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Sample records for adsorption chromatographic xad

  1. RECOVERY OF MUTAGENICITY FROM DISINFECTED WATER BY XAD RESIN ADSORPTION COMPARED TO REVERSE OSMOSIS

    EPA Science Inventory

    Recovery of Mutagenicity from Disinfected Water Samples by XAD Resin Adsorption Compared to Reverse Osmosis

    K. M. Schenck1, T. F. Speth1, R. J. Miltner1, M. Sivaganesan1 and J. E. Simmons2

    1U.S. EPA, Office of Research and Development, NRMRL
    2U.S. EPA, Office of...

  2. CHEMICAL ANALYSIS OF REVERSE OSMOSIS MEMBRANE AND XAD RESIN ADSORPTION CONCENTRATES OF WATER DISINFECTED BY CHLORINATION OR OZONATION/CHLORINATION PROCESSES

    EPA Science Inventory


    Chemical Analysis of Reverse Osmosis Membrane and XAD Resin Adsorption Concentrates of Water Disinfected by Chlorination or Ozonation/Chlorination Processes.

    J. E. Simmons1, S.D. Richardson2, K.M. Schenck3, T. F. Speth3, R. J. Miltner3 and A. D. Thruston2

    1 NHEE...

  3. Dynamic technique for measuring adsorption in a gas chromatograph

    NASA Technical Reports Server (NTRS)

    Deuel, C. L.; Hultgren, N. W.; Mobert, M. L.

    1973-01-01

    Gas-chromatographic procedure, together with mathematical analysis of adsorption isotherm, allows relative surface areas and adsorptive powers for trace concentrations to be determined in a few minutes. Technique may be used to evaluate relative surface areas of different adsorbates, expressed as volume of adsorbent/gram of adsorbate, and to evaluate their relative adsorptive power.

  4. Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III)

    PubMed Central

    2012-01-01

    A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = –1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%). PMID:23369526

  5. The Calculation of Adsorption Isotherms from Chromatographic Peak Shapes

    ERIC Educational Resources Information Center

    Neumann, M. G.

    1976-01-01

    Discusses the relationship between adsorption isotherms and elution peak shapes in gas chromatography, and describes a laboratory experiment which involves the adsorption of hexane, cyclohexane, and benzene on alumina at different temperatures. (MLH)

  6. New Method for Evaluating Irreversible Adsorption and Stationary Phase Bleed in Gas Chromatographic Capillary Columns

    SciTech Connect

    Wright, Bob W.; Wright, Cherylyn W.

    2012-10-26

    A novel method for the evaluation of gas chromatographic (GC) column inertness has been developed using a tandem GC approach. Typically column inertness is measured by analyte peak shape evaluation. In general, silica, glass, and metal surfaces are chemically reactive and can cause analyte adsorption, which typically is observed as chromatographic peak tailing. Adsorption processes produce broad, short chromatographic peaks that confound peak area determinations because a significant portion can reside in the noise. In addition, chromatographic surfaces and stationary phases can irreversibly adsorb certain analytes without obvious degradation of peak shape. The inertness measurements described in this work specifically determine the degree of irreversible adsorption behavior of specific target compounds at levels ranging from approximately 50 picograms to 1 nanogram on selected gas chromatographic columns. Chromatographic columns with 5% phenylmethylsiloxane, polyethylene glycol (wax), trifluoropropylsiloxane, and 78% cyanopropylsiloxane stationary phases were evaluated with a variety of phosphorus- and sulfur- containing compounds selected as test compounds due to their ease of adsorption and importance in trace analytical detection. In addition, the method was shown effective for characterizing column bleed.

  7. Characterization of lysozyme adsorption in cellulosic chromatographic materials using small-angle neutron scattering.

    PubMed

    Koshari, Stijn H S; Wagner, Norman J; Lenhoff, Abraham M

    2015-06-19

    Measurements of the nanoscale structure of chromatographic adsorbents and the associated distribution of sorbed protein within the media can facilitate improvements in such media. We demonstrate a new technique for this purpose using small-angle neutron scattering (SANS) to characterize the nano- to microscale structure of the chromatographic media and sorbed protein under conditions relevant for preparative chromatographic separations. The adsorption of lysozyme on cellulosic S HyperCel™ (Pall Corporation), a strong cation exchanger, was investigated by SANS. The scattering spectrum is reduced to three contributions arising from (1) the chromatographic medium, (2) discrete protein molecules, and (3) the distribution of sorbed protein within the medium. These contributions are quantified for a range of protein loadings. The total concentration of protein in the chromatographic media can be quantified from the SANS spectrum and the protein is observed to retain its tertiary structure upon adsorption, within the resolution of the method. Further analysis of the SANS spectra shows that protein adsorption is uniform in the media. These measurement techniques provide new and valuable nanoscale information about protein sorption in chromatographic media.

  8. pH-dependence of single-protein adsorption and diffusion at a liquid chromatographic interface.

    PubMed

    Kisley, Lydia; Poongavanam, Mohan-Vivekanandan; Kourentzi, Katerina; Willson, Richard C; Landes, Christy F

    2016-02-01

    pH is a common mobile phase variable used to control protein separations due to the tunable nature of amino acid and adsorbent charge. Like other column variables such as column density and ligand loading density, pH is usually optimized empirically. Single-molecule spectroscopy extracts molecular-scale data to provide a framework for mechanistic optimization of pH. The adsorption and diffusion of a model globular protein, α-lactalbumin, was studied by single-molecule microscopy at a silica-aqueous interface analogous to aqueous normal phase and hydrophilic interaction chromatography and capillary electrophoresis interfaces at varied pH. Electrostatic repulsion resulting in free diffusion was observed at pH above the isoelectric point of the protein. In contrast, at low pH strong adsorption and surface diffusion with either no (D ∼ 0.01 μm(2) /s) or translational (D ∼ 0.3 μm(2) /s) motion was observed where the protein likely interacted with the surface through electrostatic, hydrophobic, and hydrogen bonding forces. The fraction of proteins immobilized could be increased by lowering the pH. These results show that retention of proteins at the silica interface cannot be viewed solely as an adsorption/desorption process and that the type of surface diffusion, which ultimately leads to ensemble chromatographic separations, can be controlled by tuning long-range electrostatic and short-range hydrophobic and hydrogen bonding forces with pH.

  9. Chromatographic retention and thermodynamics of adsorption of dipeptides on a chiral crown ether stationary phase.

    PubMed

    Asnin, Leonid; Sharma, Kavita; Park, Se Won

    2011-11-01

    The enantioselective adsorption of several dipeptides on the crown ether-based stationary phase ChiroSil RCA(+) was studied by means of the linear chromatography method. The retention of analytes was measured with acidified water-methanol mobile phases with varied concentration of methanol (from 60 to 90%, v/v) at different temperatures. Thermodynamic characteristics of adsorption were determined and analyzed applying extrathermodynamic relationships. A considerable difference in adsorption mechanisms of dipeptides with a chiral and achiral N-terminal fragment was proved. An explanation to this fact was proposed assuming that the enantiorecognition of the dipeptides of the first type occurred through the interaction of side groups of the N-terminus with the chiral cavity formed by the crown ether ring. The enantiorecognition of the dipeptides of the second type occurs through the interaction of the C-terminal residue with the side groups of the crown ether moiety. The study also demonstrates how extrathermodynamic concepts can be used for obtaining additional information about retention mechanisms from a limited amount of chromatographic data.

  10. Time-resolved chromatographic analysis and mechanisms in adsorption and catalysis.

    PubMed

    Roubani-Kalantzopoulou, Fani

    2009-03-01

    The main object of this review is the study of fundamentals of adsorption and heterogeneous catalysis, a benefit for the understanding of adsorptive and catalytic properties. This work aims to define and record, with the utmost accuracy, the phenomena and the possible reactions. A new methodology for the study of the adsorption is presented, which is a version of the well-known inverse gas chromatography. This reversed-flow inverse gas chromatography (RF-IGC) is technically very simple, and it is combined with a mathematical analysis that gives the possibility for the estimation of various physicochemical parameters related to adsorbent or catalyst characterization, under conditions compatible with the operation of real adsorbents and catalysts. On this base, this methodology has been successfully applied to the study of the impact of air pollutants, volatile organic and/or inorganic, on many solids such as marbles, ceramics, oxide-pigments of works of art, building materials, authentic statues of the Greek Archaeological Museums. Moreover, this methodology proved to be a powerful tool for studying the topography of active sites of heterogeneous surfaces in the nano-scale domain. Thus, some very important local quantities for the surface chemistry have been determined experimentally for many solids including thin films. These physicochemical local quantities (among which adsorption energy and entropy, surface diffusion coefficient, probability density function) have been determined from the experimental pairs of height of extra chromatographic peaks and time by a nonlinear least-squares method, through personal computer programs written in GW BASIC and lately in FORTRAN. Through the time-resolved analysis the surface characterization of the examined materials took place. In addition, the kinetic constants responsible for adsorption/desorption and surface chemical reactions have also been calculated. Thus, important answers have been provided to the following

  11. Lysozyme adsorption onto a cation-exchanger: mechanism of interaction study based on the analysis of retention chromatographic data.

    PubMed

    Marques, F S; Silva, G L; Thrash, M E; Dias-Cabral, A C

    2014-10-01

    In this study, based on the analysis of retention chromatographic data, we examined the adsorption of lysozyme onto carboxymethyl cellulose. Lysozyme retention data was collected at pH 5 and pH 8. The sodium chloride (NaCl) concentration in the mobile phase ranged from 300mM to 500mM and the temperature for this study varied from 288K to 308K. The retention measurements generated from these experimental conditions were analyzed with the Van't Hoff method, the preferential interaction model and the stoichiometric displacement model. Endothermic heats-of-adsorption and increases in entropy were observed under certain experimental conditions. These data suggest the presence of entropic driving forces such as the release of water and/or possibly structural changes in lysozyme molecules adsorbed to the surface of carboxymethyl cellulose. The modest observed exergonic adsorption ΔG° and the preferential interaction analysis corroborate the presence of water-release for this study. Additional analysis with the stoichiometric displacement model method revealed negligible changes in the structure of lysozyme molecules in contact with the surface of carboxymethyl cellulose. PMID:25193151

  12. Calibration of polydimethylsiloxane and XAD-Pocket passive air samplers (PAS) for measuring gas- and particle-phase SVOCs

    NASA Astrophysics Data System (ADS)

    Okeme, Joseph O.; Saini, Amandeep; Yang, Congqiao; Zhu, Jiping; Smedes, Foppe; Klánová, Jana; Diamond, Miriam L.

    2016-10-01

    Polydimethylsiloxane (PDMS) has seen wide use as the stationary phase of gas chromatographic columns, a passive sampler in water, and recently as a personal exposure sampler, while styrene divinyl-benzene copolymer (XAD) has been used extensively as a passive air sampler outdoors and indoors. We have introduced PDMS and XAD-Pocket as new indoor passive air samplers (PASs). The XAD-Pocket was designed to maximize the surface area-to-volume ratio of XAD and to minimize obstruction of air flow by the sampler housing. Methods were developed to expedite the use of these PASs for measuring phthalates, novel brominated flame-retardants (NFRs) and polybrominated diphenyl ethers (PBDEs) indoors. Sampling rates, Rs, (m3 day-1), were measured during a 7-week calibration study. Variability within and between analyte groups was not statistically significant. As a result, generic values of 0.8 ± 0.4 and 0.5 ± 0.3 m3 day-1 dm-2 are recommended for PDMS and XAD-Pocket for a 50-day deployment time, respectively. PDMS has a higher uptake rate and is easier to use than XAD-Pocket.

  13. Quantitative evaluation of XAD-8 and XAD-4 resins used in tandem for removing organic solutes from water

    USGS Publications Warehouse

    Malcolm, R.L.; MacCarthy, P.

    1992-01-01

    The combined XAD-8 and XAD-4 resin procedure for the isolation of dissolved organic solutes from water was found to isolate 85% or more of the organic solutes from Lake Skjervatjern in Norway. Approximately 65% of the dissolved organic carbon (DOC) was first removed on XAD-8 resin, and then an additional 20% of the DOC was removed on XAD-4 resin. Approximately 15% of the DOC solutes (primarily hydrophilic neutrals) were not sorbed or concentrated by the procedure. Of the 65% of the solutes removed on XAD-8 resin, 40% were fulvic acids, 16% were humic acids, and 9% were hydrophobic neutrals. Approximately 20% of the hydrophilic solutes that pass through the XAD-8 resin were sorbed solutes on the second resin, XAD-4 (i.e., they were hydrophobic relative to the XAD-4 resin). The fraction sorbed on XAD-4 resin was called XAD-4 acids because it represented approximately 85-90% of the hydrophilic XAD-8 acid fraction according to the original XAD-8 fractionation procedure. The recovery of hydrophobic acids (fulvic acids and humic acids) and the hydrophobic neutral fraction from XAD-8 resin was essentially quantitative at 96%, 98%, and 86%, respectively. The recovery of XAD-4 acids from the XAD-4 resin was only about 50%. The exact reason for this moderately low recovery is unknown, but could result from ??-?? bonding between these organic solutes and the aromatic matrix of XAD-4. The hydrophobic/hydrophilic solute separation on XAD-8 resin for water from background Side A and Side B of the lake was almost identical at 65 and 67%, respectively. This result suggested that both sides of the lake are similar in organic chemical composition even though the DOC variation from side to side is 20%.

  14. Efficient removal of aniline by a water-compatible microporous and mesoporous hyper-cross-linked resin and XAD-4 resin: A comparative study

    NASA Astrophysics Data System (ADS)

    Xiao, Guqing; Long, Liping

    2012-06-01

    A novel water-compatible microporous and mesoporous hyper-cross-linked resin modified with phenolic hydroxyl group (named as GQ-03) was synthesized to remove aniline in aqueous solution as compared with XAD-4. The maximum adsorption capacity of GQ-03 emerged at the molecular state for both aniline and p-cresol while the pH dependency trend of aniline adsorbed onto XAD-4 was accordant with the dissociation curve of aniline. The ionic strength influenced the adsorption obviously. The pseudo-first-order rate equation could describe the adsorption process of aniline onto GQ-03 in two stages while this equation could characterize the entire adsorption process of XAD-4. The adsorption isotherms could be correlated to the Freundlich model, higher KF and n values for GQ-03 than XAD-4. The breakthrough capacity and the total adsorption capacity of GQ-03 and XAD-4 was up to 47.2 mg mL-1 and 28.3 mg mL-1, 271.7 mg mL-1 and 115.6 mg mL-1, respectively. The size matching between the pore diameter of GQ-03 and the molecular size of aniline, and hydrogen bonding between GQ-03 and aniline resulted in the larger adsorption capacity.

  15. Comparison of humic substances isolated from peatbog water by sorption on DEAE-cellulose and amberlite XAD-2

    USGS Publications Warehouse

    Hejzlar, J.; Szpakowska, B.; Wershaw, R. L.

    1994-01-01

    Aquatic humic substances (AHS) were isolated from peatbog water by adsorption (1) on diethylaminoethyl cellulose (DEAE-C) and (2) on Amberlite XAD-2 (XAD) to compare yields of the methods and the composition of the isolated AHS. To provide a detailed comparison, the isolates were fractionated using size-exclusion and hydrophobic-interaction chromatography on Sephadex G-50. The fractions were characterized by ultraviolet-visible, infrared and 13C-nuclear magnetic spectroscopies and analyzed for elemental, functional-group, carbohydrate and amino acid compositions. More AHS adsorbed onto DEAE-C than onto XAD-2 (94 and 74%, respectively). However, only 76% of the AHS adsorbed onto DEAE-C was recovered using 0.1 M NaOH, whereas 98% of the AHS adsorbed onto XAD was released by consecutive elution with 1 M NH4OH (91%) and methanol (7%). Four main fractions of different composition were obtained from each of the alkali-desorbed AHS samples by Sephadex-gel chromatography. General agreement was found in relative amounts, spectroscopic characteristics and composition of corresponding fractions of both isolates except nitrogen content, which was significantly higher in AHS isolated with XAD, apparently due to the reaction of AHS with NH4OH used for the desorption from the resin.Aquatic humic substances (AHS) were isolated from peatbog water by adsorption (1) on diethylaminoethyl cellulose (DEAE-C) and (2) on Amberlite XAD-2 (XAD) to compare yields of the methods and the composition of the isolated AHS. To provide a detailed comparison, the isolates were fractionated using size-exclusion and hydrophobic-interaction chromatography on Sephadex G-50. The fractions were characterized by ultraviolet-visible, infrared and 13C-nuclear magnetic spectroscopies and analyzed for elemental, functional-group, carbohydrate and amino acid compositions. More AHS adsorbed onto DEAE-C than onto XAD-2 (94 and 74%, respectively). However, only 76% of the AHS adsorbed onto DEAE-C was recovered

  16. Use of lipophilic ion adsorption isotherms to determine the surface area and the monolayer capacity of a chromatographic packing, as well as the thermodynamic equilibrium constant for its adsorption.

    PubMed

    Cecchi, T

    2005-04-29

    A method that champions the approaches of two independent research groups, to quantitate the chromatographic stationary phase surface available for lipophilic ion adsorption, is presented. For the first time the non-approximated expression of the electrostatically modified Langmuir adsorption isotherm was used. The non approximated Gouy-Chapman (G-C) theory equation was used to give the rigorous surface potential. The method helps model makers, interested in ionic interactions, determine whether the potential modified Langmuir isotherm can be linearized, and, accordingly, whether simplified retention equations can be properly used. The theory cultivated here allows the estimates not only of the chromatographically accessible surface area, but also of the thermodynamic equilibrium constant for the adsorption of the amphiphile, the standard free energy of its adsorption, and the monolayer capacity of the packing. In addition, it establishes the limit between a theoretical and an empirical use of the Freundlich isotherm to determine the surface area. Estimates of the parameters characterising the chromatographic system are reliable from the physical point of view, and this greatly validates the present comprehensive approach.

  17. Isolation of organic acids from large volumes of water by adsorption chromatography

    USGS Publications Warehouse

    Aiken, George R.

    1984-01-01

    The concentrations of dissolved organic carbon from most natural waters ranges from 1 to 20 milligrams carbon per liter, of which approximately 75 percent are organic acids. These acids can be chromatographically fractionated into hydrophobic organic acids, such as humic substances, and hydrophilic organic acids. To effectively study any of these organic acids, they must be isolated from other organic and inorganic species, and concentrated. Usually, large volumes of water must be processed to obtain sufficient quantities of material, and adsorption chromatography on synthetic, macroporous resins has proven to be a particularly effective method for this purpose. The use of the nonionic Amberlite XAD-8 and Amberlite XAD-4 resins and the anion exchange resin Duolite A-7 for isolating and concentrating organic acids from water is presented.

  18. Prediction of the sorption capacities and affinities of organic chemicals by XAD-7.

    PubMed

    Yang, Kun; Qi, Long; Wei, Wei; Wu, Wenhao; Lin, Daohui

    2016-01-01

    Macro-porous resins are widely used as adsorbents for the treatment of organic contaminants in wastewater and for the pre-concentration of organic solutes from water. However, the sorption mechanisms for organic contaminants on such adsorbents have not been systematically investigated so far. Therefore, in this study, the sorption capacities and affinities of 24 organic chemicals by XAD-7 were investigated and the experimentally obtained sorption isotherms were fitted to the Dubinin-Ashtakhov model. Linear positive correlations were observed between the sorption capacities and the solubilities (SW) of the chemicals in water or octanol and between the sorption affinities and the solvatochromic parameters of the chemicals, indicating that the sorption of various organic compounds by XAD-7 occurred by non-linear partitioning into XAD-7, rather than by adsorption on XAD-7 surfaces. Both specific interactions (i.e., hydrogen-bonding interactions) as well as nonspecific interactions were considered to be responsible for the non-linear partitioning. The correlation equations obtained in this study allow the prediction of non-linear partitioning using well-known chemical parameters, namely SW, octanol-water partition coefficients (KOW), and the hydrogen-bonding donor parameter (αm). The effect of pH on the sorption of ionizable organic compounds (IOCs) could also be predicted by combining the correlation equations with additional equations developed from the estimation of IOC dissociation rates. The prediction equations developed in this study and the proposed non-linear partition mechanism shed new light on the selective removal and pre-concentration of organic solutes from water and on the regeneration of exhausted XAD-7 using solvent extraction.

  19. Comparison of XAD macroporous resins for the concentration of fulvic acid from aqueous solution

    USGS Publications Warehouse

    Aiken, G.R.

    1979-01-01

    Five macroreticular, nonlonlc AmberlHe XAD resins were evaluated for concentration and Isolation of fulvlc acid from aqueous solution. The capacity of each resin for fulvlc acid was measured by both batch and column techniques. Elution efficiencies were determined by desorptlon with 0.1 N NaOH. Highest recoveries were obtained with the acrylic ester resins which proved to be most efficient for both adsorption and elution of fulvlc acid. Compared to the acrylic ester resins, usefulness of the styrene dvlnybenzene resins to remove fulvlc acid is limited because of slow diffusion-controlled adsorption and formation of charge-transfer complexes, which hinders elution. ?? 1979 American Chemical Society.

  20. Adsorption/desorption characteristics and separation of anthocyanins from muscadine (Vitis rotundifolia) juice pomace by use of macroporous adsorbent resins.

    PubMed

    Sandhu, Amandeep K; Gu, Liwei

    2013-02-20

    In this study, the adsorption/desorption characteristics of anthocyanins on five Amberlite resins (FPX-66, XAD-7HP, XAD-16N, XAD-1180, and XAD-761) were evaluated. FPX-66 and XAD-16N showed the highest adsorption and desorption capacities and ratios for anthocyanins from muscadine pomace extract, while XAD-7HP had the lowest adsorption and desorption capacities and ratios. On the basis of static adsorption and desorption tests, three resins (FPX-66, XAD-16N, and XAD-1180) were selected for adsorption kinetics and isotherms. The adsorption mechanism was better explained by the pseudo-first-order kinetics for FPX-66 and XAD-16N; however, for XAD-1180, pseudo-second-order kinetics was the most suitable model. The experimental data fitted best to Langmuir isotherm model for all three resins. Dynamic testing was done on a column packed with FPX-66 resin and breakthrough volume was reached at 17 bed volumes of muscadine pomace water extract during adsorption. Three bed volumes of aqueous ethanol (70%) resulted in complete desorption. Resin adsorption resulted in a concentrated pomace extract that contained 13% (w/w) anthocyanins with no detectable sugars. PMID:23368425

  1. Chromatogram Handler: A unique computer program that efficiently processes data generated in liquid chromatographic investigations of organic ligand adsorption on mineral surfaces

    NASA Astrophysics Data System (ADS)

    Kreller, David I.; Young, Stephen P.; Mendez, Eladio A.; McGunigale, Samantha L.

    2012-09-01

    We describe a unique C# computer program developed in our laboratory to efficiently manipulate data generated when a novel liquid chromatographic (LC) 'pulsed addition' technique is used to study organic ligand interactions with mineral surfaces. We are not aware of the existence of a program of this nature elsewhere. Geochemically-relevant ligands studied include dissolved organic matter (DOM) mixtures and single component low molecular weight organic acids. Although our LC system has three optical (absorbance and fluorescence) detection channels, the utility can process data from experiments in which data was collected in one, two or three detection channels. If not automated, data management and processing for the technique is prohibitively complex and time-consuming, due large data volumes and the number of operations involved. The input for the utility in a processing run is the set of detector output files generated during an LC experiment. During processing, the utility generates an MS Excel output file within which, for each detection channel: (i) chromatographic peak areas and peak retention times are determined, (ii) area-normalized per-injection and cumulative adsorption densities are calculated, and (iii) graphical representations of various quantities calculated from the raw data are automatically generated. When processing data from experiments with multiple detection channels, the utility additionally prepares graphs that compare recovery values calculated from data in different detection channels, and calculates (and plots) spectroscopic/chromatographic indices which are ratios of signals in various detection channels. The utility was programmed to perform these additional operations on data from multi-channel experiments because (i) 'Interchannel' comparisons of recovery provide insight into the differing surface behavior of distinct DOM sub-fractions, and (ii) the spectroscopic indices provide a useful new form of data that provides insight into

  2. Enrichment and purification of marine polyphenol phlorotannins using macroporous adsorption resins.

    PubMed

    Kim, Jiyoung; Yoon, Minseok; Yang, Hyejin; Jo, Jinho; Han, Daeseok; Jeon, You-Jin; Cho, Suengmok

    2014-11-01

    Phlorotannins are one of the most important bioactive polyphenols; however, their purification using chromatographic methods has not been explored. Here, we studied purification of phlorotannins from the crude phlorotannin extract (CPhE) of the brown seaweed Ecklonia cava using macroporous adsorption resins. For purification of phlorotannins, four resins (HP-20, SP-850, XAD-7HP, and XAD-2) were screened. Among them, HP-20 resin showed the highest adsorption and desorption capacities. In static adsorption tests, the adsorption capacity of HP-20 increased with increasing temperature (25-45°C). Optimal conditions for the dynamic experiments can be summarized as follows: total phlorotannin content (TPhC) in loading solution: 1.5mg PGE/mL, processing volume: 4 BV, flow rate: 1 mL/min, temperature: 45°C, desorption solvent: 40% ethanol solution. After purification, TPhC (452 mg PGE/g) and arsenic (180 μg/g) of CPhE increased and decreased to 905 mg PGE/g and 48 μg/g, respectively. Recovery rate of phlorotannins from CPhE was 92%.

  3. Enrichment and purification of marine polyphenol phlorotannins using macroporous adsorption resins.

    PubMed

    Kim, Jiyoung; Yoon, Minseok; Yang, Hyejin; Jo, Jinho; Han, Daeseok; Jeon, You-Jin; Cho, Suengmok

    2014-11-01

    Phlorotannins are one of the most important bioactive polyphenols; however, their purification using chromatographic methods has not been explored. Here, we studied purification of phlorotannins from the crude phlorotannin extract (CPhE) of the brown seaweed Ecklonia cava using macroporous adsorption resins. For purification of phlorotannins, four resins (HP-20, SP-850, XAD-7HP, and XAD-2) were screened. Among them, HP-20 resin showed the highest adsorption and desorption capacities. In static adsorption tests, the adsorption capacity of HP-20 increased with increasing temperature (25-45°C). Optimal conditions for the dynamic experiments can be summarized as follows: total phlorotannin content (TPhC) in loading solution: 1.5mg PGE/mL, processing volume: 4 BV, flow rate: 1 mL/min, temperature: 45°C, desorption solvent: 40% ethanol solution. After purification, TPhC (452 mg PGE/g) and arsenic (180 μg/g) of CPhE increased and decreased to 905 mg PGE/g and 48 μg/g, respectively. Recovery rate of phlorotannins from CPhE was 92%. PMID:24874368

  4. Correlation of HPLC retention data of triazines with the inhibition of DHFR from L1210 cells: Development of new chromatographic adsorption parameter in QSAR

    SciTech Connect

    Valko, K.; Fellegvari, I.; Katti, A.; Otvos, L.

    1988-01-01

    The use of chromatographic retention measurements for quantitative structure-activity relationships (QSAR) was investigated by the development of an adjusted logarithmic retention factor. Retention data of 15 triazine derivatives, which inhibit dihydrofolate reductase were measured by HPLC on octyl-silica and silica gel columns. From these data two parameters were calculated. First, the intercept of the plot of the logarithmic retention factor versus acetonitrile concentration was calculated from the reversed-phase retention measurements (log k'o) and, second, the difference between the logarithmic retention factor at high ammonium salt concentration and low ammonium salt concentration in the mobile phase was calculated from retention measurements on the silica gel column. The first parameter represents hydrophobic properties and the second parameter characterizes adsorption properties of the triazine derivatives. The results show a correlation between the two above mentioned parameters and the inhibition of L1210/71 cell growth.

  5. Sodium citrate and potassium phosphate as alternative adsorption buffers in hydrophobic and aromatic thiophilic chromatographic purification of plasmid DNA from neutralized lysate.

    PubMed

    Bonturi, Nemailla; Radke, Vanessa Soraia Cortez Oliveira; Bueno, Sônia Maria Alves; Freitas, Sindélia; Azzoni, Adriano Rodrigues; Miranda, Everson Alves

    2013-03-01

    The number of studies on gene therapy using plasmid vectors (pDNA) has increased in recent years. As a result, the demand for preparations of pDNA in compliance with recommendations of regulatory agencies (EMEA, FDA) has also increased. Plasmid DNA is often obtained through fermentation of transformed Escherichia coli and purification by a series of unit operations, including chromatography. Hydrophobic interaction chromatography (HIC) and thiophilic aromatic chromatography (TAC), both using ammonium sulfate buffers, are commonly employed with success. This work was aimed at studying the feasibility of utilizing alternative salts in the purification of pDNA from neutralized lysate with phenyl-agarose (HIC) and mercaptopyrimidine-agarose (TAC) adsorbents. Their selectivity toward sc pDNA was evaluated through adsorption studies using 1.5 mol/L sodium citrate and 2.0 mol/L potassium phosphate as adsorption buffers. Chromatography with mercaptopyrimidine-agarose adsorbent and 1.5 mol/L sodium citrate was able to recover 91.1% of the pDNA with over 99.0% removal of gDNA and endotoxin. This represents a potential alternative for the primary recovery of sc pDNA. However, the most promising result was obtained using 2.0 mol/L potassium phosphate buffer and a mercaptopyrimidine-agarose column. In a single chromatographic step, this latter buffer/adsorbent system recovered 68.5% of the pDNA with 98.8% purity in accordance with the recommendations of regulatory agencies with regard to RNA and endotoxin impurity.

  6. Studies on the adsorption of cell impurities from plasmid-containing lysates to phenyl boronic acid chromatographic beads.

    PubMed

    Gomes, A Gabriela; Azevedo, Ana M; Aires-Barros, M Raquel; Prazeres, D Miguel F

    2011-12-01

    Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins.

  7. Studies on the adsorption of cell impurities from plasmid-containing lysates to phenyl boronic acid chromatographic beads.

