    A terahertz (THz) frequency synthesizer based on photomixing of two near-infrared lasers with a sub-THz to THz frequency offset is a powerful tool for spectroscopy of polar gas molecules due to its broad spectral coverage; however, its frequency accuracy and resolution are relatively low. To tune the output frequency continuously and widely while maintaining its traceability to a frequency standard, we developed a photomixing THz synthesizer phase-locked to dual optical frequency combs (OFCs). While the phase-locking to dual OFCs ensured continuous tuning within a spectral range of 120 GHz, in addition to the traceability to the frequency standard, use of a broadband uni-traveling carrier photodiode for photomixing enabled the generation of CW-THz radiation within a frequency range from 0.2 to 1.5 THz. We demonstrated THz frequency-domain spectroscopy of gas-phase acetonitrile CH3CN and its isotope CH3 13CN in the frequency range of 0.600-0.720 THz using this THz synthesizer. Their rotational transitions were assigned with a frequency accuracy of 8.42 × 10-8 and a frequency resolution of 520 kHz. Furthermore, the concentration of the CH3CN gas at 20 Pa was determined to be (5.41 ± 0.05) × 1014 molecules/cm3 by curve fitting analysis of the measured absorbance spectrum, and the mixture ratio of the mixed CH3CN/CH3 13CN gas was determined to be 1:2.26 with a gas concentration of 1014-1015 molecules/cm3. The developed THz synthesizer is highly promising for high-precision THz-FDS of low-pressure molecular gases and will enable the qualitative and quantitative analyses of multiple gases.

  16. Use of oleic-acid functionalized nanoparticles for the magnetic solid-phase microextraction of alkylphenols in fruit juices using liquid chromatography-tandem mass spectrometry.

    PubMed

    Viñas, Pilar; Pastor-Belda, Marta; Torres, Aitor; Campillo, Natalia; Hernández-Córdoba, Manuel

    2016-05-01

    Magnetic nanoparticles of cobalt ferrite with oleic acid as the surfactant (CoFe2O4/oleic acid) were used as sorbent material for the determination of alkylphenols in fruit juices. High sensitivity and specificity were achieved by liquid chromatography and detection using both diode-array (DAD) and electrospray-ion trap-tandem mass spectrometry (ESI-IT-MS/MS) in the selected reaction monitoring (SRM) mode of the negative fragment ions for alkylphenols (APs) and in positive mode for ethoxylate APs (APEOs). The optimized conditions for the different variables influencing the magnetic separation procedure were: mass of magnetic nanoparticles, 50mg, juice volume, 10mL diluted to 25mL with water, pH 6, stirring for 10min at room temperature, separation with an external neodymium magnet, desorption with 3mL of methanol and orbital shaking for 5min. The enriched organic phase was evaporated and reconstituted with 100µL acetonitrile before injecting 30µL into a liquid chromatograph with a mobile phase composed of acetonitrile/0.1% (v/v) formic acid under gradient elution. Quantification limits were in the range 3.6 to 125ngmL(-1). The recoveries obtained were in the 91-119% range, with RSDs lower than 14%. The ESI-MS/MS spectra permitted the correct identification of both APs and APEOs in the fruit juice samples. PMID:26946030

  17. Simultaneous determination of chromium(III), aluminum(III), and iron(II) in tannery sludge acid extracts by reversed-phase high-performance liquid chromatography

    SciTech Connect

    Lopez, A.; Passino, R.; Tiravanti, G. ); Rotunno, T.; Palmisano, F.; Zambonin, P.G. )

    1991-07-01

    A new chromatographic method for the simultaneous determination of Cu(II), Zn(II), Cr(III), Al(III), and Fe(III) or Fe(II) has been developed. The method is based on precolumn formation of stable metal-8-hydroxyquinoline chelates, their separation on a C-18 reversed-phase column by HPLC, and their UV-vis detection at 400 nm. The experimental conditions giving the highest chelate yields resulted: pH 4.2; T = 90C; reaction time 30 min; reaction mixture composition methanol (66.7%)/acetonitrile (13.3%)/water (20%) (v/v/v) plus 10 mM 8-hydroxyquinoline. The mobile-phase composition giving the best resolution of Cr(III)- and Al(III)-8-hydroxyquinoline chromatographic peaks has been optimized by the simplex algorithm: acetonitrile (13.5%)/methanol (29%)/0.1 acetate buffer pH 6.8 (13.5%) (v/v/v) plus 100 mM 8-hydroxyquinoline. The method has been applied to synthetic solutions as well as, after sample pretreatment on XAD-7 resin, to real sulfuric acid extracts of tannery sludges. As for this latter matrix, additional information on Cr and Fe oxidation states has been obtained, combining the proposed method with atomic absorption spectroscopy and ion chromatography.

  18. Multiwalled Carbon Nanotubes-Dispersive Solid-Phase Extraction Coupled with UPLC-ESI-MS-MS for Simultaneous Determination of 10 Illegal Adulterants in Antihypertensive Functional Foods.

    PubMed

    Hu, Jielan; Zeng, Li; He, Ling; You, Fan; Sun, Chengjun

    2016-05-01

    A reliable method for simultaneous determination of 10 illegal adulterants including chlortalidone, hydrochlorothiazide, indapamide, metoprolol, nifedipine, nimodipine, nitrendipine, reserpine, triamterene and valsartan in antihypertensive functional foods by ultra-high-performance liquid chromatography coupled with electrospray ionization-tandem mass spectrometry is presented in this article. The target chemicals were extracted with acetonitrile ultrasonically and cleaned up using multiwalled carbon nanotubes-dispersive solid-phase extraction. The separation was performed on a Waters ACQUITY UPLC BEH C18 Column (2.1 × 100 mm, 1.7 µm) with acetonitrile, 0.1% formic acid and 10 mmol/L ammonium acetate solution as mobile phase at a flow rate of 0.2 mL/min. Multiple reaction monitoring was applied for detection and sildenafil was used as the internal standard. The correlation coefficients of the method were >0.995, with the limits of detection of 0.022-0.30 ng/mL and the limits of quantification of 0.075-0.99 ng/mL. The interday and intraday relative standard deviations were <9.77% and the recoveries were in the range of 85.8-109%. The established method has been applied for the analysis of real samples, and reserpine was detected in a tonic wine sample with a content of 60.1 ± 3.2 mg/L. PMID:26850731

  19. Determination of nitroxynil in cow milk by reversed-phase high-performance liquid chromatography with dual-electrode coulometric detection.

    PubMed

    Takeba, K; Matsumoto, M; Nakazawa, H

    1992-04-01

    A sensitive and specific method is described for the determination of nitroxynil (fasciolicide) residues in cow milk. The milk samples were extracted with acetone and acetonitrile, following clean-up using a simple liquid-liquid extraction step. Nitroxynil was separated from the matrix peaks by reversed-phase high-performance liquid chromatography and detected using dual-electrode coulometric detection. The mobile phase was a mixture (20:80, v/v) of acetonitrile and 0.05 M potassium dihydrogenphosphate with the pH adjusted to 4.0. The flow-rate was 1 ml/min at 40 degrees C. The applied potentials of detectors 1 and 2 were maintained at -0.7 and +0.2 V, respectively. Average recoveries (n = 5) of nitroxynil from milk samples spiked at concentrations of 0.01 and 0.1 micrograms/ml were found to be 92.0% and 97.0% with coefficients of variation of 6.2% and 2.2%, respectively. The detection limit of nitroxynil in milk was 0.7 ng/ml. During the analysis of 30 raw cow milk and 140 market milk samples, nitroxynil was detected at a level of 4 ng/ml in one raw cow milk sample. PMID:1522179

  20. Determination of Triazine Herbicides in Drinking Water by Dispersive Micro Solid Phase Extraction with Ultrahigh-Performance Liquid Chromatography-High-Resolution Mass Spectrometric Detection.

    PubMed

    Chen, Dawei; Zhang, Yiping; Miao, Hong; Zhao, Yunfeng; Wu, Yongning

    2015-11-11

    A novel dispersive micro solid phase extraction (DMSPE) method based on a polymer cation exchange material (PCX) was applied to the simultaneous determination of the 30 triazine herbicides in drinking water with ultrahigh-performance liquid chromatography-high-resolution mass spectrometric detection. Drinking water samples were acidified with formic acid, and then triazines were adsorbed by the PCX sorbent. Subsequently, the analytes were eluted with ammonium hydroxide/acetonitrile. The chromatographic separation was performed on an HSS T3 column using water (4 mM ammonium formate and 0.1% formic acid) and acetonitrile (0.1% formic acid) as the mobile phase. The method achieved LODs of 0.2-30.0 ng/L for the 30 triazines, with recoveries in the range of 70.5-112.1%, and the precision of the method was better than 12.7%. These results indicated that the proposed method had the advantages of convenience and high efficiency when applied to the analysis of the 30 triazines in drinking water. PMID:26487365

  1. An aqueous normal-phase chromatography coupled with tandem mass spectrometry method for determining unbound brain-to-plasma concentration ratio of AZD1775, a Wee1 kinase inhibitor, in patients with glioblastoma.

    PubMed

    Wu, Jianmei; Sanai, Nader; Bao, Xun; LoRusso, Patricia; Li, Jing

    2016-08-15

    A rapid, sensitive, and robust aqueous normal-phase chromatography method coupled with tandem mass spectrometry was developed and validated for the quantitation of AZD1775, a Wee-1 inhibitor, in human plasma and brain tumor tissue. Sample preparation involved simple protein precipitation with acetonitrile. Chromatographic separation was achieved on ethylene bridged hybrid stationary phases (i.e., Waters XBridge Amide column) under an isocratic elution with the mobile phase consisting of acetonitrile/ammonium formate in water (10mM, pH 3.0) (85:15,v/v) at a flow rate of 0.8mL/min for 5min. The lower limit of quantitation (LLOQ) was 0.2ng/mL of AZD1775 in plasma and tissue homogenate. The calibration curve was linear over AZD1775 concentration range of 0.2-1000ng/mL in plasma and tissue homogenate. The intra- and inter-day precision and accuracy were within the generally accepted criteria for bioanalytical method (<15%). The method was successfully applied to assess the penetration of AZD1775 across the blood-brain tumor barrier, as assessed by the unbound brain-to-plasma ratio, in patients with glioblastoma. PMID:27318641

  2. Structure of and hydrogen bonding in a 3:2 inclusion compound of N-methylmorpholine betaine hydrochloride with acetonitrile

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Z.; Szafran, M.; Antkowiak, A.; Grundwald-Wyspianska, M.; Nowak, E.; Gdaniec, M.; Kosturkiewicz, Z.

    2002-03-01

    N-Methylmorpholine betaine hydrochloride (MMB·HCl) forms a 3:2 inclusion compound with acetonitrile. The crystal structure of the compound has been determined at 100 K from a twinned crystal to be trigonal with the space group Poverline3; a= b=16.767(2), c=6.996(1) Å, γ=120°. The host framework is constructed from the ionic pairs formed by the chlorine anion and the protonated, at the carboxylate group, betaine cation. The cation and anion are joined by the O-H⋯Cl - hydrogen bond of the length 2.974(2) Å and angle 173(3)°. The guest molecules are included in two kinds of channels formed in the host matrix. The narrow channel runs parallel to the z axis at x=2/3, y=1/3 and is filled with acetonitrile molecules situated at the three-fold axis. The second channel, also parallel to the z axis, joins large cavities with the center at 0,0,1/2 of overline3 symmetry. The cavity accommodates two guest molecules which exhibit disorder in the crystal. There are only van der Waals interactions between the host and the guest. FTIR spectra of MMB·HCl and its deuterated analog have been discussed.

  3. Infrared spectra and structure of isomeric (cyanophenyl)acetonitriles and their carbanions: an ab initio force field treatment

    NASA Astrophysics Data System (ADS)

    Binev, I. G.; Tsenov, J. A.; Velcheva, E. A.; Radomirska, V. B.; Juchnovski, I. N.

    1996-05-01

    The structures of o-, m- and p-(cyanophenyl)acetonitrile molecules and their carbanions were studied on the basis of infrared spectroscopic data and ab initio force field calculations. The assignment was given for the 3100-1100 cm -1 bands of the substances studied. The scaled theoretical infrared band frequencies agree well with those measured experimentally. An excellent linear correlation ( R = 0.999) was found between the theoretical and experimental vCN frequencies of both molecules and carbanions. The calculations predict well the strong increase in intensity (1.5- to 70-fold) of the vCN, v8 and v19 bands, which accompanies the conversion of the isomeric (cyanophenyl)acetonitrile molecules into the corresponding carbanions. The structures of the lithium, sodium and potassium derivatives of the nitriles studied in dimethyl sulphoxide are close to those of the kinetically free carbanions. The carbanionic centres are practically planar; the cyano groups carry considerable negative charges, but their influences on the carbanionic centres are mainly inductive. The carbanionic charges are delocalized over the phenylene rings (0.35-0.40 e-), methide (0.22-0.29 e-), α-cyano (0.24-0.27 e-) and ring-cyano (0.08-0.14 e-) groups.

  4. Direct Determination of Equilibrium Potentials for Hydrogen Oxidation/Production by Open Circuit Potential Measurements in Acetonitrile

    SciTech Connect

    Roberts, John A. S.; Bullock, R. Morris

    2013-04-01

    Open circuit potentials were measured for acetonitrile solutions of a variety of acids and their conjugate bases under 1 atm H2. Acids examined were triethylammonium, dimethylformamidium, 2,6-dichloroanilinium, 4-cyanoanilinium, 4-bromoanilinium, and 4-anisidinium salts. These potentials, along with the pKa values of the acids, establish the value of the standard hydrogen electrode (SHE) potential in acetonitrile as -0.028(4) V vs the ferrocenium/ferrocene couple. Dimethylformamidium forms homoconjugates and other aggregates with dimethylformamide; open circuit potentials (OCPs) were used to quantify the extent of these reactions. Overpotentials for electrocatalytic hydrogen production and oxidation were determined from open circuit potentials and voltammograms of acidic or basic catalyst solutions under H2. For these solutions, agreement between OCP values and potentials calculated using the Nernst equation is within 12 mV. Finally, use of the measured equilibrium potential allows direct comparison of catalytic systems in different media; it requires neither pKa values, homoconjugation constants, nor the SHE potential.

  5. Satellite mobile data service for Canada

    NASA Technical Reports Server (NTRS)

    Egan, Glenn R.; Sward, David J.

    1990-01-01

    A commercial mobile satellite system which is to be constructed and operated in Canada is examined. This is done in two phases. First, mobile data services was introduced. Hub equipment and 3000 mobile data terminals were supplied. Over the satellite tests were performed. The mobile data service provides full two way digital messaging automatic vehicle location and fleet management services. The second phase is to construct, launch and make operational the MSAT satellite and associated network control facilities. The implementation is examined of the mobile data service in Canada, including the technical description. Marketing and applications are also examined.

  6. Satellite mobile data service for Canada

    NASA Astrophysics Data System (ADS)

    Egan, Glenn R.; Sward, David J.

    A commercial mobile satellite system which is to be constructed and operated in Canada is examined. This is done in two phases. First, mobile data services was introduced. Hub equipment and 3000 mobile data terminals were supplied. Over the satellite tests were performed. The mobile data service provides full two way digital messaging automatic vehicle location and fleet management services. The second phase is to construct, launch and make operational the MSAT satellite and associated network control facilities. The implementation is examined of the mobile data service in Canada, including the technical description. Marketing and applications are also examined.

  7. Mass spectrometry and ion mobility spectrometry of G-quadruplexes. A study of solvent effects on dimer formation and structural transitions in the telomeric DNA sequence d(TAGGGTTAGGGT).

    PubMed

    Ferreira, Rubén; Marchand, Adrien; Gabelica, Valérie

    2012-05-01

    We survey here state of the art mass spectrometry methodologies for investigating G-quadruplexes, and will illustrate them with a new study on a simple model system: the dimeric G-quadruplex of the 12-mer telomeric DNA sequence d(TAGGGTTAGGGT), which can adopt either a parallel or an antiparallel structure. We will discuss the solution conditions compatible with electrospray ionisation, the quantification of complexes using ESI-MS, the interpretation of ammonium ion preservation in the complexes in the gas phase, and the use of ion mobility spectrometry to resolve ambiguities regarding the strand stoichiometry, or separate and characterise different structural isomers. We also describe that adding electrospray-compatible organic co-solvents (methanol, ethanol, isopropanol or acetonitrile) to aqueous ammonium acetate increases the stability and rate of formation of dimeric G-quadruplexes, and causes structural transitions to parallel structures. Structural changes were probed by circular dichroism and ion mobility spectrometry, and the excellent correlation between the two techniques validates the use of ion mobility to investigate G-quadruplex folding. We also demonstrate that parallel G-quadruplex structures are easier to preserve in the gas phase than antiparallel structures. PMID:22465284

  8. Three-phase solvent systems for the comprehensive separation of a wide variety of compounds from Dicranostigma leptopodum by high-speed counter-current chromatography.

    PubMed

    Liu, Yanjuan; Chen, Xiaofen; Liu, JunXi; Di, Duolong

    2015-06-01

    A three-phase solvent system was efficiently applied for high-speed counter-current chromatography to separate secondary metabolites with a wide range of hydrophobicity in Dicranostigma leptopodum. The three-phase solvent system of n-hexane/methyl tert-butyl ether/acetonitrile/0.5% triethylamine (2:2:3:2, v/v/v/v) was selected for high-speed counter-current chromatography separation. The separation was initiated by filling the column with a mixture of intermediate phase and lower phase as a stationary phase followed by elution with upper phase to separate the hydrophobic compounds. Then the mobile phase was switched to the intermediate phase to elute the moderately hydrophobic compounds, and finally the polar compounds still retained in the column were fractionated by eluting the column with the lower phase. In this research, 12 peaks were eluted out in one-step operation within 110 min, among them, eight compounds with acceptable purity were obtained and identified. The purities of β-sitosterol, protopine, allocryptopine, isocorydione, isocorydine, coptisine, berberrubine, and berberine were 94.7, 96.5, 97.9, 86.6, 98.9, 97.6, 95.7, and 92.8%, respectively. PMID:25864484

  9. [Determination of oleanic acid and paeoniflorin in Paeonia lactiflora by ultrasound-assisted ionic liquid-reversed phase liquid chromatography].

    PubMed

    Liu, Wei; Li, Dong-dong; Yang, Hong-shuai; Chen, Yuan-yuan; Wei, Jin-feng; Kang, Wen-yi; Guo, Xiu-chun

    2015-02-01

    Four kinds of ionic liquids [BMIM] Br, [BMIM] BF4, [BMIM] PF6, [HMIM] PF6 were used to analyze the content of oleanic acid and paeoniflorin in Paeonia lactiflora with ultrasonic-assisted extraction coupled with HPLC. The chromatographic column, Purospher star RP-C18 (4.6 mm x 250 mm, 5 μm), was used. Acetonitrile and water (90:10) as mobile phase was used to determine the content of oleanic acid with a gradient elution and flow rate at 1.00 mL · min(-1), detection wavelength at 210 nm, chromatographic column temperature at room temperature. Paeoniflorin content was determined using acetonitrile and water (18:82) as mobile phase with a gradient elution and flow rate at 1.00 mL · min(-1), detection wavelength at 250 nm, the chromatographic column temperature at room temperature. The result show that oleanic acid has the highest extraction yield when the conditions are solid-liquid ratio of 1:80 (g · mL(-1)), and the [BMIM] Br methanol solution concentration of 0.6 mol · L(-1). Under the optimal extraction conditions, the content of oleanic acid from 0.24 to 3.76 μg showed a good linearity (r = 0.9999), the average recovery was 97.20%. Paeoniflorin has the highest extraction yield when the conditions are solid-liquid ratio of 1:130 (g · mL(-1)), and the [C4 MIM] PF6 methanol solution concentration of 0.6 mol · L(-1). Under the optimal extraction conditions, paeoniflorin content from 0.42 to 4.20 μg showed a good lin- earity (r = 1.000), the average recovery was 98.84%. This method is simple and reliable, its repeatability is also very good. It has important significance in the study P. lactiflora of ionic liquid microextraction. PMID:26084167

  10. An integrated electrophoretic mobility control device with split design for signal improvement in liquid chromatography-electrospray ionization mass spectrometry analysis of aminoglycosides using a heptafluorobutyric acid containing mobile phase.

    PubMed

    Hung, Sih-Hua; Yu, Meng-Ju; Wang, Nan-Hsuan; Hsu, Ren-Yu; Wei, Guor-Jien; Her, Guor-Rong

    2016-08-24

    Electrophoretic mobility control (EMC) was used to alleviate the adverse effect of the ion-pairing agent heptafluorobutyric acid (HFBA) in the liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) analysis of aminoglycosides. Aminoglycosides separated by LC were directed to a connecting column before their detection via ESI. Applying an electric field across the connecting column caused the positively charged aminoglycosides to migrate toward the mass spectrometer whereas the HFBA anions remained in the junction reservoir, thus alleviating the ion suppression caused by HFBA. To accommodate the flow rate of a narrow-bore column, minimize the effect of electrophoretic mobility on separation, and facilitate the operation, an integrated EMC device with a split design was fabricated. With the proposed EMC device, the signals of aminoglycosides were enhanced by a factor of 5-85 without affecting the separation efficiency or elution order. For the analysis of aminoglycosides in bovine milk, the proposed approach demonstrates a sensitivity that is at least 10 times below the maximum residue limits set by most countries. PMID:27497008

  11. Differential mobility spectrometry of isomeric protonated dipeptides: modifier and field effects on ion mobility and stability.

    PubMed

    Blagojevic, Voislav; Chramow, Alexander; Schneider, Bradley B; Covey, Thomas R; Bohme, Diethard K

    2011-05-01

    The ability to resolve isomeric protonated dipeptides was investigated with the new technique of differential ion mobility mass spectrometry that uses "modifier" molecules to enhance differential mobility. Two pairs of protonated peptides [glycine-alanine (GlyAla) and alanine-glycine (AlaGly), glycine-serine (GlySer) and serine-glycine (SerGly)] and eight different modifiers (water, 2-propanol, 1,5-hexadiene, 2-chloropropane, chlorobenzene, dichloromethane, acetonitrile, and cyclohexane) were used in the initial study. Separation of the protonated peptides was found to be dependent on the mass and proton affinity of the modifier and combinations of functionalities present in the modifier and the analyte ion. Six of the eight modifiers (water, 2-propanol, chlorobenzene, cyclohexane, dichloromethane, and acetonitrile) were able to separate the protonated isomeric peptide pairs, and generally, modifiers with electron-rich groups performed the best. In the presence of some modifiers, a reduction of ion current was observed under the highest field conditions (>115 Td). Dopant-catalyzed isomerization, likely by proton-transport catalysis, and field-induced fragmentation may have contributed to these losses. Two high vapor pressure modifiers, 1,5-hexadiene and 2-chloropropane, significantly influenced ion formation leading to the formation of stable cluster populations that could be observed in the mass spectrometer. Although not a major concern, both fragmentation and influence of modifier evaporation warrant further studies in order to fully understand and possibly eliminate them. PMID:21504141

  12. Simultaneous Determination of 10 Adulterants in Antihypertensive Functional Foods Using Multi-Walled Carbon Nanotubes-Dispersive Solid-Phase Extraction Coupled with High Performance Liquid Chromatography.