    PubMed

    Gomes, A Gabriela; Azevedo, Ana M; Aires-Barros, M Raquel; Prazeres, D Miguel F

    2011-12-01

    Plasmid DNA (pDNA) is purified directly from alkaline lysis-derived Escherichia coli (E. coli) lysates by phenyl boronate (PB) chromatography. The method explores the ability of PB ligands to bind covalently, but reversibly, to cis-diol-containing impurities like RNA and lipopolysaccharides (LPS), leaving pDNA in solution. In spite of this specificity, cis-diol free species like proteins and genomic DNA (gDNA) are also removed. This is a major advantage since the process is designed to keep the target pDNA from binding. The focus of this paper is on the study of the secondary interactions between the impurities (RNA, gDNA, proteins, LPS) in a pDNA-containing lysate and 3-amino PB controlled pore glass (CPG) matrices. Runs were designed to evaluate the role of adsorption buffer composition, feed type (pH, salt content), CPG matrix and sample pretreatment (RNase A, isopropanol precipitation). Water was chosen as the adsorption buffer over MgCl(2) solutions since it maximised pDNA yield (96.2±4.9%) and protein removal (61.3±3.0%), while providing for a substantial removal of RNA (65.5±3.5%) and gDNA (44.7±14.1%). Although the use of pH 3.5 maximised removal of impurities (~75%), the best compromise between plasmid yield (~96%) and RNA clearance (~60-70%) was obtained for a pH of 5.2. Plasmid yield was maximal (>96%) when the concentration of acetate and potassium ions in the incoming lysate feed were 1.7 M and 1.0 M, respectively. The pre-treatment of lysates with RNase A deteriorated the performance since the resulting oligoribonucleotides lack the cis-diol group at their 3' termini. Overall, the results support the idea that charge transfer interactions between the boron atom at acidic pH and electron donor groups in the aromatic bases of nucleic acids and side residues of proteins are responsible for the non-specific removal of gDNA, RNA and proteins. PMID:22024344

  8. A model predictive control approach for the Italian LBE XADS

    NASA Astrophysics Data System (ADS)

    Cammi, Antonio; Casella, Francesco; Luzzi, Lelio; Milano, Alessandro; Ricotti, Marco E.

    2008-06-01

    In this paper, model predictive control (MPC) is applied to the Italian 80 MW th experimental accelerator driven system (XADS), referring to a simple, non-linear model for the dynamic simulation of the plant, which has been developed and described in a previous work [A. Cammi, L. Luzzi, A.A. Porta, M.E. Ricotti, Prog. Nucl. Energ. 48 (2006) 578], in order to describe the interactions among the different subsystems: i.e., the accelerator-core coupling, the lead bismuth eutectic (LBE) primary system, the secondary system with diathermic oil and air coolers batteries, which reject the thermal power to the environment. Hereinafter, a model predictive controller is proposed, with the objective to minimize the difference between the average temperature of the diathermic oil and its reference value, while also minimizing the variations of the control input, which is the air coolers mass flow rate. The dynamic response of the LBE-XADS has been evaluated with reference to a reduction of 20% in the reactor power from nominal load conditions: this transient is very demanding for the overall plant, nevertheless the obtained results indicate the effectiveness of the proposed controller.

  9. Adsorption of halogenated hydrocarbons from aqueous solutions by wetted and nonwetted hydrophobic and hydrophilic sorbents: Equilibria

    SciTech Connect

    Rexwinkel, G.; Heesink, B.B.M.; Swaaij, W.P.M. van

    1999-12-01

    Single-solute adsorption equilibria of 1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethene, trans-1,2-dichloroethene, chloroform, 2,4-dichlorophenol, and dichloromethane dissolved in water have been measured, using both wetted and nonwetted hydrophobic Amberlite XAD-4 resin at 20 C. The results could be described by means of Freundlich isotherms indicating the heterogeneity of the Amberlite XAD-4 surface. Wetted and nonwetted Amberlite XAD-4 showed identical adsorption capacities. The influence of the ionic strength on the adsorption capacity of Amberlite XAD-4 for 1,1,1-trichloroethane has been measured by adding KCI to the aqueous solution. The apparent adsorption capacity was found to increase with salt concentration due to the salting-out effect. Adsorption equilibria of dichloromethane, which is generally regarded as a key component with regard to water treatment demands, have also been measured using several other synthetic resins, as well as activated carbon. The order of increasing adsorption capacity was found to be Amberlite XAD-7 {le} Amberlite XAD-4 {approximately} Dowex XUS 43493.00 {le} Norit ROW 0.8 SUPRA {le} Ambersorb XE-572 {le} Ambersorb XE-563.

  10. Comparison of extracts and toxicities of organic compounds in drinking water concentrated by single and composite XAD resins.

    PubMed

    Zhou, Xue; Xiang, Lunhui; Wu, Fenghong; Peng, Xiaoling; Xie, Hong; Wang, Jiachun; Yang, Kedi; Lu, Wenqing; Wu, Zhigang

    2013-12-01

    We compared extracts and toxicities of organic compounds (OCs) in drinking water concentrated by composite XAD-2/8 resin (mixed with an equal volume of XAD-2 and XAD-8 resins) with those extracted by single XAD-2 (non-polar) and XAD-8 (polar) resins. Drinking water was processed from raw water of the Han River and the Yangtze River in Wuhan section, China. The extraction efficiency of all resins was controlled at 30%. The types of extracted OCs were detected by gas chromatography-mass spectrometry, and the cytotoxicity and genotoxicity were assessed by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and comet assays, respectively, in human hepatoma HepG2 cells. Our results showed that XAD-2/8 extracted a larger variety of OCs, compared with XAD-8 and XAD-2. The cytotoxicity and genotoxicity of extracted OCs were in the order of XAD-8> XAD-2/8> XAD-2 at almost all tested concentrations after 24 h treatment (P < 0.05). Our findings suggest that single XAD resin selectively extracts either polar or non-polar OCs, which would lead to over- or under-estimation of the toxicity of drinking water. Nevertheless, composite resin extracts both polar and non-polar OCs, and could be utilized as a useful extraction technique to evaluate the level and toxicity of OCs in drinking water.

  11. Influences of wind on the uptake of XAD passive air sampler in the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Wang, Xiaoping; Liu, Xiande

    2016-04-01

    The passive air sampler based on XAD-2 resin (XAD-PAS) is a useful tool for studying the long-range atmospheric transport of persistent organic pollutants (POPs) in the remote or high-altitude regions. Due to its opening bottom, the sampling processes of XAD-PAS was influenced by wind or air turbulence. By now, there were no studies focusing on the wind impact on the sampling rates (R values) in field. In this study, three sampling sites in the Tibetan Plateau, a high-altitude region with large range of wind speed (v), were chosen to calibrate XAD-PAS. In the low-wind regions, the R values fitted for the predicted values by ambient tempratrue (T) and air pressure (P). In the windy regions, not only T and P but also v impacted the R values, and an equation for estimating the R values was developed in the windy regions. Air turbulence may introduce the uncertainties of the R values, therefore, the improved type with spoilers on the bottom of XAD-PAS were designed to decrease the uncertainties. The observed R values of the improved XAD-PAS in field were good agreement with the predicted R values only by T^1.75/P, indicating that the improved XAD-PAS can decrease the influence of wind.

  12. Adsorption and desorption characteristics of adlay bran free phenolics on macroporous resins.

    PubMed

    Yang, Qingyun; Zhao, Mouming; Lin, Lianzhu

    2016-03-01

    In this study, the adsorption and desorption characteristics of six macroporous resins including XAD-7HP, XAD-16, HP-20, HP-2MGL, SP-207 and SP-825 for enrichment of adlay bran free phenolics were studied. XAD-16, SP-207 and SP-825 were chosen for further study due to their strong adsorption and desorption capacities. XAD-16, SP-207 and SP-825 had similar phenolics adsorption/desorption behaviors. Pseudo-second-order kinetics model and Freundlich isotherm model were suitable for describing the whole exothermic and physical adsorption processes of adlay bran free phenolics on XAD-16, SP-207 and SP-825. After treatment with gradient elution on XAD-16 resin column, the free phenolics were mostly enriched (from 89.61 to 1015.26mg/100g) in 50% ethanol fraction. The oxygen radical absorbance capacity of 50% ethanol fraction was eight times higher than that of the crude extract. Therefore, the production of highly concentrated phenolics might expand the application of adlay bran used as a bioactive ingredient in functional food.

  13. CTEPP STANDARD OPERATING PROCEDURE FOR PRE-CLEANING FILTERS AND XAD-2 (SOP-5.10)

    EPA Science Inventory

    This SOP summarizes the method for pre-cleaning XAD-2 resin and quartz fiber filters. The procedure provides a cleaning method to help reduce potential background contamination in the resin and filters.

  14. Removal and Recovery of Some From Simulated Nuclear Waste Radionuclides Using Amberlite XAD-16-Pyridylazo Resorcinol (AXAD-PR) Composite

    NASA Astrophysics Data System (ADS)

    Akçağlar, Sevil

    2016-04-01

    In this study, Amberlite XAD-16-Pyridylazo resorcinol composite (AXAD-PR) were developed under laboratory conditions to detect the removals and recoveries of U(IV) and Am(III) from simulated nuclear wastes by adsorption and desorption processes. The effects of contacting time (5, 15, 25 and 200 min), of AXAD-PR concentrations (5, 25, 50 and 100 mg/l), of temperatures (15, 30 and 45°C), increasing U(IV) and Am(III) concentrations (1, 5, 10, 15, 20, 30 and 40) and pH levels (acidic, basic and neutral conditions) on the removals and recoveries of U(IV) and Am(III) radionuclides were investigated. The data obtained showed that the maximum adsorption yields of U(IV) and Am(III) were found to be 96% and 95%, respectively, after 25 min using 25 mg/l AXAD-PR at 30°C at an acidic pH of 5. The adsorption kinetic of radionuclides to AXAD-PR isotherm was in accordance with Langmuir. The AXAD-PR can be reused and can be used again. The regeneration of the composite is possible and can be attained a desorption efficiency of 99% using 0.4 M HNO3 acid solution from 25 mg/l prepared AXAD-PR.

  15. Determination of volatile organic compounds in different microenvironments by multibed adsorption and short-path thermal desorption followed by gas chromatographic-mass spectrometric analysis.

    PubMed

    Kuntasal, Oznur Oğuz; Karman, Deniz; Wang, Daniel; Tuncel, Semra G; Tuncel, Gürdal

    2005-12-16

    A multiphase assurance approach was developed for the accurate and precise determination of volatile organic compounds (VOCs) in different microenvironments. This approach includes (i) development of a method including adsorption of VOCs onto a multisorbent media followed by short-path thermal desorption (SPTD) pre-concentration and gas chromatography (GC) coupled to a mass spectrometry (MS) quantification, (ii) validation of the sampling and analytical method and (iii) validation of the data using a multidimensional procedure. Tenax TA and Carbopack B sorbent combinations were used to collect 102 individual VOCs ranging from C5 to C12. Method parameters including thermal desorption temperature, desorption time and cryofocusing temperature were optimized. The average recoveries and method detection limits (MDL) for the target analytes were in the range 80-100% and 0.01-0.14 ppbv, respectively. The method also showed good linearity (R2 > 0.99) and precision (<8%) values. Validation of the method was performed under real environmental conditions at a gas station, in an office and a residential household to examine the influence of variation in meteorological conditions such as temperature and relative humidity and a wide range of VOC concentrations. The sampling and analytical method resulted in successful determination of VOC in different microenvironments. Finally, validation of the data was performed by assessing fingerprint and time series plots and correlation matrices together with meteorological parameters such as mixing height, wind speed and temperature. The data validation procedure provided detection of both faulty data and air pollution episodes.

  16. The presence of dichloromethane on cleaned XAD-2 resin: A potential problem and solutions

    SciTech Connect

    Chuang, J.C.; Holdren, M.W. ); Wilson, N.K. )

    1990-06-01

    Preparation of XAD-2 resin for indoor air sampling with commonly used cleaning methods, such as Soxhlet extraction with dichloromethane (DCM) followed by vacuum drying and nitrogen purging, can lead to elevated DCM levels (> 100 ppb) in the sampled indoor air, which result from DCM remaining in the resin after cleaning. Since DCM is a suspect human carcinogen, indoor human exposure to DCM should be minimized. Several procedures to remove residual DCM after Soxhlet extraction were evaluated. Removal by fluidizing the XAD-2 resin bed in a drying column with a nitrogen stream at 40{degree}C was best. The effectiveness of this procedure was demonstrated in parallel air sampling with a syringe sampler and with a prototype quiet sampler equipped with a quartz fiber filter and an XAD-2 cartridge in series. Sampling was conducted in an office and in residence. With the modified procedures, indoor DCM levels were at typical indoor values. (< 10 ppb).

  17. Presence of dichloromethane on cleaned XAD-2 resin: A potential problem and solutions

    SciTech Connect

    Chuang, J.C.; Holdren, M.W.; Wilson, N.K.

    1990-01-01

    Preparation of XAD-2 resin for indoor air sampling with commonly used cleaning methods, such as Soxhlet extraction with dichloromethane (DCM) followed by vacuum drying and nitrogen purging, can lead to elevated DCM levels (>100 ppb) in the sampled indoor air, which result from DCM remaining in the resin after cleaning. Since DCM is a suspect human carcinogen, indoor human exposure to DCM should be minimized. Several procedures to remove residual DCM after Soxhlet extraction were evaluated. Removal by fluidizing the XAD-2 resin bed in a drying column with a nitrogen stream at 40C was best. The effectiveness of this procedure was demonstrated in parallel air sampling with a syringe sampler and with a prototype quiet sampler equipped with a quartz fiber filter and an XAD-2 cartridge in series. Sampling was conducted in an office and in residences. With the modified procedures, indoor DCM levels were at typical indoor values (<10 ppb).

  18. Adsorption properties of macroporous adsorbent resins for separation of anthocyanins from mulberry.

    PubMed

    Chen, Yao; Zhang, Weijie; Zhao, Ting; Li, Fang; Zhang, Min; Li, Jing; Zou, Ye; Wang, Wei; Cobbina, Samuel J; Wu, Xiangyang; Yang, Liuqing

    2016-03-01

    In this study, the adsorption/desorption characteristics of mulberry anthocyanins (MA) on five types of macroporous resins (XAD-7HP, AB-8, HP-20, D-101 and X-5) were evaluated, XAD-7HP and AB-8 showed higher adsorption/desorption capacities. On the basis of static adsorption test, XAD-7HP and AB-8 resins were selected for kinetics, isotherms and thermodynamics. The adsorption mechanism indicated that the process was better explained by pseudo-first-order kinetics and the Langmuir isotherm model, and the thermodynamics tests showed that the processes were exothermic, spontaneous and thermodynamically feasible. Dynamic tests were performed on a column packed with XAD-7HP and AB-8, and breakthrough volume was reached at 15 and 14 bed volumes of MA solution, respectively. The purity of the fraction by 40% ethanol elution on XAD-7HP reached 93.6%, from which cyanidin-3-glucoside and cyanidin-3-rutinoside were identified by HPLC-ESI-MS/MS. The method could be used to prepare high purity anthocyanins from mulberry fruits as well as other plants.

  19. Adsorption properties of macroporous adsorbent resins for separation of anthocyanins from mulberry.

    PubMed

    Chen, Yao; Zhang, Weijie; Zhao, Ting; Li, Fang; Zhang, Min; Li, Jing; Zou, Ye; Wang, Wei; Cobbina, Samuel J; Wu, Xiangyang; Yang, Liuqing

    2016-03-01

    In this study, the adsorption/desorption characteristics of mulberry anthocyanins (MA) on five types of macroporous resins (XAD-7HP, AB-8, HP-20, D-101 and X-5) were evaluated, XAD-7HP and AB-8 showed higher adsorption/desorption capacities. On the basis of static adsorption test, XAD-7HP and AB-8 resins were selected for kinetics, isotherms and thermodynamics. The adsorption mechanism indicated that the process was better explained by pseudo-first-order kinetics and the Langmuir isotherm model, and the thermodynamics tests showed that the processes were exothermic, spontaneous and thermodynamically feasible. Dynamic tests were performed on a column packed with XAD-7HP and AB-8, and breakthrough volume was reached at 15 and 14 bed volumes of MA solution, respectively. The purity of the fraction by 40% ethanol elution on XAD-7HP reached 93.6%, from which cyanidin-3-glucoside and cyanidin-3-rutinoside were identified by HPLC-ESI-MS/MS. The method could be used to prepare high purity anthocyanins from mulberry fruits as well as other plants. PMID:26471611

  20. Adsorption characteristics and preparative separation of chaetominine from Aspergillus fumigatus mycelia by macroporous resin.

    PubMed

    Liu, Changqing; Jiao, Ruihua; Yao, Lingyun; Zhang, Yupeng; Lu, Yanhua; Tan, Renxiang

    2016-03-15

    Chaetominine (CHA) is a quinazolinone alkaloid with strong anti-cancer activity produced by Aspergillus fumigatus CY018. For recovering CHA from A. fumigates efficiently, adsorption and desorption capacities of eight macroporous resins were tested in this work. Based on batch experiments, XAD-16 resin was revealed the best adsorption and desorption performance among all the tested resins. Then, adsorption kinetics and adsorption isotherms were constructed on XAD-16 resin, and the experimental data were fitted well to the pseudo first-order kinetics and Freundlick isotherm model. In the dynamic adsorption and desorption, the purity of CHA increased from 0.0314% (w/w) in the crude extract to 57.86% in the final product with recovery yield of 70.56% by a one-step treatment. Moreover, the experiments were also performed in a lab scale-up scale, in which the purity and recovery of CHA were 56.12% (w/w) and 68.02%, respectively. In addition, XAD-16 resin could be recycled 3 times for CHA separation after regeneration without adverse effects on adsorption/desorption performance. These results suggested that XAD-16 resin adsorption could act as a useful and economic method for recovering CHA from A. fumigatus.

  1. A comparison of surface water natural organic matter in raw filtered water samples, XAD, and reverse osmosis isolates.

    PubMed

    Maurice, Patricia A; Pullin, Michael J; Cabaniss, Stephen E; Zhou, Qunhui; Namjesnik-Dejanovic, Ksenija; Aiken, George R

    2002-05-01

    This research compared raw filtered waters (RFWs), XAD resin isolates (XAD-8 and XAD-4), and reverse osmosis (RO) isolates of several surface water samples from McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). RO and XAD-8 are two of the most common techniques used to isolate natural organic matter (NOM) for studies of composition and reactivity; therefore, it is important to understand how the isolates differ from bulk (unisolated) samples and from one another. Although, any comparison between the isolation methods needs to consider that XAD-8 is specifically designed to isolate the humic fraction, whereas RO concentrates a broad range of organic matter and is not specific to humics. The comparison included for all samples: weight average molecular weight (Mw), number average molecular weight (Mn), polydispersity (rho), absorbance at 280 nm normalized to moles C (epsilon280) (RFW and isolates); and for isolates only: elemental analysis, % carbon distribution by 13C NMR, and aqueous FTIR spectra. As expected, RO isolation gave higher yield of NOM than XAD-8, but also higher ash content, especially Si and S. Mw decreased in the order: RO > XAD-8 > RFW > XAD-4. The Mw differences of isolates compared with RFW may be due to selective isolation (fractionation), or possibly in the case of RO to condensation or coagulation during isolation. 13C NMR results were roughly similar for the two methods, but the XAD-8 isolate was slightly higher in 'aromatic' C and the RO isolate was slightly higher in heteroaliphatic and carbonyl C. Infrared spectra indicated a higher carboxyl content for the XAD-8 isolates and a higher ester:carboxyl ratio for the RO isolates. The spectroscopic data thus are consistent with selective isolation of more hydrophobic compounds by XAD-8, and also with potential ester hydrolysis during that process, although further study is needed to determine whether ester hydrolysis does indeed occur. Researchers choosing between

  2. A comparison of surface water natural organic matter in raw filtered water samples, XAD, and reverse osmosis isolates

    USGS Publications Warehouse

    Maurice, P.A.; Pullin, M.J.; Cabaniss, S.E.; Zhou, Q.; Namjesnik-Dejanovic, K.; Aiken, G.R.

    2002-01-01

    This research compared raw filtered waters (RFWs), XAD resin isolates (XAD-8 and XAD-4), and reverse osmosis (RO) isolates of several surface water samples from McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). RO and XAD-8 are two of the most common techniques used to isolate natural organic matter (NOM) for studies of composition and reactivity; therefore, it is important to understand how the isolates differ from bulk (unisolated) samples and from one another. Although, any comparison between the isolation methods needs to consider that XAD-8 is specifically designed to isolate the humic fraction, whereas RO concentrates a broad range of organic matter and is not specific to humics. The comparison included for all samples: weight average molecular weight (Mw), number average molecular weight (Mn), polydispersity (??), absorbance at 280nm normalized to moles C (??280) (RFW and isolates); and for isolates only: elemental analysis, % carbon distribution by 13C NMR, and aqueous FTIR spectra. As expected, RO isolation gave higher yield of NOM than XAD-8, but also higher ash content, especially Si and S. Mw decreased in the order: RO>XAD-8>RFW>XAD-4. The Mw differences of isolates compared with RFW may be due to selective isolation (fractionation), or possibly in the case of RO to condensation or coagulation during isolation. 13C NMR results were roughly similar for the two methods, but the XAD-8 isolate was slightly higher in 'aromatic' C and the RO isolate was slightly higher in heteroaliphatic and carbonyl C. Infrared spectra indicated a higher carboxyl content for the XAD-8 isolates and a higher ester:carboxyl ratio for the RO isolates. The spectroscopic data thus are consistent with selective isolation of more hydrophobic compounds by XAD-8, and also with potential ester hydrolysis during that process, although further study is needed to determine whether ester hydrolysis does indeed occur. Researchers choosing between XAD and RO

  3. A comparison of surface water natural organic matter in raw filtered water samples, XAD, and reverse osmosis isolates.

    PubMed

    Maurice, Patricia A; Pullin, Michael J; Cabaniss, Stephen E; Zhou, Qunhui; Namjesnik-Dejanovic, Ksenija; Aiken, George R

    2002-05-01

    This research compared raw filtered waters (RFWs), XAD resin isolates (XAD-8 and XAD-4), and reverse osmosis (RO) isolates of several surface water samples from McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). RO and XAD-8 are two of the most common techniques used to isolate natural organic matter (NOM) for studies of composition and reactivity; therefore, it is important to understand how the isolates differ from bulk (unisolated) samples and from one another. Although, any comparison between the isolation methods needs to consider that XAD-8 is specifically designed to isolate the humic fraction, whereas RO concentrates a broad range of organic matter and is not specific to humics. The comparison included for all samples: weight average molecular weight (Mw), number average molecular weight (Mn), polydispersity (rho), absorbance at 280 nm normalized to moles C (epsilon280) (RFW and isolates); and for isolates only: elemental analysis, % carbon distribution by 13C NMR, and aqueous FTIR spectra. As expected, RO isolation gave higher yield of NOM than XAD-8, but also higher ash content, especially Si and S. Mw decreased in the order: RO > XAD-8 > RFW > XAD-4. The Mw differences of isolates compared with RFW may be due to selective isolation (fractionation), or possibly in the case of RO to condensation or coagulation during isolation. 13C NMR results were roughly similar for the two methods, but the XAD-8 isolate was slightly higher in 'aromatic' C and the RO isolate was slightly higher in heteroaliphatic and carbonyl C. Infrared spectra indicated a higher carboxyl content for the XAD-8 isolates and a higher ester:carboxyl ratio for the RO isolates. The spectroscopic data thus are consistent with selective isolation of more hydrophobic compounds by XAD-8, and also with potential ester hydrolysis during that process, although further study is needed to determine whether ester hydrolysis does indeed occur. Researchers choosing between

  4. RECOVERY OF MUTAGENICITY FROM DISINFECTED WATER SAMPLES BY XAD RESIN ADSORPTION COMPARED TO REVERSE OSMOSIS

    EPA Science Inventory

    the presence of a complex misture of disinfection byproducts in drinking waters continues to cause concern over the potential long-term health effects of exposure to these compounds. Most of these compounds are present at ug/L levels or less. Consequently, some method of concentr...

  5. 2, 4 dichlorophenol (2, 4-DCP) sorption from aqueous solution using granular activated carbon and polymeric adsorbents and studies on effect of temperature on activated carbon adsorption.

    PubMed

    Ghatbandhe, A S; Yenkie, M K N

    2008-04-01

    Adsorption equilibrium, kinetics and thermodynamics of 2,4-dichlorophenol (2,4-DCP), one of the most commonly used chlorophenol, onto bituminous coal based Filtrasorb-400 grade granular activated carbon, were studied in aqueous solution in a batch system with respect to temperature. Uptake capacity of activated carbon found to increase with temperature. Langmuir isotherm models were applied to experimental equilibrium data of 2, 4-DCP adsorption and competitive studies with respect to XAD resin were carried out. Equilibrium data fitted very well to the Langmuir equilibrium model. Adsorbent monolayer capacity 'Q0, Langmuir constant 'b' and adsorption rate constant 'k(a)' were evaluated at different temperatures for activated carbon adsorption. This data was then used to calculate the energy of activation of adsorption and also the thermodynamic parameters, namely the free energy of adsorption, deltaG0, enthalpy of adsorption, deltaH0 and the entropy of adsorption deltaS0. The obtained results showed that the monolayer capacity increases with the increase in temperatures. The obtained values of thermodynamic parameters showed that adsorption of 2,4 DCP is an endothermic process. Synthetic resin was not found efficient to adsorb 2,4 DCP compared to activated carbon. The order of adsorption efficiencies of three resins used in the study found as XAD7HP > XAD4 > XAD1180.

  6. Equilibrium and heat of adsorption of diethyl phthalate on heterogeneous adsorbents

    SciTech Connect

    Zhang, W.M.; Xu, Z.W.; Pan, B.C.; Hong, C.H.; Jia, K.; Jiang, P.J.; Zhang, Q.J.; Pan, B.J.

    2008-09-15

    Removal of phthalate esters from water has been of considerable concern recently. In the present study, the adsorptive removal performance of diethyl phthalate (DEP) from water was investigated with the aminated polystyrene resin (NDA-101) and oxidized polystyrene resin (NDA-702). In addition, the commercial homogeneous polystyrene resin (XAD-4) and acrylic ester resin (Amberlite XAD-7) as well as coal-based granular activated carbon (AC-750) were chosen for comparison. The corresponding equilibrium isotherms are well described by the Freundlich equation and the adsorption capacities for DEP followed the order NDA-702 > NDA-101 > AC-750 > XAD-4 > XAD-7. Analysis of adsorption mechanisms suggested that these adsorbents spontaneously adsorb DEP molecules driven mainly by enthalpy change, and the adsorption process was derived by multiple adsorbent-adsorbate interactions such as hydrogen bonding, {pi}-{pi} stacking, and micropore filling. The information related to the adsorbent surface heterogeneity and the adsorbate-adsorbate interaction was obtained by Do's model. All the results indicate that heterogeneous resins NDA-702 and NDA-101 have excellent potential as an adsorption material for the removal of DEP from the contaminated water.

  7. Preconcentration of lead with Amberlite XAD-2 and Amberlite XAD-7 based chelating resins for its determination by flame atomic absorption spectrometry.

    PubMed

    Tewari, P K; Singh, Ajai K

    2002-03-11

    Four chelating matrices prepared by coupling Amberlite XAD-2 with chromotropic acid (AXAD-2-CA or 1), pyrocatechol (AXAD-2-PC or 2) and thiosalicylic acid (AXAD-2-TSA or 3) through azo spacer and impregnation of Amberlite XAD-7 with xylenol orange (AXAD-7-XO or 4) have been studied for enrichment of lead(II). All the four resins quantitatively sorb Pb(II) at pH 3.0-8.0 when the flow rate is maintained between 2 and 10 mlmin(-1). HNO(3) (0.5-4.0 M) instantaneously elutes Pb(II) from all the four chelating resins. The sorption capacity is in the range 16.0-186.0 mumolg(-1) and loading half time (t(1/2)) between 3.2 and 15.5 min. The tolerance limits of electrolytes (NaCl, NaBr, NaNO(3), Na(2)SO(4), Na(3)PO(4)) and cations (Ca and Mg) are reported. Phosphate interferes in the sorption with 3 and 4. The limit of detection and limit of quantification have been found to be in the ranges 2.44-7.87 and 2.76-8.64 ngml(-1), respectively. Lead has been determined in river (RSD approximately 2.6-12.8%) and tap (RSD approximately 1.8-7.2%) water samples. PMID:18968550

  8. Determination of trace amounts of lead and manganese in water samples after simultaneous preconcentration onto modified amberlite XAD-4 resin.

    PubMed

    Mobarakeh, Sayed Zia Mohammadi; Afzali, Darush; Taher, Mohammad Ali; Dargahi, Roza

    2009-01-01

    A procedure for simultaneous separation and preconcentration of trace amounts of manganese and lead has been proposed. It is based on the adsorption of manganese and lead ions onto a column of Amberlite XAD-4 resin loaded with pyrocatechol reagent. Manganese and lead were quantitatively retained on the column in the pH range 4.0-6.5 at a flow rate of 2 mL/min. The manganese and lead ions were eluted with 5.0 mL of 4 M HNO3 solutions. Manganese and lead were measured by flame atomic absorption spectrometry. In this case, 100.0 ng manganese and 1000.0 ng lead were concentrated in the column from 800 mL of aqueous sample, where their concentrations were as low as 0.125 and 1.25 ng/mL, respectively. Seven replicate determinations of mixtures of 1.0 microg/mL manganese and 2.0 microg/mL lead in the final solution gave a mean absorbance of 0.1926 and 0.0832 with RSD values of +/- 1.1 and +/- 1.2%, respectively. The LODs were 1.76 ng/mL for Mn(ll) and 37.28 ng/mL for Pb(ll) (3 delta(bl)/m) in the final solution, with a preconcentration factor of 160. Sensitivities for 1% absorbance for Mn(ll) and Pb(ll) were 7.0 and 74.7 ng/mL, respectively. The interference of a large number of anions and cations has been studied and the optimized conditions were used for determination of trace amounts of manganese and lead in various environmental and standard samples. PMID:19916395

  9. Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers.