    PubMed

    Zeng, Li; Li, Yongxin; Wu, Xin; Zhang, Jing; Xie, Juan; Sun, Chengjun

    2015-10-01

    Consumption of functional foods based on extracts from selected herbs to alleviate hypertension is an increasingly common practice in China. Adulteration of these foods with pharmaceuticals can significantly impact a consumer's health. To control the quality of the functional foods effectively, a method for the simultaneous determination of 10 common adulterants including chlortalidone, hydrochlorothiazide, indapamide, metoprolol, nifedipine, nimodipine, nitrendipine, reserpine, triamterene and valsartan in antihypertensive functional foods was developed. The target chemicals in samples were ultrasonically extracted with acetonitrile, and then cleaned-up with multi-walled carbon natotubes-dispersive solid-phase extraction. Finally, the analytes were separated with a C18 column using binary mobile phases consisting of acetonitrile and 0.03 mol/L KH2PO4 solutions (pH 3.0). The flow rate of the mobile phase was 0.80 mL/min, and the column temperature was 35°C. The detection wavelength was set at 220 nm. The limits of detection and quantification of the method ranged from 0.014 to 0.053 and 0.047 to 0.178 μg/mL, respectively. The recoveries of the method were in the range of 80.1-98.1% with relative standard deviations <9.53%. The method was successfully applied to the determination of the target chemicals in real samples and simulated samples, and respirine was detected in one tonic wine sample with a concentration of 56.8 ± 1.2 mg/L. PMID:25840433

  13. Application of optically pure amines as chiral auxiliaries to develop trichloro-s-triazine-based new chiral derivatizing reagents for reversed-phase high-performance liquid chromatographic enantioseparation of DL-selenomethionine.

    PubMed

    Bhushan, Ravi; Lal, Manohar

    2013-08-01

    (R)-(+)-naphthylethyl amine and (S)-(+)-1-benzyl-3-aminopyrrolidine were incorporated as chiral auxiliaries, by nucleophilic substitution of chlorine atoms, in cyanuric chloride (CC) or its 6-butoxy derivative. There were obtained four new chiral derivatizing reagents (CDRs) as two dichloro and two monochloro triazine reagents. The CDRs so obtained were characterized and their optical purity was ascertained. Diastereomers of dl-selenomethionine were synthesized under microwave irradiation for 60 or 90 s (at 80% power of 800 W). Reversed-phase high-performance liquid chromatographic separation of diastereomers was carried out on a C18 column using mixtures of acetonitrile with aqueous trifluoroacetic acid as mobile phase. The detection was made at 230 nm using a photodiode array detector. The separation behaviors in terms of retention times and resolutions were compared. The separation method was validated for limit of detection, linearity, accuracy, precision, and recovery. PMID:23529857

  14. Solvation of fluoro-acetonitrile in water by 2D-IR spectroscopy: A combined experimental-computational study

    SciTech Connect

    Cazade, Pierre-André; Das, Akshaya K.; Tran, Halina; Kläsi, Felix; Hamm, Peter; Bereau, Tristan; Meuwly, Markus

    2015-06-07

    The solvent dynamics around fluorinated acetonitrile is characterized by 2-dimensional infrared spectroscopy and atomistic simulations. The lineshape of the linear infrared spectrum is better captured by semiempirical (density functional tight binding) mixed quantum mechanical/molecular mechanics simulations, whereas force field simulations with multipolar interactions yield lineshapes that are significantly too narrow. For the solvent dynamics, a relatively slow time scale of 2 ps is found from the experiments and supported by the mixed quantum mechanical/molecular mechanics simulations. With multipolar force fields fitted to the available thermodynamical data, the time scale is considerably faster—on the 0.5 ps time scale. The simulations provide evidence for a well established CF–HOH hydrogen bond (population of 25%) which is found from the radial distribution function g(r) from both, force field and quantum mechanics/molecular mechanics simulations.

  15. Carbon-hydrogen vs. carbon-carbon bond cleavage of 1,2-diarylethane radical cations in acetonitrile-water

    SciTech Connect

    Camaioni, D.M.; Franz, J.A.

    1984-05-04

    Radical cations of 1,2-diarylethanes and 1-phenyl-2-arylethanes (Ar = phenyl, p-tolyl, p-anisyl) were generated in acidic 70% acetonitrile-water by Cu/sup 2 +/-catalyzed peroxydisulfate oxidation. The radical cations fragment mainly by loss of benzylic protons (C-H cleavage) rather than by alkyl C-C bond cleavage. The 1,2-diarylethanol products undergo further selective oxidation to aryl aldehydes and arylmethanols via rapid equilibration of diarylethane and diarylethanol radical cations. The radical cation of 2,3-dimethyl-2,3-diphenylbutane fragments efficiently by C-C cleavage, forming cumyl radical and cumyl cation. Oxidations of bibenzyl-bicumyl mixtures show selective oxidation of bicumyl dependent on total substrate concentration, providing evidence of equilibrating radical cations and showing that bicumyl fragments faster than bibenzyl loses protons. The effects of reaction conditions and substrate structure on reactivity are discussed.

  16. IR spectra and structure of (4-nitrophenyl)acetonitrile and of its carbanion: experimental and ab initio studies

    NASA Astrophysics Data System (ADS)

    Binev, Y. I.; Petrova, R. R.; Tsenov, J. A.; Binev, I. G.

    2000-01-01

    The structures of (4-nitrophenyl)acetonitrile and of its carbanion were studied on the basis of both quantitative IR spectra and ab initio force field calculations. The spectral and structural changes, which take place in the course of the conversion of the parent molecule into the carbanion, are essential and spread over the whole species. In agreement between theory and experiment, the conversion studied causes strong frequency decreases (down to 136 cm -1) and intensity increases (up to 90-fold) of the cyano and nitro stretching bands. The molecule→carbanion conversion is accompanied by both quinoidization of the phenylene ring and a change in the configuration of the methylenic carbon atom: from tetrahedral in the molecule it becomes planar in the carbanion. The carbanionic charge is delocalized over the carbanionic center (0.40 e -), phenylene (0.24 e -), nitro (0.21 e -) and cyano (0.15 e -) groups.

  17. Temperature deactivation of excited Tb{sup 3+} in the presence of 1, 2-dioxetane in acetonitrile

    SciTech Connect

    Ableeva, N.Sh.; Voloshin, A.I.; Ostakhov, S.S.

    1994-10-01

    Quenching the fluorescence (FL) of terbium perchlorate by 2,2{prime}-adamantane-2,2{prime}-dioxide (1) was shown to have a chemical character and was caused by the formation of the [1...Tb{sup 3+}] complex. The dependence of the lifetime ({tau}) of FL of Tb{sup *3+} in acetonitrile on the temperature and concentration of 1 has been studied. The temperature dependence of {tau} is caused by a rearrangement of the inner sphere of the aquasolvate complexes of Tb{sup 3+}, which leads to the replacement of H{sub 2}O with MeCN and 1. The energy of replacing the H{sub 2}O molecule in the inner sphere of complexes with a solvent molecule has been calculated.

  18. High hole mobility tin-doped polycrystalline germanium layers formed on insulating substrates by low-temperature solid-phase crystallization

    NASA Astrophysics Data System (ADS)

    Takeuchi, Wakana; Taoka, Noriyuki; Kurosawa, Masashi; Sakashita, Mitsuo; Nakatsuka, Osamu; Zaima, Shigeaki

    2015-07-01

    We investigated the effects of incorporation of 0%-2% tin (Sn) into amorphous germanium (Ge) on its crystallization behavior and electrical properties. Incorporation of only 0.2% Sn caused the polycrystallization temperature of Ge to lower from 450 to 430 °C, while a polycrystalline Ge1-xSnx layer with high crystallinity compared to that of polycrystalline Ge was formed by incorporation of 2% Sn. A polycrystalline Ge1-xSnx layer with a low Sn content of 2% annealed at 450 °C exhibited a Hall hole mobility as high as 130 cm2/V s at room temperature even though it possessed a small grain size of 20-30 nm. The Hall hole mobility of a poly-Ge1-xSnx layer with an Sn content of 2% was four times higher than that of a polycrystalline Ge layer and comparable to that of single-crystalline silicon.

  19. [Preparation of 1 µm non-porous C18 silica gel stationary phase for chiral-pressurized capillary electrochromatography].

    PubMed

    Lu, Yangfang; Wang, Hui; Wang, Guiming; Wang, Yan; Gu, Xue; Yan, Chao

    2015-03-01

    Non-porous C18 silica gel stationary phase (1 µm) was prepared and applied to chiral separation in pressurized capillary electrochromatography (pCEC) for the enantioseparation of various basic compounds. The non-porous silica particles (1 µm) were synthesized using modified St6ber method. C18 stationary phase (1 µm) was prepared by immobilization of chloro-dimethyl-octadecylsilane. Using carboxymethyl-β-cyclodextrin (CM-β-CD) as the chiral additive, the pCEC conditions including the content of acetonitrile (ACN), concentration of buffer, pH, the concentration of chiral additive and flow rate as well as applied voltage were investigated to obtain the optimal pCEC conditions for the separation of four basic chiral compounds. The column provided an efficiency of up to 190,000 plates/m. Bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, and esmolol hydrochloride were baseline separated under the conditions of 5 mmol/L ammonium acetate buffer at pH 4. 0 with 20% (v/ v) acetonitrile, and 15 mmol/L CM-β-CD as the chiral additive. The applied voltage was 2 kV and flow rate was 0.03 mL/min with splitting ratio of 300:1. The resolution were 1.55, 2.82, 1. 69, 1. 70 for bupropion hydrochloride, clenbuterol hydrochloride, metoprolol tartrate, esmolol hydrochloride, respectively. The C18 coverage was improved by repeating silylation method. The synthesized 1 µm C18 packings have better mechanical strength and longer service life because of the special, non-porous structure. The column used in pCEC mode showed better separation of the racemates and a higher rate compared with those used in the capillary liquid chromatography (cLC) mode. This study provided an alternative way for the method of pCEC enantioseparation with chiral additives in the mobile phase and demonstrated the feasibility of micron particle stationary phase in chiral separation. PMID:26182460

  20. Thermodynamics of various F420 coenzyme models as sources of electrons, hydride ions, hydrogen atoms and protons in acetonitrile.

    PubMed

    Xia, Ke; Shen, Guang-Bin; Zhu, Xiao-Qing

    2015-06-14

    32 F420 coenzyme models with alkylation of the three different N atoms (N1, N3 and N10) in the core structure (XFH(-)) were designed and synthesized and the thermodynamic driving forces (defined in terms of the molar enthalpy changes or the standard redox potentials in this work) of the 32 XFH(-) releasing hydride ions, hydrogen atoms and electrons, the thermodynamic driving forces of the 32 XFH˙ releasing protons and hydrogen atoms and the thermodynamic driving forces of XF(-)˙ releasing electrons in acetonitrile were determined using titration calorimetry and electrochemical methods. The effects of the methyl group at N1, N3 and N10 and a negative charge on N1 and N10 atoms on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were examined; the results show that seating arrangements of the methyl group and the negative charge have remarkably different effects on the thermodynamic properties of the F420 coenzyme models and their related reaction intermediates. The effects of the substituents at C7 and C8 on the six thermodynamic driving forces of the F420 coenzyme models and their related reaction intermediates were also examined; the results show that the substituents at C7 and C8 have good Hammett linear free energy relationships with the six thermodynamic parameters. Meanwhile, a reasonable determination of possible reactions between members of the F420 family and NADH family in vivo was given according to a thermodynamic analysis platform constructed using the elementary step thermodynamic parameter of F420 coenzyme model 2FH(-) and NADH model MNAH releasing hydride ions in acetonitrile. The information disclosed in this work can not only fill a gap in the chemical thermodynamics of F420 coenzyme models as a class of very important organic sources of electrons, hydride ions, hydrogen atoms and protons, but also strongly promote the fast development of the chemistry and applications of F420 coenzyme

  1. Low-temperature growth of nitrogen-doped carbon nanofibers by acetonitrile catalytic CVD using Ni-based catalysts

    NASA Astrophysics Data System (ADS)

    Iwasaki, Tomohiro; Makino, Yuri; Fukukawa, Makoto; Nakamura, Hideya; Watano, Satoru

    2016-06-01

    To synthesize nitrogen-doped carbon nanofibers (N-CNFs) at high growth rates and low temperatures less than 673 K, nickel species (metallic nickel and nickel oxide) supported on alumina particles were used as the catalysts for an acetonitrile catalytic chemical vapor deposition (CVD) process. The nickel:alumina mass ratio in the catalysts was fixed at 0.05:1. The catalyst precursors were prepared from various nickel salts (nitrate, chloride, sulfate, acetate, and lactate) and then calcined at 1073 K for 1 h in oxidative (air), reductive (hydrogen-containing argon), or inert (pure argon) atmospheres to activate the nickel-based catalysts. The effects of precursors and calcination atmosphere on the catalyst activity at low temperatures were studied. We found that the catalysts derived from nickel nitrate had relatively small crystallite sizes of nickel species and provided N-CNFs at high growth rates of 57 ± 4 g-CNF/g-Ni/h at 673 K in the CVD process using 10 vol% hydrogen-containing argon as the carrier gas of acetonitrile vapor, which were approximately 4 times larger than that of a conventional CVD process. The obtained results reveal that nitrate ions in the catalyst precursor and hydrogen in the carrier gas can contribute effectively to the activation of catalysts in low-temperature CVD. The fiber diameter and nitrogen content of N-CNFs synthesized at high growth rates were several tens of nanometers and 3.5 ± 0.3 at.%, respectively. Our catalysts and CVD process may lead to cost reductions in the production of N-CNFs.

  2. Studies on the nuances of the electrochemically induced room temperature isomerization of cis-stilbene in acetonitrile and ionic liquids.

    PubMed

    Abdul-Rahim, Omar; Simonov, Alexandr N; Boas, John F; Rüther, Thomas; Collins, David J; Perlmutter, Patrick; Bond, Alan M

    2014-03-20

    Electrochemical reduction of cis-stilbene occurs by two well-resolved one-electron reduction steps in acetonitrile with (n-Bu)4NPF6 as the supporting electrolyte and in N-butyl-N-methylpyrrolidinium (Pyrr1,4(+)) and (trimethylamine)(dimethylethylamine)-dihydroborate bis(trifluoromethylsulfonyl)amide (NTf2(-)) ionic liquids (ILs). Mechanistic details of the electroreduction have been probed by dc and Fourier transformed ac voltammetry, simulation of the voltammetry, bulk electrolysis, and EPR spectroscopy. The first one-electron reduction induces fast cis to trans isomerization in CH3CN and ILs, most likely occurring via disproportionation of cis-stilbene radical anions and fast transformation of the cis-dianion to the trans-configuration. The second reduction process is chemically irreversible in CH3CN due to protonation of the dianion but chemically reversible in highly aprotic ILs under high cis-stilbene concentration conditions. Increase of the (n-Bu)4NPF6 supporting electrolyte concentration (0.01-1.0 M) in CH3CN induces substantial positive shifts in the potentials for reduction of cis-stilbene, consistent with strong ion pairing of the anion radical and dianion with (n-Bu)4N(+). However, protection by ion pairing against protonation of the stilbene dianions or electrochemically induced cis-trans-stilbene isomerization is not achieved. Differences in electrode kinetics and reversible potentials for cis-stilbene(0/•-) and trans-stilbene(0/•-) processes are less pronounced in the Pyrr1,4-NTf2 ionic liquid than in the molecular solvent acetonitrile. PMID:24558952

  3. Cluster-continuum quasichemical theory calculation of the lithium ion solvation in water, acetonitrile and dimethyl sulfoxide: an absolute single-ion solvation free energy scale.

    PubMed

    Carvalho, Nathalia F; Pliego, Josefredo R

    2015-10-28

    Absolute single-ion solvation free energy is a very useful property for understanding solution phase chemistry. The real solvation free energy of an ion depends on its interaction with the solvent molecules and on the net potential inside the solute cavity. The tetraphenyl arsonium-tetraphenyl borate (TATB) assumption as well as the cluster-continuum quasichemical theory (CC-QCT) approach for Li(+) solvation allows access to a solvation scale excluding the net potential. We have determined this free energy scale investigating the solvation of the lithium ion in water (H2O), acetonitrile (CH3CN) and dimethyl sulfoxide (DMSO) solvents via the CC-QCT approach. Our calculations at the MP2 and MP4 levels with basis sets up to the QZVPP+diff quality, and including solvation of the clusters and solvent molecules by the dielectric continuum SMD method, predict the solvation free energy of Li(+) as -116.1, -120.6 and -123.6 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively (1 mol L(-1) standard state). These values are compatible with the solvation free energy of the proton of -253.4, -253.2 and -261.1 kcal mol(-1) in H2O, CH3CN and DMSO solvents, respectively. Deviations from the experimental TATB scale are only 1.3 kcal mol(-1) in H2O and 1.8 kcal mol(-1) in DMSO solvents. However, in the case of CH3CN, the deviation reaches a value of 9.2 kcal mol(-1). The present study suggests that the experimental TATB scale is inconsistent for CH3CN. A total of 125 values of the solvation free energy of ions in these three solvents were obtained. These new data should be useful for the development of theoretical solvation models. PMID:26395146

  4. Identification and separation of the organic compounds in coal-gasification condensate waters. [5,5 dimethyl hydantoin, dihydroxy benzenes, acetonitrile

    SciTech Connect

    Mohr, D.H. Jr.; King, C.J.

    1983-08-01

    A substantial fraction of the organic solutes in condensate waters from low-temperature coal-gasification processes are not identified by commonly employed analytical techniques, have low distriution coefficients (K/sub C/) into diisopropyl ether (DIPE) or methyl isobutyl ketone (MIBK), and are resistant to biological oxidation. These compounds represent an important wastewater-treatment problem. Analytical techniques were developed to detect these polar compounds, and the liquid-liquid phase equilibria were measured with several solvents. A high-performance liquid - chromatography (HPLC) technique was employed to analyze four condensate-water samples from a slagging fixed-bed gasifier. A novel sample-preparation technique, consisting of an azeotropic distillation with isopropanol, allowed identification of compounds in the HPLC eluant by combined gas chromatography and mass spectrometry. 5,5-dimethyl hydantoin and related compounds were identified in condensate waters for the first time, and they account for 1 to 6% of the chemical oxygen demand (COD). Dimethyl hydatoin has a K/sub D/ of 2.6 into tributyl phosphate (TBP) and much lower K/sub D/ values into six other solvents. It is also resistant to biological oxidation. Phenols (59 to 76% of the COD), dihydroxy benzenes (0.02 to 9.5% of the COD), and methanol, acetonitrile, and acetone (15% of the COD in one sample) were also detected. Extraction with MIBK removed about 90% of the COD. MIBK has much higher K/sub D/ values than DIPE for dihydroxy benzenes. Chemical reactions occurred during storage of condensate-water samples. The reaction products had low K/sub D/ values into MIBK. About 10% of the COD had a K/sub D/ of nearly zero into MIBK. These compounds were not extracted by MIBK over a wide range of pH. 73 references, 6 figures, 35 tables.

  5. Efficiency in supercritical fluid chromatography with different superficially porous and fully porous particles ODS bonded phases.

    PubMed

    Lesellier, E

    2012-03-01

    The chromatographic efficiency, in terms of plate number per second, was dramatically improved by the introduction of sub-two microns particles with ultra-high pressure liquid chromatography (UHPLC). On the other hand, the recent development of superficially porous particles, called core-shell or fused-core particles, appears to allow the achievement of the same efficiency performances at higher speed without high pressure drops. CO₂-based mobile phases exhibiting much lower viscosities than aqueous based mobile phases allow better theoretical efficiencies, even with 3-5 μm particles, but with relative low pressure drops. They also allow much higher flow rates or much longer columns while using conventional instruments capable to operate below 400 bar. Moreover, the use of superficially porous particles in SFC could enhance the chromatographic performances even more. The kinetic behavior of ODS phases bonded on these particles was studied, with varied flow rates, outlet (and obviously inlet) pressures, temperatures, by using a homologous series (alkylbenzenes) with 10% modifier (methanol or acetonitrile) in the carbon dioxide mobile phase. Results were also compared with classical fully porous particles, having different sizes, from 2.5 to 5 μm. Superior efficiency (N) and reduced h were obtained with these new ODS-bonded particles in regards to classical ones, showing their great interest for use in SFC. However, surprising behavior were noticed, i.e. the increase of the theoretical plate number vs. the increase of the chain length of the compounds. This behavior, opposite to the one classically reported vs. the retention factor, was not depending on the outlet pressure, but on the flow rate and the temperature changes. The lower radial trans-column diffusion on this particle types could explain these results. This diffusion reduction with these ODS-bonded superficially porous particles seems to decrease with the increase of the residence time of compounds

  6. Factors influencing high voltage performance of coconut char derived carbon based electrical double layer capacitor made using acetonitrile and propylene carbonate based electrolytes

    NASA Astrophysics Data System (ADS)

    Hu, Changzheng; Qu, Weiguo; Rajagopalan, Ramakrishnan; Randall, Clive

    2014-12-01

    Symmetric EDLCs made using high purity carbon electrodes derived from coconut char were tested using 1 M Tetraethylammonium hexafluorophosphate dissolved in two different solvents namely acetonitrile and propylene carbonate. The cell voltage of the capacitor made using propylene carbonate can be extended to 3.5 V and it exhibited good cycling and thermal stability upto 70 °C while the voltage was limited to below 3.0 V in acetonitrile. XPS analysis of the positive and negative electrodes of EDLCs post cycling showed that the primary degradation products were related to ring opening reactions in propylene carbonate based electrolytes while water played a key role in degradation of acetonitrile based EDLCs.

  7. Hirshfeld and DFT analysis of the N-heterocyclic carbene proligand methylenebis(N-butylimidazolium) as the acetonitrile-solvated diiodide salt.

    PubMed

    Cebollada, Andrea; Vellé, Alba; Sanz Miguel, Pablo J

    2016-06-01

    N-Heterocyclic carbene (NHC) based systems are usually exploited in the exploration of catalytic mechanisms and processes in organocatalysis, and homo- and heterogeneous catalysis. However, their molecular structures have not received adequate attention. The NHC proligand methylenebis(N-butylimidazolium) has been synthesized as the acetonitrile solvate of the diiodide salt, C15H26N4(2+)·2I(-)·CH3CN [1,1'-methylenebis(3-butylimidazolium) diiodide acetonitrile monosolvate], and fully characterized. An interesting cation-anion connection pattern has been identified in the crystal lattice, in which three iodide anions interact simultaneously with the cisoid-oriented cation. A Hirshfeld surface analysis reveals the predominance of hydrogen bonding over anion-π interactions. This particular arrangement is observed in different methylene-bridged bis(imidazolium) cations bearing chloride or bromide counter-anions. Density functional theory (DFT) calculations with acetonitrile as solvent reproduce the geometry of the title cation. PMID:27256692

  8. A novel dispersive micro solid phase extraction using PCX as the sorbent for the determination of melamine and cyromazine in milk and milk powder by UHPLC-HRMS/MS.