    PubMed

    Sun, Yue; Li, Xiao-Tao; Xu, Chao; Chen, Jin-Long; Li, Ai-Min; Zhang, Quan-Xing

    2005-01-01

    Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

  10. Sorption of a diverse set of organic chemical vapors onto XAD-2 resin: Measurement, prediction and implications for air sampling

    NASA Astrophysics Data System (ADS)

    Hayward, Stephen J.; Lei, Ying D.; Wania, Frank

    2011-01-01

    The wide-spread use of styrene-divinylbenzene-copolymeric resin (XAD-2) in air sampling necessitates a quantitative understanding of its sorption characteristics for organic chemicals. Inverse Gas Chromatography (IGC) was used to measure the sorption of a diverse set of 52 organic chemicals to XAD-2 at temperatures between 40 °C and 100 °C and at relative humidities between 0 and 87%. Even though relative humidity has been shown to influence sorption to other sorbents, it did not significantly influence most chemicals' sorption to XAD-2, indicating that water does not form a strong physical barrier to sorption on XAD-2 at high relative humidity. The resin-air partition coefficients ( KXAD) determined by IGC and the enthalpies of sorption derived from them were regressed against solute descriptors to derive poly-parameter Linear Free Energy Relationships (ppLFERs) which allow the estimation of KXAD for chemicals which are not sufficiently volatile to be amenable to IGC and for temperatures outside the experimental range. KXAD values at 20 °C estimated for a set of 296 chemicals for which solute descriptors are available, including polychlorinated biphenyls, polycyclic aromatic hydrocarbons, and pesticides, indicate that for many of the substances commonly found in the atmosphere sorption is higher to XAD-2 than to poly-urethane foam, another popular air sampling sorbent.

  11. Microminiature gas chromatographic column

    NASA Technical Reports Server (NTRS)

    Donaldson, R. W., Jr.

    1972-01-01

    Techniques commonly used for fabrication of integrated circuits are utilized to produce long capillary tubes for microminiature chromatographs. Method involves bonding of flat silicon plate to top of spirally grooved silicon chip to close groove and form capillary column.

  12. Liquid chromatographic extraction medium

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1994-01-01

    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  13. Liquid chromatographic extraction medium

    DOEpatents

    Horwitz, E.P.; Dietz, M.L.

    1994-09-13

    A method and apparatus are disclosed for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water. 1 fig.

  14. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, F.T.

    Intermetallic compounds with the CaCu/sub 5/ type of crystal structure, particularly LaNiCo/sub 4/ and CaNi/sub 5/, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation column. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale multi-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen cn produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  15. Chromatographic hydrogen isotope separation

    DOEpatents

    Aldridge, Frederick T.

    1981-01-01

    Intermetallic compounds with the CaCu.sub.5 type of crystal structure, particularly LaNiCo.sub.4 and CaNi.sub.5, exhibit high separation factors and fast equilibrium times and therefore are useful for packing a chromatographic hydrogen isotope separation colum. The addition of an inert metal to dilute the hydride improves performance of the column. A large scale mutli-stage chromatographic separation process run as a secondary process off a hydrogen feedstream from an industrial plant which uses large volumes of hydrogen can produce large quantities of heavy water at an effective cost for use in heavy water reactors.

  16. Simultaneous spectrophotometric determination of trace amounts of uranium, thorium, and zirconium using the partial least squares method after their preconcentration by alpha-benzoin oxime modified Amberlite XAD-2000 resin.

    PubMed

    Ghasemi, Jahan B; Zolfonoun, E

    2010-01-15

    A new solid phase extraction method for separation and preconcentration of trace amounts of uranium, thorium, and zirconium in water samples is proposed. The procedure is based on the adsorption of U(VI), Th(IV) and Zr(IV) ions on a column of Amberlite XAD-2000 resin loaded with alpha-benzoin oxime prior to their simultaneous spectrophotometric determination with Arsenazo III using orthogonal signal correction partial least squares method. The enrichment factor for preconcentration of uranium, thorium, and zirconium was found to be 100. The detection limits for U(VI), Th(IV) and Zr(IV) were 0.50, 0.54, and 0.48microgL(-1), respectively. The precision of the method, evaluated as the relative standard deviation obtained by analyzing a series of 10 replicates, was below 4% for all elements. The practical applicability of the developed sorbent was examined using synthetic seawater, natural waters and ceramic samples. PMID:20006073

  17. Beta2-agonist extraction procedures for chromatographic analysis.

    PubMed

    dos Ramos, F J

    2000-06-01

    Normally, different procedures were necessary to prepare sample matrices for chromatographic determination of beta2-agonists. The present review includes sampling, pre-treatment and extraction/purification for urine, plasma, liver, meat, feeds, hair and milk powder, as previous steps for chromatographic analysis of beta2-agonists. Six methodologies were especially revised for extraction/purification namely, liquid-liquid extraction, solid-phase extraction (SPE), matrix solid-phase dispersion, immunoaffinity chromatography, dialysis and supercritical fluid extraction. SPE was discussed in detail and five mechanisms were described: adsorption, apolar, polar, ion-exchange and mixed phase. A brief conclusion in this field was also outlined.

  18. A Simplified Method for Sampling and Analysis of High Volume Surface Water for Organic Contaminants Using XAD-2

    USGS Publications Warehouse

    Datta, S.; Do, L.V.; Young, T.M.

    2004-01-01

    A simple compressed-gas driven system for field processing and extracting water for subsequent analyses of hydrophobic organic compounds is presented. The pumping device is a pneumatically driven pump and filtration system that can easily clarify at 4L/min. The extraction device uses compressed gas to drive filtered water through two parallel XAD-2 resin columns, at about 200 mL/min. No batteries or inverters are required for water collection or processing. Solvent extractions were performed directly in the XAD-2 glass columns. Final extracts are cleaned-up on Florisil cartridges without fractionation and contaminants analyzed by GC-MS. Method detection limits (MDLs) and recoveries for dissolved organic contaminants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides are reported along with results of surface water analysis for the San Francisco Bay, CA.

  19. Application of XAD-resin based passive air samplers to assess local (roadside) and regional patterns of persistent organic pollutants.

    PubMed

    Barthel, Paul; Thuens, Sabine; Shunthirasingham, Chubashini; Westgate, John N; Wania, Frank; Radke, Michael

    2012-07-01

    We used XAD-resin based passive air samplers (PAS) to measure atmospheric levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) at five ombrotrophic bogs in Eastern Canada. The aims of our study were to investigate the influence of local roads on contaminant levels in the bogs, to derive the regional pattern of atmospheric concentrations, and to assess the uncertainties of the method. Expanded uncertainties based on the duplicate PAS deployed at 24 sites were good for the PAHs, while the deployment period of approx. 100 days was too short to yield acceptable uncertainties for PCBs. The regional PAH distribution was in good agreement with the calculated source proximity of the sampled bogs. We conclude that XAD-resin based PAS deployed for comparatively short periods are well suited for measuring atmospheric concentrations of volatile PAHs, while in remote regions longer deployment is necessary for less volatile PAHs and for PCBs. PMID:22516712

  20. Comparison of the mutagenic activity of XAD4 and blue rayon extracts of surface water and related drinking water samples.

    PubMed

    Kummrow, Fábio; Rech, Celia M; Coimbrão, Carlos A; Roubicek, Deborah A; Umbuzeiro, Gisela de A

    2003-11-10

    The combination of mutagenicity tests and selective extraction methodologies can be useful to indicate the possible classes of genotoxic organic contaminants in water samples. Treated and source water samples from two sites were analyzed: a river under the influence of an azo dye-processing plant discharge and a reservoir not directly impacted with industrial discharges, but contaminated with untreated domestic sewage. Organic extraction was performed in columns packed with XAD4 resin, that adsorbs a broad class of mutagenic compounds like polycyclic aromatic hydrocarbons (PAHs), arylamines, nitrocompounds, quinolines, antraquinones, etc., including the halogenated disinfection by-products; and with blue rayon that selectively adsorbs polycyclic planar structures. The organic extracts were tested for mutagenicity with the Salmonella assay using TA98 and TA100 strains and the potencies were compared. A protocol for cleaning the blue rayon fibers was developed and the efficiency of the reused fibers was analyzed with spiked samples. For the river water samples under the influence of the azo-type dye-processing plant, the mutagenicity was much higher for both blue rayon and XAD4 extracts when compared to the water from the reservoir not directly impacted with industrial discharges. For the drinking water samples, although both sites showed mutagenic responses with XAD4, only samples from the site under the influence of the industrial discharge showed mutagenic activity with the blue rayon extraction, suggesting the presence of polycyclic compounds in those samples. As expected, negative results were found with the blue rayon extracts of the drinking water collected from the reservoir not contaminated with industrial discharges. In this case, it appears that using the blue rayon to extract drinking water samples and comparing the results with the XAD resin extracts we were able to distinguish the mutagenicity caused by industrial contaminants from the halogenated

  1. Regulation of isoflavone production in hydroponically grown Pueraria montana (kudzu) by cork pieces, XAD-4, and methyl jasmonate.

    PubMed

    Kirakosyan, Ara; Kaufman, Peter B; Chang, Soo Chul; Warber, Sara; Bolling, Steven; Vardapetyan, Hrachik

    2006-12-01

    A mini-hydroponic growing system was employed for seedlings of kudzu vine (Pueraria montana) and contents of isoflavones (daidzein, genistein, daidzin, genistin, and puerarin) from shoot and root parts of seedlings were analyzed quantitatively. In addition, exogenous cork pieces, polymeric adsorbent, XAD-4, and universal elicitor, methyl jasmonate (MeJA), were used to regulate the production of these isoflavones. It was shown that cork pieces up-regulate the production of daidzein and genistein up to seven- and eight-fold greater than the levels obtained for control roots. In contrast, levels of glucosyl conjugates, daidzin and genistin, decrease up to five- and eight-fold, respectively. Cork treatment also induces the excretion of the root isoflavone constituents into the growth medium. Minimal levels of isoflavones are absorbed by the cork pieces. XAD-4 stimulates the production of glucosyl conjugates, daidzin and genistin, in root parts about 1.5-fold greater than that obtained in control roots. These are the highest amounts of daidzin and genistin that are observed (5.101 and 6.759 mg g(-1) dry weight, respectively). In contrast to these two adsorbents, MeJA increases the accumulation of isoflavones in shoot rather than in root parts of seedlings, about three- to four-fold over control levels, with the exception of genistein. These studies reveal new observations on the regulation of isoflavone production in hydroponically grown Pueraria montana plants by two adsorbents (cork pieces and XAD-4) and MeJA elicitor. PMID:16841218

  2. Regulation of isoflavone production in hydroponically grown Pueraria montana (kudzu) by cork pieces, XAD-4, and methyl jasmonate.

    PubMed

    Kirakosyan, Ara; Kaufman, Peter B; Chang, Soo Chul; Warber, Sara; Bolling, Steven; Vardapetyan, Hrachik

    2006-12-01

    A mini-hydroponic growing system was employed for seedlings of kudzu vine (Pueraria montana) and contents of isoflavones (daidzein, genistein, daidzin, genistin, and puerarin) from shoot and root parts of seedlings were analyzed quantitatively. In addition, exogenous cork pieces, polymeric adsorbent, XAD-4, and universal elicitor, methyl jasmonate (MeJA), were used to regulate the production of these isoflavones. It was shown that cork pieces up-regulate the production of daidzein and genistein up to seven- and eight-fold greater than the levels obtained for control roots. In contrast, levels of glucosyl conjugates, daidzin and genistin, decrease up to five- and eight-fold, respectively. Cork treatment also induces the excretion of the root isoflavone constituents into the growth medium. Minimal levels of isoflavones are absorbed by the cork pieces. XAD-4 stimulates the production of glucosyl conjugates, daidzin and genistin, in root parts about 1.5-fold greater than that obtained in control roots. These are the highest amounts of daidzin and genistin that are observed (5.101 and 6.759 mg g(-1) dry weight, respectively). In contrast to these two adsorbents, MeJA increases the accumulation of isoflavones in shoot rather than in root parts of seedlings, about three- to four-fold over control levels, with the exception of genistein. These studies reveal new observations on the regulation of isoflavone production in hydroponically grown Pueraria montana plants by two adsorbents (cork pieces and XAD-4) and MeJA elicitor.

  3. Preconcentration of cobalt with N-(dithiocarboxy)sarcosine and amberlite xad-4 resin.

    PubMed

    Sakai, Y; Mori, N

    1986-02-01

    Cobalt reacts with N-(dithiocarboxy)sarcosine (DTCS) to form a 1:3 Co:DTCS complex which is so stable that after its formation no decomposition occurs even in 4M hydrochloric acid. The complex is sorbed on a column of Amberlite XAD-4 copolymer from an acidic solution and eluted with 10 ml of a 1:1:3 v v mixture of 1.0M ammonia solution (pH = 9), 0.1M EDTA and methanol. The absorbance of the eluted chelate is measured at 320 nm against water ( = 2.15 x 10(4) l.mole(-1).cm(-1)). The recovery of cobalt from 1 litre of tap-water or sea-water is quantitative. The effect of diverse ions can be eliminated by the addition of EDTA after chelation of the cobalt. The copper complex with DTCS is partly sorbed on the column because of its slow rate of decomposition by EDTA, but most of the copper chelate sorbed can be eluted with hydrochloric acid and any co-eluted with the cobalt chelate can be completely decomposed by heating the eluate. Cobalt enrichment factors of at least 100 are obtained, so the method is applicable to the determination of cobalt at the ng ml level.

  4. Chromatographic methods of fractionation.

    PubMed

    Friesen, A D

    1987-01-01

    Chromatography's functional versatility, separation efficiency, gentle non-denaturing separating process and ease of automation and scale-up make it attractive for industrial scale protein purification. The Winnipeg Rh Institute's new Plasma Fractionation facility is an example of the use of chromatography for the large scale purification of plasma protein fractions. The fractionation facility has a capacity to process 800 litres of plasma per batch into blood clotting factor VIII and IX, albumin and intravenous immune serum globulin (i.v. ISG). Albumin and i.v. ISG are purified using ion exchange columns of DEAE-Sepharose (230 litre size), DEAE-Biogel (150 litre size) and CM-Sepharose (150 litre size). The chromatographic process is automated using a Modicon 584 Programmable Logic Controller to regulate valves, pumps and sensors which control plasma flow during fractionation. The stainless steel tanks and piping are automatically cleaned-in-place. The high degree of automation and cleaning provides efficient operation and sanitary processing. Chromatographic methods (DEAE-Sepharose and metal chelation) are also being used at the pilot scale to purify the human blood products superoxide dismutase and hemoglobin from outdated red blood cells. Characterization of the protein fractions produced by chromatography has shown them to be of equal or higher quality than fractions produced by other techniques.

  5. Microminiature gas chromatograph

    DOEpatents

    Yu, Conrad M.

    1996-01-01

    A microminiature gas chromatograph (.mu.GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode.

  6. Microminiature gas chromatograph

    DOEpatents

    Yu, C.M.

    1996-12-10

    A microminiature gas chromatograph ({mu}GC) comprising a least one silicon wafer, a gas injector, a column, and a detector. The gas injector has a normally closed valve for introducing a mobile phase including a sample gas in a carrier gas. The valve is fully disposed in the silicon wafer(s). The column is a microcapillary in silicon crystal with a stationary phase and is mechanically connected to receive the mobile phase from the gas injector for the molecular separation of compounds in the sample gas. The detector is mechanically connected to the column for the analysis of the separated compounds of sample gas with electronic means, e.g., ion cell, field emitter and PIN diode. 7 figs.

  7. Comparisons of sorption of aquatic humic matter by DAX-8 and XAD-8 resins from solid-state (13)C NMR spectroscopy's point of view.

    PubMed

    Peuravuori, J; Ingman, P; Pihlaja, K; Koivikko, R

    2001-10-31

    Aquatic humic solutes were separated in parallel by the non-ionic macroporous DAX-8 and XAD-8 resins from four different fresh water sources. On average, the sorptive power of the DAX-8 resin does not differ systematically from that of the XAD-8 resin. The DAX-8 resin seems to have more precise column characteristics compared with the XAD-8 resin. There was no significant difference between the major elemental compositions of the parallel humic-solute bulks obtained by these two resins. According to the (13)C NMR spectroscopy the content and quality of aliphatic carbons, especially those representing terminal methyl groups or methylene carbons, were the most systematic and powerful discriminating factors between the humic extracts obtained by these two resins. Generally speaking the DAX-8 and XAD-8 resins seem to isolate humic-solute bulks almost equally, although the content of aliphatics is slightly greater for the former, producing mixtures with similar structural compositions for general purposes. The structural composition and quantity of the humic-solute mixture isolable with a weakly basic DEAE-cellulose anion exchange resin differs partially from any humic fraction obtained by non-ionic sorbing solids. The environmental impact was also visible on the quality of the structural fine-chemistry of the different humic isolates obtained both by the DAX-8 and XAD-8 resins. PMID:18968420

  8. A mass transfer model for the fixed-bed adsorption of ferulic acid onto a polymeric resin: axial dispersion and intraparticle diffusion.

    PubMed

    Davila-Guzman, Nancy E; Cerino-Córdova, Felipe J; Soto-Regalado, Eduardo; Loredo-Cancino, Margarita; Loredo-Medrano, José A; García-Reyes, Refugio B

    2016-08-01

    In this study, amberlite XAD-16 (XAD-16) bed column system was used to remove ferulic acid (FA) from aqueous solutions. Laboratory-scale column experiments were conducted in downflow fixed bed at initial FA concentration of 1 g/L, initial pH 3, and 25°C. The performance of the adsorbent bed under different flow rates (1.3-7.7 mL/min) was studied. The bed utilization efficiency was in the range of 64.64-72.21% at the studied flow rates. A mass transfer model considering both axial dispersion and intraparticle diffusion was developed to predict the breakthrough curves of FA adsorption on XAD-16. This model predicted the experimental data better than Bohart-Adams model and Thomas model, based on the low deviation between predicted and experimental data. The axial dispersion coefficient value varied from 6.45 × 10(-6) to 1.10 × 10(-6) m(2)/s at flow rate from 1.3 to 7.7 mL/min, whereas the intraparticle diffusion coefficient was 1.04 × 10(-10) m(2)/s, being this last resistance the rate-limiting step. In conclusion, axial dispersion and intraparticle diffusion phenomena play the major role in predicting the adsorption of FA onto XAD-16 in fixed-bed columns.

  9. Isolation of organic acids from large volumes of water by adsorption on macroporous resins

    USGS Publications Warehouse

    Aiken, George R.; Suffet, I.H.; Malaiyandi, Murugan

    1987-01-01

    Adsorption on synthetic macroporous resins, such as the Amberlite XAD series and Duolite A-7, is routinely used to isolate and concentrate organic acids from forge volumes of water. Samples as large as 24,500 L have been processed on site by using these resins. Two established extraction schemes using XAD-8 and Duolite A-7 resins are described. The choice of the appropriate resin and extraction scheme is dependent on the organic solutes of interest. The factors that affect resin performance, selectivity, and capacity for a particular solute are solution pH, resin surface area and pore size, and resin composition. The logistical problems of sample handling, filtration, and preservation are also discussed.

  10. Dual liquid and gas chromatograph system

    DOEpatents

    Gay, Don D.

    1985-01-01

    A chromatographic system that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a non-transparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extremely low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

  11. Dual liquid and gas chromatograph system

    DOEpatents

    Gay, D.D.

    A chromatographic system is described that utilizes one detection system for gas chromatographic and micro-liquid chromatographic determinations. The detection system is a direct-current, atmospheric-pressure, helium plasma emission spectrometer. The detector utilizes a nontransparent plasma source unit which contains the plasma region and two side-arms which receive effluents from the micro-liquid chromatograph and the gas chromatograph. The dual nature of this chromatographic system offers: (1) extreme flexibility in the samples to be examined; (2) extreme low sensitivity; (3) element selectivity; (4) long-term stability; (5) direct correlation of data from the liquid and gas samples; (6) simpler operation than with individual liquid and gas chromatographs, each with different detection systems; and (7) cheaper than a commercial liquid chromatograph and a gas chromatograph.

  12. Comparison of XAD with other dissolved lignin isolation techniques and a compilation of analytical improvements for the analysis of lignin in aquatic settings

    USGS Publications Warehouse

    Spencer, R.G.M.; Aiken, G.R.; Dyda, R.Y.; Butler, K.D.; Bergamaschi, B.A.; Hernes, P.J.

    2010-01-01

    This manuscript highlights numerous incremental improvements in dissolved lignin measurements over the nearly three decades since CuO oxidation of lignin phenols was first adapted for environmental samples. Intercomparison of the recovery efficiency of three common lignin phenol concentration and isolation techniques, namely XAD, C18 with both CH3OH (C18M) and CH3CN (C18A) used independently for priming and elution steps, and tangential flow filtration (TFF) for a range of aquatic samples including fresh, estuarine and marine waters, was undertaken. With freshwater samples XAD8-1, C18M and TFF were all observed to recover ca. 80-90% of the lignin phenols and showed no fractionation effects with respect to diagnostic lignin parameters. With estuarine and marine samples more lignin phenols were recovered with C18M and XAD8-1 than TFF because of the increased prevalence of low molecular weight lignin phenols in marine influenced samples. For marine systems, differences were also observed between diagnostic lignin parameters isolated via TFF vs. C18M and XAD8-1 as a result of the high molecular weight lignin phenols being less degraded than the bulk. Therefore, it is recommended for future studies of marine systems that only one technique is utilized for ease of intercomparison within studies. It is suggested that for studies solely aimed at recovering bulk dissolved lignin in marine environments that C18M and XAD8-1 appear to be more suitable than TFF as they recover more lignin. Our results highlight that, for freshwater samples, all three common lignin phenol concentration and isolation techniques are comparable to whole water concentrated by rotary evaporation (i.e. not isolated) but, that for marine systems, the choice of concentration and isolation techniques needs to be taken into consideration with respect to both lignin concentration and diagnostic parameters. Finally, as the study highlights XAD8-1 to be a suitable method for the isolation of dissolved lignin

  13. Solid phase extraction of gold(III) on Amberlite XAD-2000 prior to its flame atomic absorption spectrometric determination.

    PubMed

    Elci, Latif; Sahan, Derya; Basaran, Aydan; Soylak, Mustafa

    2007-09-01

    A solid phase extraction method for the determination of gold(III) at trace levels by flame atomic absorption spectrometer (FAAS) was developed. The method was based on retention of gold as chloro complexes through the Amberlite XAD-2000. The effect of some analytical parameters including hydrochloric acid concentration, sample volume, sample and eluent flow rates, eluent volume, eluent concentration and interfering ions on the recovery of gold(III) was investigated. The retention of gold(III) from 1.5 mol l(-1) HCl solution and the recovery of gold with 0.07 mol l(-1) NH3 solution were quantitative (>or=95%). The relative standard deviation (RSD) was calculated as 3.2% (n = 10). The detection limit for gold was 2 microg l(-1). The accuracy was checked with the determination of gold spiked an artificial seawater and a pure copper samples.

  14. Solid phase extraction of gold(III) on Amberlite XAD-2000 prior to its flame atomic absorption spectrometric determination.

    PubMed

    Elci, Latif; Sahan, Derya; Basaran, Aydan; Soylak, Mustafa

    2007-09-01

    A solid phase extraction method for the determination of gold(III) at trace levels by flame atomic absorption spectrometer (FAAS) was developed. The method was based on retention of gold as chloro complexes through the Amberlite XAD-2000. The effect of some analytical parameters including hydrochloric acid concentration, sample volume, sample and eluent flow rates, eluent volume, eluent concentration and interfering ions on the recovery of gold(III) was investigated. The retention of gold(III) from 1.5 mol l(-1) HCl solution and the recovery of gold with 0.07 mol l(-1) NH3 solution were quantitative (>or=95%). The relative standard deviation (RSD) was calculated as 3.2% (n = 10). The detection limit for gold was 2 microg l(-1). The accuracy was checked with the determination of gold spiked an artificial seawater and a pure copper samples. PMID:17180414

  15. Monitoring of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere of southern Luxembourg using XAD-2 resin-based passive samplers.

    PubMed

    Schummer, Claude; Appenzeller, Brice M; Millet, Maurice

    2014-02-01

    XAD-2 resin-based passive samplers (PAS) with dimensions adapted to 100 mL accelerated solvent extraction cells were used to study the temporal and spatial variations of 17 PAHs on five sites in the atmosphere of southern Luxembourg. This new design allowed extracting the PAS without emptying the resin from the shelter. PAH analyses were done with gas chromatography-tandem mass spectrometry. PAS were deployed for 1 year with varying sampling periodicities, and 16 PAHs were detected with concentrations ranging from 1 ng/PAS for chrysene to 9,727 ng/PAS for naphthalene. The PAS were found adapted to the monitoring of temporal and spatial variations for lightweight PAHs (up to four aromatic rings) though not for heavy PAHs with five aromatic rings or more, as these compounds are preferably in the particle phase of the atmosphere and the amount of these PAHs trapped on the PAS will be too low.

  16. Reproductive responses of male fathead minnows exposed to wastewater treatment plant effluent, effluent treated with XAD8 resin, and an environmentally relevant mixture of alkylphenol compounds

    USGS Publications Warehouse

    Barber, L.B.; Lee, K.E.; Swackhamer, D.L.; Schoenfuss, H.L.

    2007-01-01

    On-site, continuous-flow experiments were conducted during August and October 2002 at a major metropolitan wastewater treatment plant (WWTP) to determine if effluent exposure induced endocrine disruption as manifested in the reproductive competence of sexually mature male fathead minnows (Pimephales promelas). The fathead minnows were exposed in parallel experiments to WWTP effluent and WWTP effluent treated with XAD8 macroreticular resin to remove the hydrophobic-neutral fraction which contained steroidal hormones, alkylphenolethoxylates (APEs), and other potential endocrine disrupting compounds (EDCs). The effluent composition varied on a temporal scale and the continuous-flow experiments captured the range of chemical variability that occurred during normal WWTP operations. Exposure to WWTP effluent resulted in vitellogenin induction in male fathead minnows, with greater response in October than in August. Concentrations of ammonia, APEs, 17??-estradiol, and other EDCs also were greater in October than in August, reflecting a change in effluent composition. In the October experiment, XAD8 treatment significantly reduced vitellogenin induction in the male fathead minnows relative to the untreated effluent, whereas in August, XAD8 treatment had little effect. During both experiments, XAD8 treatment removed greater than 90% of the APEs. Exposure of fish to a mixture of APEs similar in composition and concentration to the WWTP effluent, but prepared in groundwater and conducted at a separate facility, elicited vitellogenin induction during both experiments. There was a positive relation between vitellogenin induction and hepatosomatic index (HSI), but not gonadosomatic index (GSI), secondary sexual characteristics index (SSCI), or reproductive competency. In contrast to expectations, the GSI and SSCI increased in males exposed to WWTP effluent compared to groundwater controls. The GSI, SSCI, and reproductive competency were positively affected by XAD8 treatment of

  17. Chemical characterization of the ambient organic aerosol soluble in water: 1. Isolation of hydrophobic and hydrophilic fractions with a XAD-8 resin

    NASA Astrophysics Data System (ADS)

    Sullivan, Amy P.; Weber, Rodney J.

    2006-03-01

    Group separation of the aqueous extract of fine particles bearing water-soluble organic carbon (WSOC) provides unique insights into the sources of organic carbon (OC). XAD-8 resin coupled with a Total Organic Carbon analyzer allows for direct quantification. We term the fraction of WSOC not retained by a XAD-8 resin column at pH 2 as hydrophilic WSOC (WSOCxp); this includes saccharides, amines, and carbonyls and aliphatic monocarboxylic/dicarboxylic/oxocarboxylic acids with less than 4 or 5 carbons. The fraction of WSOC retained by XAD-8, termed the hydrophobic fraction (WSOCxr), include aromatic acids, phenols, organic nitrates, cyclic acids, and carbonyls and monocarboxylic/dicarboxylic acids with greater than 3 or 4 carbons. However, only aromatic compounds (or aromatic-like compounds with similar properties) can subsequently be extracted from XAD-8 with high efficiency. By coupling a Particle-into-Liquid Sampler with this technique, online measurements of WSOC, WSOCxp, and WSOCxr are possible. Urban measurements from St. Louis and Atlanta, on a carbon mass basis, show an increase in the mean WSOC fraction from winter (51%) to summer (61%), due to increases in the WSOCxp/OC from 0.25 to 0.35. During a summer Atlanta PM event, WSOC to OC was 0.75, driven largely by increases in the WSOCxp. The results are consistent with the view that in the summer, there are increased amounts of oxygenated polar compounds, possibly from secondary organic aerosol production, and that these compounds account for an even larger fraction of OC during stagnation events. A companion paper describes a method to further group speciate these XAD-8 isolated fractions.

  18. Reproductive responses of male fathead minnows exposed to wastewater treatment plant effluent, effluent treated with XAD8 resin, and an environmentally relevant mixture of alkylphenol compounds.

    PubMed

    Barber, Larry B; Lee, Kathy E; Swackhamer, Deborah L; Schoenfuss, Heiko L

    2007-04-20

    On-site, continuous-flow experiments were conducted during August and October 2002 at a major metropolitan wastewater treatment plant (WWTP) to determine if effluent exposure induced endocrine disruption as manifested in the reproductive competence of sexually mature male fathead minnows (Pimephales promelas). The fathead minnows were exposed in parallel experiments to WWTP effluent and WWTP effluent treated with XAD8 macroreticular resin to remove the hydrophobic-neutral fraction which contained steroidal hormones, alkylphenolethoxylates (APEs), and other potential endocrine disrupting compounds (EDCs). The effluent composition varied on a temporal scale and the continuous-flow experiments captured the range of chemical variability that occurred during normal WWTP operations. Exposure to WWTP effluent resulted in vitellogenin induction in male fathead minnows, with greater response in October than in August. Concentrations of ammonia, APEs, 17beta-estradiol, and other EDCs also were greater in October than in August, reflecting a change in effluent composition. In the October experiment, XAD8 treatment significantly reduced vitellogenin induction in the male fathead minnows relative to the untreated effluent, whereas in August, XAD8 treatment had little effect. During both experiments, XAD8 treatment removed greater than 90% of the APEs. Exposure of fish to a mixture of APEs similar in composition and concentration to the WWTP effluent, but prepared in groundwater and conducted at a separate facility, elicited vitellogenin induction during both experiments. There was a positive relation between vitellogenin induction and hepatosomatic index (HSI), but not gonadosomatic index (GSI), secondary sexual characteristics index (SSCI), or reproductive competency. In contrast to expectations, the GSI and SSCI increased in males exposed to WWTP effluent compared to groundwater controls. The GSI, SSCI, and reproductive competency were positively affected by XAD8 treatment of

  19. Purification of olive mill wastewater phenols through membrane filtration and resin adsorption/desorption.

    PubMed

    Zagklis, Dimitris P; Vavouraki, Aikaterini I; Kornaros, Michael E; Paraskeva, Christakis A

    2015-03-21

    Olive tree cultivation has a long history in the Mediterranean countries, and even today consists an important cultural, economic, and environmental aspect of the area. The production of olive oil through 3-phase extraction systems, leads to the co-production of large quantities of olive mill wastewater (OMW), with toxic compounds that inhibit its biodegradation. Membrane filtration has been used for the exploitation of this byproduct, through the isolation of valuable phenolic compounds. In the current work, a fraction of the waste occurring from a membrane process was used. More specifically the reverse osmosis concentrate, after a nanofiltration, containing the low-molecular-weight compounds, was further treated with resin adsorption/desorption. The non ionic XAD4, XAD16, and XAD7HP resins were implemented, for the recovery of phenols and their separation from carbohydrates. The recovered phenolic compounds were concentrated through vacuum evaporation reaching a final concentration of 378 g/L in gallic acid equivalents containing 84.8 g/L hydroxytyrosol.

  20. Purification of olive mill wastewater phenols through membrane filtration and resin adsorption/desorption.

    PubMed

    Zagklis, Dimitris P; Vavouraki, Aikaterini I; Kornaros, Michael E; Paraskeva, Christakis A

    2015-03-21

    Olive tree cultivation has a long history in the Mediterranean countries, and even today consists an important cultural, economic, and environmental aspect of the area. The production of olive oil through 3-phase extraction systems, leads to the co-production of large quantities of olive mill wastewater (OMW), with toxic compounds that inhibit its biodegradation. Membrane filtration has been used for the exploitation of this byproduct, through the isolation of valuable phenolic compounds. In the current work, a fraction of the waste occurring from a membrane process was used. More specifically the reverse osmosis concentrate, after a nanofiltration, containing the low-molecular-weight compounds, was further treated with resin adsorption/desorption. The non ionic XAD4, XAD16, and XAD7HP resins were implemented, for the recovery of phenols and their separation from carbohydrates. The recovered phenolic compounds were concentrated through vacuum evaporation reaching a final concentration of 378 g/L in gallic acid equivalents containing 84.8 g/L hydroxytyrosol. PMID:25497019

  1. Ask the experts: chromatographic baselines.

    PubMed

    Smith, Graeme; James, Christopher A; Scott, Rebecca; Woolf, Eric

    2014-05-01

    Bioanalysis invited a selection of leading researchers to express their views on chromatographic baseline assignment in the bioanalytical laboratory. The topics discussed include the challenges presented with ensuring automated baseline assignment is correct, when reintegration is necessary, regulation and consistency in terminology. Their enlightening responses provide a valuable insight into developing an industry consensus towards reintegration. An accompanying commentary article in this issue, authored by Howard Hill and colleagues (Huntingdon Life Sciences), provides background to this much debated topic.

  2. Characterization of methacrylate chromatographic monoliths bearing affinity ligands.

    PubMed

    Černigoj, Urh; Vidic, Urška; Nemec, Blaž; Gašperšič, Jernej; Vidič, Jana; Lendero Krajnc, Nika; Štrancar, Aleš; Podgornik, Aleš

    2016-09-16

    We investigated effect of immobilization procedure and monolith structure on chromatographic performance of methacrylate monoliths bearing affinity ligands. Monoliths of different pore size and various affinity ligands were prepared and characterized using physical and chromatographic methods. When testing protein A monoliths with different protein A ligand densities, a significant nonlinear effect of ligand density on dynamic binding capacity (DBC) for IgG was obtained and accurately described by Langmuir isotherm curve enabling estimation of protein A utilization as a function of ligand density. Maximal IgG binding capacity was found to be at least 12mg/mL exceeding theoretical monolayer adsorption value of 7.8mg/mL assuming hexagonal packing and IgG hydrodynamic diameter of 11nm. Observed discrepancy was explained by shrinkage of IgG during adsorption on protein A experimentally determined through calculated adsorbed IgG layer thickness of 5.4nm from pressure drop data. For monoliths with different pore size maximal immobilized densities of protein A as well as IgG dynamic capacity linearly correlates with monolith surface area indicating constant ligand utilization. Finally, IgGs toward different plasma proteins were immobilized via the hydrazide coupling chemistry to provide oriented immobilization. DBC was found to be flow independent and was increasing with the size of bound protein. Despite DBC was lower than IgG capacity to immobilized protein A, ligand utilization was higher. PMID:27554023

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

    PubMed

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

    2014-10-01

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

  4. Vibrational Spectroscopy of Chromatographic Interfaces

    SciTech Connect

    Jeanne E. Pemberton

    2011-03-10

    Chromatographic separations play a central role in DOE-supported fundamental research related to energy, biological systems, the environment, and nuclear science. The overall portfolio of research activities in the Separations and Analysis Program within the DOE Office of Basic Energy Sciences includes support for activities designed to develop a molecular-level understanding of the chemical processes that underlie separations for both large-scale and analytical-scale purposes. The research effort funded by this grant award was a continuation of DOE-supported research to develop vibrational spectroscopic methods to characterize the interfacial details of separations processes at a molecular level.

  5. Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst.

    PubMed

    Oh, Jungmin; Sreedhar, Balamurali; Donaldson, Megan E; Frank, Timothy C; Schultz, Alfred K; Bommarius, Andreas S; Kawajiri, Yoshiaki

    2016-09-30

    Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested.

  6. Transesterification of propylene glycol methyl ether in chromatographic reactors using anion exchange resin as a catalyst.

    PubMed

    Oh, Jungmin; Sreedhar, Balamurali; Donaldson, Megan E; Frank, Timothy C; Schultz, Alfred K; Bommarius, Andreas S; Kawajiri, Yoshiaki

    2016-09-30

    Reactive chromatography using an anion exchange resin is proposed for a transesterification reaction of propylene glycol methyl ether (DOWANOL™ PM) with ethyl acetate to produce propylene glycol methyl ether acetate (DOWANOL™ PMA). This reaction is studied in batch and chromatographic reactors catalyzed by an anion exchange resin. Several anion exchange resins are tested and compared based on the performance of resin as an adsorbent and a catalyst. A chromatographic column is packed with a selected catalyst, AMBERLITE™ IRA904, and both reaction and chromatographic elution are studied at different temperatures and feed concentrations. The resulting chromatograms are fitted to a mathematical model to obtain adsorption equilibrium and reaction kinetic parameters by the inverse method. Compared to esterification investigated in a previous study, transesterification has advantages such as a higher conversion at lower temperature and easy removal of the byproduct which may lead to higher productivity. Deactivation of anion exchange resins is observed and potential solutions are suggested. PMID:27623064

  7. Polymer adsorption

    NASA Astrophysics Data System (ADS)

    Joanny, Jean-Francois

    2008-03-01

    The aim of this talk is to review Pierre-Gilles deGennes' work on polymer adsorption and the impact that it has now in our understanding of this problem. We will first present the self-consistent mean-field theory and its applications to adsorption and depletion. De Gennes most important contribution is probably the derivation of the self-similar power law density profile for adsorbed polymer layers that we will present next, emphasizing the differences between the tail sections and the loop sections of the adsorbed polymers. We will then discuss the kinetics of polymer adsorption and the penetration of a new polymer chain in an adsobed layer that DeGennes described very elegantly in analogy with a quantum tunneling problem. Finally, we will discuss the role of polymer adsorption for colloid stabilization.

  8. Solid phase extraction of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions with 1-(2-thiazolylazo)-2-naphthol loaded Amberlite XAD-1180.

    PubMed

    Tokalioğlu, Serife; Yilmaz, Vedat; Kartal, Senol

    2009-05-01

    A new method for separation and preconcentration of trace amounts of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) ions in various matrices was proposed. The method is based on the adsorption and chelation of the metal ions on a column containing Amberlite XAD-1180 resin impregnated with 1-(2-thiazolylazo)-2-naphthol (TAN) reagent prior to their determination by flame atomic absorption spectrometry (FAAS). The effect of pH, type, concentration and volume of eluent, sample volume, flow rates of sample and elution solutions, and interfering ions have been investigated. The optimum pH for simultaneous retention of all the metal ions was 9. Eluent for quantitative elution was 20 ml of 2 mol l(-1) HNO(3). The optimum sample and eluent flow rates were found as 4 ml min(-1), and also sample volume was 500 ml, except for Mn (87% recovery). The sorption capacity of the resin was found to be 0.77, 0.41, 0.57, and 0.30 mg g(-1) for Cu(II), Ni(II), Cd(II), and Mn(II), respectively. The preconcentration factor of the method was 200 for Cu(II), 150 for Pb(II), 100 for Cd(II) and Ni(II), and 50 for Mn(II). The recovery values for all of the metal ions were > or = 95% and relative standard deviations (RSDs) were < or = 5.1%. The detection limit values were in the range of 0.03 and 1.19 microg l(-1). The accuracy of the method was confirmed by analysing the certified reference materials (TMDA 54.4 fortified lake water and GBW 07605 tea samples) and the recovery studies. This procedure was applied to the determination of Cu(II), Ni(II), Pb(II), Cd(II) and Mn(II) in waste water and lake water samples.

  9. PROBING REACTIVITY OF DISSOLVED ORGANIC MATTER FOR DISINFECTION BY-PRODUCT FORMATION USING XAD-8 RESIN ADSORPTION AND ULTRAFILTRATION FRACTIONATION. (R828045)

    EPA Science Inventory

    The disinfection by-product (DBP) reactivity (yield and speciation upon reaction with chlorine) of dissolved organic matter (DOM) isolated from two surface waters was investigated. The source waters, each having significantly different specific ultraviolet absorbance (SUVA

  10. BROAD SPECTRUM ANALYSIS FOR TRACE ORGANIC POLLUTANTS IN LARGE VOLUMES OF WATER BY XAD RESINS-COLUMN DESIGN-FACTS AND MYTHS.

    USGS Publications Warehouse

    Gibs, J.; Wicklund, A.; Suffet, I.H.

    1986-01-01

    The 'rule of thumb' that large volumes of water can be sampled for trace organic pollutants by XAD resin columns which are designed by small column laboratory studies or pure compounds is examined and shown to be a problem. A theory of multicomponent breakthrough is presented as a frame of reference to help solve the problem and develop useable criteria to aid the design of resin columns. An important part of the theory is the effect of humic substances on the breakthrough character of multicomponent chemical systems.

  11. Experimental adsorption isotherms based on inverse gas chromatography.

    PubMed

    Kalogirou, E; Bassiotis, I; Artemiadi, Th; Margariti, S; Siokos, V; Roubani-Kalantzopoulou, F

    2002-09-01

    A new chromatographic perturbation method is used for studying the adsorption-desorption equilibrium in various gas-solid heterogeneous systems. It is the reversed-flow method giving accurate and precise values of many physicochemical constants including the basic and necessary adsorption isotherm values. For four inorganic oxides, namely, Cr2O3, Fe2O3, TiO2 and PbO, and two aromatic hydrocarbons (benzene, toluene) these adsorption isotherms have been determined through a non-linear model. PMID:12385379

  12. An open tubular ion chromatograph.

    PubMed

    Yang, Bingcheng; Zhang, Min; Kanyanee, Tinakorn; Stamos, Brian N; Dasgupta, Purnendu K

    2014-12-01

    We describe an open tubular ion chromatograph (OTIC) that uses anion exchange latex coated 5 μm radius silica and 9.8 μm radius poly(methyl methacrylate) tubes and automated time/pressure based hydrodynamic injection for pL-nL scale injections. It is routinely possible to generate 50,000 plates or more (up to 150,000 plates/m, columns between 0.3 and 0.8 m have been used), and as such, fast separations are possible, comparable to or in some cases better than the current practice of IC. With an optimized admittance detector, nonsuppressed detection permits LODs of submicromolar to double digit micromolar for a variety of analytes. However, large volume injections are possible and can significantly improve on this. A variety of eluents, the use of organic modifiers, and variations of eluent pH can be used to tailor a given separation. The approach is discussed in the context of extraterrestrial exploration, especially Mars, where the existence of large amounts of perchlorate in the soil needs to be confirmed. These columns can survive drying and freezing, and small footprint, low power consumption, and simplicity make OTIC a good candidate for such a mission. PMID:25394230

  13. A Quantitative Gas Chromatographic Ethanol Determination.

    ERIC Educational Resources Information Center

    Leary, James J.

    1983-01-01

    Describes a gas chromatographic experiment for the quantitative determination of volume percent ethanol in water ethanol solutions. Background information, procedures, and typical results are included. Accuracy and precision of results are both on the order of two percent. (JN)

  14. Gas Chromatographic Determination of Enrivonmentally Significant Pesticides.

    ERIC Educational Resources Information Center

    Rudzinski, Walter E.; Beu, Steve

    1982-01-01

    A chromatographic procedure for analyzing organophosphorus pesticides (such as PCB's, nitrosamines, and phthalate esters) in orange juice is described, including a summary of the method, instrumentation, methodology, results/discussion, and calculations. (JN)

  15. A Versatile, Automatic Chromatographic Column Packing Device

    ERIC Educational Resources Information Center

    Barry, Eugene F.; And Others

    1977-01-01

    Describes an inexpensive apparatus for packing liquid and gas chromatographic columns of high efficiency. Consists of stainless steel support struts, an Automat Getriebmotor, and an associated three-pulley system capable of 10, 30, and 300 rpm. (MLH)

  16. Determination of trace heavy metals in soil and sediments by atomic spectrometry following preconcentration with Schiff bases on Amberlite XAD-4.

    PubMed

    Kara, Derya; Fisher, Andrew; Hill, Steve J

    2009-06-15

    A matrix separation and analyte preconcentration system using Amberlite XAD copolymer resins functionalized by Schiff base reactions coupled with atomic spectrometry has been developed. Three different functionalized Amberlite XAD resins were synthesized using 4-phenylthiosemicarbazide, 2,3-dihydroxybenzaldehyde and 2-thiophenecarboxaldehyde as reagents. These resins could be used to preconcentrate transition and other trace heavy metal analytes from nitric acid digests of soil and sediment samples. Analyte retention was shown to work well at pH 6.0. After treatment of the digests with sodium fluoride and buffering to pH 6, samples that contain extremely large concentrations of iron were analysed for trace analytes without the excess iron overloading the capacity of the resin. The analytes Cd, Co, Cu, Ni and Pb were preconcentrated from acid extracts of certified soil/sediment samples and then eluted with 0.1M HNO(3) directly to the detection system. Flame atomic absorption spectrometry was used as a means of detection during the studies. The efficiency of the chelating resin and the accuracy of the proposed method were evaluated by the analysis of soil (SO-2) and sediment (LGC 6157 and MESS-3) certified reference materials.

  17. Quantifying temperature and flow rate effects on the performance of a fixed-bed chromatographic reactor.

    PubMed

    Vu, Tien D; Seidel-Morgenstern, A

    2011-11-01

    Chromatographic reactors are based on coupling chemical reactions with chromatographic separation in fixed-beds. Temperature and flow rate are important parameters for the performance of such reactors. Temperature affects mainly adsorption, chemical equilibria, mass transfer and reaction kinetics, whereas flow rate influences residence time and dispersion. In order to evaluate the mentioned effects, the hydrolysis reactions of methyl formate (MF) and methyl acetate (MA) were chosen as case studies. These reactions were performed experimentally in a lab-scale fixed-bed chromatographic reactor packed with a strong acidic ion exchange resin. The chosen reactions can be considered to represent a relative fast (MF) and a relative slow (MA) reaction. The processes which take place inside the reactor were described and simulated using an isothermal equilibrium dispersive model. The essential model parameters were determined experimentally at different temperatures and flow rates. The performance of the chromatographic reactor was evaluated at several discrete constant temperature levels by quantifying product purity, productivity and yield. The work provides insight regarding the influence of temperature and flow rate on values of the model parameters and the performance criteria.

  18. Portable gas chromatograph-mass spectrometer

    DOEpatents

    Andresen, Brian D.; Eckels, Joel D.; Kimmons, James F.; Myers, David W.

    1996-01-01

    A gas chromatograph-mass spectrometer (GC-MS) for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units.

  19. Portable gas chromatograph-mass spectrometer

    DOEpatents

    Andresen, B.D.; Eckels, J.D.; Kimmons, J.F.; Myers, D.W.

    1996-06-11

    A gas chromatograph-mass spectrometer (GC-MS) is described for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units. 4 figs.

  20. Portable gas chromatograph-mass spectrometer

    SciTech Connect

    Andresen, B.D.; Eckels, J.D.; Kimmins, J.F.; Myers, D.W.

    1994-12-31

    A gas chromatograph-mass spectrometer (GC-MS) for use as a field portable organic chemical analysis instrument. The GC-MS is designed to be contained in a standard size suitcase, weighs less than 70 pounds, and requires less than 600 watts of electrical power at peak power (all systems on). The GC-MS includes: a conduction heated, forced air cooled small bore capillary gas chromatograph, a small injector assembly, a self-contained ion/sorption pump vacuum system, a hydrogen supply, a dual computer system used to control the hardware and acquire spectrum data, and operational software used to control the pumping system and the gas chromatograph. This instrument incorporates a modified commercial quadrupole mass spectrometer to achieve the instrument sensitivity and mass resolution characteristic of laboratory bench top units.

  1. Ion chromatographic determination of sulfur in fuels

    NASA Technical Reports Server (NTRS)

    Mizisin, C. S.; Kuivinen, D. E.; Otterson, D. A.

    1978-01-01

    The sulfur content of fuels was determined using an ion chromatograph to measure the sulfate produced by a modified Parr bomb oxidation. Standard Reference Materials from the National Bureau of Standards, of approximately 0.2 + or - 0.004% sulfur, were analyzed resulting in a standard deviation no greater than 0.008. The ion chromatographic method can be applied to conventional fuels as well as shale-oil derived fuels. Other acid forming elements, such as fluorine, chlorine and nitrogen could be determined at the same time, provided that these elements have reached a suitable ionic state during the oxidation of the fuel.

  2. Comparison of polyurethane foam and XAD-2 sampling matrices to measure airborne organophosphorus pesticides and their oxygen analogs in an agricultural community

    PubMed Central

    Armstrong, Jenna L.; Fenske, Richard A.; Yost, Michael G.; Tchong-French, Maria; Yu, Jianbo

    2013-01-01

    Side-by-side active air sampling for the organophosphorus (OP) pesticide, chlorpyrifos (CPF) and its oxygen analog, chlorpyrifos-oxon (CPF-O) was conducted with two recommended air sampling matrices: OSHA Versatile Sampling (OVS) tubes with XAD-2 resin, polyurethane foam (PUF) tubes, and passive PUF deposition disks. The study compared the proportion of artificially transformed CPF-O in the laboratory and in the field during a tree fruit application in Washington State. Lab results demonstrated that the NIOSH-recommended OVS tubes artificially transformed up to 32% of CPF to CPF-O during the sampling process, whereas PUF tubes had little to no artificial transformation (≤ 0.1%). In the field, the proportion of CPF-O in the sample was significantly higher on OVS tubes than on PUF tubes (p < 0.001), confirming that OVS tubes were converting a significant portion of CPF to CPF-O. In addition, PUF tubes reported measurable levels CPF-O in the field even when no artificial transformation was expected. We conclude that the PUF matrix is the superior sampling medium for OP oxygen analogs when compared to XAD-2 resin. Community-located PUF tube samples 24 hours post-application had considerably higher levels CPF-O (16–21 ng/m3) than near field samples during application (2–14 ng/m3), suggesting that the oxygen analog is volatile and formed during atmospheric transport. It is recommended that worker and community risk assessments begin to take into consideration the presence of the more toxic oxygen analogs when measuring for OP pesticide mixtures. PMID:23466277

  3. Comparison of polyurethane foam and XAD-2 sampling matrices to measure airborne organophosphorus pesticides and their oxygen analogs in an agricultural community.

    PubMed

    Armstrong, Jenna L; Fenske, Richard A; Yost, Michael G; Tchong-French, Maria; Yu, Jianbo

    2013-07-01

    Side-by-side active air sampling for the organophosphorus (OP) pesticide, chlorpyrifos (CPF) and its oxygen analog, chlorpyrifos-oxon (CPF-O) was conducted with two recommended air sampling matrices: OSHA Versatile Sampling (OVS) tubes with XAD-2 resin, polyurethane foam (PUF) tubes, and passive PUF deposition disks. The study compared the proportion of artificially transformed CPF-O in the laboratory and in the field during a tree fruit application in Washington State. Lab results demonstrated that the NIOSH-recommended OVS tubes artificially transformed up to 32% of CPF to CPF-O during the sampling process, whereas PUF tubes had little to no artificial transformation (⩽0.1%). In the field, the proportion of CPF-O in the sample was significantly higher on OVS tubes than on PUF tubes (p<0.001), confirming that OVS tubes were converting a significant portion of CPF to CPF-O. In addition, PUF tubes reported measurable levels CPF-O in the field even when no artificial transformation was expected. We conclude that the PUF matrix is the superior sampling medium for OP oxygen analogs when compared to XAD-two resin. Community-located PUF tube samples 24h post-application had considerably higher levels CPF-O (16-21ngm(-3)) than near field samples during application (2-14ngm(-3)), suggesting that the oxygen analog is volatile and formed during atmospheric transport. It is recommended that worker and community risk assessments begin to take into consideration the presence of the more toxic oxygen analogs when measuring for OP pesticide mixtures. PMID:23466277

  4. Dispersion of Chemical Solutes in Chromatographs and Reactors

    NASA Astrophysics Data System (ADS)

    Balakotaiah, Vemuri; Chang, Hsueh-Chia

    1995-04-01

    coefficient is identical to the classical unreactive Taylor-Aris coefficient. Surface reaction of any speed yields the proper asymptotic behaviour in time because the species still needs to diffuse slowly to the conduit wall. In the limit of fast surface reaction, the Taylor-Aris dispersion coefficient is reduced by a factor of 4.2, 7.1 and 4.0 for pipe, plane Poiseuille and Couette flows, respectively, as the slow-moving solutes near the wall are depleted. For the case of a linear surface reaction, we use the invariant manifold theory to derive the effective transport equation to infinite order. We also show that the radius of convergence of the invariant manifold expansion is approximately three times that of the no reaction case. We demonstrate that if adsorption/desorption is as slow as transverse diffusion, an adsorption-induced dispersion, distinct from the Taylor-Aris shear dispersion, exists. While the total dispersion may increase because of the contribution of both, the Taylor-Aris component is reduced by a physical mechanism similar to surface reaction. The adsorption/desorption induced dispersion coefficient is shown to have a maximum when the adsorption equilibrium constant is exactly 2. Nonlinear Langmuir type adsorption at large concentration is shown to introduce a nonlinear drift term which causes non-Gaussian pulse responses with long tails. These tails are detrimental to separation chromatography since they cause overlaps which increase with the length of the chromatograph.

  5. 40 CFR 1065.267 - Gas chromatograph.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas...

  6. 40 CFR 1065.267 - Gas chromatograph.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Gas chromatograph. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon Measurements § 1065.267 Gas...

  7. Nano-fabricated size exclusion chromatograph

    NASA Technical Reports Server (NTRS)

    Svehla, D.; Feldman, S.; Feldman, J.; Grunthaner, F.; Shakkottai, P.; dle Castillo, L.; White, V.

    2002-01-01

    This poster describes the development of a nano-fabricated size exclusion chromatograph (nSEC) based on the principle that molecules traveling through a microcolumn containing nano-fabricated features will have characteristics elution times that directly correlate to molecular weight.

  8. Chromatographic methods in the study of autism.

    PubMed

    Żurawicz, Ewa; Kałużna-Czaplińska, Joanna; Rynkowski, Jacek

    2013-10-01

    Research into biomarkers of autism is a new means of medical intervention in this disease. Chromatographic techniques, especially coupled with mass spectrometry, are widely used in determination of biomarkers and assessment of effectiveness of autism therapy owing to their sensitivity and selectivity. Among the chromatographic techniques gas chromatography and liquid chromatography, especially high-performance liquid chromatography, have found application in clinical trials. The high-performance liquid chromatography technique allows an analysis of liquid samples with a wide range of molecules, small and large, providing an opportunity to perform advanced assays within a short time frame. Gas chromatography with the appropriate preparation of samples (gaseous and liquid) and a selection of analysis conditions enables the separation of thermally stable, volatile and non-volatile organic substances in short runtimes. The chromatographic techniques that are currently used in metabolic studies in autism are designed to identify abnormalities in three areas: the metabolism of neurotransmitters, nutritional and metabolic status and manifestations of oxidative stress. This review presents a necessary theoretical introduction and examples of applications of chromatographic studies of disorder markers in autism.

  9. Method for the chromatographic separation of cations from aqueous samples

    DOEpatents

    Horwitz, E. Philip; Chiarizia, Renato; Dietz, Mark L.

    1997-01-01

    An extraction chromatographic material for extracting metal cations from a iquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methanediphosphonic acid on an inert particulate support.

  10. Method for the chromatographic separation of cations from aqueous samples

    DOEpatents

    Horwitz, E.P.; Chiarizia, R.; Dietz, M.L.

    1997-07-29

    An extraction chromatographic material is described for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methanediphosphonic acid on an inert particulate support. 7 figs.

  11. Method for the chromatographic separation of cations from aqueous samples

    DOEpatents

    Horwitz, E.P.; Chiarizia, R.; Dietz, M.L.

    1998-12-22

    An extraction chromatographic material is described for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methane-diphosphonic acid on an inert particulate support. 7 figs.

  12. Method for the chromatographic separation of cations from aqueous samples

    DOEpatents

    Horwitz, E. Philip; Chiarizia, Renato; Dietz, Mark L.

    1998-12-22

    An extraction chromatographic material for extracting metal cations from a liquid stream. The extraction chromatographic material is prepared by adsorbing a diesterified methanediphosphonic acid on an inert particulate support.

  13. Method to fabricate silicon chromatographic column comprising fluid ports

    DOEpatents

    Manginell, Ronald P.; Frye-Mason, Gregory C.; Heller, Edwin J.; Adkins, Douglas R.

    2004-03-02

    A new method for fabricating a silicon chromatographic column comprising through-substrate fluid ports has been developed. This new method enables the fabrication of multi-layer interconnected stacks of silicon chromatographic columns.

  14. Tadpole toxicity prediction using chromatographic systems.

    PubMed

    Fernández-Pumarega, Alejandro; Amézqueta, Susana; Fuguet, Elisabet; Rosés, Martí

    2015-10-30

    Toxicity has been emulated in tadpole species through chromatographic systems. The parameter studied to evaluate the non-specific toxicity of a compound is the narcosis concentration (Cnar), which is defined as the concentration needed for the immobilization of the organism. Because experimental investigation with animals is lengthy, costly, technically difficult, and ethically questionable, there is a great interest in developing surrogate physicochemical systems able to emulate biological systems to obtain the same information in a faster, more economic, and easier manner. In order to see which chromatographic systems would be able to emulate tadpole narcosis, both, tadpole narcosis data and data in several chromatographic and electrophoretic systems, were fitted to a linear solvation energy relationship (LSER) model. Thus, by comparison of the models it was possible to see which of the chromatographic systems were more similar to the biological one. The physicochemical systems that best emulate tadpole narcosis were an HPLC system based on an immobilized artificial membrane (IAM) column, and two micellar electrokinetic chromatography (MEKC) systems based on sodium taurocholate (STC) and a mixture of sodium dodecylsulphate (SDS) and Brij 35 as surfactants. A system based on a RP18 HPLC column also was selected for comparison because it is a common column in most analytical laboratories. To establish the models, a set of compounds with known Cnar values were analyzed in the chromatographic, and electrophoretic selected systems and, then, the retention factor (k) was correlated to the concentration of narcosis. Statistics showed that the system based on STC micelles was the best to emulate toxicity in tadpoles. The robustness and predictive ability of the developed models were validated.

  15. Emergency gas-chromatographic assay of phenobarbital and phenytoin and liquid-chromatographic assay of theophylline.

    PubMed

    Shihabi, Z K

    1978-09-01

    Phenobarbital and phenytoin are extracted and concentrated in a single step, without solvent evaporation, followed by on-column methylation and gas-chromatographic quanitation. A similar extraction step for the assay of theophylline by high-pressure liquid chromatography is described. The extraction step can be completed in less than 2 min, the chromatographic step in less than 8 min. This extraction method yields clean chromatograms, avoids evaporating health-hazardous solvents, and is applicable to other drugs.

  16. Micro-column plasma emission liquid chromatograph

    DOEpatents

    Gay, Don D.

    1984-01-01

    In a direct current plasma emission spectrometer for use in combination with a micro-column liquid chromatograph, an improved plasma source unit. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

  17. Flow in a metal hydride chromatographic column

    SciTech Connect

    Nichols, G.S.

    1990-01-01

    The flow of hydrogen isotopes in a metal hydride chromatographic column is calculated by a one-dimensional finite difference method. The Ergun equation is used to define the gas flow; and equilibrium pressure isotherms are used to define the column holdup. Solid phase loadings are shown to move as a wave front on absorption, but remain more uniform on desorption. 3 refs., 4 figs.