    PubMed

    Chen, Dawei; Zhao, Yunfeng; Miao, Hong; Wu, Yongning

    2015-03-01

    A novel dispersive micro solid phase extraction (DMSPE) cleanup method based on the PCX sorbent (a kind of cation exchange polymer material) was applied to the analysis of melamine and cyromazine residues in milk and milk powder, and ultra high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) was used as instrument detection. Milk powder samples were first extracted with 1% formic acid in acetonitrile/water (1:1 v/v), and milk samples were cleaned up directly without any pre-extraction. Then, melamine and cyromazine in the extracts or milk were adsorbed to the PCX powder. Subsequently, the analytes in PCX sorbent were eluted with ammonium hydroxide/acetonitrile (2.5:97.5 v/v) through a simple unit device equipped with 1 mL syringe and 0.22 μm nylon syringe filter. All the samples were analyzed by UHPLC-HRMS/MS on a Waters Acquity BEH HILIC column with 0.1% formic acid and 4mM ammonium formate in water/acetonitrile as the mobile phase with gradient elution. The matrix effect, recovery, and repeatability, within laboratory reproducibility, CCα and CCβ of the DMSPE cleanup method were investigated. The proposed method provided a significant improvement for the determination of melamine and cyromazine in milk and milk powder in terms of efficient, rapid, economical, and miniaturized sample preparation methods, which yielded fewer matrix effects compared with SPE method. The established cleanup method is expected to be widely applied for the sample preparation of alkaline contaminants at trace levels in the future. PMID:25618651

  9. High performance liquid chromatography for quantification of gatifloxacin in rat plasma following automated on-line solid phase extraction.

    PubMed

    Tasso, Leandro; Dalla Costa, Teresa

    2007-05-01

    An automated system using on-line solid phase extraction and HPLC with fluorimetric detection was developed and validated for quantification of gatifloxacin in rat plasma. The extraction was carried out using C(18) cartridges (BondElut), with a high extraction yield. After washing, gatifloxacin was eluted from the cartridge with mobile phase onto a C(18) HPLC column. The mobile phase consisted of a mixture of phosphoric acid (2.5mM), methanol, acetonitrile and triethylamine (64.8:15:20:0.2, v/v/v/v, apparent pH(app.) 2.8). All samples and standard solutions were chromatographed at 28 degrees C. The method developed was selective and linear for drug concentrations ranging between 20 and 600 ng/ml. Gatifloxacin recovery ranged from 95.6 to 99.7%, and the limit of quantification was 20 ng/ml. The intra and inter-assay accuracy were up to 94.3%. The precision determined not exceed 5.8% of the CV. High extraction yield up to 95% was obtained. Drug stability in plasma was shown in freezer at -20 degrees C up to 1 month, after three freeze-thaw cycles and for 24h in the autosampler after processing. The assay has been successfully applied to measure gatifloxacin plasma concentrations in pharmacokinetic study in rats. PMID:17403594

  10. LC-MS/MS method using unbonded silica column and aqueous/methanol mobile phase for the simultaneous quantification of a drug candidate and co-administered metformin in rat plasma.

    PubMed

    Discenza, Lorell; D'Arienzo, Celia; Olah, Timothy; Jemal, Mohammed

    2010-06-01

    BMS-754807 and metformin were co-administered in drug discovery studies which required the quantitation of both compounds in plasma. Since the two compounds are chemically and structurally dissimilar, developing a single bioanalytical method presented a number of chromatographic challenges including the achievement of appropriate retention times and peak shapes on a single analytical column. To address this chromatographic challenge, we investigated different LC columns under different gradient elution schemes using aqueous/organic mobile phases. Using unbonded silica column and aqueous/methanol mobile phase, we were able to obtain robust and well-resolving chromatographic conditions to support the development and implementation of a single LC-MS/MS bioanalytical method. The use of sub-2 micron particle sizes and a high flow rate, which are attainable with UPLC systems, enhanced the method. The method performance evaluation showed that the method easily met the normally used acceptance criteria for bioanalytical methods, namely a deviation of +/-15% from the nominal concentration except at lower limit of quantitation (LLOQ), where +/-20% is accepted. The reported LLOQ of 7.8 ng/ml, for both BMS-754807 and metformin, was adequate to support the pharmacokinetic studies. PMID:20451474

  11. Direct enantioseparation of nitrogen-heterocyclic pesticides on amylose-tris-(5-chloro-2-methylphenylcarbamate) by reversed-phase high-performance liquid chromatography.

    PubMed

    Yang, Wenwen; Qiu, Jing; Chen, Tianjin; Yang, Shuming; Hou, Shicong

    2012-12-01

    In this study, 11 nitrogen-heterocyclic pesticides were stereoselectively separated on amylose-tris-(5-chloro-2-methylphenylcarbamate) chiral stationary phase, using reversed-phase high-performance liquid chromatography with diode array detector and optical rotation detector at 426 nm. The effects of mobile phase composition and column temperature (5-40 °C) on separation were investigated. When acetonitrile and water were used as mobile phase, satisfactory separations were obtained on amylose-tris-(5-chloro-2-methylphenylcarbamate) for four pesticides with elution orders of (+)/(-)-simeconazole (1), (-)/(+)-nuarimol (3), (-)/(+)-carfentrazone-ethyl (4), and (-)/(+)/(-)/(+)-bromuconazole (9) and part separations for three with elution orders of (-)/(+)-famoxadone (6), (+)/(-)-fenbuconazole (10), and (-)/(+)-triapenthenol (11). Only two chromatographic peaks on diode array detector were obtained for diclobutrazol (2), cyproconazole (5), etaconazole (7), and metconazole (8), although they should have four stereoisomers in theory because of presences of two chiral centers in molecules. The stereoisomeric optical signals of all pesticides did not reverse with temperature changes but would reverse with different solvent types for some pesticides. These results will be useful to prepare and analyze individual enantiomers of chiral pesticides. PMID:22730202

  12. Enantioselective determination of selfotel in human urine by high-performance liquid chromatography on a chiral stationary phase after derivatization with 9-fluorenylmethyl chloroformate.

    PubMed

    Knoche, B; Milosavljev, S; Gropper, S; Brunner, L A; Powell, M L

    1997-08-01

    An analytical method for the enantioselective determination of selfotel in human urine has been developed and validated. The method is based on high-performance liquid chromatography and utilizes CGS 20005 (a selfotel analog) as the internal standard. Urine samples were derivatized in situ with o-phthalic dicarboxaldehyde-3-mercaptopropionic acid and 9-fluorenylmethyl chloroformate (FMOC). Chromatographic separations of the FMOC derivatives of selfotel enantiomers and the internal standard were achieved using a column switching system consisting of an Inertsil ODS-2 column (75x4.6 mm I.D., 5 microm) and a Chiralcel OD-R column (250x4.6 mm I.D., 10 microm). The composition of the mobile phase was acetonitrile-0.1 M phosphate buffer, pH 2.50 (35:65) for the Inertsil ODS-2 column and acetonitrile-0.1 M phosphate buffer, pH 2.00 (35:65) for the Chiralcel OD-R column. The analytes were monitored using fluorescence detection at an excitation wavelength of 262 nm and an emission wavelength of 314 nm. The limit of quantification (LOQ) for this method is 0.25 microg/ml for each selfotel enantiomer. The method was successfully utilized to determine preliminary selfotel stereospecific pharmacokinetics. PMID:9300872

  13. Investigating changes in the gas-phase conformation of Antithrombin III upon binding of Arixtra using traveling wave ion mobility spectrometry (TWIMS).

    PubMed

    Zhao, Yuejie; Singh, Arunima; Li, Lingyun; Linhardt, Robert J; Xu, Yongmei; Liu, Jian; Woods, Robert J; Amster, I Jonathan

    2015-10-21

    We validate the utility of ion mobility to measure protein conformational changes induced by the binding of glycosaminoglycan ligands, using the well characterized system of Antithrombin III (ATIII) and Arixtra, a pharmaceutical agent with heparin (Hp) activity. Heparin has been used as a therapeutic anticoagulant drug for several decades through its interaction with ATIII, a serine protease inhibitor that plays a central role in the blood coagulation cascade. This interaction induces conformational changes within ATIII that dramatically enhance the ATIII-mediated inhibition rate. Arixtra is the smallest synthetic Hp containing the specific pentasaccharide sequence required to bind with ATIII. Here we report the first travelling wave ion mobility mass spectrometry (TWIMS) investigation of the conformational changes in ATIII induced by its interaction with Arixtra. Native electrospray ionization mass spectrometry allowed the gentle transfer of the native topology of ATIII and ATIII-Arixtra complex. IM measurements of ATIII and ATIII-Arixtra complex showed a single structure, with well-defined collisional cross section (CCS) values. An average 3.6% increase in CCS of ATIII occurred as a result of its interaction with Arixtra, which agrees closely with the theoretical estimation of the change in CCS based on protein crystal structures. A comparison of the binding behavior of ATIII under both denaturing and non-denaturing conditions confirmed the significance of a folded tertiary structure of ATIII for its biological activity. A Hp oligosaccharide whose structure is similar to Arixtra but missing the 3-O sulfo group on the central glucosamine residue showed a dramatic decrease in binding affinity towards ATIII, but no change in the mobility behavior of the complex, consistent with prior studies that suggested that 3-O sulfation affects the equilibrium constant for binding to ATIII, but not the mode of interaction. In contrast, nonspecific binding by a Hp

  14. Investigating changes in the gas-phase conformation of Antithrombin III upon binding of Arixtra using traveling wave ion mobility spectrometry (TWIMS)

    PubMed Central

    Zhao, Yuejie; Singh, Arunima; Li, Lingyun; Linhardt, Robert J.; Xu, Yongmei; Liu, Jian; Woods, Robert J.

    2015-01-01

    We validate the utility of ion mobility to measure protein conformational changes induced by the binding of glycosaminoglycan ligands, using the well characterized system of Antithrombin III (ATIII) and Arixtra, a pharmaceutical agent with heparin (Hp) activity. Heparin has been used as a therapeutic anticoagulant drug for several decades through its interaction with ATIII, a serine protease inhibitor that plays a central role in the blood coagulation cascade. This interaction induces conformational changes within ATIII that dramatically enhance the ATIII-mediated inhibition rate. Arixtra is the smallest synthetic Hp containing the specific pentasaccharide sequence required to bind with ATIII. Here we report the first travelling wave ion mobility mass spectrometry (TWIMS) investigation of the conformational changes in ATIII induced by its interaction with Arixtra. Native electrospray ionization mass spectrometry allowed the gentle transfer of the native topology of ATIII and ATIII–Arixtra complex. IM measurements of ATIII and ATIII–Arixtra complex showed a single structure, with well-defined collisional cross section (CCS) values. An average 3.6% increase in CCS of ATIII occurred as a result of its interaction with Arixtra, which agrees closely with the theoretical estimation of the change in CCS based on protein crystal structures. A comparison of the binding behavior of ATIII under both denaturing and non-denaturing conditions confirmed the significance of a folded tertiary structure of ATIII for its biological activity. A Hp oligosaccharide whose structure is similar to Arixtra but missing the 3-O sulfo group on the central glucosamine residue showed a dramatic decrease in binding affinity towards ATIII, but no change in the mobility behavior of the complex, consistent with prior studies that suggested that 3-O sulfation affects the equilibrium constant for binding to ATIII, but not the mode of interaction. In contrast, nonspecific binding by a Hp

  15. Social Mobility and Equality.

    ERIC Educational Resources Information Center

    Miller, S. M.

    Social mobility is generally studied in three different ways: stratum mobility, intergenerational social mobility, and intragenerational or career mobility. This paper deals with the first two types of mobility and more with intergenerational mobility than with stratum mobility. The working hypothesis of both discussions is that, in general, a…

  16. Underivatized amylose and cellulose as new stationary phases for hydrophilic interaction chromatography.

    PubMed

    Lehnert, Petr; Douša, Michal; Lemr, Karel

    2013-10-01

    Two polysaccharide stationary phases have been newly suggested for application in hydrophilic interaction chromatography (HILIC). Both columns (amylose-silica, 250 × 4.6 mm, 5 μm and cellulose-silica, 250 × 4.6 mm, 5 μm) demonstrated a satisfactory retention of polar compounds. The influence of the mobile-phase composition (acetonitrile content, pH, salt concentration) on the retention was in agreement with the HILIC concept. The phases showed a very similar behavior, typical efficiency of about 50,000 plates/m, cellulose retained test compounds somewhat more strongly. Under the experimental conditions, electrostatic (non-HILIC-type) interactions due to the dissociation of silanol groups on the silica surface did not influence the retention, noticeably. The applicability of polysaccharide stationary phases for the chromatography of polar compounds was proven by the separation of mixtures of sugars (fructose, glucose, saccharose, maltose, trehalose) or vitamins (nicotinamide, pyridoxine, riboflavin, thiamine, nicotinic acid, ascorbic acid). PMID:23983151

  17. Application of a liquid chromatographic procedure for the analysis of penicillin antibiotics in biological fluids and pharmaceutical formulations using sodium dodecyl sulphate/propanol mobile phases and direct injection.

    PubMed

    Rambla-Alegre, Maria; Martí-Centelles, Rosa; Esteve-Romero, Josep; Carda-Broch, Samuel

    2011-07-29

    A direct injection liquid chromatography procedure was developed for the simultaneous determination of four penicillin antibiotics (amoxicillin, ampicillin, cloxacillin and dicloxacillin) in pharmaceutical formulations and physiological fluids (urine) using hybrid micellar mobile phases. These antimicrobials are used to treat gastrointestinal and systemic infections. The four penicillins were analysed using a Zorbax C18 reversed-phase column and detected at 210 nm. These antibiotics were separated by an interpretive optimisation procedure based on the accurate description of the retention and shape of the chromatographic peaks. Antibiotics were eluted in less than 16 min with no interference by the urine protein band or endogenous compounds using the mobile phase 0.11 M sodium dodecyl sulphate-6% propanol-0.01 M NaH(2)PO(4) buffered at pH 3. The method was validated according to the Food and Drug Administration guideline, including analytical parameters such as linearity (R(2)>0.993), intra- and inter-day precisions (RSD, %: 0.1-4.4 and 1.2-5.9, respectively), and robustness for the four compounds. This method is sensitive enough for the routine analysis of penicillins at therapeutic urine levels, with limits of detection in the 1.5-15 ng mL(-1) range and limits of quantification of 50 ng mL(-1). Recoveries in a micellar medium and a spiked urine matrix were in the 92.4-108.2% and 96-110% ranges, respectively. Finally, the method was successfully applied to determine these antibiotics in urine samples and pharmaceutical formulations. PMID:21190691

  18. Crystal structures and thermal behavior of bis[dibenzyldimethylammonium]CuBr 4, bis[dibenzyldimethylammonium]CuCl 4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr 4 crystallized from acetonitrile and dilute HX (X=Cl or Br) solutions

    NASA Astrophysics Data System (ADS)

    Busi, Sara; Lahtinen, Manu; Valkonen, Jussi; Rissanen, Kari

    2006-08-01

    Bis[dibenzyldimethylammonium]CuBr 4, bis[dibenzyldimethylammonium]CuCl 4 and bis[dimethyldi(2-phenylethyl)ammonium]CuBr 4 were crystallized from acetonitrile and/or dilute HX solutions. Five different kinds of single crystals were obtained. In the case of bis[dibenzyldimethylammonium]CuX 4 (X=Br or Cl), the acetonitrile molecules cocrystallized into the crystal structure when acetonitrile solution was used. As a result, the isomorphic structures of Bis[dibenzyldimethylammonium]CuX 4·0.5 CH 3CN (X=Br or Cl) in monoclinic space group P2 1/ n were obtained. When a dilute HX solution was used, the bis[dibenzyldimethylammonium]CuX 4 (X=Br or Cl) crystallized without solvent molecules. The formed crystals were not isomorphous with each other as the tetrabromocuprate structure crystallized in triclinic space group and the tetrachlorocuprate structure in monoclinic space group. The third compound, bis[di(2-phenylethyl)dimethylammonium]CuBr 4, crystallized without solvent molecules from an acetonitrile solution and no measurable single crystals were obtained from a dilute HX solution. Elemental analysis and powder diffraction analysis were performed to verify the structural similarities of all formed single crystals. The powder diffraction measurements also showed that the compounds have the same structure at room temperature and at a temperature of -100 °C. The thermal behaviour of the compounds was studied by using TG/DTA and DSC measurements; the compounds decomposed in two stages. No phase transitions were observed between room temperature and the melting point. In addition, these crystals showed to be very stable in the air at room temperature as they could be kept in the air for several weeks without any marks of the decomposition.

  19. Simple setup for gas-phase H/D exchange mass spectrometry coupled to electron transfer dissociation and ion mobility for analysis of polypeptide structure on a liquid chromatographic time scale.

    PubMed

    Mistarz, Ulrik H; Brown, Jeffery M; Haselmann, Kim F; Rand, Kasper D

    2014-12-01

    Gas-phase hydrogen/deuterium exchange (HDX) is a fast and sensitive, yet unharnessed analytical approach for providing information on the structural properties of biomolecules, in a complementary manner to mass analysis. Here, we describe a simple setup for ND3-mediated millisecond gas-phase HDX inside a mass spectrometer immediately after ESI (gas-phase HDX-MS) and show utility for studying the primary and higher-order structure of peptides and proteins. HDX was achieved by passing N2-gas through a container filled with aqueous deuterated ammonia reagent (ND3/D2O) and admitting the saturated gas immediately upstream or downstream of the primary skimmer cone. The approach was implemented on three commercially available mass spectrometers and required no or minor fully reversible reconfiguration of gas-inlets of the ion source. Results from gas-phase HDX-MS of peptides using the aqueous ND3/D2O as HDX reagent indicate that labeling is facilitated exclusively through gaseous ND3, yielding similar results to the infusion of purified ND3-gas, while circumventing the complications associated with the use of hazardous purified gases. Comparison of the solution-phase- and gas-phase deuterium uptake of Leu-Enkephalin and Glu-Fibrinopeptide B, confirmed that this gas-phase HDX-MS approach allows for labeling of sites (heteroatom-bound non-amide hydrogens located on side-chains, N-terminus and C-terminus) not accessed by classical solution-phase HDX-MS. The simple setup is compatible with liquid chromatography and a chip-based automated nanoESI interface, allowing for online gas-phase HDX-MS analysis of peptides and proteins separated on a liquid chromatographic time scale at increased throughput. Furthermore, online gas-phase HDX-MS could be performed in tandem with ion mobility separation or electron transfer dissociation, thus enabling multiple orthogonal analyses of the structural properties of peptides and proteins in a single automated LC-MS workflow. PMID:25375223

  20. Spectrophotometric study on the proton transfer reaction between 2-amino-4-methylpyridine with 2,6-dichloro-4-nitrophenol in methanol, acetonitrile and the binary mixture 50% methanol+50% acetonitrile.

    PubMed

    Al-Ahmary, Khairia M; Habeeb, Moustafa M; Al-Obidan, Areej H

    2016-02-01

    Proton transfer reaction between 2-amino-4-methylpyridine (2AMP) as the proton acceptor with 2,6-dichloro-4-nitrophenol (DCNP) as the proton donor has been investigated spectrophotometrically in methanol (MeOH), acetonitrile (AN) and a binary mixture composed of 50% MeOH and 50% AN (AN-Me). The composition of the complex has been investigated utilizing Job(')s and photometric titration methods to be 1:1. Minimum-maximum absorbance equation has been applied to estimate the formation constant of the proton transfer reaction (K(PT)) where it reached high values in the investigated solvent confirming its high stability. The formation constant recorded higher value in AN compared with MeOH and mixture of AN-Me. Based on the formation of stable proton transfer complex, a sensitive spectrophotometric method was suggested for quantitative determination of 2AMP. The Lambert-Beer(')s law was obeyed in the concentration range 0.5-8 μg mL(-1) with small values of limits of detection and quantification. The solid complex between 2AMP with DCNP has been synthesized and characterized by elemental analysis to be 1:1 in concordant with the molecular stoichiometry in solution. Further analysis of the solid complex was carried out using infrared and (1)H NMR spectroscopy. PMID:26520474

  1. The Multifunctional Enzyme CYP71B15 (PHYTOALEXIN DEFICIENT3) Converts Cysteine-Indole-3-Acetonitrile to Camalexin in the Indole-3-Acetonitrile Metabolic Network of Arabidopsis thaliana[W][OA

    PubMed Central

    Böttcher, Christoph; Westphal, Lore; Schmotz, Constanze; Prade, Elke; Scheel, Dierk; Glawischnig, Erich

    2009-01-01

    Accumulation of camalexin, the characteristic phytoalexin of Arabidopsis thaliana, is induced by a great variety of plant pathogens. It is derived from Trp, which is converted to indole-3-acetonitrile (IAN) by successive action of the cytochrome P450 enzymes CYP79B2/B3 and CYP71A13. Extracts from wild-type plants and camalexin biosynthetic mutants, treated with silver nitrate or inoculated with Phytophthora infestans, were comprehensively analyzed by ultra-performance liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry. This metabolomics approach was combined with precursor feeding experiments to characterize the IAN metabolic network and to identify novel biosynthetic intermediates and metabolites of camalexin. Indole-3-carbaldehyde and indole-3-carboxylic acid derivatives were shown to originate from IAN. IAN conjugates with glutathione, γ-glutamylcysteine, and cysteine [Cys(IAN)] accumulated in challenged phytoalexin deficient3 (pad3) mutants. Cys(IAN) rescued the camalexin-deficient phenotype of cyp79b2 cyp79b3 and was itself converted to dihydrocamalexic acid (DHCA), the known substrate of CYP71B15 (PAD3), by microsomes isolated from silver nitrate–treated Arabidopsis leaves. Surprisingly, yeast-expressed CYP71B15 also catalyzed thiazoline ring closure, DHCA formation, and cyanide release with Cys(IAN) as substrate. In conclusion, in the camalexin biosynthetic pathway, IAN is derivatized to the intermediate Cys(IAN), which serves as substrate of the multifunctional cytochrome P450 enzyme CYP71B15. PMID:19567706

  2. Spectrophotometric study on the proton transfer reaction between 2-amino-4-methylpyridine with 2,6-dichloro-4-nitrophenol in methanol, acetonitrile and the binary mixture 50% methanol + 50% acetonitrile

    NASA Astrophysics Data System (ADS)

    Al-Ahmary, Khairia M.; Habeeb, Moustafa M.; Al-Obidan, Areej H.

    2016-02-01

    Proton transfer reaction between 2-amino-4-methylpyridine (2AMP) as the proton acceptor with 2,6-dichloro-4-nitrophenol (DCNP) as the proton donor has been investigated spectrophotometrically in methanol (MeOH), acetonitrile (AN) and a binary mixture composed of 50% MeOH and 50% AN (AN-Me). The composition of the complex has been investigated utilizing Job's and photometric titration methods to be 1:1. Minimum-maximum absorbance equation has been applied to estimate the formation constant of the proton transfer reaction (KPT) where it reached high values in the investigated solvent confirming its high stability. The formation constant recorded higher value in AN compared with MeOH and mixture of AN-Me. Based on the formation of stable proton transfer complex, a sensitive spectrophotometric method was suggested for quantitative determination of 2AMP. The Lambert-Beer's law was obeyed in the concentration range 0.5-8 μg mL- 1 with small values of limits of detection and quantification. The solid complex between 2AMP with DCNP has been synthesized and characterized by elemental analysis to be 1:1 in concordant with the molecular stoichiometry in solution. Further analysis of the solid complex was carried out using infrared and 1H NMR spectroscopy.

  3. Analysis of Triacylglycerol and Fatty Acid Isomers by Low-Temperature Silver-Ion High Performance Liquid Chromatography with Acetonitrile in Hexane as Solvent: Limitations of the Methodology

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Silver ion HPLC (Ag HPLC), utilizing columns containing silver ions bonded to a silica substrate and acetonitrile in hexane as solvent, has proven to be a powerful technology for the analysis of geometric (cis or trans) or positional fatty acids, fatty acid ester (primarily methyl ester; FAME), or t...

  4. The role of low levels of water in the electrochemical oxidation of α-tocopherol (vitamin E) and other phenols in acetonitrile.

    PubMed

    Tan, Ying Shan; Chen, Shanshan; Hong, Wan Mei; Kan, Jia Min; Kwek, Edwin Swee Hee; Lim, Shi Yu; Lim, Zhen Hui; Tessensohn, Malcolm E; Zhang, Yinlu; Webster, Richard D

    2011-07-28

    The phenol, α-tocopherol, can be electrochemically oxidised in a -2e(-)/-H(+) process to form a diamagnetic cation that is long-lived in dry organic solvents such as acetonitrile and dichloromethane, but in the presence of water quickly reacts to form a hemiketal. Variable scan rate cyclic voltammetry experiments in acetonitrile with carefully controlled amounts of water between 0.010 M-0.6 M were performed in order to determine the rate of reaction of the diamagnetic cation with water. The water content of the solvent was accurately determined by Karl Fischer coulometric titrations and the voltammetric data were modelled using digital simulation techniques. The oxidation peak potential of α-tocopherol measured during cyclic voltammetry experiments was found to shift to less positive potentials as increasing amounts of water (0.01-0.6 M) were added to the acetonitrile, which was interpreted based on hydrogen-bonding interactions between the phenolic hydrogen atom and water. Several other phenols were examined and they displayed similar voltammetric features to α-tocopherol, suggesting that interactions of phenols with trace amounts of water were a common occurrence in acetonitrile. The H-bonding interactions of α-tocopherol with water were also examined via NMR and UV-vis spectroscopies, with the voltammetric and spectroscopic studies extended to include other coordinating solvents (dimethyl sulfoxide and pyridine). PMID:21670827

  5. CsSnI[subscript 3]: Semiconductor or Metal? High Electrical Conductivity and Strong Near-Infrared Photoluminescence from a Single Material. High Hole Mobility and Phase-Transitions

    SciTech Connect

    Chung, In; Song, Jung-Hwan; Im, Jino; Androulakis, John; Malliakas, Christos D.; Li, Hao; Freeman, Arthur J.; Kenney, John T.; Kanatzidis, Mercouri G.

    2012-10-29

    CsSnI{sub 3} is an unusual perovskite that undergoes complex displacive and reconstructive phase transitions and exhibits near-infrared emission at room temperature. Experimental and theoretical studies of CsSnI{sub 3} have been limited by the lack of detailed crystal structure characterization and chemical instability. Here we describe the synthesis of pure polymorphic crystals, the preparation of large crack-/bubble-free ingots, the refined single-crystal structures, and temperature-dependent charge transport and optical properties of CsSnI{sub 3}, coupled with ab initio first-principles density functional theory (DFT) calculations. In situ temperature-dependent single-crystal and synchrotron powder X-ray diffraction studies reveal the origin of polymorphous phase transitions of CsSnI{sub 3}. The black orthorhombic form of CsSnI{sub 3} demonstrates one of the largest volumetric thermal expansion coefficients for inorganic solids. Electrical conductivity, Hall effect, and thermopower measurements on it show p-type metallic behavior with low carrier density, despite the optical band gap of 1.3 eV. Hall effect measurements of the black orthorhombic perovskite phase of CsSnI{sub 3} indicate that it is a p-type direct band gap semiconductor with carrier concentration at room temperature of {approx} 10{sup 17} cm{sup -3} and a hole mobility of {approx} 585 cm{sup 2} V{sup -1} s{sup -1}. The hole mobility is one of the highest observed among p-type semiconductors with comparable band gaps. Its powders exhibit a strong room-temperature near-IR emission spectrum at 950 nm. Remarkably, the values of the electrical conductivity and photoluminescence intensity increase with heat treatment. The DFT calculations show that the screened-exchange local density approximation-derived band gap agrees well with the experimentally measured band gap. Calculations of the formation energy of defects strongly suggest that the electrical and light emission properties possibly result from

  6. [Preparation of triterpene saponins from Platycodon grandiflorum by two-dimensional hydrophilic interaction liquid chromatography-reversed phase liquid chromatography].

    PubMed

    Xing, Qianqian; Fu, Qing; Jin, Yu; Liang, Xinmiao

    2014-07-01

    A two-dimensional (2-D) preparative liquid chromatography method was developed for the preparation of triterpene saponins from Platycodon grandiflorum using hydrophilic interaction liquid chromatography (HILIC) coupled with reversed phase liquid chromatography (RPLC). At first, the crude extract was obtained from Platycodon grandiflorum by boiled alcohol precipitation. Then, the concentrated crude extracts were continuously pretreated using solid phase extraction (SPE) under reversed-phase and hydrophilic-phase modes to remove the impurities. Subsequently, XAmide column (150 mm x 20 mm, 5 microm) was selected to separate the triterpene saponin constituents under HILIC mode using water and acetonitrile as mobile phases. From 6 min to 25 min, each fraction was collected per minute under time-triggered mode and 20 fractions were collected. The 18th fraction (JG23) was selected for further purification. The column of Atlantis PrepT3 (100 mm x 30 mm, 5 microm) was chosen and two monomeric compounds were obtained. The two compounds with over 90% purity were identified as deapiplatycoside E and platycoside E with mass spectrometry (MS) and nuclear magnetic resonance (NMR). This 2-D HILIC-RPLC method with high orthogonality can be used in the preparation of triterpene saponins from natural products. PMID:25255571

  7. Volatile organic compound (VOC) emissions characterization during the flow-back phase of a hydraulically refractured well in the Uintah Basin, Utah using mobile PTR-MS measurements

    NASA Astrophysics Data System (ADS)

    Geiger, F.; Warneke, C.; Brown, S. S.; De Gouw, J. A.; Dube, W. P.; Edwards, P.; Gilman, J.; Graus, M.; Helleis, F.; Kofler, J.; Lerner, B. M.; Orphal, J.; Petron, G.; Roberts, J. M.; Zahn, A.

    2014-12-01

    Ongoing improvements in advanced technologies for crude oil and natural gas extraction from unconventional reserves, such as directional drilling and hydraulic fracturing, have greatly increased the production of fossil fuels within recent years. The latest forecasts even estimate an enhancement of 56% in total natural gas production due to increased development of shale gas, tight gas and offshore natural gas resources from 2012 to 2040 with the largest contribution from shale formations [US EIA: Annual Energy Outlook 2014]. During the field intensive 'Energy and Environment - Uintah Basin Winter Ozone Study (UBWOS)', measurements of volatile organic compounds (VOCs) were made using proton-transfer-reactions mass spectrometry (PTR-MS) at the ground site Horse Pool and using a mobile laboratory in the Uintah Basin, Utah, which is a region well known for intense fossil fuel production. A reworked gas well in the Red Wash fields was sampled regularly within two weeks performing mobile laboratory measurements downwind of the well site. The well had been recently hydraulically refractured at that time and waste water was collected into an open flow-back pond. Very high mixing ratios of aromatic hydrocarbons (C6-C13) up to the ppm range were observed coming from condensate and flow-back reservoirs. The measurements are used to determine sources of specific VOC emissions originating from the different parts of the well site and mass spectra are used to classify the air composition in contrast to samples taken at the Horse Pool field site and crude oil samples from South Louisiana. Enhancement ratios and time series of measured peak values for aromatics showed no clear trend, which indicates changes in emissions with operations at the site.

  8. Insight into the retention processes of phthalate metabolites on different liquid chromatography stationary phases for the development of improved separation methods.

    PubMed

    Gómara, B; Lebrón-Aguilar, R; González, M J; Quintanilla-López, J E

    2015-12-01

    The retention behavior of nine MPAEs has been studied, using commercial LC columns with octadecylsilane (ODS), phenyl, and amide-type SPs. First, it was found that the use of methanol in the mobile phase is not advisable, because induce a transesterification reaction of MPAEs in the electrospray ion source, regardless of the SP used. On the other hand, different responses were observed when representing the logarithm of retention factors (k) vs. the volume fraction of ACN (φ) in the mobile phase, for the three SPs tested. A quite linear trend was obtained for ODS (at φ values below 0.80) and Phenyl columns. On the contrary, the Amide column shows a striking U-shape trend, typical of both hydrophobic and hydrophilic retention mechanisms. Therefore, the separation process was mainly hydrophobic in the ODS and phenyl SPs, but in the amide-type a dual retention mechanism was found, showing zones with predominant hydrophobic or hydrophilic interactions, depending on both the compound and the experimental conditions. A high content of acetonitrile (>75%) and low concentration of formic acid in the mobile phase promote the hydrophilic separation mechanism for MPAEs on the amide SP. So, this dual separation mechanism can be modulated modifying the pH and content of organic modifier in the mobile phase, allowing greater flexibility to develop improved methods. Taking advantage of this, a separation method was optimized in this amide column using a Box-Wilson Central Composite experimental design, which allows separating the studied MPAEs with a time-saving of around 40% comparing to the conventional phenyl SP. PMID:26553955

  9. Silica-based polypeptide-monolithic stationary phase for hydrophilic chromatography and chiral separation.

    PubMed

    Zhao, Licong; Yang, Limin; Wang, Qiuquan

    2016-05-13

    Glutathione (GSH)-, somatostatin acetate (ST)- and ovomucoid (OV)-functionalized silica-monolithic stationary phases were designed and synthesized for HILIC and chiral separation using capillary electrochromatography (CEC). GSH, ST and OV were covalently incorporated into the silica skeleton via the epoxy ring-opening reaction between their amino groups and the glycidyl moiety in γ-glycidoxypropyltrimethoxysilane (GPTMS) together with polycondensation and copolymerization of tetramethyloxysilane and GPTMS. Not only could the direction and electroosmotic flow magnitude on the prepared GSH-, ST- and OV-silica hybrid monolithic stationary phases be controlled by the pH of the mobile phase, but also a typical HILIC behavior was observed so that the nucleotides and HPLC peptide standard mixture could be baseline separated using an aqueous mobile phase without any acetonitrile during CEC. Moreover, the prepared monolithic columns had a chiral separation ability to separate dl-amino acids. The OV-silica hybrid monolithic column was most effective in chiral separation and could separate dl-glutamic acid (Glu) (the resolution R=1.07), dl-tyrosine (Tyr) (1.57) and dl-histidine (His) (1.06). Importantly, the chiral separation ability of the GSH-silica hybrid monolithic column could be remarkably enhanced when using gold nanoparticles (AuNPs) to fabricate an AuNP-mediated GSH-AuNP-GSH-silica hybrid monolithic column. The R of dl-Glu, dl-Tyr and dl-His reached 1.19, 1.60 and 2.03. This monolithic column was thus applied to separate drug enantiomers, and quantitative separation of all four R/S drug enantiomers were achieved with R ranging from 4.36 to 5.64. These peptide- and protein-silica monolithic stationary phases with typical HILIC separation behavior and chiral separation ability implied their promise for the analysis of not only the future metabolic studies, but also drug enantiomers recognition. PMID:27083263

  10. Mobile Customer Relationship Management and Mobile Security

    NASA Astrophysics Data System (ADS)

    Sanayei, Ali; Mirzaei, Abas

    The purpose of this study is twofold. First, in order to guarantee a coherent discussion about mobile customer relationship management (mCRM), this paper presents a conceptualization of mCRM delineating its unique characteristics because of Among the variety of mobile services, considerable attention has been devoted to mobile marketing and in particular to mobile customer relationship management services. Second, the authors discusses the security risks in mobile computing in different level(user, mobile device, wireless network,...) and finally we focus on enterprise mobile security and it's subgroups with a series of suggestion and solution for improve mobile computing security.

  11. Thionations using a P4S10-pyridine complex in solvents such as acetonitrile and dimethyl sulfone.

    PubMed

    Bergman, Jan; Pettersson, Birgitta; Hasimbegovic, Vedran; Svensson, Per H

    2011-03-18

    Tetraphosphorus decasulfide (P(4)S(10)) in pyridine has been used as a thionating agent for a long period of time. The moisture-sensitive reagent has now been isolated in crystalline form, and the detailed structure has been determined by X-ray crystallography. The thionating power of this storable reagent has been studied and transferred to solvents such as acetonitrile in which it has proven to be synthetically useful and exceptionally selective. Its properties have been compared with the so-called Lawesson reagent (LR). Particularly interesting are the results from thionations at relatively high temperatures (∼165 °C) in dimethyl sulfone as solvent. Under these conditions, for instance, acridone and 3-acetylindole could quickly be transformed to the corresponding thionated derivatives. Glycylglycine similarly gave piperazinedithione. At these temperatures, LR is inefficient due to rapid decomposition. The thionated products are generally cleaner and more easy to obtain because in the crystalline reagent, impurities which invariably are present in the conventional reagents, P(4)S(10) in pyridine or LR, have been removed. PMID:21341727

  12. Vibrational spectroscopic characterization of stable solvates in the LiClO 4/formamide:acetonitrile system

    NASA Astrophysics Data System (ADS)

    Alves, Wagner A.

    2007-03-01

    Raman and infrared (IR) experiments of extremely high concentrated solutions (1.0-5.0 M) of lithium perchlorate in equimolar formamide (FA) and acetonitrile (ACN) mixture were carried out. Raman quantitative analyses performed in the C dbnd O and C tbnd N bands of FA and ACN, respectively, the appearance of a new IR band in the N-H stretching region and the presence of the band at 939 cm -1 were interpreted in terms of a solvent separated ion pairs model. In salt concentrations higher than 3.0 M, a weak band at 945 cm -1 (contact ion pairs) can also be seen. Indeed, the mixture of solvents with considerable differences in the acid-base characters allows to prepare electrolytic solutions where the contact ion pairs formation is low. A coordination number of 4 for the lithium cation is suggested and this value is in full agreement with other authors. Fundamental aspects and the importance of the present system for the development of new lithium-based rechargeable batteries are also discussed.

  13. Rate theory of solvent exchange and kinetics of Li(+) - BF4 (-)/PF6 (-) ion pairs in acetonitrile.

    PubMed

    Dang, Liem X; Chang, Tsun-Mei

    2016-09-01

    In this paper, we describe our efforts to apply rate theories in studies of solvent exchange around Li(+) and the kinetics of ion pairings in lithium-ion batteries (LIBs). We report one of the first computer simulations of the exchange dynamics around solvated Li(+) in acetonitrile (ACN), which is a common solvent used in LIBs. We also provide details of the ion-pairing kinetics of Li(+)-[BF4] and Li(+)-[PF6] in ACN. Using our polarizable force-field models and employing classical rate theories of chemical reactions, we examine the ACN exchange process between the first and second solvation shells around Li(+). We calculate exchange rates using transition state theory and weighted them with the transmission coefficients determined by the reactive flux, Impey, Madden, and McDonald approaches, and Grote-Hynes theory. We found the relaxation times changed from 180 ps to 4600 ps and from 30 ps to 280 ps for Li(+)-[BF4] and Li(+)-[PF6] ion pairs, respectively. These results confirm that the solvent response to the kinetics of ion pairing is significant. Our results also show that, in addition to affecting the free energy of solvation into ACN, the anion type also should significantly influence the kinetics of ion pairing. These results will increase our understanding of the thermodynamic and kinetic properties of LIB systems. PMID:27608999

  14. Thermodynamic and transport properties of spiro-(1,1')-bipyrrolidinium tetrafluoroborate and acetonitrile mixtures: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Qing-Yin, Zhang; Peng, Xie; Xin, Wang; Xue-Wen, Yu; Zhi-Qiang, Shi; Shi-Huai, Zhao

    2016-06-01

    Organic salts such as spiro-(1,1')-bipyrrolidinium tetrafluoroborate ([SBP][BF4]) dissolved in liquid acetonitrile (ACN) are a new kind of organic salt solution, which is expected to be used as an electrolyte in electrical double layer capacitors (EDLCs). To explore the physicochemical properties of the solution, an all-atom force field is established on the basis of AMBER parameter values and quantum mechanical calculations. Molecular dynamics (MD) simulations are carried out to explore the liquid structure and physicochemical properties of [SBP][BF4] electrolyte at room temperature. The computed thermodynamic and transport properties match the available experimental results very well. The microscopic structures of [SBP][BF4] salt solution are also discussed in detail. The method used in this work provides an efficient way of predicting the properties of organic salt solvent as an electrolyte in EDLCs. Project supported by the National Natural Science Foundation of China (Grant Nos. 21476172 and 51172160), the National High Technology Research and Development Program of China (Grant No. 2013AA050905), and the Natural Science Foundation of Tianjin, China (Grant Nos. 12JCZDJC28400, 14RCHZGX00859, 14JCTPJC00484, and 14JCQNJC07200).

  15. Diffusion-controlled reactions in supercritical CHF[sub 3] and CO[sub 2]/acetonitrile mixtures

    SciTech Connect

    Roberts, C.B.; Zhang, J.; Chateauneuf, J.E.; Brennecke, J.F. )

    1993-10-20

    We present results of the triplet-triplet annihilation (TTA) process of benzophenone (Ph[sub 2]C = O) and the self-termination reaction of benzyl radical (PhCH[sub 2]) to investigate the possibility of diffusion-controlled processes being hindered or enhanced in supercritical fluids (SCFs) or fluid mixtures. However, both reactions occur essentially at the diffusion-control limit in supercritical fluoroform (CHF[sub 3]) and carbon dioxide (CO[sub 2]) doped with 1 mol % acetonitrile (CH[sub 3]CN) when spin statistical factors are taken into account. The reaction kinetics were measured by laser flash photolysis at various pressures above the critical pressure along three isotherms. This study corroborates our earlier report of these reactions in supercritical CO[sub 2] and ethane (C[sub 2]H[sub 6]). In all of the fluids and fluid mixture, the locally higher density of the solvent around the solutes in no way enhances or slows the bimolecular annihilation or termination reaction. In addition, there is no evidence of enhanced solute-solute interaction. Finally, we studied the photocleavage of dibenzyl ketone (DBK) and the subsequent decarbonylation of the phenylacetyl radical (PhCH[sub 2]CO) and did not observe any enhanced cage effects or anomalous behavior due to the increased local density. 54 refs., 6 figs.

  16. Protective effects of 6-hydroxy-1-methylindole-3-acetonitrile on cisplatin-induced oxidative nephrotoxicity via Nrf2 inactivation.

    PubMed

    Moon, Ji Hee; Shin, Ji-Sun; Kim, Jong-Bin; Baek, Nam-In; Cho, Young-Wuk; Lee, Yong Sup; Kay, Hee Yeon; Kim, Soo-dong; Lee, Kyung-Tae

    2013-12-01

    We previously demonstrated the ethanol extract of the roots of Brassica rapa protects against cisplatin-induced nephrotoxicity by attenuating oxidative stress. Here, we investigated the nephroprotective effects of 6-hydroxy-1-methylindole-3-acetonitrile (6-HMA), which was isolated from the roots of B. rapa, on cisplatin-induced toxicity in renal epithelial LLC-PK1 cells and in rats with acute renal injury. Pretreatment of LLC-PK1 cells with 6-HMA ameliorated cisplatin-induced cytotoxicity caused by oxidative stress, as was demonstrated by reductions in the levels of reactive oxygen species (ROS) and malondialdehyde (MDA) and increased levels of glutathione (GSH). In addition, 6-HMA inhibited cisplatin-induced heme oxygenase-1 (HO-1) expression, possibly due to the suppression of the nuclear translocation and binding activity of NF-E2-related factor 2 (Nrf2). Furthermore, 6-HMA administered rats showed lower levels of blood urea nitrogen (BUN), creatinine, and urinary lactate dehydrogenase (LDH) than cisplatin alone-treated rats in cisplatin-induced renal injury model. Moreover, 6-HMA inhibited the cisplatin-induced formation of MDA and GSH depletion and increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR). Taken together, these findings indicate 6-HMA is a major active constituent from the roots of B. rapa to have a protective effect against cisplatin-induced nephrotoxicity by attenuating oxidative stress. PMID:23989062

  17. Identification of the amino-acetonitrile derivative monepantel (AAD 1566) as a new anthelmintic drug development candidate

    PubMed Central

    Gauvry, N.; Schorderet Weber, S.; Skripsky, T.; Bouvier, J.; Wenger, A.; Schroeder, F.; Desaules, Y.; Hotz, R.; Goebel, T.; Hosking, B. C.; Pautrat, F.; Wieland-Berghausen, S.; Ducray, P.