  18. The use of canisters/GC-MS and a portable gas chromatograph to characterize emissions from an air stripper

    SciTech Connect

    Figueroa, C.M.; Bennett, J.L.

    1994-12-31

    Demonstrating and maintaining removal efficiencies for various volatile organic compounds (VOCs) in an air stripper/carbon adsorption system would ideally be done through continuous real-time monitoring. However, especially for state funded cleanup operations, cost considerations and timeliness of decisions become the overriding factors. Method TO-14, consisting of whole air samples obtained in stainless steel canisters shipped for GC-MS analysis, is the conventional method to speciate and quantitate VOCs at the sub-parts per billion levels found in the carbon adsorption system outlet. Unfortunately, method TO-14 does not provide real time information, and can be expensive. This paper summarizes the results obtained from using both method TO-14 and a portable gas chromatograph with a photoionization detector to characterize emissions from an air-stripper/carbon adsorption system. Field experience indicates that a combination of both methods can achieved the desired results at a reasonable cost.

  19. Determinations of gas-liquid partition coefficients using capillary chromatographic columns. Alkanols in squalane.

    PubMed

    Tascon, Marcos; Romero, Lílian M; Acquaviva, Agustín; Keunchkarian, Sonia; Castells, Cecilia

    2013-06-14

    This study focused on an investigation into the experimental quantities inherent in the determination of partition coefficients from gas-liquid chromatographic measurements through the use of capillary columns. We prepared several squalane - (2,6,10,15,19,23-hexamethyltetracosane) - containing columns with very precisely known phase ratios and determined solute retention and hold-up times at 30, 40, 50 and 60°C. We calculated infinite dilution partition coefficients from the slopes of the linear regression of retention factors as a function of the reciprocal of the phase ratio by means of fundamental chromatographic equations. In order to minimize gas-solid and liquid-solid interface contributions to retention, the surface of the capillary inner wall was pretreated to guarantee a uniform coat of stationary phase. The validity of the proposed approach was first tested by estimating the partition coefficients of n-alkanes between n-pentane and n-nonane, for which compounds data from the literature were available. Then partition coefficients of sixteen aliphatic alcohols in squalane were determined at those four temperatures. We deliberately chose these highly challenging systems: alcohols in the reference paraffinic stationary phase. These solutes exhibited adsorption in the gas-liquid interface that contributed to retention. The corresponding adsorption constant values were estimated. We fully discuss here the uncertainties associated with each experimental measurement and how these fundamental determinations can be performed precisely by circumventing the main drawbacks. The proposed strategy is reliable and much simpler than the classical chromatographic method employing packed columns.

  20. Serum 25-hydroxyvitamin D assay. Evalution of chromatographic and non-chromatographic procedures.

    PubMed

    Skinner, R K; Wills, M R

    1977-11-01

    A competitive protein binding assay for serum 25-hydroxyvitamin D is described in which normal human serum is used as the source of binding protein. A serum sample is extracted with diethyl ether/methanol and then chromatographed using silica gel. Validation of the method is reported. Silica gel chromatography is compared with LH20 chromatography. The method is also compared with extraction techniques using diethyl ether and ethanol without subsequent chromatography. It is concluded that chromatography with either silica gel or LH20 is essential. The non-chromatographic methods investigated, in addition to giving much higher values than chromatographic methods, did not meet validation requirements with respect to accuracy and behaviour of samples on dilution.

  1. A model free method for estimation of complicated adsorption isotherms in liquid chromatography.

    PubMed

    Forssén, Patrik; Fornstedt, Torgny

    2015-08-28

    Here we show that even extremely small variations in the adsorption isotherm can have a tremendous effect on the shape of the overloaded elution profiles and that the earlier in the adsorption isotherms the variation take place, the larger its impact on the shape of the elution profile. These variations are so small that they can be "hidden" by the discretization and in the general experimental noise when using traditional experimental methods, such as frontal analysis, to measure adsorption isotherms. But as the effects of these variations are more clearly visible in the elution profiles, the Inverse Method (IM) of adsorption isotherm estimation is an option. However, IM usually requires that one selects an adsorption isotherm model prior to the estimation process. Here we show that even complicated models might not be able to estimate the adsorption isotherms with multiple inflection points that small variations might give rise to. We therefore developed a modified IM that, instead of fixed adsorption isotherm models, uses monotone piecewise interpolation. We first validated the method with synthetic data and showed that it can be used to estimate an adsorption isotherm, which accurately predicts an extremely "strange" elution profile. For this case it was impossible to estimate the adsorption isotherm using IM with a fixed adsorption model. Finally, we will give an example of a real chromatographic system where adsorption isotherm with inflection points is estimated by the modified IM.

  2. Fractionation of Natural Organic Matter Upon Adsorption to the Bacterium, Bacillus subtilis

    NASA Astrophysics Data System (ADS)

    Manecki, M.; Maurice, P. A.; Fein, J. B.

    2001-12-01

    High pressure size exclusion chromatography (HPSEC) was used to measure changes in molecular weight distribution and average molecular weight upon adsorption of fulvic acid onto Bacillus subtilis at pH 3-7. The FA was an XAD-8 extract from a stream in the New Jersey Pine Barrens (USA), and had a weight average molecular weight of 1890 Da. Adsorption of aqueous FA onto B.subtilis was relatively fast, with steady state attained within 2 hours. An adsorption isotherm at pH 4.5 revealed a strong affinity of FA for the B.subtilis surface. The maximum adsorption capacity of a 20g bacteria/L suspension was greater than 9 mg C/L of FA at pH 4.5. Adsorption of FA onto B.subtilis was strongly pH dependent, increasing markedly with decreasing pH over the pH range 3-7. Comparison of HPSEC analysis of control (FA not reacted with bacteria) versus reacted samples showed that in all experiments, the weight average molecular weight (Mw) of FA remaining in solution decreased by several hundred Da. The observed decrease in solution Mw upon adsorption indicated that the higher molecular weight FA components adsorbed preferentially to the bacterial surfaces, at all studied pH values (3-7). Additionally, there was a low molecular weight FA fraction that did not adsorb, even at low pH. Our results suggest that hydrophobic interactions may be important for FA sorption to B.subtilis and that low molecular weight, more hydrophilic components may thus be less likely to adsorb than higher molecular weight, more hydrophobic components.

  3. High pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, Christian G.; Sakaji, Richard H.

    1985-01-01

    A gradient mixer which effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum "band-broadening".

  4. High-pressure liquid chromatographic gradient mixer

    DOEpatents

    Daughton, C.G.; Sakaji, R.H.

    1982-09-08

    A gradient mixer effects the continuous mixing of any two miscible solvents without excessive decay or dispersion of the resultant isocratic effluent or of a linear or exponential gradient. The two solvents are fed under low or high pressure by means of two high performance liquid chromatographic pumps. The mixer comprises a series of ultra-low dead volume stainless steel tubes and low dead volume chambers. The two solvent streams impinge head-on at high fluxes. This initial nonhomogeneous mixture is then passed through a chamber packed with spirally-wound wires which cause turbulent mixing thereby homogenizing the mixture with minimum band-broadening.

  5. Hand-held multiple system gas chromatograph

    DOEpatents

    Yu, Conrad M.

    2001-01-01

    A multiple parallel hand-held gas chromatograph (GC) system which includes several independent GCs. Each independent GC has its own injector, separation column, detector and oven and the GCs are mounted in a light weight hand-held assembly. Each GC operates independently and simultaneously. Because of different coatings in different separation columns, different retention times for the same gas will be measured. Thus, for a GC system with multiple parallel GCs, the system can measure, in a short period, different retention times and provide a cross-reference in the determination of the measured gas and to become a two-dimensional system for direct field use.

  6. Packed multi-channels for parallel chromatographic separations in microchips.

    PubMed

    Nagy, Andrea; Gaspar, Attila

    2013-08-23

    Here we report on a simple method to fabricate microfluidic chip incorporating multi-channel systems packed by conventional chromatographic particles without the use of frits. The retaining effectivities of different bottlenecks created in the channels were studied. For the parallel multi-channel chromatographic separations several channel patterns were designed. The obtained multipackings were applied for parallel separations of dyes. The implementation of several chromatographic separation units in microscopic size makes possible faster and high throughput separations.

  7. Versatile gas/particle ion chromatograph.

    PubMed

    Ullah, S M Rahmat; Takeuchi, Masaki; Dasgupta, Purnendu K

    2006-02-01

    A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv.

  8. Versatile gas/particle ion chromatograph.

    PubMed

    Ullah, S M Rahmat; Takeuchi, Masaki; Dasgupta, Purnendu K

    2006-02-01

    A new, compact gas/particle ion chromatograph has been developed for measuring ionic constituents in PM2.5 (particulate matter of aerodynamic diameter < or = 2.5 microm) and water-soluble ionogenic gases. The instrument has separate sampling channels for gases and particles. In one, a membrane denuder collects soluble gases for preconcentration and analysis. In the other, a cyclone removes larger particles, a membrane denuder removes soluble gases, and a continuously wetted hydrophilic filter collects particles. A single, multiport, syringe pump handles liquid transport, and one conductivity detector measures anions and ammonium for both channels. Electrodialytically generated gradient hydroxide eluent permits 20 min chromatographic runs. Gas/particle samples are each collected for 40 min, butthe sampling intervals are staggered by 20 min. Liquid samples from the gas denuder and particle collector are aspirated and preconcentrated on sequential cation and anion concentrators and transferred respectively to an ammonia transfer device and an anion separation column. The flow configuration results in an ammonium peak before anion peaks in the chromatogram. The system measures ammonia, organic acids (such as acetic, formic, and oxalic acids), HCl, HONO, SO2, HNO3, and the corresponding ions in the aerosol phase. Low ng/m3 to sub-ng/m3 limits of detection (LODs) are attained for most common gases and particulate constituents, the LODs for gaseous SO2 to NH3 range, for example, from sub parts per trillion by volume (sub-pptv) to approximately 5 pptv. PMID:16509343

  9. Flame atomic absorption spectrometric (FAAS) determination of copper, iron and zinc in food samples after solid-phase extraction on Schiff base-modified duolite XAD 761.

    PubMed

    Ghaedi, M; Mortazavi, K; Montazerozohori, M; Shokrollahi, A; Soylak, M

    2013-05-01

    The present study involves the development of solid-phase extraction (SPE) procedure for the preconcentration of trace amounts of copper (Cu(2+)), iron (Fe(3+)) and zinc (Zn(2+)) ions on duolite XAD 761 modified by bis(2-hydroxyacetophenone)-2,2-dimethyl-1,3-propanediimine(BHAPDMPDI). The complexation between the metal ions and the proposed ligand was investigated potentiometrically. The metal ions retained on the sorbent were quantitatively determined via complexation with BHAPDMPDI. The complexed metal ions were efficiently eluted using 6 mL of 4 mol L(-1) nitric acid in acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ions were optimized. Using the optimized parameters, the linear response of the SPE method for Cu(2+), Zn(2+) and Fe(3+) ions were in the ranges of 0.01-0.34, 0.01-0.28 and 0.02-0.31 μg mL(-1), respectively, and the detection limits for Cu(2+), Zn(2+) and Fe(3+) ions were 1.8, 1.6 and 2.4 μg mL(-1), respectively. The proposed method exhibits a preconcentration factor of 208 for all of the ions studied and an enhancement factor for Cu(2+), Fe(3+) and Zn(2+) ions of 34, 28 and 38, respectively. The presented results demonstrate the successful application of the proposed method for the determination of these metal ions in some real samples with high recoveries (> 95%) and reasonable relative standard deviation (RDS <5%).

  10. Flame atomic absorption spectrometric (FAAS) determination of copper, iron and zinc in food samples after solid-phase extraction on Schiff base-modified duolite XAD 761.

    PubMed

    Ghaedi, M; Mortazavi, K; Montazerozohori, M; Shokrollahi, A; Soylak, M

    2013-05-01

    The present study involves the development of solid-phase extraction (SPE) procedure for the preconcentration of trace amounts of copper (Cu(2+)), iron (Fe(3+)) and zinc (Zn(2+)) ions on duolite XAD 761 modified by bis(2-hydroxyacetophenone)-2,2-dimethyl-1,3-propanediimine(BHAPDMPDI). The complexation between the metal ions and the proposed ligand was investigated potentiometrically. The metal ions retained on the sorbent were quantitatively determined via complexation with BHAPDMPDI. The complexed metal ions were efficiently eluted using 6 mL of 4 mol L(-1) nitric acid in acetone. The influences of the analytical parameters, including pH, amounts of the ligand and the solid phase, eluent conditions and sample volume, on the recoveries of the metal ions were optimized. Using the optimized parameters, the linear response of the SPE method for Cu(2+), Zn(2+) and Fe(3+) ions were in the ranges of 0.01-0.34, 0.01-0.28 and 0.02-0.31 μg mL(-1), respectively, and the detection limits for Cu(2+), Zn(2+) and Fe(3+) ions were 1.8, 1.6 and 2.4 μg mL(-1), respectively. The proposed method exhibits a preconcentration factor of 208 for all of the ions studied and an enhancement factor for Cu(2+), Fe(3+) and Zn(2+) ions of 34, 28 and 38, respectively. The presented results demonstrate the successful application of the proposed method for the determination of these metal ions in some real samples with high recoveries (> 95%) and reasonable relative standard deviation (RDS <5%). PMID:23498267

  11. Chromatographic behavior of the enantiomers of 2,2,2-trifluoro-1-(9-anthryl)ethanol on a quinidine-carbamate chiral stational phase

    SciTech Connect

    Asnin, Leonid; Gotmar, Gustaf; Guiochon, Georges A

    2005-08-01

    The enantioseparation of 2,2,2-trifluoro-1-(9-anthryl)ethanol on silica-bonded quinidine carbamate was examined under linear chromatographic conditions. The significant impact of nonselective adsorption on the retention was demonstrated. The influences of a polar additive in the mobile phase on the retention, the selectivity and the thermodynamic quantities of the retention were measured. A small effect of the pressure on the selectivity and on the accuracy of the thermodynamic measurements was observed.

  12. Dextran-grafted cation exchanger based on superporous agarose gel: adsorption isotherms, uptake kinetics and dynamic protein adsorption performance.

    PubMed

    Shi, Qing-Hong; Jia, Guo-Dong; Sun, Yan

    2010-07-30

    A novel chromatographic medium for high-capacity protein adsorption was fabricated by grafting dextran (40kDa) onto the pore surfaces of superporous agarose (SA) beads. The bead was denoted as D-SA. D-SA, SA and homogeneous agarose (HA) beads were modified with sulfopropyl (SP) group to prepare cation exchangers, and the adsorption and uptake of lysozyme on all three cation-exchange chromatographic beads (SP-HA, SP-SA and SP-D-SA) were investigated at salt concentrations of 6-50mmol/L. Static adsorption experiments showed that the adsorption capacity of SP-D-SA (2.24mmol/g) was 78% higher than that of SP-SA (1.26mmol/g) and 54% higher than that of SP-HA (1.45mmol/g) at a salt concentration of 6mmol/L. Moreover, salt concentration had less influence on the adsorption capacity and dissociation constant of SP-D-SA than it did on SP-HA, suggesting that dextran-grafted superporous bead is a more potent architecture for chromatographic beads. In the dynamic uptake of lysozyme to the three cation-exchange beads, the D(e)/D(0) (the ratio of effective pore diffusivity to free solution diffusivity) values of 1.6-2.0 were obtained in SA-D-SA, indicating that effective pore diffusivities of SP-D-SA were about two times higher than free solution diffusivity for lysozyme. At 6mmol/L NaCl, the D(e) value in SA-D-SA (22.0x10(-11)m(2)/s) was 14.4-fold greater than that in SP-HA. Due to the superior uptake kinetics in SA-D-SA, the highest dynamic binding capacity (DBC) and adsorption efficiency (the ratio of DBC to static adsorption capacity) was likewise found in SP-D-SA. It is thus confirmed that SP-D-SA has combined the advantages of superporous matrix structure and drafted ligand chemistry in mass transport and offers a new opportunity for the development of high-performance protein chromatography.

  13. Adsorption Refrigeration System

    SciTech Connect

    Wang, Kai; Vineyard, Edward Allan

    2011-01-01

    Adsorption refrigeration is an environmentally friendly cooling technology which could be driven by recovered waste heat or low-grade heat such as solar energy. In comparison with absorption system, an adsorption system has no problems such as corrosion at high temperature and salt crystallization. In comparison with vapor compression refrigeration system, it has the advantages of simple control, no moving parts and less noise. This paper introduces the basic theory of adsorption cycle as well as the advanced adsorption cycles such as heat and mass recovery cycle, thermal wave cycle and convection thermal wave cycle. The types, characteristics, advantages and drawbacks of different adsorbents used in adsorption refrigeration systems are also summarized. This article will increase the awareness of this emerging cooling technology among the HVAC engineers and help them select appropriate adsorption systems in energy-efficient building design.

  14. Gas-Chromatographic Determination Of Water In Freon PCA

    NASA Technical Reports Server (NTRS)

    Melton, Donald M.

    1994-01-01

    Gas-chromatographic apparatus measures small concentrations of water in specimens of Freon PCA. Testing by use of apparatus faster and provides greater protection against accidental contamination of specimens by water in testing environment. Automated for unattended operation. Also used to measure water contents of materials, other than Freon PCA. Innovation extended to development of purgeable sampling accessory for gas chromatographs.

  15. Detection system for a gas chromatograph

    DOEpatents

    Hayes, John M.; Small, Gerald J.

    1984-01-01

    A method and apparatus are described for the quantitative analysis of vaporizable compounds, and in particular of polycyclic aromatic hydrocarbons which may be induced to fluoresce. The sample to be analyzed is injected into a gas chromatography column and is eluted through a narrow orifice into a vacuum chamber. The free expansion of the eluted sample into the vacuum chamber creates a supersonic molecular beam in which the sample molecules are cooled to the extent that the excited vibrational and rotational levels are substantially depopulated. The cooled molecules, when induced to fluoresce by laser excitation, give greatly simplified spectra suitable for analytical purposes. The laser induced fluorimetry provides great selectivity, and the gas chromatograph provides quantitative transfer of the sample to the molecular beam.

  16. Fast gas chromatographic separation of biodiesel.

    SciTech Connect

    Pauls, R. E.

    2011-05-01

    A high-speed gas chromatographic method has been developed to determine the FAME distribution of B100 biodiesel. The capillary column used in this work has dimensions of 20 m x 0.100 mm and is coated with a polyethylene glycol film. Analysis times are typically on the order of 4-5 min depending upon the composition of the B100. The application of this method to a variety of vegetable and animal derived B100 is demonstrated. Quantitative results obtained with this method were in close agreement with those obtained by a more conventional approach on a 100 m column. The method, coupled with solid-phase extraction, was also found suitable to determine the B100 content of biodiesel-diesel blends.

  17. Chromatographic and electrophoretic approaches in ink analysis.

    PubMed

    Zlotnick, J A; Smith, F P

    1999-10-15

    Inks are manufactured from a wide variety of substances that exhibit very different chemical behaviors. Inks designed for use in different writing instruments or printing methods have quite dissimilar components. Since the 1950s chromatographic and electrophoretic methods have played important roles in the analysis of inks, where compositional information may have bearing on the investigation of counterfeiting, fraud, forgery, and other crimes. Techniques such as paper chromatography and electrophoresis, thin-layer chromatography, high-performance liquid chromatography, gas chromatography, gel electrophoresis, and the relatively new technique of capillary electrophoresis have all been explored as possible avenues for the separation of components of inks. This paper reviews the components of different types of inks and applications of the above separation methods are reviewed. PMID:10572985

  18. Interface for liquid chromatograph-mass spectrometer

    DOEpatents

    Andresen, B.D.; Fought, E.R.

    1989-09-19

    A moving belt interface is described for real-time, high-performance liquid chromatograph (HPLC)/mass spectrometer (MS) analysis which strips away the HPLC solvent as it emerges from the end of the HPLC column and leaves a residue suitable for mass-spectral analysis. The interface includes a portable, stand-alone apparatus having a plural stage vacuum station, a continuous ribbon or belt, a drive train magnetically coupled to an external drive motor, a calibrated HPLC delivery system, a heated probe tip and means located adjacent the probe tip for direct ionization of the residue on the belt. The interface is also capable of being readily adapted to fit any mass spectrometer. 8 figs.

  19. Interface for liquid chromatograph-mass spectrometer

    DOEpatents

    Andresen, Brian D.; Fought, Eric R.

    1989-01-01

    A moving belt interface for real-time, high-performance liquid chromatograph (HPLC)/mass spectrometer (MS) analysis which strips away the HPLC solvent as it emerges from the end of the HPLC column and leaves a residue suitable for mass-spectral analysis. The interface includes a portable, stand-alone apparatus having a plural stage vacuum station, a continuous ribbon or belt, a drive train magnetically coupled to an external drive motor, a calibrated HPLC delivery system, a heated probe tip and means located adjacent the probe tip for direct ionization of the residue on the belt. The interface is also capable of being readily adapted to fit any mass spectrometer.

  20. Gas Chromatographic Detectors for Exobiology Flight Experiments

    NASA Technical Reports Server (NTRS)

    Kojiro, Daniel R.; Humphry, Donald E.; Takeuchi, Nori; Chang, Sherwood (Technical Monitor)

    1997-01-01

    Exobiology flight experiments require highly sensitive instrumentation for in situ chemical analysis of the volatile chemical species that occur in the atmospheres and surfaces of various bodies within the solar system. The complex mixtures encountered place a heavy burden on the analytical instrumentation to detect and identify all species present. Future missions to Mars', comets, or planetary moons such as Europa, will perform experiments with complex analyses. In addition, instrumentation for such missions must perform under severely restricted conditions with limited resources. To meet these analytical requirements, improved methods and highly sensitive yet smaller instruments must continually be developed with increasingly greater capabilities. We describe here efforts to achieve this objective, for past and future missions, through the development of new or the improvement of existing sensitive, miniaturized gas chromatographic detectors.

  1. FTIR gas chromatographic analysis of perfumes

    NASA Astrophysics Data System (ADS)

    Diederich, H.; Stout, Phillip J.; Hill, Stephen L.; Krishnan, K.

    1992-03-01

    Perfumes, natural or synthetic, are complex mixtures consisting of numerous components. Gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) techniques have been extensively utilized for the analysis of perfumes and essential oils. A limited number of perfume samples have also been analyzed by FT-IR gas chromatographic (GC-FTIR) techniques. Most of the latter studies have been performed using the conventional light pipe (LP) based GC-FTIR systems. In recent years, cold-trapping (in a matrix or neat) GC-FTIR systems have become available. The cold-trapping systems are capable of sub-nanogram sensitivities. In this paper, comparison data between the LP and the neat cold-trapping GC- FTIR systems is presented. The neat cold-trapping interface is known as Tracer. The results of GC-FTIR analysis of some commercial perfumes is also presented. For comparison of LP and Tracer GC-FTIR systems, a reference (synthetic) mixture containing 16 major and numerous minor constituents was used. The components of the mixture are the compounds commonly encountered in commercial perfumes. The GC-FTIR spectra of the reference mixture was obtained under identical chromatographic conditions from an LP and a Tracer system. A comparison of the two sets of data thus generated do indeed show the enhanced sensitivity level of the Tracer system. The comparison also shows that some of the major components detected by the Tracer system were absent from the LP data. Closer examination reveals that these compounds undergo thermal decomposition on contact with the hot gold surface that is part of the LP system. GC-FTIR data were obtained for three commercial perfume samples. The major components of these samples could easily be identified by spectra search against a digitized spectral library created using the Tracer data from the reference mixture.

  2. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everwhere else around the annulus. The rotation of the sorbent bed causes the separation components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m0-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory.

  3. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everywhere else around the annulus. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory. 17 references, 9 figures, 1 table.

  4. High-capacity pressurized continuous chromatograph

    SciTech Connect

    Begovich, J.M.; Byers, C.H.; Sisson, W.G.

    1983-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. The feed material is continuously introduced at a stationary point at the top of the bed, and eluent is allowed to flow everywhere else around the annulus. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6m-long device with a 12.7-mm-wide annulus. The effects of annulus width and diameter have been studied using the same device with annulus widths up to 114.3 mm. With this largest width, approximately 96% of the area available within the outer cylinder is devoted to the rotating sorbent bed. Further annulus-width studies have been pursued on units with 89- and 445-mm diameters. These geometric extensions to the basic concept allow extremely large capacity increases with minimal loss in separation and no increase in chromatograph diameter. The effects associated with increased feed concentration have also been studied. In this effort as well as in the annulus-width program, the separation of copper, nickel, and cobalt components from a carbonate solution was studied in detail. The nickel and cobalt components are found in the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. Nominally 50-..mu..m-diam Dowex 50W-X8 cation exchange resin was used as the bed material. The nickel concentration of the feed was varied tenfold, from 136.1 to approximately 1400 meq/L. The combined effects of the bed loading and annulus width were studied and compared with nonlinear theory. 9 figures, 1 table.

  5. Chromatographic determination of amino acids in foods.

    PubMed

    Peace, Robert W; Gilani, G Sarwar

    2005-01-01

    Amino acids in foods exist in a free form or bound in peptides, proteins, or nonpeptide bonded polymers. Naturally occurring L-amino acids are required for protein synthesis and are precursors for essential molecules, such as co-enzymes and nucleic acids. Nonprotein amino acids may also occur in animal tissues as metabolic intermediates or have other important functions. The development of bacterially derived food proteins, genetically modified foods, and new methods of food processing; the production of amino acids for food fortification; and the introduction of new plant food sources have meant that protein amino acids and amino acid enantiomers in foods can have both nutritional and safety implications for humans. There is, therefore, a need for the rapid and accurate determination of amino acids in foods. Determination of the total amino acid content of foods requires protein hydrolysis by various means that must take into account variations in stability of individual amino acids and resistance of different peptide bonds to the hydrolysis procedures. Modern methods for separation and quantitation of free amino acids either before or after protein hydrolysis include ion exchange chromatography, high performance liquid chromatography (LC), gas chromatography, and capillary electrophoresis. Chemical derivatization of amino acids may be required to change them into forms amenable to separation by the various chromatographic methods or to create derivatives with properties, such as fluorescence, that improve their detection. Official methods for hydrolysis and analysis of amino acids in foods for nutritional purposes have been established. LC is currently the most widely used analytical technique, although there is a need for collaborative testing of methods available. Newer developments in chromatographic methodology and detector technology have reduced sample and reagent requirements and improved identification, resolution, and sensitivity of amino acid analyses

  6. Study of XAD-2 adsorbent for the enrichment of trace levels of phthalate esters in hydroalcoholic food beverages and analysis by gas chromatography coupled with flame ionization and ion-trap mass spectrometry detectors.

    PubMed

    Cinelli, Giuseppe; Avino, Pasquale; Notardonato, Ivan; Centola, Angela; Russo, Mario Vincenzo

    2014-03-01

    An analytical method based on solid-phase extraction (SPE) with Amberlite XAD-2 adsorbent used as stationary phase for determining phthalate esters (PAEs) in hydroalcoholic food beverages by GC-FID (and peak confirmation by GC-IT/MS) has been set up. The XAD-2 resin shows excellent properties for determining PAEs in solutions at very large alcoholic range (10-40% v/v): 500mL of hydroalcoholic solution spiked with a PAE mixture solution (20pgμL(-1) of each PAE) and containing 25gL(-1) of NaCl are passed onto a cartridge containing 500mg XAD-2 adsorbent and re-extracted for GC analysis. The effects of NaCl concentration (0, 12, 25 and 50gL(-1)) and different solvents (CS2, toluene, acetone, n-hexane, ethyl acetate) are extensively studied as well the PAE recoveries both in hydroalcoholic aqueous solutions (ranging between 94% and 103% with a Relative Standard Deviation, RSD, below 8.3) and spiked (5, 10 and 25pgμL(-1) of each PAE) real samples (between 90% and 106% with a RSD below 9.9). The correlation coefficients (R(2)) of each PAE vary between 0.9830 and 0.9950 and they are calculated in the linear range 5-100pgμL(-1). The limits of detection (LOD) in GC-FID vary between 1.21 and 2.51pgμL(-1) (RSD⩽11.1) whereas the Limits of Quantification (LOQ) range between 2.42 and 5.03pgμL(-1) (RSD⩽8.9) whereas the infra-day and inter-day repeatabilities calculated as RSD for hydroalcoholic solutions, are between 6.5% and 13.7%. PMID:24176330

  7. Quality by design--thermodynamic modelling of chromatographic separation of proteins.

    PubMed

    Mollerup, Jørgen M; Hansen, Thomas Budde; Kidal, Steffen; Staby, Arne

    2008-01-11

    A desired goal of the PAT framework is to design and develop well-understood processes that will consistently ensure a predefined quality at the end of the manufacturing process. Such procedures would be consistent with the basic tenet of quality by design and could reduce risks to quality and regulatory concerns while improving efficiency. To support a more in-depth understanding of the design and development of a chromatographic purification process the paper discusses the general thermodynamic principles of ligand-binding and models of multi-component adsorption in ion-exchange and hydrophobic chromatography. The parameters in the models are easy to determine and have a well-defined physical significance. Examples demonstrate how the model parameters can be determined from experimental data and in order to validate the model, simulated chromatograms are compared to the corresponding experimental chromatograms. Finally it is demonstrated how a simulation can be used to explain an aberration.

  8. Unusual sintering behavior of porous chromatographic zirconia produced by polymerization-induced colloid aggregation

    SciTech Connect

    Lorenzano-Porras, C.F.; Reeder, D.H.; Annen, M.J.; Carr, P.W.; McCormick, A.V.

    1995-08-01

    The effects of sintering temperature and duration on the pore structure of chromatographic zirconia particles produced by the controlled polymerization-induced aggregation of 1,000 {angstrom} colloids are studied with an eye toward optimally strengthening the aggregates and eliminating small pores while preserving large pores. Nitrogen adsorption and mercury porosimetry are used to estimate the surface area, pore volume, and pore size distribution. Pulsed field gradient NMR measurements of solvent diffusion are used to estimate the diffusion tortuosity of the pore space. Initially of course, the pore volume and surface area decrease significantly, the decrease being more pronounced at higher temperatures. With prolonged sintering, the pore size, pore volume, and surface area change much more slowly, but the diffusion tortuosity seems to be minimized at a sintering temperature and time at which pores are allowed to redistribute so as to optimize large pores. The aggregates synthesized by this aggregation method apparently produce metastable large pores which are not easily collapsed.