    2008-01-01

    Anthelmintic resistance has become a global phenomenon in gastro-intestinal nematodes of farm animals, including multi-drug resistance against the three major classes of anthelmintics. There is an urgent need for an anthelmintic with a new mode of action. The recently discovered amino-acetonitrile derivatives (AADs) offer a new class of synthetic chemicals with anthelmintic activity. The evaluation of AADs was pursued applying in vitro assays and efficacy and tolerability studies in rodents, sheep, and cattle. Amongst various suitable compounds, AAD 1566 eliminated many tested pathogenic nematode species, both at larval and adult stages, at a dose of 2.5 mg/kg bodyweight in sheep and 5.0 mg/kg bodyweight in cattle. The same doses were sufficient to cure animals infected with resistant or multi-drug-resistant nematode isolates. These findings, complemented by the good tolerability and low toxicity to mammals, suggest that AAD 1566, monepantel, would be a suitable anthelmintic drug development candidate. PMID:18594861

  18. Identification of 2-[4-[(4-Methoxyphenyl)methoxy]-phenyl]acetonitrile and Derivatives as Potent Oct3/4 Inducers.

    PubMed

    Cheng, Xinlai; Dimou, Eleni; Alborzinia, Hamed; Wenke, Frank; Göhring, Axel; Reuter, Stefanie; Mah, Nancy; Fuchs, Heiko; Andrade-Navarro, Miguel A; Adjaye, James; Gul, Sheraz; Harms, Christoph; Utikal, Jochen; Klipp, Edda; Mrowka, Ralf; Wölfl, Stefan

    2015-06-25

    Reprogramming somatic cells into induced-pluripotent cells (iPSCs) provides new access to all somatic cell types for clinical application without any ethical controversy arising from the use of embryonic stem cells (ESCs). Established protocols for iPSCs generation based on viral transduction with defined factors are limited by low efficiency and the risk of genetic abnormality. Several small molecules have been reported as replacements for defined transcriptional factors, but a chemical able to replace Oct3/4 allowing the generation of human iPSCs is still unavailable. Using a cell-based High Throughput Screening (HTS) campaign, we identified that 2-[4-[(4-methoxyphenyl)methoxy]phenyl]acetonitrile (1), termed O4I1, enhanced Oct3/4 expression. Structural verification and modification by chemical synthesis showed that O4I1 and its derivatives not only promoted expression and stabilization of Oct3/4 but also enhanced its transcriptional activity in diverse human somatic cells, implying the possible benefit from using this class of compounds in regenerative medicine. PMID:25898186

  19. Mobile antennas for COMETS advanced mobile Satcom experiment

    NASA Technical Reports Server (NTRS)

    Hase, Yoshihiro; Tanaka, Masato; Saito, Haruo

    1995-01-01

    Advanced mobile satellite communication experiments in the Ka-band and the mm-wave will be carried out using the COMETS satellite, which is scheduled for launch in 1997. Mobile antennas will play a much more key role in high frequency systems such as COMETS than in conventional L-band mobile systems. This paper describes three types of antennas which are now being developed by the Communications Research Laboratory (CRL) for the COMETS mobile experiments. One is a mechanically steered waveguide slot array antenna, another is an electronically steered active phased array antenna, and the third is a mechanically steered torus reflector antenna. The first two antennas will be used in the Ka-band, while the latter will be used in the mm-wave.

  20. 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. PMID:26711438

  1. Photoisomerization and reorientational mobility of symmetric carbocyanines in AOT/alkane/polar solvent microemulsions

    NASA Astrophysics Data System (ADS)

    Dandapat, Manika; Basu, Saswati; Ghosh, Deborin; Mandal, Debabrata

    2014-07-01

    Molecular motion of carbocyanine fluorophores DOCI, DODCI and DTDCI were studied in AOT/n-heptane microemulsions containing added polar solvents: water, methanol or acetonitrile. The response varied remarkably depending on the nature of the fluorophore and polar solvent. When the amount of added polar solvent was low, molecular mobility was invariably retarded, due to a combination of electrostatic and hydrophobic forces that induce the guest fluorophore to cling to the AOT molecules of the host reverse micelle. However, at high amounts of added methanol or water, these interactions diminished considerably, causing increase in the mobility of the guest fluorophores up to different extents.

  2. Phase Behavior, Solid Organic Precipitation, and Mobility Characterization Studies in Support of Enhanced Heavy Oil Recovery on the Alaska North Slope

    SciTech Connect

    Shirish Patil; Abhijit Dandekar; Santanu Khataniar

    2008-12-31

    The medium-heavy oil (viscous oil) resources in the Alaska North Slope are estimated at 20 to 25 billion barrels. These oils are viscous, flow sluggishly in the formations, and are difficult to recover. Recovery of this viscous oil requires carefully designed enhanced oil recovery processes. Success of these recovery processes is critically dependent on accurate knowledge of the phase behavior and fluid properties, especially viscosity, of these oils under variety of pressure and temperature conditions. This project focused on predicting phase behavior and viscosity of viscous oils using equations of state and semi-empirical correlations. An experimental study was conducted to quantify the phase behavior and physical properties of viscous oils from the Alaska North Slope oil field. The oil samples were compositionally characterized by the simulated distillation technique. Constant composition expansion and differential liberation tests were conducted on viscous oil samples. Experiment results for phase behavior and reservoir fluid properties were used to tune the Peng-Robinson equation of state and predict the phase behavior accurately. A comprehensive literature search was carried out to compile available compositional viscosity models and their modifications, for application to heavy or viscous oils. With the help of meticulously amassed new medium-heavy oil viscosity data from experiments, a comparative study was conducted to evaluate the potential of various models. The widely used corresponding state viscosity model predictions deteriorate when applied to heavy oil systems. Hence, a semi-empirical approach (the Lindeloff model) was adopted for modeling the viscosity behavior. Based on the analysis, appropriate adjustments have been suggested: the major one is the division of the pressure-viscosity profile into three distinct regions. New modifications have improved the overall fit, including the saturated viscosities at low pressures. However, with the limited

  3. Plasma mitomycin C concentrations determined by HPLC coupled to solid-phase extraction.

    PubMed

    Paroni, R; Arcelloni, C; De Vecchi, E; Fermo, I; Mauri, D; Colombo, R

    1997-04-01

    The aim of this study was to set up a method for quantification of plasma mitomycin C (MMC) concentrations during intravesical chemotherapy delivered in the presence of local bladder hyperthermia (HT). In comparison with existing methods, this assay, characterized by relative simplicity and efficiency, resulted in the facilitation of performance with nondedicated instrumentation or nonspecialized staff. Purification from plasma matrix was carried out by solid-phase extraction under vaccuum. The purified drug was then collected directly into the vials of the HPLC autosampler. Chromatographic analysis was performed on a reversed-phase C18 column with water:acetonitrile (85:15 by vol) as the mobile phase and the UV detector set at 365 nm. The use of porfiromycin as internal standard provided a method with good within-day precision (CV 6.0% at 5 micrograms/L, n = 6), linearity (0.5-50 micrograms/L), and specificity. The lower limit of detection (< or = 0.5 microgram/L) proved to be suitable for plasma pharmacokinetics monitoring in two tested patients treated with MMC + HT for superficial bladder cancer. PMID:9105262

  4. Syringe-cartridge solid-phase extraction method for patulin in apple juice.

    PubMed

    Eisele, Thomas A; Gibson, Midori Z

    2003-01-01

    A syringe-cartridge solid-phase extraction (SPE) method was developed for determination of patulin in apple juice. A 2.5 mL portion of test sample was passed through a conditioned macroporous SPE cartridge and washed with 2 mL 1% sodium bicarbonate followed by 2 mL 1% acetic acid. Patulin was eluted with 1 mL 10% ethyl acetate in ethyl ether and determined by reversed-phase liquid chromatography using a mobile phase consisting of 81% acetonitrile, 9% water, and 10% 0.05M potassium phosphate buffer, pH 2.4. Recoveries averaged 92% and the relative standard deviation was 8.0% in test samples spiked with 50 ng/mL patulin. The method appears to be applicable for monitoring apple juice samples to meet the U.S. Food and Drug Administration compliance action level of 50 microg/kg in an industrial quality assurance laboratory environment. PMID:14979697

  5. Brick Kiln Emissions Quantified with the Aerodyne Mobile Laboratory During the Short Lived Climate Forcing (SLCF) 2013 Campaign in Guanajuato Mexico

    NASA Astrophysics Data System (ADS)

    Fortner, E.; Knighton, W. B.; Herndon, S.; Roscioli, J. R.; Zavala, M.; Onasch, T. B.; Jayne, J. T.; Worsnop, D. R.; Kolb, C. E.; Molina, L. T.

    2013-12-01

    Brick kiln emissions are suspected to be a major source of atmospheric black carbon (BC) in developing countries; and black carbon's role as a short lived climate forcing (SLCF) pollutant is widely recognized. The SLCF-Mexico brick kiln study was conducted from 12-17 March 2013 in Mexico's Guanajuato state. Three different types of brick kilns were investigated (MK2, traditional, and traditional three tier) providing data on the effects of different kiln designs on particle and gas phase emissions. The BC and gaseous combustion emissions from these kilns were measured during both the fire stage and the subsequent smoldering stage with real-time instruments deployed on the Aerodyne Mobile Laboratory, and quantified utilizing flux tracer gases released adjacent to the brick kiln. This method allows examination of the brick kiln plume's evolution as it transits downwind from the source. Particulate measurements conducted by the mobile laboratory included the multi angle absorption photometer (MAAP) to measure black carbon mass, cavity attenuated phase shift (CAPSext) monitor to measure extinction and soot particle aerosol mass spectrometer (SP-AMS) measurements of black carbon. The SP-AMS instrument combines the ability to measure black carbon with the ability to determine the chemical composition of the other particulate matter (PM) components associated with black carbon particles. The variance of PM chemical composition will be examined as a function of burning stage and kiln type and compared to other black carbon PM sources. Gas phase exhaust species measured included CO, CO2, NOx, SO2, CH4, C2H6, as well as a variety of VOCs (acetonitrile, benzene etc.) measured with a PTR-MS instrument. All of these measurements will be examined to construct emission ratios evaluating how these vary with different kiln types and different firing conditions. The evolution of particulate matter and gas phase species as they transit away from the source will also be examined.

  6. Determination of trantinterol enantiomers in human plasma by high-performance liquid chromatography - tandem mass spectrometry using vancomycin chiral stationary phase and solid phase extraction and stereoselective pharmacokinetic application.

    PubMed

    Qin, Feng; Wang, Yanjuan; Wang, Lijuan; Zhao, Longshan; Pan, Li; Cheng, Maosheng; Li, Famei

    2015-05-01

    A sensitive and enantioselective vancomycin chiral stationary phase high-performance liquid chromatography-tandem mass spectrometry method was developed for the determination of trantinterol enantiomers in human plasma. Baseline resolution was achieved using the vancomycin chiral stationary phase known as Chirobiotic V with polar ionic mobile phase consisting of acetonitrile-methanol (60:40, v/v) containing 0.01% ammonia and 0.02% acetic acid at a flow rate of 1.0 mL/min. Waters Oasis HLB C18 solid phase extraction cartridges were used in the sample preparation of trantinterol samples from plasma. The detection was performed on a triple-quadrupole tandem mass spectrometer by multiple reaction monitoring mode via electrospray ionization. The calibration curve was linear in a concentration range from 0.0606 to 30.3 ng/mL in plasma, with the lower limit of quantification of 0.0606 ng/mL. The intra- and interday precision (relative standard deviation) values were within 9.7% and the accuracy (relative error) was from -6.6 to 7.2% at all quality control levels. The method was successfully applied to a study of stereoselective pharmacokinetics in human. PMID:25782043

  7. Europium, uranyl, and thorium-phenanthroline amide complexes in acetonitrile solution: an ESI-MS and DFT combined investigation.

    PubMed

    Xiao, Cheng-Liang; Wang, Cong-Zhi; Mei, Lei; Zhang, Xin-Rui; Wall, Nathalie; Zhao, Yu-Liang; Chai, Zhi-Fang; Shi, Wei-Qun

    2015-08-28

    The tetradentate N,N'-diethyl-N,N'-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) ligand with hard-soft donor atoms has been demonstrated to be promising for the group separation of actinides from highly acidic nuclear wastes. To identify the formed complexes of this ligand with actinides and lanthanides, electrospray ionization mass spectrometry (ESI-MS) combined with density functional theory (DFT) calculations was used to probe the possible complexation processes. The 1 : 2 Eu-L species ([EuL2(NO3)](2+)) can be observed in ESI-MS at low metal-to-ligand ([M]/[L]) ratios, whereas the 1 : 1 Eu-L species ([EuL(NO3)2](+)) can be observed when the [M]/[L] ratio is higher than 1.0. However, ([UO2L(NO3)](+)) is the only detected species for the uranyl complexes. The [ThL2(NO3)2](2+) species can be observed at low [M]/[L] ratios; the 1 : 2 species ([ThL2(NO3)](3+)) and a new 1 : 1 species ([ThL(NO3)3](+)) can be detected at high [M]/[L] ratios. Collision-induced dissociation (CID) results showed that Et-Tol-DAPhen ligands can coordinate strongly with metal ions, and the coordination moieties remain intact under CID conditions. Natural bond orbital (NBO), molecular electrostatic potential (MEP), electron localization function (ELF), atoms in molecules (AIM) and molecular orbital (MO) analyses indicated that the metal-ligand bonds of the actinide complexes exhibited more covalent character than those of the lanthanide complexes. In addition, according to thermodynamic analysis, the stable cationic M-L complexes in acetonitrile are found to be in good agreement with the ESI-MS results. PMID:26200662

  8. Process-scale reversed-phase high-performance liquid chromatography purification of LL-E19020 alpha, a growth promoting antibiotic produced by Streptomyces lydicus ssp. tanzanius.

    PubMed

    Williams, D R; Carter, G T; Pinho, F; Borders, D B

    1989-12-22

    LL-E19020 alpha is a novel antibiotic produced by fermentation of the soil microorganism Streptomyces lydicus ssp. tanzanius. The compound is highly effective in inducing increases in weight gain and feed conversion efficiency in livestock. In order to obtain kilogram quantities of the material for field trials, pilot plant scale fermentations (up to 7500 l) were carried out. The antibiotic was recovered from the fermentation broth by solvent extraction. The resultant crude extract was subjected to reversed-phase (C18) chromatography on a process-scale high-performance liquid chromatography (HPLC) unit. The heart of the instrumentation is the Millipore Kiloprep chromatograph with the standard 12-l cartridge column. The laboratory housing the chromatograph has been specifically designed for this work. Tanks for mobile phase preparation are mounted on load cells for precise measurement of components. In this explosion-proof laboratory, all solvent handling areas are well ventilated and a separate breathing air system is provided for the operators. For the purification of the LL-E19020 antibiotics, the mobile phase consisted of a gradient of acetonitrile in 0.1 M ammonium acetate at pH 4.5. The effluent was monitored by UV absorbance at 325 nm. Fractions were collected across the peaks of interest and these were analyzed by analytical HPLC. The maximum yield of LL-E19020 alpha obtained in a single run was approximately 100 g. The antibiotic was recovered from the mobile phase by extraction with methylene chloride. The methylene chloride phase was concentrated under reduced pressure to yield a gummy residue which was finally freeze-dried from tertiary butanol to yield an off-white solid suitable for blending with various feed components. PMID:2613793

  9. MOBILE BED FLUX FORCE/CONDENSATION SCRUBBERS

    EPA Science Inventory

    The report gives results of an experimental determination of fine particle collection in mobile bed scrubbers. Particle collection efficiency increased greatly as the gas-phase pressure drop increased. With no water vapor condensation, the performance capability of a mobile bed s...

  10. Monitoring of N-methyl carbamate pesticide residues in water using hollow fibre supported liquid membrane and solid phase extraction

    NASA Astrophysics Data System (ADS)

    Msagati, Titus A. M.; Mamba, Bhekie B.

    The aim of this work was to develop a method for the determination of N-methyl carbamates in water involving hollow fibre supported liquid membrane (HFSLM) and solid phase extraction (SPE) as sample preparation methods. Four N-methyl carbamate pesticides, aldicarb, carbaryl, carbofuran and methiocarb sulfoxide, were simultaneously extracted and analysed by a liquid chromatograph with a diode array detector (LC-UV/DAD) and a liquid chromatograph coupled to a ion trap quadrupole mass spectrometer (LC-ESI-MS). The high performance liquid chromatography (HPLC) separation of carabamate extracts was performed on a C18 column with water-acetonitrile as the mobile phase. The mass spectrometry analyses were carried out in the positive mode, operating under both the selected ion monitoring (SIM) and full scan modes. The solid phase recoveries of the extracts ranged between 8% and 98%, with aldicarb having the highest recoveries, followed by carbaryl, carbofuran and methiocarb had the lowest recovery. The HFSLM recovery ranged between 8% and 58% and the order of recovery was similar to the SPE trend. Factors controlling the efficiency of the HFSLM extraction such as sample pH, stripping phase pH, enrichment time, stirring speed as well as organic solvent used for entrapment of analytes, were optimised to achieve the highest enrichment factors.

  11. Application of the Empore solid-phase extraction membrane to the isolation of drugs from blood. I. Amiodarone and desethylamiodarone.

    PubMed

    Lensmeyer, G L; Wiebe, D A; Doran, T

    1991-05-01

    We describe the use of a new form of solid-phase material, the Empore solid-phase extraction membrane (SPEM), for therapeutic drug monitoring. We evaluated the new extraction procedure with the companion high-performance liquid chromatographic (HPLC) method for the antiarrhythmic drug amiodarone and its metabolite, desethylamiodarone, in patients' serum. Acidified serum (250 microliters) was passed through an octyl (C8) SPEM secured in an MF-1 microfilter unit. Serum proteins and potential interferences were removed with an acetonitrile:water wash, and the retained drugs eluted with HPLC mobile phase. This eluate was injected directly onto the analytical column. Both drugs averaged 85% recovery with a linear response from a lower limit of detection at 0.05 mg/L up to 6 mg/L, and between-run precision coefficients of variation ranging from 3.1 to 6.4% over the concentration range of 0.5-3.0 mg/L. We observed significant advantages of the novel SPEM over conventional liquid-liquid or large-particle size solid-phase sorbents packed in cartridges. Minimal amounts of solvents were required, elution volume was smaller, time-consuming evaporating/concentrating steps that can influence drug stability were avoided, and little throw-away material was generated. Only the small membrane was discarded. PMID:1926279

  12. Carrier recovery techniques on satellite mobile channels

    NASA Technical Reports Server (NTRS)

    Vucetic, B.; Du, J.

    1990-01-01

    An analytical method and a stored channel model were used to evaluate error performance of uncoded quadrature phase shift keying (QPSK) and M-ary phase shift keying (MPSK) trellis coded modulation (TCM) over shadowed satellite mobile channels in the presence of phase jitter for various carrier recovery techniques.

  13. A simplified protein precipitation/mixed-mode cation-exchange solid-phase extraction, followed by high-speed liquid chromatography/mass spectrometry, for the determination of a basic drug in human plasma.

    PubMed

    Xue, Y-J; Akinsanya, J Billy; Liu, Jane; Unger, Steve E

    2006-01-01

    A simplified protein precipitation/mixed-mode cation-exchange solid-phase extraction (PPT/SPE) procedure has been investigated. A mixture of acetonitrile and methanol along with formic acid was used to precipitate plasma proteins prior to selectively extracting the basic drug. After vortexing and centrifugation, the supernatants were directly loaded onto an unconditioned Oasis MCX microElution 96-well extraction plate, where the protonated drug was retained on the negatively charged sorbent while interfering neutral lipids, steroids or other endogenous materials were washed away. Normal wash steps were deemed unnecessary and not used before sample elution. The sample extracts were analyzed under both conventional and high-speed liquid chromatography/tandem mass spectrometry (LC/MS/MS) conditions to examine the feasibility of the PPT/SPE procedure for human plasma sample clean-up. For the conventional LC/MS/MS method, chromatographic separation was achieved on a C18, 2.1 x 50 mm column with gradient elution (k' = 5.5). The mobile phase contained 0.1% formic acid in water and 0.1% formic acid in acetonitrile. For the high-speed LC/MS/MS method, chromatographic separation was achieved on a C18, 2.1 x 10 mm guard column with gradient elution (k' = 2.2, Rt = 0.26 min). The mobile phase contained 0.1% formic acid in water and 0.001% trifluoroacetic acid in acetonitrile. Detection for both conventional and high-speed LC/MS/MS methods was by positive ion electrospray tandem mass spectrometry on a ThermoElectron Finnigan TSQ Quantum Ultra, where enhanced resolution (RP 2000; 0.2 amu) was used for high-speed LC/MS/MS. The standard curve, ranging from 0.5 to 100 ng/mL, was fitted to a 1/x weighted quadratic regression model. This combined PPT/SPE procedure effectively eliminated time-consuming sorbent conditioning and wash steps, which are essential for a conventional mixed-mode SPE procedure, but retained the advantages of both PPT (removal of plasma proteins) and mixed

  14. Modem for the land mobile satellite channel

    NASA Technical Reports Server (NTRS)

    Henely, Steven J.

    1988-01-01

    This paper describes a modem which has been developed and implemented using a digital signal processor (DSP) for a land mobile satellite demonstration system. The requirements of this digital modem were determined by the characteristics of the land mobile satellite channel. This paper discusses the algorithms which implement the differentiated phase shift keying (DPSK) demodulator. An algorithm is included which estimates symbol timing independent of carrier phase without the use of a square-law nonlinearity.

  15. A validated liquid chromatographic method for the determination of polycyclic aromatic hydrocarbons in honey after homogeneous liquid-liquid extraction using hydrophilic acetonitrile and sodium chloride as mass separating agent.

    PubMed

    Koltsakidou, Anastasia; Zacharis, Constantinos K; Fytianos, Konstantinos

    2015-01-16

    In the present report, a simple and cost-effective method for the determination of twelve US EPA priority polycyclic aromatic hydrocarbons (PAHs) in honey samples after salting-assisted liquid-liquid extraction and UHPLC with fluorescence detection is proposed. The sample treatment is based on the usage of hydrophilic acetonitrile as extraction solvent and its phase separation under high salinity conditions. Due to the high sugar content of the samples the phase separation is promoted effortlessly. Several parameters affecting the extraction efficiency and method sensitivity including the concentration of the honey samples, the type and volume of the extraction solvent, the type and quantity of the inorganic salt, extraction time and centrifugation time was systematically investigated. The method was validated in-house according to the Commission Decision 2002/657/EC guidelines. The limit of detection (LOD) of the method lay between 0.02 and 0.04ngmL(-1) (corresponding to 0.08 and 0.16ngg(-1)) which are close to the quality criteria established by European Regulation (EC) 836/2011 concerning the PAHs in foodstuffs. The mean analytical bias (expressed as relative recoveries) in all spiking levels was acceptable being in the range of 54-118% while the relative standard deviation (RSD) was lower than 19%. The proposed method has been satisfactorily applied for the analysis of the selected PAHs residues in various honey samples obtained from Greek region. PMID:25543304

  16. Study of the acetonitrile poisoning of platinum cathodes on proton exchange membrane fuel cell spatial performance using a segmented cell system

    NASA Astrophysics Data System (ADS)

    Reshetenko, Tatyana V.; St-Pierre, Jean

    2015-10-01

    Due to the wide applications of acetonitrile as a solvent in the chemical industry, acetonitrile can be present in the air and should be considered a possible pollutant. In this work, the spatial proton exchange membrane fuel cell performance exposed to air with 20 ppm CH3CN was studied using a segmented cell system. The injection of CH3CN led to performance losses of 380 mV at 0.2 A cm-2 and 290 mV at 1.0 A cm-2 accompanied by a significant change in the current density distribution. The observed local currents behavior is likely attributed to acetonitrile chemisorption and the subsequent two consecutive reduction/oxidation reactions. The hydrolysis of CH3CN and its intermediate imine species resulted in NH4+ formation, which increased the high-frequency resistance of the cell and affected oxygen reduction and performance. Other products of hydrolysis can be oxidized to CO2 under the operating conditions. The reintroduction of pure air completely recovered cell performance within 4 h at 1.0 A cm-2, while at 0.2 A cm-2 the cell recovery was only partial. A detailed analysis of the current density distribution, its correlation with spatial electrochemical impedance spectroscopy data, possible CH3CN oxidation/reduction mechanisms and mitigation strategies are presented and discussed.

  17. Origin of anomalous electronic circular dichroism spectrum of RuPt2(tppz)2Cl2(PF6)4 in acetonitrile.

    PubMed

    Yu, Hua-Gen

    2014-07-24

    We report a theoretical study of the structures, energetics, and electronic spectra of the Pt(II)/Ru(II) mixed-metal complex RuPt2(tppz)2Cl2(PF6)4 (tppz = 2,3,5,6-tetra(2-pyridyl)pyrazine) in acetonitrile. The hybrid B3LYP density functional theory and its TDDFT methods were used with a complete basis set (CBS) extrapolation scheme and a conductor polarizable continuum model (C-PCM) for solvation effects. Results showed that the trinuclear complex has four types of stable conformers and/or enantiomers. They are separated by high barriers owing to the repulsive H/H geometrical constraints in tppz. A strong entropy effect was found for the dissociation of RuPt2(tppz)2Cl2(PF6)n in acetonitrile. The UV-visible and emission spectra of the complex were also simulated. They are in good agreement with experiments. In this work we have largely focused on exploring the origin of anomalous electronic circular dichroism (ECD) spectra of the RuPt2(tppz)2Cl2(PF6)4 complex in acetonitrile. As a result, a new mechanism has been proposed together with a clear illustration by using a physical model. PMID:25026322

  18. Determination of strobilurin fungicides in cotton seed by combination of acetonitrile extraction and dispersive liquid-liquid microextraction coupled with gas chromatography.

    PubMed

    Xue, Jiaying; Li, Huichen; Liu, Fengmao; Jiang, Wenqing; Chen, Xiaochu

    2014-04-01

    The simultaneous determination of four strobilurin fungicides (picoxystrobin, kresoxim-methyl, trifloxystrobin, and azoxystrobin) in cotton seed by combining acetonitrile extraction and dispersive liquid-liquid microextraction was developed prior to GC with electron capture detection. Several factors, including the type and volume of the extraction and dispersive solvents, extraction condition and time, and salt addition, were optimized. The analytes were extracted with acetonitrile from cotton seed and the clean-up was carried out by primary secondary amine. Afterwards, 60 μL of n-hexane/toluene (1:1, v/v) with a lower density than water was mixed with 1 mL of the acetonitrile extract, then the mixture was injected into 7 mL of distilled water. A 0.1 mL pipette was used to collect a few microliters of n-hexane/toluene from the top of the aqueous solution. The enrichment factors of the analytes ranged from 36 to 67. The LODs were in the range of 0.1 × 10(-3) -2 × 10(-3) mg/kg. The relative recoveries varied from 87.7 to 95.2% with RSDs of 4.1-8.5% for the four fungicides. The good performance of the method, compared with the conventional pretreatments, has demonstrated it is suitable for determining low concentrations of strobilurin fungicide residues in cotton seed. PMID:24482392

  19. A novel strategy for acetonitrile wastewater treatment by using a recombinant bacterium with biofilm-forming and nitrile-degrading capability.

    PubMed

    Li, Chunyan; Yue, Zhenlei; Feng, Fengzhao; Xi, Chuanwu; Zang, Hailian; An, Xuejiao; Liu, Keran

    2016-10-01

    There is a great need for efficient acetonitrile removal technology in wastewater treatment to reduce the discharge of this pollutant in untreated wastewater. In this study, a nitrilase gene (nit) isolated from a nitrile-degrading bacterium (Rhodococcus rhodochrous BX2) was cloned and transformed into a biofilm-forming bacterium (Bacillus subtilis N4) that expressed the recombinant protein upon isopropylthio-β-galactoside (IPTG) induction. The recombinant bacterium (B. subtilis N4-pHT01-nit) formed strong biofilms and had nitrile-degrading capability. Further testing demonstrated that biofilms formed by B. subtilis N4-pHT01-nit were highly resistant to loading shock from acetonitrile and almost completely degraded the initial concentration of acetonitrile (800 mg L(-1)) within 24 h in a moving bed biofilm reactor (MBBR) after operation for 35 d. The bacterial composition of the biofilm, identified by high-throughput sequencing, in a reactor in which the B. subtilis N4-pHT01-nit bacterium was introduced indicated that the engineered bacterium was successfully immobilized in the reactor and became dominant genus. This work demonstrates that an engineered bacterium with nitrile-degrading and biofilm-forming capacity can improve the degradation of contaminants in wastewater. This approach offers a novel strategy for enhancing the biological oxidation of toxic pollutants in wastewater. PMID:27434252

  20. A Mobile Internet Service for Self-Management of Physical Activity in People With Rheumatoid Arthritis: Challenges in Advancing the Co-Design Process During the Requirements Specification Phase

    PubMed Central

    Martin, Cathrin; H. Opava, Christina; Brusewitz, Maria; Keller, Christina; Åsenlöf, Pernilla

    2015-01-01

    Background User involvement in the development of health care services is important for the viability, usability, and effectiveness of services. This study reports on the second step of the co-design process. Objective The aim was to explore the significant challenges in advancing the co-design process during the requirements specification phase of a mobile Internet service for the self-management of physical activity (PA) in rheumatoid arthritis (RA). Methods A participatory action research design was used to involve lead users and stakeholders as co-designers. Lead users (n=5), a clinical physiotherapist (n=1), researchers (n=2) with knowledge in PA in RA and behavioral learning theories, an eHealth strategist (n=1), and an officer from the patient organization (n=1) collaborated in 4 workshops. Data-collection methods included video recordings and naturalistic observations. Results The inductive qualitative video-based analysis resulted in 1 overarching theme, merging perspectives, and 2 subthemes reflecting different aspects of merging: (1) finding a common starting point and (2) deciding on design solutions. Seven categories illustrated the specific challenges: reaching shared understanding of goals, clarifying and handling the complexity of participants’ roles, clarifying terminology related to system development, establishing the rationale for features, negotiating features, transforming ideas into concrete features, and participants’ alignment with the agreed goal and task. Conclusions Co-designing the system requirements of a mobile Internet service including multiple stakeholders was a complex and extensive collaborative decision-making process. Considering, valuing, counterbalancing, and integrating different perspectives into agreements and solutions (ie, the merging of participants’ perspectives) were crucial for moving the process forward and were considered the core challenges of co-design. Further research is needed to replicate the results

  1. Domestic mobile satellite systems in North America

    NASA Technical Reports Server (NTRS)

    Wachira, Muya

    1990-01-01

    Telest Mobile Inc. (TMI) and the American Mobile Satellite Corporation (AMSC) are authorized to provide mobile satellite services (MSS) in Canada and the United States respectively. They are developing compatible systems and are undertaking joint specification and procurement of spacecraft and ground segment with the aim of operational systems by late 1993. Early entry (phase 1) mobile data services are offered in 1990 using space segment capacity leased from Inmarsat. Here, an overview is given of these domestic MSS with an emphasis on the TMI component of the MSAT systen.

  2. 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. PMID:25898315

  3. Orthogonal separation on one beta-cyclodextrin column by switching reversed-phase liquid chromatography and hydrophilic interaction chromatography.

    PubMed

    Feng, Jia-tao; Guo, Zhi-mou; Shi, Hui; Gu, Jiang-ping; Jin, Yu; Liang, Xin-miao

    2010-06-15

    A dual retention combined with reversed-phase liquid chromatography (RP-LC) and hydrophilic interaction chromatography (HILIC) has been observed on beta-cyclodextrin (beta-CD) bonded stationary phase. A typical U-shaped retention curve was achieved owing to dual retention mechanism. Based on this observation, a beta-CD column can be operated under reversed-phase liquid chromatography (RP-LC) and hydrophilic interaction chromatography (HILIC) modes. Two-dimensional liquid chromatography (2D-LC) analysis can be realized on just a beta-CD column by switching these two different separation modes. In this study, off-line 2D-LC analysis for a natural product was carried out to prove the orthogonal separation between RP-LC and HILIC modes on a Click beta-CD column. Herba Hedyotis Diffusae, the whole grass of Hedyotis Diffusae wild was extracted with water, pretreated with macroporous resin and then first separated at RP-LC mode on the Click beta-CD column to obtain successive fractions, which were then reanalyzed at HILIC mode on the same Click beta-CD column. The result proved that both separation modes on the Click beta-CD column have good retention and peak shape, and these two separation modes have good orthogonality. 2D-LC analysis revealed abundant information in the natural product. Especially numerous minor components were enriched and separated. The mobile phase used in RP-LC and HILIC modes can be same and the switch between these two separation modes is easily realized by changing the ratio of the acetonitrile and water. Hence the mobile phase in this 2D-LC system is completely compatible. This advantage makes this combination is an appropriate 2D-LC method for the solutes having retention at both separation modes. PMID:20441989

  4. Mobile shearography

    NASA Astrophysics Data System (ADS)

    Kalms, Michael; Jueptner, Werner

    2005-04-01

    By reason of their sensitivity, accuracy and non-contact as well as non-destructive characteristics, modern optical methods such as digital speckle shearography have found an increasing interest for NDT applications on the factory floor. With new carbon filter technologies and other lightweight constructions in aircraft and automotive manufacturing, adapted examination designs and especially developed testing methods are necessary. Shearography as a coherent optical method has been widely accepted as an useful NDT tool. It is a robust interferometric method to determine locations with maximum stress on various material structures. However, limitations of this technique can be found in the bulky equipment components, the interpretation of the complex sherographic result images and at the work with non-cooperative surfaces (dark absorber, bright shining reflectors). We report a mobile shearography system that was especially designed for investigations at aircraft and automotive constructions.

  5. Models of retention of adamantylamidrazones in reversed-phase high-performance liquid chromatography

    NASA Astrophysics Data System (ADS)

    Prokopov, S. V.; Kurbatova, S. V.

    2011-05-01

    Rules governing the chromatographic behavior of some amidrazones of the adamantane series were studied under the conditions of reversed-phase high-performance liquid chromatography. The characteristics of the retention of sorbates in elution by aqueous-acetonitrile phases with various compositions were calculated. Correlations between the structure and physicochemical characteristics of sorbate molecules and their retention were studied.

  6. Rapid and sensitive analysis of phthalate metabolites, bisphenol A, and endogenous steroid hormones in human urine by mixed-mode solid-phase extraction, dansylation, and ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry.

    PubMed

    Wang, He-xing; Wang, Bin; Zhou, Ying; Jiang, Qing-wu

    2013-05-01

    Steroid hormone levels in human urine are convenient and sensitive indicators for the impact of phthalates and/or bisphenol A (BPA) exposure on the human steroid hormone endocrine system. In this study, a rapid and sensitive method for determination of 14 phthalate metabolites, BPA, and ten endogenous steroid hormones in urine was developed and validated on the basis of ultra-performance liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry. The optimized mixed-mode solid phase-extraction separated the weakly acidic or neutral BPA and steroid hormones from acidic phthalate metabolites in urine: the former were determined in positive ion mode with a methanol/water mobile phase containing 10 mM ammonium formate; the latter were determined in negative ion mode with a acetonitrile/water mobile phase containing 0.1 % acetic acid, which significantly alleviated matrix effects for the analysis of BPA and steroid hormones. Dansylation of estrogens and BPA realized simultaneous and sensitive analysis of the endogenous steroid hormones and BPA in a single chromatographic run. The limits of detection were less than 0.84 ng/mL for phthalate metabolites and less than 0.22 ng/mL for endogenous steroid hormones and BPA. This proposed method had satisfactory precision and accuracy, and was successfully applied to the analyses of human urine samples. This method could be valuable when investigating the associations among endocrine-disrupting chemicals, endogenous steroid hormones, and relevant adverse outcomes in epidemiological studies. PMID:23430180

  7. Deconvoluting the effects of buffer salt concentration in hydrophilic interaction chromatography on a zwitterionic stationary phase.

    PubMed

    West, Caroline; Auroux, Emeline

    2016-08-26

    Quantitative structure-retention relationships (QSRRs) furnish a detailed and reliable description of the role and extent of different molecular interactions that can be established between the analytes and the chromatographic system. Among QSRRs, the solvation parameter model using Abraham descriptors has gained acceptance as a general tool to explore the factors affecting retention in chromatographic systems. We have previously shown how a modified version of the solvation parameter model, with two extra terms to take account of interactions occurring with ionic and ionizable species (with positive and/or negative charges), could be applied to the characterization of hydrophilic interaction chromatographic (HILIC) systems. In the present study, we will show how this methodology can be used to evaluate the effects of increasing buffer salt concentration on retention and separation in a HILIC system. A commercial stationary phase possessing a sulfobetaine zwitterionic bonded ligand (Nucleodur HILIC) was used with a mobile phase composed of 80% acetonitrile and 20% pwwH4 ammonium acetate buffer, with aqueous buffer concentrations varying from 10 to 100mM, resulting in overall concentrations ranging from 2 to 20mM in the mobile phase. Retention factors were measured for a selection of 76 probe analytes. The chosen compounds are small molecules presenting a wide diversity of molecular structures and are relevant to biomedical and pharmaceutical applications. The QSRR models obtained allow for a rationalization of the interactions contributing to retention and separation in the HILIC system considered and shed some light on the effect of varying buffer salt concentration, namely the progressive transition from ion-exchange and electrostatic-repulsion mechanisms to hydrophilic partitioning. PMID:27475992

  8. [Determination of residual sulfonamides in meat by high performance liquid chromatography with solid-phase extraction].

    PubMed

    Zhang, Yan; Wu, Yinliang

    2005-11-01

    A method was developed for determining residual sulfonamides (SAs) such as sulfamethazine (SM2), sulfamonomethoxine (SMM), sulfamethiazole (SMZ), sulfadimethoxine (SDM) and sulfaquinoxaline (SQ) in pork and chicken using solid-phase extraction (SPE) and high performance liquid chromatography (HPLC) with a photodiode array detector. The samples were extracted with ethyl acetate. An NH2 column was used for clean up. For the HPLC determination, an Intersil ODS-2 column was used with a mixture of methanol-acetonitrile-water-acetic acid (2: 2: 9: 0.2, v/v) as the mobile phase. The detection limits (S/N = 3) were 3 microg/kg for SM2, SMM and SMZ, and 7 microg/kg for SDM and SQ. The quantitation limits (S/N = 10) were 10 microg/kg for SM2, SMM and SMZ, and 25 microg/kg for SDM and SQ. The linear ranges were 30 - 5 000 microg/L for SM2, SMM and SMZ, and 60 - 5 000 microg/L for SDM and SQ. The recoveries were between 73.2% and 97.3% with the relative standard deviations between 2.5% and 11.6% originated from the spiked level of 50 microg/kg. PMID:16498995

  9. 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

  10. Isolation of tetracyclines in milk using a solid-phase extracting column and water eluent.

    PubMed

    Furusawa, Naoto

    2003-01-01

    An isolating method using a solid-phase extraction (SPE) ISOLUTE(R) C8 endcapped syringe-column for routine monitoring of residual tetracyclines (TCs) (oxytetracycline (OTC), tetracycline (TC), chlortetracycline (CTC), and doxycycline (DC)) in cow's milk is presented. In the simplest and most environmentally harmless method, milk samples could be applied directly to the SPE column, following which all TCs were eluted with water. No organic solvents were used at all. The purified sample was injected into a high-performance liquid chromatography (HPLC) with a photo-diode array detector (PDAD). For the HPLC determination/identification, a LiChrospher(R) 100 RP-8 endcapped column and a mobile phase of acetonitrile -7% (v v(-1)) acetic acid solution (in water) (35:65, v v(-1)) with a PDAD was used. The total time required for the analysis of one sample was <40 min. Average recoveries (spiked 0.1-1.0 mug ml(-1) each drug) and their standard deviations were >80 and <5%, respectively. PMID:18968895

  11. [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. PMID:21574401

  12. Cooperating mobile robots

    DOEpatents

    Harrington, John J.; Eskridge, Steven E.; Hurtado, John E.; Byrne, Raymond H.

    2004-02-03

    A miniature mobile robot provides a relatively inexpensive mobile robot. A mobile robot for searching an area provides a way for multiple mobile robots in cooperating teams. A robotic system with a team of mobile robots communicating information among each other provides a way to locate a source in cooperation. A mobile robot with a sensor, a communication system, and a processor, provides a way to execute a strategy for searching an area.

  13. Determination of pyronaridine in whole blood by automated solid phase extraction and high-performance liquid chromatography.

    PubMed

    Blessborn, Daniel; Lindegårdh, Niklas; Ericsson, Orjan; Hellgren, Urban; Bergqvist, Yngve

    2003-06-01

    A new extraction procedure for the analysis of pyronaridine in whole blood is presented. A weak cation exchanger with a carboxylic acid (CBA) sorbent was found to be a suitable solid phase sorbent for the extraction of pyronaridine. High-performance liquid chromatography with UV detection at 278 nm and an electrochemical detector at +0.75 V is used. The electrochemical detector gives higher selectivity than the UV detector. The separation was performed using a C18 reversed phase column with mobile phase of acetonitrile-phosphate buffer (0.01 mol/L, pH 2.5)- sodium perchlorate (1.0 mol/L; 22:77:1, v/v/v). The within-day RSDs were below 5% at all concentration levels between 75 nmol/L and 1500 nmol/L, and the between-day RSDs were below 14% at all concentration levels. The limit of quantification was about 50 nmol/L in 1000 microL whole blood with an RSD of 20% or less on a day-to-day basis. The stability of pyronaridine is increased if the pH is less than 3 in water solutions. In whole blood, the concentration decreases by about 10% for each freeze-thaw cycle performed. At room temperature (about 22 degrees C), pyronaridine concentration in whole blood decreases by about 10% within 12 to 24 hours. PMID:12766551

  14. Two-Dimensional Micro-TLC Phenolic Fingerprints of Selected Mentha sp. on Cyano-Bonded Polar Stationary Phase.

    PubMed

    Hawrył, Mirosław A; Niemiec, Małgorzata A; Słomka, Kamil; Waksmundzka-Hajnos, Monika; Szymczak, Grażyna

    2016-01-01

    Micro-thin-layer chromatography in two-dimensional (2D-mTLC) mode in normal- (NP) and reversed-phase (RP) systems by use of cyanopropyl-bonded stationary phases was applied to make fingerprints of 11 species of Mentha genus and two finished pharmaceutical products. Non-aqueous eluents were used in the NP systems. Mixtures of acetonitrile with water and methanol with water were used in the RP chromatographic systems. Optimization of one-dimensional systems was performed by determining RM vs. composition of mobile phase dependencies for standards occurring in various Mentha sp. On the basis of these dependencies, the most selective chromatographic systems for each run were chosen. Then most selective eluents were applied to optimize two-dimensional systems by creating RF in NP systems vs. RF in RP systems correlations. The best two-dimensional systems were chosen on the basis of R(2) values for RF vs. RF correlations (the lowest values of R(2) coefficients). The 2D-mTLC optimized systems were applied to separate phenolic compounds and make fingerprints of the examined plant materials. PMID:26673190

  15. [Simultaneous determination of 15 industrial synthetic dyes in condiment by solid phase extraction-high performance liquid chromatography].

    PubMed

    Liu, Min; Li, Xiaolin; Bie, Wei; Wang, Minglin; Feng, Qian

    2011-02-01

    A new method was established for the determination of 15 industrial synthetic dyes in condiment by solid phase extraction-high performance liquid chromatography (SPE-HPLC). The samples were extracted by methanol-water (1:1, v/v) and purified by a solid phase extraction column. Then, the chromatographic separation was achieved on a Luna C18 column by linear gradient elution. The mobile phase was 10 mmol/L ammonium acetate-acetonitrile (containing 1% acetic acid). The results showed that the 15 industrial synthetic dyes can be separated efficiently. The recoveries of the 15 industrial synthetic dyes spiked in condiment were between 84.6% and 114.2% with the relative standard deviations of 0.9% - 10.3%. The limits of detection of this method was 0.05 - 0.18 mg/kg for the 15 industrial synthetic dyes. The method is simple, sensitive, accurate, repeatable and can be used for simultaneous determination of the 15 illegally added industrial synthetic dyes. PMID:21598518

  16. Application of reversed-phase liquid chromatography and prepacked C18 cartridges for the analysis of oxytetracycline and related compounds.

    PubMed

    Fedeniuk, R W; Ramamurthi, S; McCurdy, A R

    1996-03-01

    The reversed-phase (RP) chromatographic separation of oxytetracycline (OTC) 4-epioxytetracycline (4-epiOTC), alpha-apooxytetracycline (alpha-apoOTC), and beta-apooxytetracycline (beta-apoOTC) has been accomplished on an Inertsil C8 column at ambient temperature. Using the simplex method of solvent optimization, a 0.1 M ammonium acetate buffer (pH 3.0)-acetonitrile-tetrahydrofuran (72.5:12.5:15, v/v/v) mobile phase was found to give excellent separation of the compounds. OTC, 4-epiOTC, alpha-apoOTC and beta-apoOTC were resolved in 35 min with calculated detection limits of 40, 20, 50 and 140 ng/ml, respectively. Solid-phase extraction (using RP C18 cartridges) of OTC and OTC degradation compounds from distilled water and porcine muscle was tested at four concentration levels ranging from 200 to 2000 ng/ml (g); overall mean recovery of OTC from distilled water and porcine tissue was greater than 90% and 70%, respectively. PMID:8704932

  17. Mobile Schools for a Mobile World

    ERIC Educational Resources Information Center

    Booth, Susan

    2013-01-01

    Overwhelmingly, independent schools are embracing mobile devices--laptops, iPads or other tablets, and smartphones--to enhance teaching and learning. This article describes the results of the "NAIS 2012 Mobile Learning Survey." Among its findings were that 75 percent of NAIS-member schools currently use mobile learning devices in at…

  18. Design characteristics of the Sludge Mobilization System

    SciTech Connect

    McMahon, C.L.