  9. An advanced hybrid reprocessing system based on UF{sub 6} volatilization and chromatographic separation

    SciTech Connect

    Wei, Yuezhou; Liu, Ruiqin; Wu, Yan; Zu, Jianhua; Zhao, Long; Mimura, Hitoshi; Shi, Weiqun; Chai, Zhifang; Yang, Jinling; Ding, Youqian

    2013-07-01

    To recover U, Pu, MA (Np, Am, Cm) and some specific fission products FPs (Cs, Sr, Tc, etc.) from various spent nuclear fuels (LWR/FBR: Oxide, Metal Fuels), we are studying an advanced hybrid reprocessing system based on UF6 volatilization (Pyro) and chromatographic separation (Aqueous). Spent fuels are de-cladded by means of thermal and mechanical methods and then applied to the fluorination/volatilization process, which selectively recovers the most amount of U. Then, the remained fuel components are converted to oxides and dissolved by HNO{sub 3} solution. Compared to U, since Pu, MA and FPs are significantly less abundant in spent fuels, the scale of the aqueous separation process could become reasonably small and result in less waste. For the chromatographic separation processes, we have prepared different types of porous silica-based organic/inorganic adsorbents with fast diffusion kinetics, improved chemical stability and low pressure drop in a packed column. So they are advantageously applicable to efficient separation of the actinides and FP elements from the fuel dissolved solution. In this work, adsorption and separation behavior of representative actinides and FP elements was studied. Small scale separation tests using simulated and genuine fuel dissolved solutions were carried out to verify the feasibility of the proposed process. (authors)

  10. Chromatographic and traditional albumin isotherms on cellulose: a model for wound protein adsorption on modified cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Albumin is the most abundant protein found in healing wounds. Traditional and chromatogrpahic protein isotherms of albumin binding on modified cotton fibers are useful in understanding albumin binding to cellulose wound dressings. An important consideration in the design of cellulosic wound dressin...

  11. A Simple Adsorption Experiment

    ERIC Educational Resources Information Center

    Guirado, Gonzalo; Ayllon, Jose A.

    2011-01-01

    The study of adsorption phenomenon is one of the most relevant and traditional physical chemistry experiments performed by chemistry undergraduate students in laboratory courses. In this article, we describe an easy, inexpensive, and straightforward way to experimentally determine adsorption isotherms using pieces of filter paper as the adsorbent…

  12. Chromatographic analysis of olopatadine in hydrophilic interaction liquid chromatography.

    PubMed

    Maksić, Jelena; Jovanović, Marko; Rakić, Tijana; Popović, Igor; Ivanović, Darko; Jančić-Stojanović, Biljana

    2015-01-01

    In this paper, chromatographic analysis of active substance olopatadine hydrochloride, which is used in eye drops as antihistaminic agent, and its impurity E isomer by hydrophilic interaction liquid chromatography (HILIC) and application of design of experiments (DoE) methodology are presented. In addition, benzalkonium chloride is very often used as a preservative in eye drops. Therefore, the evaluation of its chromatographic behavior in HILIC was carried out as well. In order to estimate chromatographic behavior and set optimal chromatographic conditions, DoE methodology was applied. After the selection of important chromatographic factors, Box-Behnken design was utilized, and on the basis of the obtained models factor effects were examined. Then, multi-objective robust optimization is performed aiming to obtain chromatographic conditions that comply with several quality criteria simultaneously: adequate and robust separation of critical peak pair and maximum retention of the first eluting peak. The optimal conditions are identified by using grid point search methodology. The experimental verification confirmed the adequacy of the defined optimal conditions. Finally, under optimal chromatographic conditions, the method was validated and applicability of the proposed method was confirmed.

  13. Chromatographic Separations of Enantiomers and Underivatized Oligosaccharides

    SciTech Connect

    Liu, Ying

    2004-01-01

    My graduate research has focused on separation science and bioanalytical analysis, which emphasized in method development. It includes three major areas: enantiomeric separations using high performance liquid chromatography (HPLC), Super/subcritical fluid chromatography (SFC), and capillary electrophoresis (CE); drug-protein binding behavior studies using CE; and carbohydrate analysis using liquid chromatograph-electrospray ionization mass spectrometry (LC-ESI-MS). Enantiomeric separations continue to be extremely important in the pharmaceutical industry. An in-depth evaluation of the enantiomeric separation capabilities of macrocyclic glycopeptides CSPs with SFC mobile phases was investigated using a set of over 100 chiral compounds. It was found that the macrocyclic based CSPs were able to separate enantiomers of various compounds with different polarities and functionalities. Seventy percent of all separations were achieved in less than 4 min due to the high flow rate (4.0 ml/min) that can be used in SFC. Drug-protein binding is an important process in determining the activity and fate of a drug once it enters the body. Two drug/protein systems have been studied using frontal analysis CE method. More sensitive fluorescence detection was introduced in this assay, which overcame the problem of low sensitivity that is common when using UV detection for drug-protein studies. In addition, the first usage of an argon ion laser with 257 nm beam coupled with CCD camera as a frontal analysis detection method enabled the simultaneous observation of drug fluorescence as well as the protein fluorescence. LC-ESI-MS was used for the separation and characterization of underivatized oligosaccharide mixtures. With the limits of detection as low as 50 picograms, all individual components of oligosaccharide mixtures (up to 11 glucose-units long) were baseline resolved on a Cyclobond I 2000 column and detected using ESI-MS. This system is characterized by high chromatographic

  14. Adsorption bed models used in simulation of atmospheric control systems

    NASA Technical Reports Server (NTRS)

    Davis, S. H.

    1978-01-01

    Two separate techniques were used to obtain important basic data for the adsorption of seven liquid and eight gaseous trace contaminants. A columetric system used in previous HSC studies was modified to determine the HSC capacity of all the contaminants. A second study of six of the liquids was performed in a gas chromatorgraph. The results of these two studies are reported in two parts. First, a brief summary of the chromatographic results are given. Second, a thesis is given which reports in some detail the results of the volumetric studies. Comparison of the data that are common to both studies are also included.

  15. Liquid chromatographic analysis of coal surface properties

    SciTech Connect

    Kwon, K.C.

    1991-01-01

    The main objectives of this proposed research are to refine further the inverse liquid chromatography technique for the study of surface properties of raw coals, treated coals and coal minerals in water, to evaluate relatively surface properties of raw coals, treated coals and coal minerals by inverse liquid chromatography, and to evaluate floatability of various treated coals in conjunction with surface properties of coals. Alcohols such as methanol, ethanol, isopropanol, isobutanol, tert-butanol, heptanol, 1-hexadecanol, 2-methyl-pentanol, 4-methyl-2-penthanol (methylisobutyl carbinol), n-octanol, s-octanol, and cyclohexanol as probe compounds are utilized to evaluate hydrophilicity of coals and coal minerals. N-alkanes such as hexane, heptane and octane, and stearic acid are employed as probe compounds to evaluate hydrophobicity of coals and coal minerals. Aromatic compounds such as benzene and toluene as probe compounds are used to examine aromaticity of coal surface. Aromatic acids such as o-cresol, m-cresol, p-cresol, phenol and B-naphthol are used to detect aromatic acidic sites of coal surface. Hydrophilicity, hydrophobicity and aromaticity of surfaces for either raw coals or treated coals in water are relatively determined by evaluating both equilibrium physical/chemical adsorption and dynamic adsorption of probe compounds on various raw coals and treated coals to compare affinities of coals for water.

  16. High performance hand-held gas chromatograph

    SciTech Connect

    Yu, C M; Koo, J C

    2001-01-10

    Gas chromatography is a prominent technique for separating complex gases and then analyzing the relative quantities of the separate components. This analytical technique is popular with scientists in a wide range of applications, including environmental restoration for air and water pollution, and chemical and biological analysis. Today the analytical instrumentation community is to working towards moving the analysis away from the laboratory to the point of origin of the sample (''the field'') to achieve real-time data collection and lower analysis costs. The Microtechnology Center of Lawrence Livermore National Laboratory, has developed a hand-held, real-time detection gas chromatograph (GC) through Micro-Electro-Mechanical-System (MEMS) technology. The total weight of this GC is approximately 8 pounds, and it measures 8 inches by 5 inches by 3 inches. It consumes approximately 12 watts of electrical power and has a response time on the order of 2 minutes. The current detector is a glow discharge detector with a sensitivity of parts per billion. The average retention time is about 30 to 45 seconds. Under optimum conditions, the calculated effective plate number is 40,000. The separation column in the portable GC is fabricated completely on silicon wafers. Silicon is a good thermal conductor and provides rapid heating and cooling of the column. The operational temperature can be as high as 350 degrees Celsius. The GC system is capable of rapid column temperature ramping and cooling operations. These are especially important for organic and biological analyses in the GC applications.

  17. First-generation hybrid MEMS gas chromatograph.

    PubMed

    Lu, Chia-Jung; Steinecker, William H; Tian, Wei-Cheng; Oborny, Michael C; Nichols, Jamie M; Agah, Masoud; Potkay, Joseph A; Chan, Helena K L; Driscoll, Jeffrey; Sacks, Richard D; Wise, Kensall D; Pang, Stella W; Zellers, Edward T

    2005-10-01

    The fabrication, assembly, and initial testing of a hybrid microfabricated gas chromatograph (microGC) is described. The microGC incorporates capabilities for on-board calibration, sample preconcentration and focused thermal desorption, temperature-programmed separations, and "spectral" detection with an integrated array of microsensors, and is designed for rapid determinations of complex mixtures of environmental contaminants at trace concentrations. Ambient air is used as the carrier gas to avoid the need for on-board gas supplies. The microsystem is plumbed through an etched-Si/glass microfluidic interconnection substrate with fused silica capillaries and employs a miniature commercial pump and valve subsystem for directing sample flow. The latest performance data on each system component are presented followed by first analytical results from the working microsystem. Tradeoffs in system performance as a function of volumetric flow rate are explored. The determination of an 11-vapor mixture of typical indoor air contaminants in less than 90 s is demonstrated with projected detection limits in the low part-per-billion concentration range for a preconcentrated air-sample volume of 0.25 L.

  18. Studies on improved integrated membrane-based chromatographic process for bioseparation

    NASA Astrophysics Data System (ADS)

    Xu, Yanke

    To improve protein separation and purification directly from a fermentation broth, a novel membrane filtration-cum-chromatography device configuration having a relatively impermeable coated zone near the hollow fiber module outlet has been developed. The integrated membrane filtration-cum-chromatography unit packed with chromatographic beads on the shell side of the hollow fiber unit enjoys the advantages of both membrane filtration and chromatography; it allows one to load the chromatographic media directly from the fermentation broth or lysate and separate the adsorbed proteins through the subsequent elution step in a cyclic process. Interfacial polymerization was carried out to coat the bottom section of the hollow fiber membrane while leaving the rest of the hollow fiber membrane unaffected. Myoglobin (Mb), bovine serum albumin (BSA) and a-lactalbumin (a-LA) were used as model proteins in binary mixtures. Separation behaviors of binary protein mixtures were studied in devices using either an ultrafiltration (UF) membrane or a microfiltration (MF) membrane. Experimental results show that the breakthrough time and the protein loading capacities were dramatically improved after coating in both UF and MF modules. For a synthetic yeast fermentation broth feed, the Mb and a-LA elution profiles for the four consecutive cyclic runs were almost superimposable. Due to the lower transmembrane flux in this device plus the periodical washing-elution during the chromatographic separation, fouling was not a problem as it is in conventional microfiltration. A mathematical model describing the hydrodynamic and protein loading behaviors of the integrated device using UF membrane with a coated zone was developed. The simulation results for the breakthrough agree well with the experimental breakthrough curves. The optimal length of the coated zone was obtained from the simulation. A theoretical analysis of the protein mass transfer was performed using a diffusion-convection model

  19. Adsorption behavior of alpha -cypermethrin on cork and activated carbon.

    PubMed

    Domingues, Valentina F; Priolo, Giuseppe; Alves, Arminda C; Cabral, Miguel F; Delerue-Matos, Cristina

    2007-08-01

    Studies were undertaken to determine the adsorption behavior of alpha -cypermethrin [R)-alpha -cyano-3-phenoxybenzyl(1S)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate, and (S)-alpha-cyano-3-phenoxybenzyl (1R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate] in solutions on granules of cork and activated carbon (GAC). The adsorption studies were carried out using a batch equilibrium technique. A gas chromatograph with an electron capture detector (GC-ECD) was used to analyze alpha -cypermethrin after solid phase extraction with C18 disks. Physical properties including real density, pore volume, surface area and pore diameter of cork were evaluated by mercury porosimetry. Characterization of cork particles showed variations thereby indicating the highly heterogeneous structure of the material. The average surface area of cork particles was lower than that of GAC. Kinetics adsorption studies allowed the determination of the equilibrium time - 24 hours for both cork (1-2 mm and 3-4 mm) and GAC. For the studied alpha -cypermethrin concentration range, GAC revealed to be a better sorbent. However, adsorption parameters for equilibrium concentrations, obtained through the Langmuir and Freundlich models, showed that granulated cork 1-2 mm have the maximum amount of adsorbed alpha-cypermethrin (q(m)) (303 microg/g); followed by GAC (186 microg/g) and cork 3-4 mm (136 microg/g). The standard deviation (SD) values, demonstrate that Freundlich model better describes the alpha -cypermethrin adsorption phenomena on GAC, while alpha -cypermethrin adsorption on cork (1-2 mm and 3-4 mm) is better described by the Langmuir. In view of the adsorption results obtained in this study it appears that granulated cork may be a better and a cheaper alternative to GAC for removing alpha -cypermethrin from water.

  20. Separative analyses of a chromatographic column packed with a core-shell adsorbent for lithium isotope separation

    SciTech Connect

    Sugiyama, T.; Sugura, K.; Enokida, Y.; Yamamoto, I.

    2015-03-15

    Lithium-6 is used as a blanket material for sufficient tritium production in DT fueled fusion reactors. A core-shell type adsorbent was proposed for lithium isotope separation by chromatography. The mass transfer model in a chromatographic column consisted of 4 steps, such as convection and dispersion in the column, transfer through liquid films, intra-particle diffusion and and adsorption or desorption at the local adsorption sites. A model was developed and concentration profiles and time variation in the column were numerically simulated. It became clear that core-shell type adsorbents with thin porous shell were saturated rapidly relatively to fully porous one and established a sharp edge of adsorption band. This is very important feature because lithium isotope separation requires long-distance development of adsorption band. The values of HETP (Height Equivalent of a Theoretical Plate) for core-shell adsorbent packed column were estimated by statistical moments of the step response curve. The value of HETP decreased with the thickness of the porous shell. A core-shell type adsorbent is, then, useful for lithium isotope separation. (authors)

  1. Orthogonal chromatographic descriptors for modelling Caco-2 drug permeability.

    PubMed

    Deconinck, E; Verstraete, T; Van Gyseghem, E; Vander Heyden, Y; Coomans, D

    2012-03-01

    The use of chromatographic descriptors as alternative for Caco-2 permeability in drug absorption screening was evaluated. Therefore, retentions were measured on 17 Reversed-Phase Liquid Chromatographic systems, considered to be orthogonal or dissimilar, and an Immobilized Artificial Membrane (IAM) system. Retentions on a Micellar Liquid Chromatography system were taken from the literature. From this set of systems, those found dissimilar for the used data set were selected. The retention factors on these systems were then used as descriptors in QSAR modelling. Modelling was performed using Stepwise Multiple Linear Regression. This resulted in a model using only two chromatographic systems with good descriptive and acceptable predictive properties. A high qualitative model was obtained by combining both chromatographic systems selected in the previous model with a lipophilicity parameter (the squared Moriguchi n-octanol/water partition coefficient) and the molecular volume.

  2. GAS CHROMATOGRAPHIC TECHNIQUES FOR THE MEASUREMENT OF ISOPRENE IN AIR

    EPA Science Inventory

    The chapter discusses gas chromatographic techniques for measuring isoprene in air. Such measurement basically consists of three parts: (1) collection of sufficient sample volume for representative and accurate quantitation, (2) separation (if necessary) of isoprene from interfer...

  3. CHROMATOGRAPHIC AND MASS SPECTRAL STUDIES OF PERFLUOROOCTANESULFONATE AND THREE PERFLUOROOCTANESULFONAMIDES

    EPA Science Inventory

    The chromatographic and mass spectral characteristics of perfluorooctanesulfonate (PFOS) and three nitrogen-substituted perfluorooctanesulfonamides have been obtained. A methyl/phenol mixed phase fused silica capillary column was used for GC analysis, while a C18 reversed phase ...

  4. Mechanisms of chain adsorption on porous substrates and critical conditions of polymer chromatography.

    PubMed

    Cimino, Richard T; Rasmussen, Christopher J; Brun, Yefim; Neimark, Alexander V

    2016-11-01

    Polymer adsorption is a ubiquitous phenomenon with numerous technological and healthcare applications. The mechanisms of polymer adsorption on surfaces and in pores are complex owing to a competition between various entropic and enthalpic factors. Due to adsorption of monomers to the surface, the chain gains in enthalpy yet loses in entropy because of confining effects. This competition leads to the existence of critical conditions of adsorption when enthalpy gain and entropy loss are in balance. The critical conditions are controlled by the confining geometry and effective adsorption energy, which depends on the solvent composition and temperature. This phenomenon has important implications in polymer chromatography, since the retention at the critical point of adsorption (CPA) is chain length independent. However, the mechanisms of polymer adsorption in pores are poorly understood and there is an ongoing discussion in the theoretical literature about the very existence of CPA for polymer adsorption on porous substrates. In this work, we examine the mechanisms of chain adsorption on a model porous substrate using Monte Carlo (MC) simulations. We distinguish three adsorption mechanisms depending on the chain location: on external surface, completely confined in pores, and also partially confined in pores in so-called "flower" conformations. The free energies of different conformations of adsorbed chains are calculated by the incremental gauge cell MC method that allows one to determine the partition coefficient as a function of the adsorption potential, pore size, and chain length. We confirm the existence of the CPA for chain length independent separation on porous substrates, which is explained by the dominant contributions of the chain adsorption at the external surface, in particular in flower conformations. Moreover, we show that the critical conditions for porous and nonporous substrates are identical and depend only on the surface chemistry. The theoretical

  5. Mechanisms of chain adsorption on porous substrates and critical conditions of polymer chromatography.

    PubMed

    Cimino, Richard T; Rasmussen, Christopher J; Brun, Yefim; Neimark, Alexander V

    2016-11-01

    Polymer adsorption is a ubiquitous phenomenon with numerous technological and healthcare applications. The mechanisms of polymer adsorption on surfaces and in pores are complex owing to a competition between various entropic and enthalpic factors. Due to adsorption of monomers to the surface, the chain gains in enthalpy yet loses in entropy because of confining effects. This competition leads to the existence of critical conditions of adsorption when enthalpy gain and entropy loss are in balance. The critical conditions are controlled by the confining geometry and effective adsorption energy, which depends on the solvent composition and temperature. This phenomenon has important implications in polymer chromatography, since the retention at the critical point of adsorption (CPA) is chain length independent. However, the mechanisms of polymer adsorption in pores are poorly understood and there is an ongoing discussion in the theoretical literature about the very existence of CPA for polymer adsorption on porous substrates. In this work, we examine the mechanisms of chain adsorption on a model porous substrate using Monte Carlo (MC) simulations. We distinguish three adsorption mechanisms depending on the chain location: on external surface, completely confined in pores, and also partially confined in pores in so-called "flower" conformations. The free energies of different conformations of adsorbed chains are calculated by the incremental gauge cell MC method that allows one to determine the partition coefficient as a function of the adsorption potential, pore size, and chain length. We confirm the existence of the CPA for chain length independent separation on porous substrates, which is explained by the dominant contributions of the chain adsorption at the external surface, in particular in flower conformations. Moreover, we show that the critical conditions for porous and nonporous substrates are identical and depend only on the surface chemistry. The theoretical

  6. Effect of temperature on competitive adsorption of the solute and the organic solvent in reversed-phase liquid chromatography.

    PubMed

    Poplewska, Izabela; Piatkowski, Wojciech; Antos, Dorota

    2006-01-27

    In analysis of the temperature effect on chromatographic separations the influence of the adsorption of organic solvent on the retention properties of solute is generally not taken into account. In fact, adsorption behavior of solutes is strongly affected by competitive adsorption of organic solvents, which is temperature dependent. In this work changes of adsorption equilibrium of an organic solvent as well as a solute with temperature have been analyzed. Data of the excess adsorption of methanol from aqueous solutions on octadecyl-bonded silica have been acquired at different temperature. Experiments have been performed over a relatively narrow temperature range corresponding to typical chromatographic conditions, i.e., 10-50 degrees C. The competitive adsorption equilibria of model solutes (i.e., two homologous compounds: cyclopentanone and cyclohexanone) have been measured at different temperature and composition of the mobile phase. Temperature alterations to the retention properties were found to result from combined effects of changes in adsorption behavior of the organic solvent and of the solute. The influence of temperature on the separation selectivity has been considered.

  7. Adsorption and removal kinetics of phosphonate from water using natural adsorbents.

    PubMed

    Kumar, R Anil; Velayudhan, K T; Ramachandran, V; Bhai, R Susheela; Unnikrishnan, G; Vasu, K

    2010-01-01

    The removal of phosphonate from water was studied using some natural adsorbents. Potassium phosphonate is a fungicide used for the control of Phytophthora capsici, which is prevalent in black pepper (Piper nigrum L.). Batch adsorption kinetic experiments were conducted on the adsorption of phosphonate onto the adsorbents. The concentration of phosphonate was measured on a high-performance liquid chromatograph fitted with a conductivity detector. The percentage removal of phosphonate by powdered laterite stone (PLS) from water was 40.4%, within a residence time of 15 minutes. The mechanisms of the rate of adsorption were analyzed and compared using the pseudo-second-order, Elovich, and intraparticle diffusion models. The experimental data was found to correlate well with the pseudo-second-order kinetic model, indicating adsorption as a chemisorption process. A possible reaction in the phosphonate-PLS system also has been proposed. The PLS can be used as a low-cost natural adsorbent for phosphonate removal from water.

  8. Gas chromatographic separation of hydrogen isotopes using metal hydrides

    SciTech Connect

    Aldridge, F.T.

    1984-05-09

    A study was made of the properties of metal hydrides which may be suitable for use in chromatographic separation of hydrogen isotopes. Sixty-five alloys were measured, with the best having a hydrogen-deuterium separation factor of 1.35 at 60/sup 0/C. Chromatographic columns using these alloys produced deuterium enrichments of up to 3.6 in a single pass, using natural abundance hydrogen as starting material. 25 references, 16 figures, 4 tables.

  9. Method for liquid chromatographic extraction of strontium from acid solutions

    DOEpatents

    Horwitz, E. Philip; Dietz, Mark L.

    1992-01-01

    A method and apparatus for extracting strontium and technetium values from biological, industrial and environmental sample solutions using a chromatographic column is described. An extractant medium for the column is prepared by generating a solution of a diluent containing a Crown ether and dispersing the solution on a resin substrate material. The sample solution is highly acidic and is introduced directed to the chromatographic column and strontium or technetium is eluted using deionized water.

  10. Chromatographic separation of fructose from date syrup.

    PubMed

    Al Eid, Salah M

    2006-01-01

    The objective of this study is to provide a process for separating fructose from a mixture of sugars containing essentially fructose and glucose, obtained from date palm fruits. The extraction procedure of date syrup from fresh dates gave a yield of 86.5% solids after vacuum drying. A process for separating fructose from an aqueous solution of date syrup involved adding the date syrup solutions (20, 30 and 40% by weight) to a chromatographic column filled with Dowex polystyrene strong cation exchange gel matrix resin Ca2 + and divinylbenzene, a functional group, sulfonic acid, particle size 320 microm, with a flow rate of 0.025 and 0.05 bed volume/min, under 30 and 70 degrees C column temperature. After the date sugar solution batch, a calculated quantity of water was added to the column. Glucose was retained by the resin more weakly than fructose and proceeded faster into the water batch flowing ahead. Three fractions were collected: a glucose-rich fraction, a return fraction, and a fructose-rich fraction. The return fraction is based on when the peaks of fructose and glucose were reached, which could be determined by means of an analyzer (polarimeter) based on the property of glucose and fructose solutions to turn the polarization level of polarized light. A high yield of fructose is obtained at 70 degrees C column temperature with a flow rate of 0.025 bed volume/min and date syrup solution containing 40% sugar concentration. The low recovery by weight obtained using date syrup solutions having a sugar concentration of 20 and 30%, encourages the use of a concentration of 40%. However, with the 40% date syrup supply the average concentrations of glucose and fructose in the return fractions were more than 40%, which can be used for diluting the thick date syrup solution extracted from dates.

  11. Chromatographic separation of fructose from date syrup.

    PubMed

    Al Eid, Salah M

    2006-01-01

    The objective of this study is to provide a process for separating fructose from a mixture of sugars containing essentially fructose and glucose, obtained from date palm fruits. The extraction procedure of date syrup from fresh dates gave a yield of 86.5% solids after vacuum drying. A process for separating fructose from an aqueous solution of date syrup involved adding the date syrup solutions (20, 30 and 40% by weight) to a chromatographic column filled with Dowex polystyrene strong cation exchange gel matrix resin Ca2 + and divinylbenzene, a functional group, sulfonic acid, particle size 320 microm, with a flow rate of 0.025 and 0.05 bed volume/min, under 30 and 70 degrees C column temperature. After the date sugar solution batch, a calculated quantity of water was added to the column. Glucose was retained by the resin more weakly than fructose and proceeded faster into the water batch flowing ahead. Three fractions were collected: a glucose-rich fraction, a return fraction, and a fructose-rich fraction. The return fraction is based on when the peaks of fructose and glucose were reached, which could be determined by means of an analyzer (polarimeter) based on the property of glucose and fructose solutions to turn the polarization level of polarized light. A high yield of fructose is obtained at 70 degrees C column temperature with a flow rate of 0.025 bed volume/min and date syrup solution containing 40% sugar concentration. The low recovery by weight obtained using date syrup solutions having a sugar concentration of 20 and 30%, encourages the use of a concentration of 40%. However, with the 40% date syrup supply the average concentrations of glucose and fructose in the return fractions were more than 40%, which can be used for diluting the thick date syrup solution extracted from dates. PMID:16849117

  12. Hybrid adsorptive membrane reactor

    NASA Technical Reports Server (NTRS)

    Tsotsis, Theodore T. (Inventor); Sahimi, Muhammad (Inventor); Fayyaz-Najafi, Babak (Inventor); Harale, Aadesh (Inventor); Park, Byoung-Gi (Inventor); Liu, Paul K. T. (Inventor)

    2011-01-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  13. Hybrid adsorptive membrane reactor

    DOEpatents

    Tsotsis, Theodore T.; Sahimi, Muhammad; Fayyaz-Najafi, Babak; Harale, Aadesh; Park, Byoung-Gi; Liu, Paul K. T.

    2011-03-01

    A hybrid adsorbent-membrane reactor in which the chemical reaction, membrane separation, and product adsorption are coupled. Also disclosed are a dual-reactor apparatus and a process using the reactor or the apparatus.

  14. The use of molecular-statistical methods for the calculation of thermodynamic characteristics of adsorption for identification of organic compounds by gas chromatography-mass spectrometry

    NASA Astrophysics Data System (ADS)

    Buryak, Alexey K.

    2002-08-01

    The current state of research on the theoretical description of adsorption in the Henry region by semiempirical molecular-statistical procedures, as applied to identification of organic compounds in complex mixtures, is considered. Various approaches to correcting the atom-atom potential parameters used to determine thermodynamic characteristics of adsorption are compared. Examples of calculations involved in the chromatographic and chromatography-mass spectrometric identification of model and real organic compounds including isomers are given. The bibliography includes 89 references.

  15. Miscible viscous fingering with linear adsorption on the porous matrix

    NASA Astrophysics Data System (ADS)

    Mishra, M.; Martin, M.; De Wit, A.

    2007-07-01

    Viscous fingering between miscible fluids of different viscosities can affect the dispersion of finite samples in porous media. In some applications, as typically in chromatographic separations or pollutant dispersion in underground aquifers, adsorption onto the porous matrix of solutes (the concentration of which rules the viscosity of the solution) can affect the fingering dynamics. Here, we investigate theoretically the influence of such an adsorption on the stability and nonlinear properties of viscous samples displaced in a two-dimensional system by a less viscous and miscible carrying fluid. The model is based on Darcy's law for the evolution of the fluid velocity coupled to a diffusion-convection equation for the concentration of a solute in the mobile phase inside the porous medium. The adsorption-desorption dynamics of the solute onto the stationary phase is assumed to be at equilibrium, to follow a linear isotherm and is characterized by a retention parameter κ' equal to the adsorption-desorption equilibrium constant K multiplied by the phase ratio F. In practice, retention on the porous matrix renormalizes the log-mobility ratio by a factor (1+κ'). Correspondingly, a linear stability analysis and nonlinear simulations of the model show that an increase of κ' leads to a stabilization of viscous fingering with fingers appearing on a dimensional time scale multiplied by (1+κ')3 and with a dimensional wavelength multiplied by (1+κ').

  16. Chromatographic behaviors of proteins on cation-exchange column.

    PubMed

    Li, Rong; Chen, Guo-Liang; Zhao, Wen-Ming

    2004-12-01

    A weak cation-exchanger (XIDACE-WCX) has been synthesized by the indirect method. The chromatographic characteristics of the synthesized packing was studied in detail. The standard protein mixture and lysozyme from egg white were separated with the prepared chromatographic column. The chromatographic thermodynamics of proteins was studied in a wide temperature range. Thermodynamic parameters standard enthalpy change (deltaH0) and standard entropy change (deltaS0) and compensation temperature (beta) at protein denaturation were determined in the chromatographic system. By using obtained deltaS0, the conformational change of proteins was judged in the chromatographic process. The linear relationship between deltaH0 and deltaS0 can be used to identify the identity of the protein retention mechanism in the weak cation-exchange chromatography. The interaction between weak cation-exchanger and metal ions was investigated. Several metal chelate columns were prepared. The effects of introducing metal ion into the naked column on protein retention and the retention mechanism of proteins in the metal chalet affinity chromatography were discussed. PMID:15689030

  17. Comparative study for separation of atmospheric humic-like substance (HULIS) by ENVI-18, HLB, XAD-8 and DEAE sorbents: elemental composition, FT-IR, 1H NMR and off-line thermochemolysis with tetramethylammonium hydroxide (TMAH).

    PubMed

    Fan, Xingjun; Song, Jianzhong; Peng, Ping'an

    2013-11-01

    Humic-like substances (HULIS) are significant constituents of aerosols, and the isolation and characterization of HULIS by solid-phase extraction methods are dependent on the sorbents used. In this study, we used the following five methods: ENVI-18, HLB-M, HLB-N, XAD-8 and DEAE, to isolate atmospheric HULIS at an urban site. Then we conducted a comparative investigation of the HULIS chemical characteristics by means of elemental analysis, Fourier transform infrared spectroscopy, (1)H nuclear magnetic resonance spectroscopy and off-line thermochemolysis with tetramethylammonium hydroxide. The results indicate that HULIS isolated using different methods show many similarities in chemical composition and structure. Some differences were however also observed between the five isolated HULIS: HULISHLB-M contains a relatively high content of OCH group, compared to HULISENVI-18 and HULISXAD-8; HULISXAD-8 contains a relatively high content of hydrophobic and aromatic components, compared to HULISENVI-18 and HULISHLB-M; HULISDEAE contains the highest content of aromatic functional groups, as inferred by (1)H NMR spectra, but a great amount of salts generally present in the HULISDEAE and thereby limited the choices for characterizing the materials (i.e., elemental analysis and TMAH thermochemolysis); HULISHLB-N has relatively high levels of H and N, a high N/C atomic ratio, and includes N-containing functional groups, which suggests that it has been altered by 2% ammonia introduced in the eluents. In summary, we found that ENVI-18, HLB-M, and XAD-8 are preferable methods for isolation and characterization of HULIS in atmospheric aerosols. These results also suggest that caution is required when applying DEAE and HLB-N isolating methods for characterizing atmospheric HULIS.

  18. Recovery of polyphenols from rose oil distillation wastewater using adsorption resins--a pilot study.

    PubMed

    Rusanov, Krasimir; Garo, Eliane; Rusanova, Mila; Fertig, Orlando; Hamburger, Matthias; Atanassov, Ivan; Butterweck, Veronika

    2014-11-01

    The production of rose oil from rose flowers by water steam distillation leaves a water fraction of the distillate as main part of the waste. Therefore, the rose oil distillation wastewater represents a serious environmental problem due to the high content of polyphenols which are difficult to decompose and have to be considered as biopollutants when discarded into the drainage system and rivers. On the other hand, natural polyphenols are valuable compounds with useful properties as bioactive substances. Until now there is no established practice for processing of rose oil distillation wastewater and utilization of contained substances. Thus, it was the aim of this study to develop a strategy to separate this wastewater into a polyphenol depleted water fraction and a polyphenol enriched fraction which could be developed into innovative value-added products. In a first step, the phytochemical profile of rose oil distillation wastewater was determined. Its HPLC-PDA-MS analysis revealed the presence of flavan-3-ols, flavanones, flavonols and flavones. In a second step, the development of a stepwise concentration of rose oil distillation wastewater was performed. The concentration process includes a filtration process to eliminate suspended solids in the wastewater, followed by adsorption of the contained phenolic compounds onto adsorption resins (XAD and SP). Finally, desorption of the polyphenol fraction from the resin matrix was achieved using ethanol and/or aqueous ethanol. The result of the process was a wastewater low in soluble organic compounds and an enriched polyphenol fraction (RF20 SP-207). The profile of this fraction was similar to that of rose oil distillation wastewater and showed the presence of flavonols such as quercetin and kaempferol glycosides as major metabolites. These compounds were isolated from the enriched polyphenol fraction and their structures confirmed by NMR. In summary, a pilot medium scale system was developed using adsorption resins

  19. Recovery of polyphenols from rose oil distillation wastewater using adsorption resins--a pilot study.

    PubMed

    Rusanov, Krasimir; Garo, Eliane; Rusanova, Mila; Fertig, Orlando; Hamburger, Matthias; Atanassov, Ivan; Butterweck, Veronika

    2014-11-01

    The production of rose oil from rose flowers by water steam distillation leaves a water fraction of the distillate as main part of the waste. Therefore, the rose oil distillation wastewater represents a serious environmental problem due to the high content of polyphenols which are difficult to decompose and have to be considered as biopollutants when discarded into the drainage system and rivers. On the other hand, natural polyphenols are valuable compounds with useful properties as bioactive substances. Until now there is no established practice for processing of rose oil distillation wastewater and utilization of contained substances. Thus, it was the aim of this study to develop a strategy to separate this wastewater into a polyphenol depleted water fraction and a polyphenol enriched fraction which could be developed into innovative value-added products. In a first step, the phytochemical profile of rose oil distillation wastewater was determined. Its HPLC-PDA-MS analysis revealed the presence of flavan-3-ols, flavanones, flavonols and flavones. In a second step, the development of a stepwise concentration of rose oil distillation wastewater was performed. The concentration process includes a filtration process to eliminate suspended solids in the wastewater, followed by adsorption of the contained phenolic compounds onto adsorption resins (XAD and SP). Finally, desorption of the polyphenol fraction from the resin matrix was achieved using ethanol and/or aqueous ethanol. The result of the process was a wastewater low in soluble organic compounds and an enriched polyphenol fraction (RF20 SP-207). The profile of this fraction was similar to that of rose oil distillation wastewater and showed the presence of flavonols such as quercetin and kaempferol glycosides as major metabolites. These compounds were isolated from the enriched polyphenol fraction and their structures confirmed by NMR. In summary, a pilot medium scale system was developed using adsorption resins

  20. Ion-exchange chromatographic analysis of peroxynitric acid.

    PubMed

    Nakashima, Yoichi; Ikawa, Satoshi; Tani, Atsushi; Kitano, Katsuhisa

    2016-01-29

    Ion-exchange chromatographic analysis of peroxynitric acid (O2NOOH) was performed by combining an acidic eluate with an UV-vis detector and immersing the separation column in an ice-water bath. The decomposition behavior of peroxynitric acid in the solution was also studied using this system. The fraction for the peroxynitric acid peak was collected. Ion-exchange chromatographic analysis of this fraction, after standing at room temperature for 24h, showed that the decomposition products were mainly nitrate ions with a very small amount of nitrous acid. The peroxynitric acid peak area correlated perfectly with the total amount of decomposition products. The ion-exchange chromatographic isolation allowed us to evaluate the molar extinction coefficient of peroxynitric acid precisely in a wider wavelength range than previous reports. The value decreases monotonically from 1729±26M(-1)cm(-1) at 200nm to 12.0±0.5M(-1)cm(-1) at 290nm.

  1. On-line gas chromatographic analysis of airborne particles

    DOEpatents

    Hering, Susanne V.; Goldstein, Allen H.

    2012-01-03

    A method and apparatus for the in-situ, chemical analysis of an aerosol. The method may include the steps of: collecting an aerosol; thermally desorbing the aerosol into a carrier gas to provide desorbed aerosol material; transporting the desorbed aerosol material onto the head of a gas chromatography column; analyzing the aerosol material using a gas chromatograph, and quantizing the aerosol material as it evolves from the gas chromatography column. The apparatus includes a collection and thermal desorption cell, a gas chromatograph including a gas chromatography column, heated transport lines coupling the cell and the column; and a quantization detector for aerosol material evolving from the gas chromatography column.

  2. Biospecific affinity chromatographic purification of octopine dehydrogenase from molluscs.

    PubMed

    Mulcahy, P; Griffin, T; O'Carra, P

    1997-02-01

    The development of a biospecific affinity chromatographic method for the purification of octopine dehydrogenase from molluscs is described. The method utilizes immobilized NAD+ derivatives in conjunction with soluble specific substrates to promote binding. Using this method, octopine dehydrogenase has been purified to electrophoretic homogeneity in a single chromatographic step from three different marine invertebrate sources [the queen scallop, Chlamys opercularis (adductor muscle), the great scallop, Pecten maximus (adductor muscle), and the squid Loligo vulgaris (mantle muscle)]. However, the system is not applicable to the purification of octopine dehydrogenase from some other marine invertebrate sources investigated (the mussel Mytilus edulis and the topshell Monodonta lineata). PMID:9116492

  3. Gas-liquid chromatographic determination of morphine, heroin, and cocaine.

    PubMed

    Prager, M J; Harrington, S M; Governo, T F

    1979-03-01

    Morphine, heroin, and cocaine are quantitatively determined with the same gas-liquid chromatographic system. The compounds are separated on a 6 ft X 2 mm id glass column packed with a 1:1 mixture of 5% SE-30 on 80--100 mesh Chromosorb W and 3% OV-17 on 80--100 mesh Varaport 30. The column is temperature-programmed. Flame ionization detector responses are measured with a computer-based data system. Heroin and cocaine are chromatographed directly; morphine is derivatized first. The procedure was evaluated with previously analyzed commercial and forensic samples. Accuracy and precision were 5 and 3%, respectively. PMID:447602

  4. Reactor-chromatographic determination of vinyl chloride in polyvinyl chloride

    SciTech Connect

    Berezkin, V.G.

    1986-08-01

    The authors carry out a chromatographic study of the volatile products that evolve when various grades of domestic polyvinyl chloride are heated, to determine the concentration of residual monomer. To find vinyl chloride in complex mixtures of air pollutants the authors used sorptive reaction concentration of impurities. This new combination of methods is based on preliminary separation at the sampling stage of impurities that interfere in the analysis, followed by concentration of the desired components in a trap with an adsorbent, and chromatographic determination of the concentrated trace materials. The method obtains low vinyl chloride concentrations (down to 10/sup -4/-10/sup -5/ wt. %) with +/-5 relative error.

  5. New Adsorption Methods.

    ERIC Educational Resources Information Center

    Wankat, Phillip C.

    1984-01-01

    Discusses a simple method for following the movement of a solute in an adsorption or ion exchange system. This movement is used to study a variety of operational methods, including continuous flow and pulsed flow counter-current operations and simulated counter-current systems. Effect of changing thermodynamic variables is also considered. (JM)

  6. Sulfate adsorption on goethite

    SciTech Connect

    Rietra, R.P.J.J.; Hiemstra, T.; Riemsdijk, W.H. van

    1999-10-15

    Recent spectroscopic work has suggested that only one surface species of sulfate is dominant on hematite. Sulfate is therefore a very suitable anion to test and develop adsorption models for variable charge minerals. The authors have studied sulfate adsorption on goethite covering a large range of sulfate concentrations, surface coverages, pH values, and electrolyte concentrations. Four different techniques were used to cover the entire range of conditions. For characterization at low sulfate concentrations, below the detection limit of sulfate with ICP-AES, the authors used proton-sulfate titrations at constant pH. Adsorption isotherms were studied for the intermediate sulfate concentration range. Acid-base titrations in sodium sulfate and electromobility were used for high sulfate concentrations. All the data can be modeled with one adsorbed species if it is assumed that the charge of adsorbed sulfate is spatially distributed in the interface. The charge distribution of sulfate follows directly from modeling the proton-sulfate adsorption stoichoimemtry sine this stoichiometry is independent of the intrinsic affinity constant of sulfate. The charge distribution can be related to the structure of the surface complex by use of the Pauling bond valence concept and is in accordance with the microscopic structure found by spectroscopy. The intrinsic affinity constant follows from the other measurements. Modeling of the proton-ion stoichoimetry with the commonly used 2-pK models, where adsorbed ions are treated as point charges, is possible only if at least two surface species for sulfate are used.

  7. SEPARATION BY ADSORPTION

    DOEpatents

    Lowe, C.S.

    1959-06-16

    Separation of Pu from fission products by adsorption on hydrous aluminum silicate is described. The Pu in a HNO/sub 3/ solution is oxidized to the hexavalent state and contacted with the silicate which adsorbs fission products. (T.R.H.)

  8. Multiple-acid equilibria in adsorption of carboxylic acids from dilute aqueous solution

    SciTech Connect

    Husson, S.M.; King, C.J.

    1999-02-01

    Equilibria were measured for adsorption of carboxylic acids from aqueous, binary-acid mixtures of lactic and succinic acids and acetic and formic acids onto basic polymeric sorbents. The experimentally determined adsorption isotherms compared well with model predictions, confirming that simple extensions from adsorption of individual acids apply. Fixed-bed studies were carried out that establish the efficacy of chromatographic fractionation of lactic and succinic acids using basic polymeric sorbents. Finally, sequential thermal and solvent regeneration of lactic and acetic acid-laden sorbents was investigated as a method to fractionate among coadsorbed volatile and nonvolatile acids. Essentially complete removal of the acetic acid from the acid-laden sorbent was achieved by vaporization under the conditions used; a small amount of loss of lactic acid (about 11%) was observed.

  9. Binary and ternary adsorption of n-alkane mixtures on activated carbon

    SciTech Connect

    Kalies, G.; Braeuer, P.; Messow, U.

    1999-06-15

    The adsorption isotherms of the binary n-alkane mixtures n-hexane/n-octane, n-octane/n-tetradecane, and n-hexane/n-tetradecane on the activated carbon TA 95 are measured at 298 K and described with mathematical functions. About 40 experimental values of the adsorption excess of the ternary mixture n-hexane/n-octane/n-tetradecane on activated carbon TA 95 at 298 K are gas chromatographically measured inside the ternary triangle. The ternary data are represented in the three-dimensional space with the help of transformation of coordinates and by utilization of the conception of the quasi-two-component representation of the mole fractions. A consistency test for the specific wetting Gibbs energies calculated from the binary data is carried out. The possibilities for a mathematical prediction of ternary data from adsorption data for the constituent binary mixtures are proved.

  10. Separation of phenolic compounds with modified adsorption resin from aqueous phase products of hydrothermal liquefaction of rice straw.

    PubMed

    Chen, Kaifei; Lyu, Hang; Hao, Shilai; Luo, Gang; Zhang, Shicheng; Chen, Jianmin

    2015-04-01

    Hydrothermal liquefaction can be used to convert rice straw into an aqueous phase product that contains valuable phenolic compounds. In experiments, commercial adsorption resin XAD-4 was modified by a benzene ring - α,α'-dichloro-p-xylene (DCX) - in order to separate the phenolic compounds from the aqueous phase product; and, the optimal conditions for separation were explored. The results showed that, after modification of the resin, its adsorption capacity improved by 50%, due to increases in surface area, pore volume and micropore volume. The selectivity of the resin increased when the benzene ring was introduced as the ring formed hydrogen bonds with the compounds. The optimal conditions for separation were desorption agent of 40%, 45% and 55% ethanol solution, a flow rate of 2.5-5 mL/min, and a ratio of the sample volume to the column volume was 1:1. The total content of phenolic compounds in aqueous solution increased from 18% to 78% after separation.

  11. Note on the chromatographic analyses of marine polyunsaturated fatty acids

    USGS Publications Warehouse

    Schultz, D.M.; Quinn, J.G.

    1977-01-01

    Gas-liquid chromatography was used to study the effects of saponification/methylation and thin-layer chromatographic isolation on the analyses of polyunsaturated fatty acids. Using selected procedures, the qualitative and quantitative distribution of these acids in marine organisms can be determined with a high degree of accuracy. ?? 1977 Springer-Verlag.

  12. Derivatization procedure for gas chromatographic determination of hydroxylamine

    SciTech Connect

    Pesselman, R.L.; Foral, M.J.; Langer, S.H.

    1987-04-15

    Hydroxylamine has been of special interest recently because of the possibilities of manufacturing it by using electrochemical methods in which ammonia might also be formed. Its general chemistry and applications have been described elsewhere. Presently, there are two gas chromatographic methods reported for the determination of hydroxylamine in aqueous media. The first involves reacting the hydroxylamine to form acetone oxime and subsequently injecting the aqueous solution directly into a gas chromatograph equipped with nitrogen and flame ionization detectors. The second involves oxidizing hydroxylamine to nitrous oxide and trapping the gas for determination in an electron capture equipped gas chromatograph. Limits of detection are in the micromolar range for the former and the nanomolar range for the latter. Here, an alternate gas chromatographic procedure for determining hydroxylamine as the acetone oxime is described. Neither direct aqueous injection nor elaborate instrumentation is required. Extraction of the oxime into an ether phase allows for concentrating the analyte ad facilitates the use of an internal standard. The limitations and inconveniences of direct aqueous injection are avoided included column degradation and filament burnout in mass spectrometry detectors.

  13. Optimizing Chromatographic Separation: An Experiment Using an HPLC Simulator

    ERIC Educational Resources Information Center

    Shalliker, R. A.; Kayillo, S.; Dennis, G. R.

    2008-01-01

    Optimization of a chromatographic separation within the time constraints of a laboratory session is practically impossible. However, by employing a HPLC simulator, experiments can be designed that allow students to develop an appreciation of the complexities involved in optimization procedures. In the present exercise, a HPLC simulator from "JCE…

  14. Chromatographic fingerprints analysis for evaluation of Ginkgo Biloba products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The leaf extract of Ginkgo biloba has purported value for improving mental capacities in Alzheimer’s patients. The flavonoids and the terpene lactones are considered to be the two main active components that influence human health. This paper compared an LC/UV chromatographic fingerprint method wi...

  15. Chromatographic profiles of Ginkgo biloba leaves and selected products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An LC-DAD-ESI/MS method was developed to obtain chromatographic profiles for the flavonoids and terpene lactones of Ginkgo biloba leaves and selected G. biloba products. The method was used to identify 46 glycosylated flavonols and flavones, 3 free flavonol aglycones, catechin, 10 biflavones, a dihy...

  16. Radioimmunoassay of methaqualone in human urine compared with chromatographic methods.

    PubMed

    Mulé, S J; Kogan, M; Jukofsky, D

    1978-09-01

    The 125I-radioimmunoassay for methaqualone in human urine was evaluated by a comparison with newly modified gas-liquid chromatographic and thin-layer chromatographic methods. The statistically significant sensitivity value for the radioimmunoassay was at 2 microgram of methaqualone per liter of urine. The coefficient of variation was 2.88 +/- 0.39% interassay and 2.71 +/- 0.16% intraassay. There was cross-reactivity only with metabolites of methaqualone, 4'-hydroxymethaqualone being twice as sensitively measured as methaqualone. There was complete agreement between results by radioimmunoassay and by gas-liquid chromatography in 96.7% of the samples analyzed. Only 1.2% of the radioimmunoassay values were false positives, and 2.1% false negatives (phi = 0.8917, P less than 0.001). Comparisons between the thin-layer chromatographic data and the gas-liquid chromatographic or radioimmunoassay data showed less agreement because of the 50- to 200-fold higher sensitivity of the latter two techniques. Gas-liquid chromatography therefore appears to represent the best reference method for the evaluation of the radioimmunoassay, which appears to be a very sensitive and reliable technique for detecting methaqualone and its metabolites in human urine.

  17. [Gas chromatographic analysis of benzodiazepines. 2. Diazepam and its metabolites].

    PubMed

    Heidbrink, V V; Mallach, H J; Moosmayer, A

    1975-04-01

    A gas-chromatographic method is reported which completely resolves diazepam and its major metabolites and thus enables the specific quantitation of these compounds after extraction from serum and urine. The sensitivity limits are about 3 ng/ml if 4 ml serum or urine are extracted.

  18. Carbonaceous materials for adsorptive refrigerators

    NASA Astrophysics Data System (ADS)

    Buczek, B.; Wolak, E.

    2012-06-01

    Carbon monoliths prepared from hard coal precursors were obtained. The porous structure of the monoliths was evaluated on the basis of nitrogen adsorption — desorption equilibrium data. The investigated monoliths have a well-developed microporous structure with significant specific surface area (S BET ). Equilibrium studies of methanol vapour adsorption were used to characterize the methanol adsorptive capacity that was determined using a volumetric method. The heat of wetting by methanol was determined in order to estimate the energetic effects of the adsorption process. The results of the investigations show that all monoliths exhibit high adsorption capacity and high heat of wetting with methanol.

  19. Control of ice chromatographic retention mechanism by changing temperature and dopant concentration.

    PubMed

    Tasaki, Yuiko; Okada, Tetsuo

    2011-12-15

    A liquid phase coexists with solid water ice in a typical binary system, such as NaCl-water, in the temperature range between the freezing point and the eutectic point (t(eu)) of the system. In ice chromatography with salt-doped ice as the stationary phase, both solid and liquid phase can contribute to solute retention in different fashions; that is, the solid ice surface acts as an adsorbent, while a solute can be partitioned into the liquid phase. Thus, both adsorption and partition mechanisms can be utilized for ice chromatographic separation. An important feature in this approach is that the liquid phase volume can be varied by changing the temperature and the concentration of a salt incorporated into the ice stationary phase. Thus, we can control the relative contribution from the partition mechanism in the entire retention because the liquid phase volume can be estimated from the freezing depression curve. Separation selectivity can thereby be modified. The applicability of this concept has been confirmed for the solutes of different adsorption and partition abilities. The predicted retention based on thermodynamics basically agrees well with the corresponding experimental retention. However, one important inconsistency has been found. The calculation predicts a step-like discontinuity of the solute retention at t(eu) because the phase diagram suggests that the liquid phase abruptly appears at t(eu) when the temperature increases. In contrast, the corresponding experimental plots are continuous over the wider range including the subeutectic temperatures. This discrepancy is explained by the existence of the liquid phase below t(eu). A difference between predicted and measured retention factors allows the estimation of the volume of the subeutectic liquid phase. PMID:22053829

  20. Preparation and chromatographic evaluation of zwitterionic stationary phases with controllable ratio of positively and negatively charged groups.

    PubMed

    Cheng, Xiao-Dong; Hao, Yan-Hong; Peng, Xi-Tian; Yuan, Bi-Feng; Shi, Zhi-Guo; Feng, Yu-Qi

    2015-08-15

    The present study described the preparation and application of zwitterionic stationary phases (ACS) with controllable ratio of positively charged tertiary amine groups and negatively charged carboxyl groups. Various parameters, including water content, pH values and ionic strength of the mobile phase, were investigated to study the chromatographic characteristics of ACS columns. The prepared ACS columns demonstrated a mix-mode retention mechanism composed of surface adsorption, partitioning and electrostatic interactions. The elemental analysis of different batches of the ACS phases demonstrated good reproducibility of the preparation strategy. Additionally, various categories of compounds, including nucleosides, water-soluble vitamins, benzoic acid derivatives and basic compounds were successively employed to evaluate the separation selectivity of the prepared ACS stationary phases. These ACS phases exhibited entirely different selectivity and retention behavior from each other for various polar analytes, demonstrating the excellent application potential in the analysis of polar compounds in HILIC. PMID:25966373

  1. Chromatographic characterisation, under highly aqueous conditions, of a molecularly imprinted polymer binding the herbicide 2,4-dichlorophenoxyacetic acid.

    PubMed

    Legido-Quigley, C; Oxelbark, J; De Lorenzi, E; Zurutuza-Elorza, A; Cormack, P A G

    2007-05-15

    The affinity of a 2,4-dichlorophenoxyacetic acid (2,4-D) molecularly imprinted polymer (MIP), which was synthesised directly in an aqueous organic solvent, for its template (2,4-D) was studied and compared with the affinity exhibited by two other reference (control) polymers, NIPA and NIPB, for the same analyte. Zonal chromatography was performed to establish the optimal selectivity, expressed as imprinting factor (IF), under chromatographic conditions more aqueous than those described so far in the literature. Frontal analysis (FA) was performed on columns packed with these polymers, using an optimized mobile phase composed of methanol/phosphate buffer (50/50, v/v), to extract adsorption isotherm data and retrieve binding parameters from the best isotherm model. Surprisingly, the template had comparable and strong affinity for both MIP (K = 3.8x10(4) M(-1)) and NIPA (K = 1.9x10(4) M(-1)), although there was a marked difference in the saturation capacities of selective and non-selective sites, as one would expect for an imprinted polymer. NIPB acts as a true control polymer in the sense that it has relatively low affinity for the template (K = 8.0x10(2) M(-1)). This work provides the first frontal chromatographic characterization of such a polymer in a water-rich environment over a wide concentration range. The significance of this work stems from the fact that the chromatographic approach used is generic and can be applied readily to other analytes, but also because there is an increasing demand for well-characterised imprinted materials that function effectively in aqueous media and are thus well-suited for analytical science applications involving, for example, biofluids and environmental water samples.

  2. High-performance liquid chromatographic strategies for the determination and confirmation of anticoagulant rodenticide residues in animal tissues.

    PubMed

    Hunter, K

    1985-03-15

    A comprehensive approach to the analysis of anticoagulant rodenticide residues in animal tissues based on high-performance liquid chromatography (HPLC) has been developed. Residues of warfarin, coumatetralyl, difenacoum, brodifacoum, bromadiolone, diphacinone and chlorophacinone were extracted with chloroformacetone (1:1, v/v). Extracts were cleaned-up by an integrated gel permeation and adsorption chromatographic procedure which divided the rodenticides into two groups. Residues were then determined and confirmed using normal-phase, ion-pair and weak ion-exchange HPLC techniques. Ion-pair gradient separation resolved all seven rodenticides in a single chromatographic analysis. UV detection methods were employed for all seven rodenticides. Use of a diode array detection system permitted additional confirmation of residues down to 0.1 mg kg-1 by matching UV spectra and derivatives of spectra. Sensitive fluorescence detection was possible for the coumarin-based rodenticides but not for diphacinone and chlorophacinone. Post-column pH-switching fluorescence detection methods were shown to be superior to other methods of fluorescence detection of coumarin-based rodenticides. Recoveries from spiked liver tissue were around 90% at levels from 0.05 to 1 mg kg-1. Detection limits of around 0.002 mg kg-1 for most rodenticides and of 0.01 mg kg-1 for warfarin could be achieved with animal tissue extracts. PMID:3988841

  3. Extracorporeal adsorption of endotoxin.

    PubMed

    Staubach, K H; Rosenfeldt, J A; Veit, O; Bruch, H P

    1997-02-01

    In a porcine endotoxin shock model using a continuous intravenous endotoxin infusion of 250 ng/kg body weight per hour, the cardiorespiratory and hematologic parameters were studied while applying a new on-line polymyxin B immobilized adsorption system. This preliminary report shows that the new adsorbent can remove endotoxin selectively from the circulation and confers a good amount of protection from endotoxin-induced cardiopulmonary decompensation as well as hematologic alterations. Survival time could be extended from 216 min to 313 min. Whereas cardiac output and mean arterial pressure declined critically after 3 h in the controls, the treated group remained stable for another 3 h. These data show that endotoxin adsorption by polymyxin B coupled covalently to acrylic spheres as an adjunctive on-line measure in the septic syndrome seems feasible. PMID:10225785

  4. Regenerable adsorption system

    NASA Technical Reports Server (NTRS)

    Roychoudhury, Subir (Inventor); Perry, Jay (Inventor); Walsh, Dennis (Inventor)

    2006-01-01

    A method for regenerable adsorption includes providing a substrate that defines at least one layer of ultra short channel length mesh capable of conducting an electrical current therethrough, coating at least a portion of the substrate with a desired sorbent for trace contaminant control or CO.sub.2 sorption, resistively heating the substrate, and passing a flowstream through the substrate and in contact with the sorbent.

  5. Gas chromatographic method for the determination of hexaconazole residues in black tea*

    PubMed Central

    Karthika, Chinnachamy; Sachin, Paul James

    2008-01-01

    A highly reliable, quantitative and sensitive analytical method for determining the residues of the fungicide, hexaconazole in black tea is described. The proposed method is based on liquid-liquid extraction followed by gas chromatographic determination, using nitrogen phosphorus detector (GC-NPD) for the identification and quantitation of hexaconazole. The most appropriate solvent mixture for extracting hexaconazole residues from black tea was n-hexane:acetone at 1:1 (v/v). The extract was cleaned up by adsorption column chromatography using activated florisil. Performance of the method was assessed by evaluating quality parameters such as recovery value, repeatability, reproducibility, linearity and limits of detection and quantitation. When the method was assessed for repeatability, the percentage of recovery ranged between 86% and 96% while the relative standard deviation was between 0.30% and 2.35%. In studies on reproducibility the recovery ranged from 81% to 85% and relative standard deviation from 1.68% to 5.13%, implying that the method was reliable. A field trial was conducted to verify the application of this method with real samples. Results prove that the validated method was suitable for extracting hexaconazole residues. PMID:18257139

  6. Loading capacity and chromatographic behavior of a porous graphitic carbon column for polychlorinated biphenyls

    USGS Publications Warehouse

    Echols, K.R.; Gale, R.W.; Feltz, K.; O'Laughlin, J.; Tillitt, D.E.; Schwartz, T.R.

    1998-01-01

    A porous graphitic carbon column (Hypercarb) was used for the fractionation of polychlorinated biphenyls (PCBs) into classes of 2-4 ortho chlorines, 1 ortho chlorine and 0 ortho chlorine congeners. A method was developed that combined the fractionation of PCBs, polychlorinated dibenzo- p-dioxins and dibenzofurans in a variety of biotic environmental samples. Many of these samples have high concentrations of PCBs which cause fractionation problems as adsorption sites on the graphitic surface are occupied. The loading capacity of the column for PCBs was determined by injecting up to 1 mg of total PCBs and monitoring changes in chromatographic behavior of tetra-/di-ortho, mono-ortho and non-ortho substituted PCBs. Effective loading capacities were 1 mg for tetra-/di-ortho PCBs, but only 3- 5 ??g for non-ortho PCBs and about 2 ??g for mono-ortho PCBs. Loading capacity of the PGC column for environmental fish and avian egg samples was determined to depend on the mono-ortho and non-ortho PCB levels found in these samples.