    1990-09-30

    Radioactive waste stored in underground tanks at the West Valley Demonstration Project is being processed into low-level waste and solidified in cement. High-level waste also stored underground will be vitrified and solidified into canistered glass logs. To move the waste from where it resides at the Waste Tank Farm to the Vitrification Facility requires equipment to prepare the storage tanks for low-level and high-level waste processing, equipment to mobilize and mix the radioactive sludge into a homogeneous slurry, and equipment to transfer the slurry for vitrification. The design of the Sludge Mobilization System has incorporated the necessary components to effect the preparation and transfer of waste in five operational phases. The first phase of the Sludge Mobilization System, which began in 1987, prepared the waste tanks to process radioactive liquid for delivery to the Cement Solidification System and to support the mobilization equipment. The second phase, beginning in 1991, will wash the sludge that remains after the liquid supernatant is decanted to prepare it for mobilization operations. The third phase will combine the contents of various waste tanks into one tank. The fourth phase will resuspend and mix the contents of the high-level waste tank. The fifth and final phase of the Sludge Mobilization System will entail transferring the waste mixture to the Vitrification Facility for processing into glass logs. Provisions for recycling the waste streams or slurries within the tank farm or for returning process streams to the Waste Tank Farm from the Vitrification Facility are also included in the final phase. This document addresses the Sludge Mobilization System equipment design characteristics in terms of its use in each of the five operational phases listed above.

  19. Polypyrrole/montmorillonite nanocomposite as a new solid phase microextraction fiber combined with gas chromatography-corona discharge ion mobility spectrometry for the simultaneous determination of diazinon and fenthion organophosphorus pesticides.

    PubMed

    Jafari, Mohammad T; Saraji, Mohammad; Sherafatmand, Hossein

    2014-03-01

    A novel solid phase microextraction (SPME) fiber was prepared and coupled with gas chromatography corona discharge ion mobility spectrometry (GC-CD-IMS) based on polypyrrole/montmorillonite nanocomposites for the simultaneous determination of diazinon and fenthion. The nanocomposite polymer was coated using a three-electrode electrochemical system and directly deposited on a Ni-Cr wire by applying a constant potential. The scanning electron microscopy images revealed that the new fiber exhibited a rather porous and homogenous surface. The thermal stability of the fabricated fiber was investigated by thermogravimetric analysis. The effects of different parameters influencing the extraction efficiency such as extraction temperature and time, salt addition, stirring rate, the amount of nanoclay, and desorption temperature were investigated and optimized. The method was exhaustively evaluated in terms of sensitivity, recovery, and reproducibility. The linearity ranges of 0.05-10 and 0.08-10 μg L(-1), and the detection limits of 0.020 and 0.035 μg L(-1) were obtained for diazinon and fenthion, respectively. The relative standard deviation values were calculated to be lower than 5% and 8% for intra-day and inter-day, respectively. Finally, the developed method was applied to determine the diazinon and fenthion (as model compounds) in cucumber, lettuce, apple, tap and river water samples. The satisfactory recoveries revealed the capability of the two-dimensional separation technique (retention time in GC and drift time in IMS) for the analysis of complex matrices extracted by SPME. PMID:24528846

  20. Analysis of paralytic shellfish toxins using high-field asymmetric waveform ion mobility spectrometry with liquid chromatography-mass spectrometry.

    PubMed

    Beach, Daniel G; Melanson, Jeremy E; Purves, Randy W

    2015-03-01

    The analysis of paralytic shellfish toxins (PSTs) by liquid chromatography-mass spectrometry remains a challenge because of their high polarity, large number of analogues and the complex matrix in which they occur. Here we investigate the potential utility of high-field asymmetric waveform ion mobility spectrometry (FAIMS) as a gas-phase ion separation tool for analysis of PSTs by mass spectrometry. We investigate the separation of PSTs using FAIMS with two divergent goals: using FAIMS as a primary separation tool for rapid screening by electrospray ionization (ESI)-FAIMS-MS or combined with LC in a multidimensional LC-ESI-FAIMS-MS separation. First, a survey of the parameters that affect the sensitivity and selectivity of PST analysis by FAIMS was carried out using ESI-FAIMS-MS. In particular, the use of acetonitrile as a gas additive in the carrier gas flow offered good separation of all PST epimeric pairs. A second set of FAIMS conditions was also identified, which focussed PSTs to a relatively narrow CV range allowing development of an LC-ESI-FAIMS-MS method for analysis of PST toxins in complex mussel tissue extracts. The quantitative capabilities of this method were evaluated by analysing a PST containing mussel tissue matrix material. Results compared favourably with analysis by an established LC-post-column oxidation-fluorescence method with recoveries ranging from 70 to 106%, although sensitivity was somewhat reduced. The current work represents the first successful separation of PST isomers using ion mobility and shows the promise of FAIMS as a tool for analysis of algal biotoxins in complex samples and outlines some critical requirements for its future improvement. PMID:25619987

  1. [Simultaneous determination of six perfluorinated organic compounds in feed by using polyamide solid-phase extraction with ultra performance liquid chromatography-tandem mass spectrometry].

    PubMed

    Lin, Qin; Fu, Fengfu; Chen, Guonan; Zheng, Xiaoyan; Dai, Ming

    2014-07-01

    A method for the determination of six perfluorinated organic compounds (PFCs) in feed has been developed. It is based on polyamide solid-phase extraction (SPE) together with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted by acidified acetonitrile. The extraction solution was enriched by a polyamide SPE cartridge under acidic condition, and cleaned-up using methanol, eluted by 5% (v/v) ammonia/methanol solvent and determined by UPLC-MS/MS. The UPLC separation was carried out on an Acquity BEH C18 column (100 mm x 2.1 mm, 1.7 microm). The mobile phases were 5 mmol/L ammonium acetate and acetonitrile with a gradient elution. Under the optimal conditions, the PFCs were analyzed under multiple reaction monitoring (MRM) mode with negative electrospray ionization. The isotope internal standard method was used to determine the six PFCs, and improve the quantitative accuracy. All of the target compounds exhibited good linearity (r > 0.995) over a concentration range of 0.5-25 microg/L. The detection limits of the six PFCs were all smaller than 0.1 microg/kg. The mean recoveries of the six PFCs were in the range of 94.2% to 108.9% with the relative standard deviations (RSDs) of 1.8% - 8.6% (n = 6). The method for the determination of PFCs in feed is low-cost, favorable effect and suitable for the detection of complex matrix samples. PMID:25255564

  2. Adsorption mechanisms and effect of temperature in reversed-phase liquid chromatography. meaning of the classical Van't Hoff plot in chromatography.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2006-07-01

    The effect of temperature on the adsorption and retention behaviors of a low molecular weight compound (phenol) on a C18-bonded silica column (C18-Sunfire, Waters) from aqueous solutions of methanol (20%) or acetonitrile (15%) was investigated. The results of the measurements were interpreted successively on the basis of the linear (i.e., overall retention factors) and the nonlinear (i.e., adsorption isotherms, surface heterogeneity, saturation capacities, and equilibrium constants) chromatographic methods. The confrontation of these two approaches confirmed the impossibility of a sound physical interpretation of the conventional Van't Hoff plot. The classical linear chromatography theory assumes that retention is determined by the equilibrium thermodynamics of analytes between a homogeneous stationary phase and a homogeneous mobile phase (although there may be two or several types of interactions). From values of the experimental retention factors in a temperature interval and estimates of the activity coefficients at infinite dilution in the same temperature interval provided by the UNIFAC group contribution method, evidence is provided that such a retention model cannot hold. The classical Van't Hoff plot appears meaningless and its linear behavior a mere accident. Results from nonlinear chromatography confirm these conclusions and provide explanations. The retention factors seem to fulfill the Van't Hoff equation, not the Henry constants corresponding to the different types of adsorption sites. The saturation capacities and the adsorption energies are clearly temperature dependent. The temperature dependence of these characteristics of the different assorption sites are different in aqueous methanol and acetonitrile solutions. PMID:16808477

  3. Rapid determination of chlormequat in meat by dispersive solid-phase extraction and hydrophilic interaction liquid chromatography (HILIC)-electrospray tandem mass spectrometry.

    PubMed

    Li, Chunmei; Jin, Fen; Yu, Zhiyong; Qi, Yamei; Shi, Xiaomei; Wang, Miao; Shao, Hua; Jin, Maojun; Wang, Jing; Yang, Mingqi

    2012-07-11

    A rapid method for analyzing trace levels of chlormequat (CQ) in meat samples by hydrophilic interaction liquid chromatography (HILIC)-electrospray tandem mass spectrometry was developed. The samples were extracted with acetonitrile, followed by a rapid cleanup through a dispersive solid-phase extraction (DSPE) technique with octadecyl (C18) DSPE sorbents. The chromatographic separation was achieved within 6 min using a HILIC column with 10 mM ammonium acetate and 0.1% (v/v) formic acid in water/acetonitrile (v/v, 40:60) as the mobile phase. Quantification was performed using a matrix-matched calibration curve, which was linear in the range of the 0.05-100 μg/L. The limit of detection (LOD) was estimated at 0.03 μg/kg for CQ on the basis of a peak to peak signal noise (S/N = 3). The limit of quantification (LOQ) was 0.1 μg/kg on the basis of the lowest spiked concentration with suitable precision and accuracy. The average recovery of CQ in spiked meat samples was 86.4-94.7% at 2, 20, and 200 μg/kg. Finally, this method was applied to determine CQ in the livestock and poultry meats purchased from markets in Beijing in 2011. CQ was detected in all 12 samples, and the concentration was 0.4-636.0 μg/kg. Concentrations in a chicken sample (636.0 μg/kg) and a goat meat sample (486.0 μg/kg) were found to be 15.9 and 2.43 times the corresponding Codex maximum residue limits, respectively. PMID:22686367

  4. Simultaneous analysis of several non-steroidal anti-inflammatory drugs in human urine by high-performance liquid chromatography with normal solid-phase extraction.

    PubMed

    Hirai, T; Matsumoto, S; Kishi, I

    1997-05-01

    A practical and reproducible high-performance liquid chromatographic method using normal solid-phase extraction has been developed for the simultaneous analysis of twelve non-steroidal anti-inflammatory drugs (NSAIDs) in human urine. A urine specimen mixed with acetate buffer pH 5.0 was purified by solid-phase extraction on a Sep-Pak Silica cartridge. The analyte was chromatographed by a reversed-phase Inertsil ODS-2 column using a phosphate buffer-acetonitrile at pH 5.0 as the mobile phase, and the effluent from the column was monitored at 230 or 320 nm. Absolute recoveries were greater than 73% for all of the twelve NSAIDs. The present method enabled simple manipulation and isocratic HPLC with UV analysis as well as high sensitivity of 0.005 microg/ml for naproxen, and 0.05 microg/ml for sulindac, piroxicam, loxoprofen, ketoprofen, felbinac, fenbufen, flurbiprofen, diclofenac, ibuprofen and mefenamic acid as the quantitation limit in human urine using indomethacin as an internal standard. PMID:9188827

  5. High-throughput salting-out assisted liquid-liquid extraction with acetonitrile for the determination of anandamide in plasma of hemodialysis patients with liquid chromatography tandem mass spectrometry.

    PubMed

    Xiong, Xin; Zhang, Lei; Cheng, Litao; Mao, Wei

    2015-09-01

    Anandamide (AEA) is an endocannabinoid present in human plasma that is associated with several physiological functions and disease states. However, low AEA plasma levels pose challenges in terms of analytical characterization. Classical liquid-based lipid extraction and solid-phase extraction require complicated procedures and the drying down of relatively large volumes of solvents, making them unsuitable for high-throughput analysis. Here a high-throughput salting-out assisted liquid-liquid extraction (SALLE) method with acetonitrile and mass spectrometry compatible salts for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of AEA in human plasma has been developed and validated. The seamless interface of SALLE and LC-MS eliminated the drying-down step, only 100 μL of plasma is required and minimal volumes of organic solvent are used. Good reproducibility, accuracy and precision were demonstrated during the method validation. The method is linear up to 10 ng/mL with a lower limit of quantitation of 0.1 ng/mL for AEA, the accuracy for AEA was from 93.3 to 96.7% and the precision was <8.57%. This new methodology was successfully applied to analysis of clinical samples from maintenance hemodialysis patients. PMID:25622579

  6. Development of a modified acetonitrile-based extraction procedure followed by ultra-high performance liquid chromatography-tandem mass spectrometry for the analysis of psychiatric drugs in sediments.

    PubMed

    Santos, Lúcia H M L M; Ramalhosa, Maria João; Ferreira, Marta; Delerue-Matos, Cristina

    2016-03-11

    An analytical method based on a modified Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) extraction procedure followed by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed for the analysis of psychiatric drugs in sediments. An optimized approach was applied in sample preparation by using basic acetonitrile as extraction solvent. Extraction was followed by a clean-up using dispersive solid phase extraction (dSPE) to remove matrix interfering compounds. The analytical method was validated in terms of sensitivity, linearity, recovery, intra- and inter-day precisions and method detection and quantification limits. Under optimized conditions, limits of detection ranged from 0.01ngg(-1) to 2.08ngg(-1); and recoveries between 47 and 110% with relative standard deviation (RSD) below 5%. The developed methodology was applied to sediments of two Portuguese rivers (Douro and Lima rivers) and nine out of eleven psychiatric drugs were detected in sediments at concentrations up to 26.4ngg(-1) (dry weight). To the best of our knowledge, it was the first time that the human metabolites norfluoxetine and norsertraline were detected in river sediments at levels of few nanograms per gram. PMID:26879455

  7. catena-Poly[[tris­(acetonitrile-κN)praseodymium(III)]tris­(μ-trifluoro­methane­sulfonato-κ2 O:O′)

    PubMed Central

    Apostolidis, Christos; Walter, Olaf

    2013-01-01

    In the colourless title compound, [Pr(CF3O3S)3(CH3CN)3]n, the three trifluoro­methane­sulfonate anions form three bridges via O:O′-coordination between two PrIII atoms. The structure contains [Pr(NCMe)3-μ2(OTf)3—Pr(NCMe)3-μ2(OTf)3]n (NCMe is acetonitrile; OTf is trifluoromethanesulfonate) chains parallel to the a axis. The PrIII atom is nine-coordinate in a distorted tricapped trigonal-prismatic environment. PMID:23476322

  8. Oxygen transfer from an intramolecularly coordinated diaryltellurium oxide to acetonitrile. Formation and combined AIM and ELI-D analysis of a novel diaryltellurium acetimidate.

    PubMed

    Mallow, Ole; Bolsinger, Jens; Finke, Pamela; Hesse, Malte; Chen, Yu-Sheng; Duthie, Andrew; Grabowsky, Simon; Luger, Peter; Mebs, Stefan; Beckmann, Jens

    2014-08-01

    The reaction of the intramolecularly coordinated diaryltellurium(IV) oxide (8-Me2NC10H6)2TeO with acetonitrile proceeds with oxygen transfer and gives rise to the formation of the novel zwitterionic diaryltelluronium(IV) acetimidate (8-Me2NC10H6)2TeNC(O)CH3 (1) in 57% yield. Hydrolysis of 1 with hydrochloric acid affords acetamide and the previously known diarylhydroxytelluronium(IV) chloride [(8-Me2NC10H6)2Te(OH)]Cl. PMID:25026100

  9. Pilot-Tone System for Mobile Communications

    NASA Technical Reports Server (NTRS)

    Davarian, F.

    1986-01-01

    In mobile communication system called tone-calibrated technique, pilot tone provides phase- and amplitude-calibration reference to enable coherent demodulation of signal at receiver despite fading. Signal received by or from mobile terminal faded due to motion of terminal and propagation of signal along multiple paths. Fading introduces random amplitude modulation and phase modulation with bandwidth of twice Doppler frequency shift. Degrading effects of multipath fading reduced. Tonecalibrated technique for use with phase-modulated data or telephony systems using Manchester digital pulse-code modulation.

  10. Mobile Bipolaron

    SciTech Connect

    Bonca, J.; Katrasnik, T.; Trugman, S. A.

    2000-04-03

    We explore the properties of the bipolaron in a 1D Holstein-Hubbard model with dynamical quantum phonons. Using a recently developed variational method combined with analytical strong coupling calculations, we compute correlation functions, effective mass, bipolaron isotope effect, and the phase diagram. The two site bipolaron has a significantly reduced mass and isotope effect compared to the on-site bipolaron, and is bound in the strong coupling regime up to twice the Hubbard U naively expected. The model can be described in this regime as an effective t-J-V model with nearest neighbor repulsion. These are the most accurate bipolaron calculations to date. (c) 2000 The American Physical Society.

  11. Physicochemical characteristics of the sorption of 4-aminoquinoline derivatives from water-acetonitrile solutions on nonpolar sorbents

    NASA Astrophysics Data System (ADS)

    Paramonova, A. S.; Kurbatova, S. B.; Zemtsova, M. N.

    2014-02-01

    Regularities of the retention of certain 4-aminoquinoline derivatives in the conditions of the reversed phase type of high performance liquid chromatography (HPLC) on octadecyl silica (ODS) and hypercrosslinked polystyrene (HCLPS) are studied. The correlation between the structure of aminoquinolines and their chromatographic retention is demonstrated.

  12. Headspace solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry for the simultaneous determination of atrazine and ametryn in soil and water samples.

    PubMed

    Mohammadi, Abdorreza; Ameli, Akram; Alizadeh, Naader

    2009-05-15

    A simple and rapid headspace solid-phase microextraction (HS-SPME) based method is presented for the simultaneous determination of atrazine and ametryn in soil and water samples by ion mobility spectrometry (IMS). A dodecylsulfate-doped polypyrrole (PPy-DS), synthesized by electrochemical method, was applied as a laboratory-made fiber for SPME. The HS-SPME system was designed with a cooling device on the upper part of the sample vial and a circulating water bath for adjusting the sample temperature. The extraction properties of the fiber to spiked soil and water samples with atrazine and ametryn were examined, using a HS-SPME device and thermal desorption in injection port of IMS. Parameters affecting the extraction efficiency such as the volume of water added to the soil, pH effect, extraction time, extraction temperature, salt effect, desorption time, and desorption temperature were investigated. The HS-SPME-IMS method with PPy-DS fiber, provided good repeatability (RSDs<10 %), simplicity, good sensitivity and short analysis times for spiked soil (200 ng g(-1)) and water samples (100 and 200 ng mL(-1)). The calibration graphs were linear in the range of 200-4000 ng g(-1) and 50-2800 ng mL(-1) for soil and water respectively (R(2)>0.99). Detection limits for atrazine and ametryn were 37 ng g(-1) (soil) and 23 ng g(-1) (soil) and 15 ng mL(-1) (water) and 10 ng mL(-1) (water), respectively. To evaluate the accuracy of the proposed method, atrazine and ametryn in the three kinds of soils and two well water samples were determined. Finally, comparing the HS-SPME results for extraction and determination of selected triazines using PPy-DS fiber with the other methods in literature shows that the proposed method has comparable detection limits and RSDs and good linear ranges. PMID:19269479

  13. Absence of many-body mobility edges

    NASA Astrophysics Data System (ADS)

    De Roeck, Wojciech; Huveneers, Francois; Müller, Markus; Schiulaz, Mauro

    2016-01-01

    Localization transitions as a function of temperature require a many-body mobility edge in energy, separating localized from ergodic states. We argue that this scenario is inconsistent because local fluctuations into the ergodic phase within the supposedly localized phase can serve as mobile bubbles that induce global delocalization. Such fluctuations inevitably appear with a low but finite density anywhere in any typical state. We conclude that the only possibility for many-body localization to occur is lattice models that are localized at all energies. Building on a close analogy with a model of assisted two-particle hopping, where interactions induce delocalization, we argue why hot bubbles are mobile and do not localize upon diluting their energy. Numerical tests of our scenario show that previously reported mobility edges cannot be distinguished from finite-size effects.

  14. Application of molecularly imprinted polymer solid-phase extraction for salivary cotinine.

    PubMed

    Vitor, Ricardo Vilela; Martins, Matheus Coutinho Gonçalves; Figueiredo, Eduardo Costa; Martins, Isarita

    2011-06-01

    A method constituted by molecularly imprinted solid-phase extraction (MISPE) with high-performance liquid chromatography coupled to diode array detector (HPLC-DAD) was developed for cotinine analysis in saliva samples. For this purpose, the separation was carried out with a C18 reversed-phase column at 20 °C. The mobile phase which was composed of a mixture of 09:91 (v/v) acetonitrile/phosphate buffer, pH 6.3, was delivered with isocratic flow rate at 1.4 mL min(-1). Employing MISPE, the best conditions were achieved with 1.5 mL of saliva plus 1.5 mL of 0.1 mol L(-1) of acetate buffer, pH 5.5, which were then passed through a cartridge previously conditioned with 2 mL acetonitrile, 2 mL methanol, and 2 mL of 0.1 mol L(-1) sodium acetate buffer, pH 5.5. The washing was carried out with 1 mL deionized water, 1 mL of 0.1 mol L(-1) sodium hydroxide, and 1 mL hexane; finally; the cotinine elution was carried out with 3 mL methanol/water (97.5: 2.5, v/v). Linearity ranged from 30 to 500 ng mL(-1) with r > 0.99. Intra-assay, interassay precision, and accuracy ranged from 3.1% to 10.1%, 5.2% to 15.9%, and 99.22% to 111.17%, respectively. The detection and quantification limits were 10 and 30 ng mL(-1), respectively. This investigation has provided a reliable method for routine cotinine determination in saliva, and it is an important tool for monitoring cigarette smoke exposure in smokers. The method was applied in five smokers' samples who consumed around five to 20 cigarettes per day and the values of cotinine in saliva were from 66.7 to 316.16 ng mL(-1). PMID:21448605

  15. Photoreduction of benzophenone by acetonitrile: correlation of rates of hydrogen abstraction from RH with the ionization potentials of the radicals R

    SciTech Connect

    Naguib, Y.M.A.; Steel, C.; Cohen, S.G.; Young, M.A.

    1987-05-21

    Triplet benzophenone (/sup 4/K) abstracts a hydrogen from acetonitrile with a rate constant of 130 +/- 30 M/sup -1/ s/sup -1/. Despite this low rate constant acetonitrile is not really an inert solvent and at low light fluxes, where T-T annihilation is not a major fate of the triplet, a major decay path for /sup 4/K is hydrogen abstraction with resulting pinacol (K/sub 2/H/sub 2/) formation (phi/sub K/sub 2/H/sub 2/ approx. = 0.1 at t = 0). Both K/sub 2/H/sub 2/ formation and /sup 3/K lifetime rapidly decrease with irradiation due to the light absorbing transients (LAT's) which are formed along with K/sub 7/H/sub 2/ from ketyl radicals (KH). The rate constants per hydrogen (k/sub H/) for abstraction from R-H by the electrophilic /sup 3/K correlate well with the ionization potentials (IP) of the corresponding radicals (R).

  16. Determination of pinocembrin in human plasma by solid-phase extraction and LC/MS/MS: application to pharmacokinetic studies.

    PubMed

    Yan, Bei; Cao, Guoying; Sun, Taohua; Zhao, Xi; Hu, Xin; Yan, Jiling; Peng, Yueying; Shi, Aixin; Li, Yang; Xue, Wei; Li, Min; Li, Kexin; Liu, Yingfa

    2014-12-01

    A sensitive, fast and specific method for the quantitation of pinocembrin in human plasma based on high-performance liquid chromatography-tandem mass spectrometry (LC/MS/MS) was developed and validated. Clonazepam was used as the internal standard (IS). After solid-phase extraction of 500 μL plasma, pinocembrin and the IS were separated on a Luna C8 column using the mobile phase composed of acetonitrile-0.3 mm ammonium acetate solution (65:35, v/v) at a flow rate of 0.25 mL/min in isocratic mode. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring via an electrospray ionization source in negative mode by AB SCIEX Qtrap 5500. The assay was linear from 1 to 400 ng/mL, with within- and between-run accuracy (relative error) from -1.82 to 0.54%, and within- and between-run precision (CV) below 5.25%. The recovery was above 88% for the analyte at 1, 50 and 300 ng/mL. This analytical method was successful for the determination of pinocembrin in human plasma and applied to a pharmacokinetic study of pinocembrin injection in healthy volunteers after intravenous drip administration. PMID:24733513

  17. Matrix solid-phase dispersion extraction and high-performance liquid chromatographic determination of residual sulfonamides in chicken.

    PubMed

    Kishida, K; Furusawa, N

    2001-12-01

    Simultaneous determination of the six sulfonamides (SAs) sulfadiazine, sulfadimidine, sulfamonomethoxine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline in chicken using matrix solid-phase dispersion (MSPD) with neutral aluminium oxide as an MSPD sorbent and high-performance liquid chromatography (HPLC) is presented. In the present MSPD, six SAs could be isolated by only one step, elution with a 70% (v/v) aqueous ethanol solution, without the sorbent conditioning and the sorbent-tissue matrix washing. For the HPLC determination, a LiChrospher 100 RP-8 and a mixture of 1% acetic acid solution (pH 3.0, in water)-acetonitrile-N,N-dimethylformamide (78:22:5, v/v/v) as the mobile phase with a photodiode array detector were used. Average recoveries were greater than 87.6% with relative standard deviations between 0.5 and 8.6%. The total time and amount of solvent required for the analysis of one sample were <1.5 h and <12 ml, respectively. PMID:11765084

  18. 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

  19. Determination of tetracyclines residues in honey by on-line solid-phase extraction high-performance liquid chromatography.

    PubMed

    Li, Jiantao; Chen, Ligang; Wang, Xiao; Jin, Haiyan; Ding, Lan; Zhang, Kun; Zhang, Hanqi

    2008-06-15

    An automated system using on-line solid-phase extraction (SPE) high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection was developed for the determination of tetracyclines (TCs), such as tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC), metacycline (MC), and doxycycline (DC) in honey. One milliliter diluted honey sample was injected into a conditioned C18 SPE column and the matrix was washed out with water for 3 min. By rotation of the switching valve, TCs were eluted and transferred to the analytical column by the chromatographic mobile phase. Chromatographic conditions were optimized. TCs were separated in less than 8 min with a gradient elution using a mixture of 0.8% formic acid and acetonitrile. The UV detection was performed at 365 nm. The conditions for on-line SPE, including solvent and total time for loading sample and washing matrix were also optimized. Time for extraction and separation decreased greatly. For the five kinds of TCs, the limits of detection (LODs) at a signal-to-noise of 3 ranged from 5 to 12 ng g(-1). The relative standard deviations (R.S.D.) for the determination of TCs ranged from 3.4 to 7.1% within a day and ranged from 3.2 to 8.9% in 3 days, respectively. PMID:18585209

  20. 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

  1. [Determination of three sweeteners in vinegars by solid phase extraction-high performance liquid chromatography/tandem mass spectrometry].

    PubMed

    Yin, Feng; Ding, Zhaowei; Cao, Xue; Gao, Jie; Jiang, Deming; Kuang, Denghui; Gu, Yanping; He, Guoliang

    2011-06-01

    A solid phase extraction-high performance liquid chromatography/electrospray ionization-tandem mass spectrometry (SPE-HPLC/ESI-MS/MS) method for the determination of 3 sweeteners (acesulfame (AK), sodium saccharin (SA), sodium cyclamate (SC)) in vinegars has been developed. The sample was diluted with acidic water, then purified and enriched with a weak anion exchange SPE column. The HPLC separation was performed on a Pursuit C18 column (150 mm x 2.0 mm, 3 microm) by gradient elution with 10 mmol/L ammonium acetate containing 0.1% (v/v) ammonia water and acetonitrile as the mobile phases. The analytes were detected by ESI--MS/MS in multiple reaction monitoring (MRM) mode to satisfy qualitative and quantitative detections. Good linearities (r2 > 0.99) were obtained over the range of 0.01 - 0.50 mg/L. The limits of quantification (LOQs) for SA, AK and SC were 10, 5 and 5 microg/kg, respectively. The average recoveries ranged from 72.1% to 96.8% at the spiked levels of 0.01 and 0.1 mg/L with the relative standard deviations (RSDs) less than 15%. This method is accurate, highly sensitive for qualitative and quantitative analysis of the 3 sweeteners in vinegars. PMID:22032168

  2. 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

  3. SOFCo mobile planar solid oxide generator

    SciTech Connect

    Khandkar, A.C.; Privette, R.M.

    1995-08-01

    This paper presents results from the first phase of a three phase, four-year program with the objective of designing and demonstrating a 10 kW mobile electric power generator operating on logistic fuel. Objectives of the first phase include: the development of a preliminary system design, an assessment of technologies critical to system performance, and the fabrication of three multi-stack test units.

  4. Mobile Router Technology Development

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Stewart, David H.; Bell, Terry L.; Kachmar, Brian A.; Shell, Dan; Leung, Kent

    2002-01-01

    Cisco Systems and NASA have been performing joint research on mobile routing technology under a NASA Space Act Agreement. Cisco developed mobile router technology and provided that technology to NASA for applications to aeronautic and space-based missions. NASA has performed stringent performance testing of the mobile router, including the interaction of routing and transport-level protocols. This paper describes mobile routing, the mobile router, and some key configuration parameters. In addition, the paper describes the mobile routing test network and test results documenting the performance of transport protocols in dynamic routing environments.

  5. Trace determination of sulfonamides residues in meat with a combination of solid-phase microextraction and liquid chromatography-mass spectrometry.

    PubMed

    Lu, Kuan-Hui; Chen, Chung-Yu; Lee, Maw-Rong

    2007-05-15

    An integrated method of combining solid-phase microextraction (SPME) with liquid chromatography-mass spectrometry (LC-MS) was evaluated for determination trace amount of sulfonamides in meat products. Eight commonly used sulfonamides, sulfadiazine (SDZ), sulfathiazole (STZ), sulfamerazine (SMR), sulfamethazine (SMT), sulfamonomethoxine (SMMX), sulfamethoxazole (SMXZ), sulfaquinoxaline (SQX) and sulfadimethoxine (SDMX), were investigated in this study. Chromatography was performed on a C(18) reversed-phase column using an isocratic acetonitrile in water as the mobile phase. Fiber coated with a 65mum thickness of polydimethylsiloxane/divinylbenzene (PDMS/DVB) was used to extract sulfonamides at optimum conditions. Analytes were desorbed with static desorption in an SPME-HPLC desorbed chamber for 15min and then determined by LC-MS. The detection limits of these sulfonamides in pork were from 16mugkg(-1) (SMT) to 39mugkg(-1) (SMMX). According to the analysis, the linear range was from 50 to 2000mugkg(-1) with relative standard deviation (R.S.D.s) value below 15% (intra-day) and 19% (inter-day). The proposed method was tested by analyzing meats from a local market for sulfonamides residues. Some sulfonamides in our study were detected in the meat samples. The concentration of these residual sulfonamides ranged from 66mugkg(-1) (SDZ) to 157mugkg(-1) (SQX) in a chicken sample. The results demonstrate that the SPME-LC-MS system is highly effective in analyzing trace sulfonamides in meat products. PMID:19071729

  6. Bioanalytical method development for quantification of ulifloxacin, fenbufen and felbinac in rat plasma by solid-phase extraction (SPE) and HPLC with PDA detection.

    PubMed

    Ferrone, Vincenzo; Carlucci, Maura; Palumbo, Paola; Carlucci, Giuseppe

    2016-05-10

    A procedure based on solid-phase extraction (SPE) followed by high performance liquid chromatography (HPLC) with PDA detection has been developed for the analysis of multiple drugs in rat plasma. The analytes evaluated were ulifloxacin, fenbufen and felbinac. Eight different solid phase extraction cartridges were tested to evaluate their applicability for the isolation of drugs from rat plasma. Comparison were recovery of different drugs and reproducibility. The samples were analyzed by HPLC using a Kinetex C18 EVO column and acetonitrile-10mM ammonium acetate-methanol as the mobile phase under gradient elution conditions. SPE combined with HPLC-PDA allowed the determination of drugs over a linear range of 0.05-15 μg/mL for ulifloxacin while 0.5-50 μg/mL for felbinac and fenbufen, with limit of detection at 0.05 for ulifloxacin and 0.5 for felbinac and fenbufen. Bond Elut Plexa sorbent was found to provide the most effective clean-up, removing the greatest amount of interfering substance and simultaneously ensuring analyte recoveries higher than 93.54% with relative standard deviation (RSD) <10%. The method was applied with good accuracy and precision in the determination of ulifloxacin, fenbufen and felbinac in rat plasma obtained from rats treated with selected drugs. This method permits its application to pharmacokinetic and pharmacodynamic studies of these analytes and will facilitate detailed investigations on the interactions between new fluoroquinolones and fenbufen. PMID:26898973

  7. Quantitative determination of usnic acid in Usnea lichen and its products by reversed-phase liquid chromatography with photodiode array detector.

    PubMed

    Ji, Xiuhong; Khan, Ikhlas A

    2005-01-01

    Usnic acid, a lichen substance, has a wide range of pharmaceutical applications, including antibiotic, antimycotic, antifeedant, antitubercular, antitumor, and analgesic activities. Some products containing usnic acid are marketed as weight control supplements; however, hepatotoxicity and acute liver failures were reported as severe side effects. The usnic acid content present in the plant materials and market products was analyzed by reversed-phase high-pressure liquid chromatography with a photodiode array detector at 233 nm. A Waters XTerra RP18 (150 x 4.6 mm; 5 microm particle size) column was the stationary phase; mobile phase was aqueous 0.1% acetic acid and acetonitrile gradient at flow rate of 1.0 mL/min. The temperature was held constant at 30 degrees C. The retention time of usnic acid was approximately 13.3 min. Acetone extraction of the samples took place with sonication. The precision of the method was confirmed by a standard deviation below 3.0% (n=3) and usnic acid recovery was 99.0%. Limit of detection was 0.4 microg/mL and the response was linear from 1.4 to 570.0 microg/mL with a correlation coefficient (R2) of 0.9991. The content of usnic acid in 4 raw materials and 22 finished products was analyzed. PMID:16385974

  8. Chemical Standards in Ion Mobility Spectrometry

    PubMed Central

    Fernández-Maestre, Roberto; Harden, Charles Steve; Ewing, Robert Gordon; Crawford, Christina Lynn; Hill, Herbert Henderson

    2010-01-01

    In ion mobility spectrometry (IMS), reduced mobility values (K0) are used as a qualitative measure of gas phase ions, and are reported in the literature as absolute values. Unfortunately, these values do not always match those collected in the field. One reason for this discrepancy is that the buffer gas may be contaminated with moisture or other volatile compounds. In this study, the effect of moisture and organic contaminants in the buffer gas on the mobility of IMS standards and analytes was investigated for the first time using IMS directly coupled to mass spectrometry. 2,4-dimethylpyridine, 2,6-di-tert-butyl pyridine (DTBP), and tetrabutylammonium, tetrapropylammonium, tetraethylammonium, and tetramethylammonium chlorides were used as chemical standards. In general, the mobility of IMS standard product ions was not affected by small amounts of contamination while the mobilities of many analytes were affected. In the presence of contaminants in the buffer gas, the mobility of analyte ions is often decreased by forming ion-molecule clusters with the contaminant. To ensure the measurement of accurate reduced mobility values, two IMS standards are required: an instrument and a mobility standard. An instrument standard is not affected by contaminants in the buffer gas, and provides an accurate measurement of the instrumental parameters, such as voltage, drift length, pressure, and temperature. The mobility standard behaves like an analyte ion in that the compound’s mobility is affected by low levels of contamination in the buffer gas. Prudent use of both of these standards can lead to improved measurement of accurate reduced mobility values. PMID:20369157

  9. Chemical standards in ion mobility spectrometry

    SciTech Connect

    Fernandez-Maestre, Robert; Harden, Charles S.; Ewing, Robert G.; Crawford, Christina L.; Hill, Jr, Herbert H.

    2010-08-01

    In ion mobility spectrometry (IMS), reduced mobility values (K0) are used as a qualitative measure of gas phase ions, and are reported in the literature as absolute values. Unfortunately, these values do not always match with those collected in the field. One reason for this discrepancy is that the buffer gas may be contaminated with moisture or other volatile compounds. In this study, the effect of moisture and organic contaminants in the buffer gas on the mobility of IMS standards and analytes was investigated for the first time using IMS directly coupled to mass spectrometry. 2,4-Dimethylpyridine, 2,6-di- tertbutylpyridine (DTBP), and tetrabutylammonium, tetrapropylammonium, tetraethylammonium, and tetramethylammonium chlorides were used as chemical standards. In general, the mobility of IMS standard product ions was not affected by small amounts of contamination while the mobilities of many analytes were affected. In the presence of contaminants in the buffer gas, the mobility of analyte ions is often decreased by forming ion–molecule clusters with the contaminant. To ensure the measurement of accurate reduced mobility values, two IMS standards are required: an instrument and a mobility standard. An instrument standard is not affected by contaminants in the buffer as, and provides an accurate measurement of the instrumental parameters, such as voltage, drift length, pressure, and temperature. The mobility standard behaves like an analyte ion in that the compound’s mobility is affected by low levels of contamination in the buffer gas. Prudent use of both of these standards can lead to improved measurement of accurate reduced mobility values.

  10. Ion mobility sensor system

    DOEpatents

    Xu, Jun; Watson, David B.; Whitten, William B.

    2013-01-22

    An ion mobility sensor system including an ion mobility spectrometer and a differential mobility spectrometer coupled to the ion mobility spectrometer. The ion mobility spectrometer has a first chamber having first end and a second end extending along a first direction, and a first electrode system that generates a constant electric field parallel to the first direction. The differential mobility spectrometer includes a second chamber having a third end and a fourth end configured such that a fluid may flow in a second direction from the third end to the fourth end, and a second electrode system that generates an asymmetric electric field within an interior of the second chamber. Additionally, the ion mobility spectrometer and the differential mobility spectrometer form an interface region. Also, the first end and the third end are positioned facing one another so that the constant electric field enters the third end and overlaps the fluid flowing in the second direction.

  11. Innovative island mobile vet.

    PubMed

    Forster, Dan

    2016-06-11

    One of the UK's first mobile veterinary clinics was recently awarded a Queen's Award for Innovation. Mobile Vet was launched on the Isle of Wight in 2013 by Dan Forster and his wife Kirsty, a veterinary nurse. PMID:27288178

  12. Tandem mobile robot system

    DOEpatents

    Buttz, James H.; Shirey, David L.; Hayward, David R.

    2003-01-01

    A robotic vehicle system for terrain navigation mobility provides a way to climb stairs, cross crevices, and navigate across difficult terrain by coupling two or more mobile robots with a coupling device and controlling the robots cooperatively in tandem.

  13. Synthesis of a stationary phase based on silica modified with branched octadecyl groups by Michael addition and photoinduced thiol-yne click chemistry for the separation of basic compounds.

    PubMed

    Huang, Guang; Ou, Junjie; Wang, Hongwei; Ji, Yongsheng; Wan, Hao; Zhang, Zhang; Peng, Xiaojun; Zou, Hanfa

    2016-04-01

    A novel silica-based stationary phase with branched octadecyl groups was prepared by the sequential employment of the Michael addition reaction and photoinduced thiol-yne click chemistry with 3-aminopropyl-functionalized silica microspheres as the initial material. The resulting stationary phase denoted as SiO2 -N(C18)4 was characterized by elemental analysis, FTIR spectroscopy and Raman spectroscopy, demonstrating the existence of branched octadecyl groups in silica microspheres. The separations of benzene homologous compounds, acid compounds and amine analogues were conducted, demonstrating mixed-mode separation mechanism on SiO2 -N(C18)4 . Baseline separation of basic drugs mixture was acquired with the mobile phase of acetonitrile/H2 O (5%, v/v). SiO2 -N(C18)4 was further applied to separate Corydalis yanhusuo Wang water extracts, and more baseline separation peaks were obtained for SiO2 -N(C18)4 than those on Atlantis dC18 column. It can be expected that this new silica-based stationary phase will exhibit great potential in the analysis of basic compounds. PMID:26910263

  14. Mobility and Young Children.

    ERIC Educational Resources Information Center

    Bernard van Leer Foundation Newsletter, 1994

    1994-01-01

    This newsletter theme issue deals with the phenomenon of mobility or transience in India, Kenya, Greece, Ireland, Malaysia, Thailand and Israel. The primary focus is on mobility's effect on young children, specifically their health and education; some of the broader concerns also addressed by the newsletter are the causes of mobility and its…

  15. Mobile Student Information System

    ERIC Educational Resources Information Center

    Asif, Muhammad; Krogstie, John

    2011-01-01

    Purpose: A mobile student information system (MSIS) based on mobile computing and context-aware application concepts can provide more user-centric information services to students. The purpose of this paper is to describe a system for providing relevant information to students on a mobile platform. Design/methodology/approach: The research…

  16. Colorimetric and fluorogenic recognition of Hg2+ and Cr3+ in acetonitrile and their test paper recognition in aqueous media with the aid of rhodamine based sensors.

    PubMed

    Patidar, Rajesh; Rebary, Babulal; Paul, Parimal

    2015-03-01

    Two new rhodamine derivatives (L1 and L2) were synthesized, characterized and their ion recognition property has been investigated. Both of the ionophores exhibit colorimetric and fluorogenic response for Hg(2+) and Cr(3+) ions among large number of alkali, alkaline earth and transition metal ions tested in acetonitrile. Detail studies on determination of binding constant, binding mode, reversibility of binding, lower detection limit have been carried out. Detection of metal ions in aqueous media has also been demonstrated by preparation of simple, convenient and disposable test paper sensors with two approaches viz. filter paper and membrane filter loaded with these ionophores. Both of these methods responded sharply to both the metal ions (Hg(2+) and Cr(3+)) in aqueous solution, detectable by bared-eye. For better sensing at low concentration of metal ions, reprecipitation followed by filtration enrichment of ligands on membrane filter was employed. PMID:25666715

  17. Series behavior of lanthanoid(III) complexes with the alpha-1-Wells-Dawson heteropolyoxoanion in acetonitrile: electrochemistry and Ln coordination.

    PubMed

    Antonio, Mark R; Jing, Jing; Burton-Pye, Benjamin P; Francesconi, Lynn C

    2010-09-14

    The tetra-n-butylammonium (TBA(+)) salts for a series of lanthanoid(III) (Ln = Nd, Sm, Eu, Tb, Dy, Yb, and Y) complexes with the alpha-1-isomer of the Wells-Dawson heteropolyoxoanion, alpha-1-[P(2)W(17)O(61)](10-), were prepared and characterized by voltammetry, controlled-potential bulk electrolysis, Eu L(3)-edge XANES spectroelectrochemistry, and Ln L(3)-edge X-ray absorption spectroscopy. Aspects of the series behavior across the 4f period for the complex anions with nominal 1 : 1 Ln(III):alpha-1-[P(2)W(17)O(61)](10-) stoichiometries are detailed. The voltammetric response of the alpha-1 ligand alone in dry acetonitrile (with 0.1 M (TBA)PF(6) electrolyte) is concentration independent and remarkably well-defined with five waves attributable to W-based redox processes. The formation of heteropoly blue solutions upon electrochemical reduction results in chemical instabilities and isomerization. The deliberate addition of water turns an otherwise ideal response into a broad and poorly resolved one, wherein the first reduction process is shifted 150 mV to more positive electrode potentials. Upon its coordination with Ln(III) ions, the voltammetric response develops notable complexities with as many as ten concentration-dependent couples attributable to W-based redox processes of the Ln:alpha-1 complexes. The results from in situ Eu L(3)-edge XANES of the Eu(III):alpha-1 complex provide no evidence for the one-electron reduction of Eu(III) at controlled electrode potentials comparable to those that were previously found to form Eu(II) in the potassium salt of the corresponding Eu(III) complex upon reduction in an aqueous electrolyte. To explain the contrasting system behaviors, the Ln(III) coordination environments in the TBA(5)H(2)[(H(2)O)(n)Ln(alpha-1-P(2)W(17)O(61))] solid salts, including the extent of Ln hydration (n) upon their dissolution in acetonitrile, were determined through use of EXAFS, which demonstrates a structural uniformity among the salts and their

  18. Pyrazolone as a recognition site: Rhodamine 6G-based fluorescent probe for the selective recognition of Fe3+ in acetonitrile-aqueous solution.

    PubMed

    Parihar, Sanjay; Boricha, Vinod P; Jadeja, R N

    2015-03-01

    Two novel Rhodamine-pyrazolone-based colorimetric off-on fluorescent chemosensors for Fe(3+) ions were designed and synthesized using pyrazolone as the recognition moiety and Rhodamine 6G as the signalling moiety. The photophysical properties and Fe(3+) -binding properties of sensors L(1) and L(2) in acetonitrile-aqueous solution were also investigated. Both sensors successfully exhibit a remarkably 'turn-on' response, toward Fe(3+) , which was attributed to 1: 2 complex formation between Fe(3+) and L(1) /L(2) . The fluorescent and colorimetric response to Fe(3+) can be detected by the naked eye, which provides a facile method for the visual detection of Fe(3+) . PMID:24898853

  19. 2-{[2-Methyl-3-(2-methyl­phen­yl)-4-oxo-3,4-dihydro­quinazolin-8-yl]­oxy}acetonitrile

    PubMed Central

    El-Azab, Adel S.; Abdel-Aziz, Alaa A.-M.; Al-Omar, Mohamed A.; Ng, Seik Weng; Tiekink, Edward R. T.

    2012-01-01

    In the title compound, C18H15N3O2, the fused ring system is almost planar [the dihedral angle between the six-membered rings is 1.81 (6)°]. The 2-tolyl ring is approximately orthogonal to this plane [dihedral angle = 83.03 (7)°] as is the acetonitrile group [C—O—C—C torsion angle = 79.24 (14)°] which is also syn to the methyl substituent of the tolyl group. In the crystal, supra­molecular layers are formed in the bc plane mediated by C—H⋯O, C—H⋯N and C—H⋯π inter­actions. The tolyl group is disordered over two positions in a 0.852 (3):0.148 (3) ratio. PMID:22798783

  20. 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