  7. Micro-column plasma emission liquid chromatograph. [Patent application

    DOEpatents

    Gay, D.D.

    1982-08-12

    In a direct current plasma emission spectrometer for use in combination with a microcolumn liquid chromatograph, an improved plasma source unit is claimed. The plasma source unit includes a quartz capillary tube having an inlet means, outlet off gas means and a pair of spaced electrodes defining a plasma region in the tube. The inlet means is connected to and adapted to receive eluant of the liquid chromatograph along with a stream of plasma-forming gas. There is an opening through the wall of the capillary tube penetrating into the plasma region. A soft glass capillary light pipe is disposed at the opening, is connected to the spectrometer, and is adapted to transmit light passing from the plasma region to the spectrometer. There is also a source of electromotive force connected to the electrodes sufficient to initiate and sustain a plasma in the plasma region of the tube.

  8. TLC chromatographic-densitometric assay of ibuprofen and its impurities.

    PubMed

    Starek, Małgorzata; Krzek, Jan

    2010-11-01

    A simple and sensitive thin-layer chromatographic (TLC)-densitometric method for the quantitative estimation of S(+)-2-[4-isobutylphenyl]propionic acid (ibuprofen) and its impurities in pharmaceutical preparations has been developed. The chromatographic separation was carried out on silica gel 60 F(254) TLC plates using toluene-ethyl acetate-glacial acetic acid (17:13: 1, v/v/v) as the mobile phase. Detection was carried out densitometrically with a UV detector. The developed method has detection and quantitation limits ranging from 0.13 μg per spot to 0.72 μg per spot. For individual constituents the recovery ranged from 96.8% to 99.0%. In addition, the stability of ibuprofen solutions was investigated, including the effect of pH, temperature, and incubation time. The method is rapid, simple, and suitable for routine quality-control analysis of pharmaceuticals containing ibuprofen.

  9. An on-line calibration method for process gas chromatographs

    SciTech Connect

    Fang, M.; Wang, F.

    1995-05-01

    Gas chromatographs (GCs) used to measure gas concentrations in process streams usually need calibration for a wide range of concentrations. The gas chromatographs used in process applications are usually equipped with automatic samplers using sample loops. The sampling system can be modified to provide on-line calibration, by adding a vacuum system and a precision pressure gage. In this paper, the authors describe a method using pure gases for the calibration of automatic GCs by varying and measuring precisely the pressure of the sample loop, thus sending known quantities of gas into the column. The concentration of the gas is calculated using the ideal gas law, and they are able to calibrate GCs in a range from 1,000 ppm to 100 vol %.

  10. Can enantiomers be separated in achiral chromatographic systems?

    NASA Astrophysics Data System (ADS)

    Davankov, V. A.

    2016-10-01

    Consideration of chromatography of a nonracemic mixture on an achiral sorbent from a stereochemical point of view allows the claim that partial separation of the excess enantiomer zone from the racemate zone is possible only with analytes capable of self-associating under the conditions of the chromatographic column. It is from these positions that features of this process can be explained and conditions for its maximal proceeding formulated.

  11. Ion-exchange chromatographic analysis of peroxynitric acid.

    PubMed

    Nakashima, Yoichi; Ikawa, Satoshi; Tani, Atsushi; Kitano, Katsuhisa

    2016-01-29

    Ion-exchange chromatographic analysis of peroxynitric acid (O2NOOH) was performed by combining an acidic eluate with an UV-vis detector and immersing the separation column in an ice-water bath. The decomposition behavior of peroxynitric acid in the solution was also studied using this system. The fraction for the peroxynitric acid peak was collected. Ion-exchange chromatographic analysis of this fraction, after standing at room temperature for 24h, showed that the decomposition products were mainly nitrate ions with a very small amount of nitrous acid. The peroxynitric acid peak area correlated perfectly with the total amount of decomposition products. The ion-exchange chromatographic isolation allowed us to evaluate the molar extinction coefficient of peroxynitric acid precisely in a wider wavelength range than previous reports. The value decreases monotonically from 1729±26M(-1)cm(-1) at 200nm to 12.0±0.5M(-1)cm(-1) at 290nm. PMID:26748867

  12. Retention Study of Flavonoids Under Different Chromatographic Modes.

    PubMed

    Sentkowska, Aleksandra; Biesaga, Magdalena; Pyrzynska, Krystyna

    2016-04-01

    The goal of this study was to investigate the chromatographic behavior of selected flavonoids from their different subgroups (flavonols, flavanones, flavones and isoflavones) in hydrophilic interaction liquid chromatography (HILIC). Chromatographic measurements were made on two different HILIC columns: cross-linked DIOL (Luna HILIC) and zwitterionic sulfoalkylbetaine (SeQuant ZIC-HILIC). Separation parameters such as the content of acetonitrile and pH of an eluent were studied. On the ZIC column, the retention factors of flavonoids increased with decreasing water content in the mobile phase. The increase in pH of the aqueous component mainly affects the polarity of the analytes. DIOL stationary phase shows more or less apparent dual retention mechanism, HILIC at the acetonitrile (ACN) content ≥75% and reversed phase (RP) with lower content of organic modifier. In the presence of ammonium acetate in the mobile phase, the retention of flavonoids onto the DIOL column increases without change in the selectivity of the separations. The similar effect, but considerably smaller was observed for aglycones on the ZIC column. The retention of studied glycosides (hesperidin, rutin) decreases in the presence of salt in the mobile phase. The significantly higher mass spectrometry sensitivity was observed under HILIC conditions in comparison with the most often used RP LC due to much higher content of ACN in the mobile phase. Finally, under optimal chromatographic conditions, the method was validated and applied for the determination of flavonoids in chamomile (Matricaria chamomilla L.) infusion. PMID:26668302

  13. Trace adsorption of positively charged proteins onto Sepharose FF and Sepharose FF-based anion exchangers.

    PubMed

    Yu, Lin-Ling; Sun, Yan

    2012-08-31

    Agarose-based matrices have been widely used in ion exchange chromatography (IEC). We have herein observed that positively charged proteins (lysozyme and cytochrome c) are adsorbed on the agarose-based anion-exchangers (Q and DEAE Sepharose FF gels) in a capacity of 10-40 μg/mL. In contrast, negatively charged protein (bovine serum albumin) is not adsorbed to Sepharose FF and SP Sepharose FF gels. Elemental analysis of the gel indicated that the residual anionic sulfate groups in agarose would have worked as the cation exchange groups for the positively charged proteins. The trace adsorption behavior of lysozyme onto Sepharose FF and Sepharose FF-based anion exchangers was studied and the effects of NaCl concentration and cation group density on the adsorption were examined for better understanding of the trace adsorption in chromatographic processes. At NaCl concentrations less than 0.05 mol/L, which is the normal adsorption condition in IEC, the trace adsorption kept at a high level, so this trace adsorption cannot be avoided in the ionic strength range of routine IEC operations. Grafting poly(ethylenimine) (PEI) chain of 60 kDa to a cation group density of 700 mmol/L could reduce the adsorption capacity to about 20 μg/mL, but further reduction was not possible by increasing the cation group density to 1200 mmol/L. Therefore, attentions need to be paid to the phenomenon in protein purification practice using agarose-based matrices. The research is expected to call attentions to the trace adsorption on agarose-based matrices and to the importance in the selection of the suitable solid matrices in the production of high-purity protein products in large-scale bioprocesses.

  14. Flame Atomic Absorption Spectrometric Determination of Trace Metal Ions in Environmental and Biological Samples After Preconcentration on a Newly Developed Amberlite XAD-16 Chelating Resin Containing p-Aminobenzene Sulfonic Acid.

    PubMed

    Islam, Aminul; Ahmad, Akil; Laskar, Mohammad Asaduddin

    2015-01-01

    Amberlite® XAD-16 was functionalized with p-aminobenzene sulfonic acid via an azo spacer in order to prepare a new chelating resin, which was then characterized by water regain value, hydrogen ion capacity, elemental analyses, and IR spectral and thermal studies. The maximum uptake of Cu(II), Ni(II), Zn(II), Co(II), Cr(III), Fe(III), and Pb(II) ions was observed in the pH range 4.0-6.0 with the corresponding half-loading times of 6.5, 7.0, 8.0, 9.0, 11.0, 8.5, and 16.5 min. The sorption data followed Langmuir isotherms and a pseudo-second-order model. Thermodynamic quantities, ΔH and ΔS, based on the variation of the distribution coefficient with temperature were also evaluated. High preconcentration factors of 60-100 up to a low preconcentration limit of 4.0-6.6 μg/L have been achieved for the metal ions. The validity of the method was checked by analyzing standard reference materials and recoveries of trace metals after spiking. The analytical applications of the method were explored by analyzing natural water, mango pulp, mint leaves, and fish. PMID:25857893

  15. Single-walled carbon nanotubes as stationary phase in gas chromatographic separation and determination of argon, carbon dioxide and hydrogen.

    PubMed

    Safavi, Afsaneh; Maleki, Norooz; Doroodmand, Mohammad Mahdi

    2010-08-24

    A chromatographic technique is introduced based on single-walled carbon nanotubes (SWCNTs) as stationary phase for separation of Ar, CO(2) and H(2) at parts per million (ppm) levels. The efficiency of SWCNTs was compared with solid materials such as molecular sieve, charcoal, multi-walled carbon nanotubes and carbon nanofibers. The morphology of SWCNTs was optimized for maximum adsorption of H(2), CO(2) and Ar and minimum adsorption of gases such as N(2), O(2), CO and H(2)O vapour. To control temperature of the gas chromatography column, peltier cooler was used. Mixtures of Ar, CO(2) and H(2) were separated according to column temperature program. Relative standard deviation for nine replicate analyses of 0.2 mL H(2) containing 10 microL of each Ar or CO(2) was 2.5% for Ar, 2.8% for CO(2) and 3.6% for H(2). The interfering effects of CO, and O(2) were investigated. Working ranges were evaluated as 40-600 ppm for Ar, 30-850 ppm for CO(2) and 10-1200 ppm for H(2). Significant sensitivity, small relative standard deviation (RSD) and acceptable limit of detection (LOD) were obtained for each analyte, showing capability of SWCNTs for gas separation and determination processes. Finally, the method was used to evaluate the contents of CO(2) in air sample.

  16. Influence of vibration of a catalyst bed on the adsorption of 1-butene on a bismuth-molybdenum catalyst

    SciTech Connect

    Barannik, G.B.; Valkov, V.; Ven'yaminov, S.A.; Schnabel, K.H.

    1982-04-01

    In a study of the thermodesorption of 1-butene on bismuth molybdates (..cap alpha..- and ..gamma..-phases), it was discovered that vibration of the catalyst bed during the adsorption of 1-butene at 30/sup 0/C results in the formation of divinyl, which is not observed in the absence of vibration. A vibrationally fluidized catalyst bed has been used to eliminate the temperature gradient over the bed, and the details of the procedure were described previously. The conclusion that divinyl forms was drawn on the basis of thermodesorption data and comfirmed by chromatographic analysis of the gaseous phase during adsorption. The thermodesorption spectrum obtained with vibration of the catalyst during adsorption differs from the spectrum for the case of adsorption without vibration and is similar to the spectrum obtained following the adsorption of divinyl. By varying the vibration time, it is possible to obtain spectra occupying intermediate positions. This phenomenon is due to the readsorption of divinyl formed during the adsorption of 1-butene and is observed only in cases in which the vibration of the catalyst was carried out in the adsorption step.

  17. Cd adsorption onto bacterial surfaces: A universal adsorption edge?

    NASA Astrophysics Data System (ADS)

    Yee, Nathan; Fein, Jeremy

    2001-07-01

    In this study, we measure the thermodynamic stability constants for proton and Cd binding onto the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa, and the Gram-positive bacteria Bacillus megaturium, Streptococcus faecalis, Staphylococcus aureus, Sporosarcina ureae, and Bacillus cereus. Potentiometric titrations and Cd-bacteria adsorption experiments yield average values for the carboxyl site pK a, site concentration, and log stability constant for the bacterial surface Cd-carboxyl complex of 5.0, 2.0 × 10 -3 mol/g and 4.0 respectively. Our results indicate that a wide range of bacterial species exhibit nearly identical Cd adsorption behavior as a function of pH. We propose that metal-bacteria adsorption is not dependent on the bacterial species involved, and we develop a generalized adsorption model which may greatly simplify the task of quantifying the effects of bacterial adsorption on dissolved mass transport in realistic geologic systems.

  18. Rethinking Critical Adsorption

    NASA Astrophysics Data System (ADS)

    Franck, Carl; Peach, Sarah; Polak, Robert D.

    1996-03-01

    Recent reflectivity experiments on near-critical mixtures of carbon disulfide and nitromethane contained in glass cells footnote Niraj S. Desai, Sarah Peach, and Carl Franck, Phys. Rev. E 52, 4129 (1995) have shown that preferential adsorption of one liquid component onto the wall can be controlled by chemical modification of the glass. The glass was treated with varying amounts of hexamethyldisilazane to decrease surface polarity and therefore enhance the adsorption of carbon disulfide in a surprisingly continuous way. The effect of the glass wall on the local liquid composition can be described by two different scaling hypotheses: using a short range field on the liquid closest to the wall, or pinning the amplitude of the order parameter at the surface. We have found that only the second approach is consistent with the experimental data, although this is difficult to reconcile with observed wetting critical phenomena. We also have reexamined the issue of substrate inhomogeneity and conclude that the substrates were indeed homogeneous on relevant length scales. Supported by the NSF under DMR-9320910 and the central facilities of the Materials Science Center at Cornell University.

  19. Global versus local adsorption selectivity

    NASA Astrophysics Data System (ADS)

    Pauzat, Françoise; Marloie, Gael; Markovits, Alexis; Ellinger, Yves

    2015-10-01

    The origin of the enantiomeric excess found in the amino acids present in the organic matter of carbonaceous meteorites is still unclear. Selective adsorption of one of the two enantiomers existing after a racemic formation could be part of the answer. Hereafter we report a comparative study of the adsorption of the R and S enantiomers of α-alanine and lactic acid on the hydroxylated { } chiral surface of α-quartz using numerical simulation techniques. Structurally different adsorption sites were found with opposite R versus S selectivity for the same molecule-surface couple, raising the problem of whether to consider adsorption as a local property or as a global response characteristic of the whole surface. To deal with the second term of this alternative, a statistical approach was designed, based on the occurrence of each adsorption site whose energy was calculated using first principle periodic density functional theory. It was found that R-alanine and S-lactic acid are the enantiomers preferentially adsorbed, even if the adsorption process on the quartz { } surface stays with a disappointingly poor enantio-selectivity. Nevertheless, it highlighted the important point that considering adsorption as a global property changes perspectives in the search for more efficient enantio-selective supports and more generally changes the way to apprehend adsorption processes in astro-chemistry/biology.

  20. Design method for adsorption beds

    NASA Technical Reports Server (NTRS)

    Blakely, R. L.; Jackson, J. K.

    1970-01-01

    Regenerable adsorption beds for long-term life support systems include synthetic geolite to remove carbon dioxide and silica gel to dehumidify the atmospheric gas prior to its passage through the geolite beds. Bed performance is evaluated from adsorption characteristics, heat and mass transfer, and pressure drop.

  1. Liquid-Phase Adsorption Fundamentals.

    ERIC Educational Resources Information Center

    Cooney, David O.

    1987-01-01

    Describes an experiment developed and used in the unit operations laboratory course at the University of Wyoming. Involves the liquid-phase adsorption of an organic compound from aqueous solution on activated carbon, and is relevant to adsorption processes in general. (TW)

  2. Adsorption and desorption kinetics of bovine serum albumin in ion exchange and hydrophobic interaction chromatography on silica matrices.

    PubMed

    Conder; Hayek

    2000-12-01

    Large scale chromatographic separation of proteins can be carried out more rapidly on rigid adsorbents than on soft gel media. The kinetics of adsorption of bovine serum albumin (BSA) have been studied on rigid adsorbents based on a wide-pore, hydrophilically-coated silica gel matrix in a packed bed (chromatographic column). Process parameters have been varied comprehensively. The effects of surface chemistry (weak anion exchanger and hydrophobic interaction), particle size and liquid flow velocity have been studied on both the adsorption and desorption processes. The relative influences of the adsorption kinetics and equilibrium isotherm on the shape of the breakthrough curve are found to vary with the process parameters in an interpretable and therefore, predictable manner. Pore diffusion resistance is dominant over the external liquid film resistance in controlling the adsorption kinetics, with Biot numbers in the range 170-2600. A two-step model based on these two resistances simulates the breakthrough curves with only limited quantitative accuracy, but gives good predictions of the effect of changes in process parameters. PMID:11080653

  3. High temperature adsorption measurements

    SciTech Connect

    Bertani, R.; Parisi, L.; Perini, R.; Tarquini, B.

    1996-12-31

    Adsorption phenomena are a rich and rather new field of study in geothermal research, in particular at very high temperature. ENEL is interested in the exploitation of geothermal regions with super-heated steam, and it is important to understand the behavior of water-rock interaction. We have analyzed in the 170-200{degrees}C temperature range four samples of Monteverdi cuttings; the next experimental effort will be at 220{degrees}C and over in 1996. The first results of the 1995 runs are collected in this paper. We can highlight four main items: (1) At relative pressures over 0.6 the capillarity forces are very important. (2) There is no significant temperature effect. (3) Adsorbed water can be present, and it is able to multiply by a factor of 15 the estimated reserve of super-heated steam only. (4) Pores smaller than 15 {Angstrom} do not contribute to the adsorbed mass.

  4. High temperature adsorption measurements

    SciTech Connect

    Bertani, R.; Parisi, L.; Perini, R.; Tarquini, B.

    1996-01-24

    Adsorption phenomena are a rich and rather new field of study in geothermal research, in particular at very high temperature. ENEL is interested in the exploitation of geothermal regions with superheated steam, and it is important to understand the behavior of water-rock interaction. We have analyzed in the 170-200 °C temperature range four samples of Monteverdi cuttings; the next experimental effort will be at 220 °C and over in 1996. The first results of the 1995 runs are collected in this paper. We can highlight four main items: 1. At relative pressures over 0.6 the capillarity forces are very important. 2. There is no significant temperature effect. 3. Adsorbed water can be present, and it is able to multiply by a factor of 15 the estimated reserve of super-heated steam only. 4. Pores smaller than 15 Å do not contribute to the adsorbed mass.

  5. Protein adsorption to poly(ethylenimine)-modified Sepharose FF. IV. Dynamic adsorption and elution behaviors.

    PubMed

    Liu, Na; Yu, Lin-Ling; Sun, Yan

    2014-10-01

    We have previously investigated bovine serum albumin (BSA) uptake to poly(ethylenimine) (PEI)-grafted Sepharose FF. It was found that there was a critical ionic capacity (cIC; 600mmol/L) for BSA, above which the protein adsorption capacity and uptake kinetics increased drastically. In this work, two poly(ethylenimine) (PEI)-grafted resins with IC values of 271mmol/L (FF-PEI-L270) and 683mmol/L (FF-PEI-L680), which were below and above the cIC, respectively, were chosen to investigate the breakthrough and linear gradient elution (LGE) behaviors of BSA. Commercially available anion exchanger, Q Sepharose FF, was used for comparison. The DBC values of FF-PEI-L680 were much higher in the entire residence time range (2-10min) than the other two resins due to its high static adsorption capacity and uptake kinetics. At a residence time of 5.0min, the DBC of FF-PEI-L680 (104mg/mL) was about seven times that of FF-PEI-L270 and three times that of Q Sepharose FF. A rise-fall trend of the DBCs with increasing ionic strength (IS) was found for all the three resins studied, indicating the presence of electrostatic exclusion for protein uptake at low IS. With increasing NaCl concentration from 20 to 200mmol/L, FF-PEI-L680 kept very high DBC values (64-114mg/mL). In addition, FF-PEI-L270 showed more favorable adsorption properties than Q Sepharose FF at 100-300mmol/L NaCl. These results proved that the three-dimensional grafting ion exchange layer on the PEI resins enhanced their tolerance to IS. In the study of LGE, the three resins showed similar elution behaviors and no distinct peak tailings were observed. The salt concentrations at the elution peaks (IR) were in the order of FF-PEI-L680>FF-PEI-L270>Q Sepharose FF, indicating that the elution for the PEI resins needed higher salt concentrations, which was also an appearance of the salt-tolerant feature of the PEI resins. When protein loading amount was increased to the value equivalent to the DBC at 10% breakthrough, the

  6. Protein adsorption to poly(ethylenimine)-modified Sepharose FF. IV. Dynamic adsorption and elution behaviors.

    PubMed

    Liu, Na; Yu, Lin-Ling; Sun, Yan

    2014-10-01

    We have previously investigated bovine serum albumin (BSA) uptake to poly(ethylenimine) (PEI)-grafted Sepharose FF. It was found that there was a critical ionic capacity (cIC; 600mmol/L) for BSA, above which the protein adsorption capacity and uptake kinetics increased drastically. In this work, two poly(ethylenimine) (PEI)-grafted resins with IC values of 271mmol/L (FF-PEI-L270) and 683mmol/L (FF-PEI-L680), which were below and above the cIC, respectively, were chosen to investigate the breakthrough and linear gradient elution (LGE) behaviors of BSA. Commercially available anion exchanger, Q Sepharose FF, was used for comparison. The DBC values of FF-PEI-L680 were much higher in the entire residence time range (2-10min) than the other two resins due to its high static adsorption capacity and uptake kinetics. At a residence time of 5.0min, the DBC of FF-PEI-L680 (104mg/mL) was about seven times that of FF-PEI-L270 and three times that of Q Sepharose FF. A rise-fall trend of the DBCs with increasing ionic strength (IS) was found for all the three resins studied, indicating the presence of electrostatic exclusion for protein uptake at low IS. With increasing NaCl concentration from 20 to 200mmol/L, FF-PEI-L680 kept very high DBC values (64-114mg/mL). In addition, FF-PEI-L270 showed more favorable adsorption properties than Q Sepharose FF at 100-300mmol/L NaCl. These results proved that the three-dimensional grafting ion exchange layer on the PEI resins enhanced their tolerance to IS. In the study of LGE, the three resins showed similar elution behaviors and no distinct peak tailings were observed. The salt concentrations at the elution peaks (IR) were in the order of FF-PEI-L680>FF-PEI-L270>Q Sepharose FF, indicating that the elution for the PEI resins needed higher salt concentrations, which was also an appearance of the salt-tolerant feature of the PEI resins. When protein loading amount was increased to the value equivalent to the DBC at 10% breakthrough, the

  7. Chromatographic selectivity study of 4-fluorophenylacetic acid positional isomers separation.

    PubMed

    Chasse, Tyson; Wenslow, Robert; Bereznitski, Yuri

    2007-07-13

    Unique properties of the fluorine atom stimulate widespread use and development of new organofluorine compounds in agrochemistry, biotechnology and pharmacology applications. However, relatively few synthetic methods exhibit a high degree of fluorination selectivity, which ultimately results in the presence of structurally related fluorinated isomers in the synthetic product. This outcome is undesirable from a pharmaceutical perspective as positional isomers possess different reactivity, biological activity and toxicity as compared to the desired product. It is advantageous to control positional isomers in the early stages of the synthetic process, as rejection and analysis of these isomers will likely become more difficult in later stages. The current work reports the development of a chromatographic analysis of 2- and 3-fluorophenylacetic acid positional isomer impurities in 4-fluorophenylacetic acid (4-FPAA), a building block in the synthesis of an active pharmaceutical ingredient. The method is employed as a part of a Quality by Design Approach to control purity of the starting material in order to eliminate the presence of undesirable positional isomers in the final drug substance. During method development, a wide range of chromatographic conditions and structurally related positional isomer probe molecules were exploited in an effort to gain insight into the specifics of the separation mechanism. For the systems studied it was shown that the choice of organic modifier played a key role in achieving acceptable separation. Further studies encompassed investigation of temperature influence on retention and selectivity of the FPAA isomers separation. Thermodynamic analysis of these data showed that the selectivity of the 2- and 4- fluorophenylacetic acids separation was dominated by an enthalpic process, while the selectivity of the 4- and 3-fluorophenylacetic acids separation was exclusively entropy driven (Delta(DeltaH degrees approximately 0). Studies of

  8. Rotating annular chromatograph for continuous metal separations and recovery

    SciTech Connect

    Begovich, J.M.; Sisson, W.G.

    1981-01-01

    Multicomponent liquid chromatographic separations have been achieved by using a slowly rotating annular bed of sorbent material. By continuously introducing the feed material to be separated at a stationary point at the top of the bed and eluent everywhere else around the annulus, elution chromatography occurs. The rotation of the sorbent bed causes the separated components to appear as helical bands, each of which has a characteristic, stationary exit point; hence, the separation process is truly continuous. The concept has been developed primarily on a 279-mm-diam by 0.6-m-long device with a 12.7-mm-wide annulus. The effect of annulus width and diameter has recently been studied using the same device with a 50.8-mm-wide annulus and another 0.6-m-long chromatograph with an 89-mm diameter and annulus widths of 6.4, 12.7, and 22.2 mm. These columns have been constructed of Plexiglas and typically operate at a gauge pressure of 175 kPa. To further study the effect of size and pressure, a new 445-mm-diam by 1-m-long column with a 31.8-mm-wide annulus has been fabricated. Its metal construction allows preparative-scale operation with a wide variety of liquids at pressures to 1.3 MPa. Three metal recovery systems have been explored: (1) separation of iron and aluminum in ammonium sulfate-sulfuric acid solutions; (2) separation of hafnium from zirconium in sulfuric acid solutions; and (3) the separation of copper, nickel, and cobalt in ammonium carbonate solutions. This last system simulates the leach liquor of the Caron process for recovering nickel and cobalt from laterite ores. It has been studied, using similar conditions, on each of the chromatographs, and the results demonstrate the effect of column dimensions on the quality and quantity of the separation. 8 figures, 1 table.

  9. Methods and apparatus for analysis of chromatographic migration patterns

    DOEpatents

    Stockham, T.G.; Ives, J.T.

    1993-12-28

    A method and apparatus are presented for sharpening signal peaks in a signal representing the distribution of biological or chemical components of a mixture separated by a chromatographic technique such as, but not limited to, electrophoresis. A key step in the method is the use of a blind deconvolution technique, presently embodied as homomorphic filtering, to reduce the contribution of a blurring function to the signal encoding the peaks of the distribution. The invention further includes steps and apparatus directed to determination of a nucleotide sequence from a set of four such signals representing DNA sequence data derived by electrophoretic means. 16 figures.

  10. Methods and apparatus for analysis of chromatographic migration patterns

    DOEpatents

    Stockham, Thomas G.; Ives, Jeffrey T.

    1993-01-01

    A method and apparatus for sharpening signal peaks in a signal representing the distribution of biological or chemical components of a mixture separated by a chromatographic technique such as, but not limited to, electrophoresis. A key step in the method is the use of a blind deconvolution technique, presently embodied as homomorphic filtering, to reduce the contribution of a blurring function to the signal encoding the peaks of the distribution. The invention further includes steps and apparatus directed to determination of a nucleotide sequence from a set of four such signals representing DNA sequence data derived by electrophoretic means.

  11. [Determining thorium level in urine with its preliminary chromatographic extraction].

    PubMed

    Kononykina, N N; Astafurov, V I; Zablotskaia, I D; Popov, V I

    1990-01-01

    The contributors propose a radiometric technique of detecting thorium in urine. The technique is based on a prior concentrating of the nuclide on phosphate residues, with its further separation in extraction-chromatographic vessel filled with diethylhexylphosphorus acid, and reextraction with oxalic acid. Measurements were made in the hard scintillator layer at 90 percent effectiveness. Thorium chemical output was at 85 +/- 3 percent, sensitivity at 5 mBk for a sample. If the sample contained an equal quantity of uranium, the percentage of cleaning thorium from uranium was 100. The proposed technique is economical, simple to perform, and is designed for natural thorium content measurements in human organism. PMID:2086364

  12. Liquid chromatographic determination of ethylenethiourea using pulsed amperometric detection.

    PubMed

    Doerge, D R; Yee, A B

    1991-11-01

    A liquid chromatographic method was developed using pulsed amperometric detection at a gold working electrode to measure residue levels of ethylenethiourea (ETU) in crops and groundwater. Use of the sequential pulsing program eliminates electrode fouling while preserving the sensitive and selective detection of ETU. Minimum detection limits in crops were 5-10 ppb (1.25-2.5 ng on-column) and 5 ppb (0.5 ng) in groundwater. The commercial availability of the pulsed electrochemical detector and its gold working electrode that remains functional with a minimum of conditioning is an improvement in method simplicity.

  13. Interpretation of dynamic frontal analysis data in solid/supercritical fluid adsorption systems. I: theory.

    PubMed

    Gritti, Fabrice; Tarafder, Abhijit; Guiochon, Georges

    2013-05-17

    A theory is proposed to relate the elution times of the adsorption front shocks of breakthrough curves recorded during classical dynamic frontal analysis (FA) experiments with selected compounds and their adsorption isotherms in solid/supercritical fluid adsorption systems. The actual density and viscosity of binary mixtures of CO2 and methanol were obtained from the NIST REPPROP software. Diluted solutions of S-naproxen were considered (<2% in mass) but the possible effects of the analyte concentration on the viscosity and the density of the eluent percolating through the column were neglected. This allows the determination of the excess adsorption isotherm (or Gibbs excess isotherm) of the adsorbed analyte in the whole column at constant mass and volumetric flow rate of pure CO2 and of the modifier solution. A local Langmuir adsorption isotherm and a constant saturation capacity were assumed in the calculations. The variation of the adsorption-desorption constant with the eluent density was taken from the experimental variation of the retention factor of S-naproxen on a chiral column packed with Whelk-O1 particles. The results show that the isotherm parameters obtained from the best adjustment of the Langmuir model to the SFC excess adsorption data deviates by less than 7% from the assumed saturation capacity and from the average of the equilibrium constant along the chromatographic column. In practice, this conclusion holds true provided that the precision of the measurement of elution times of front shocks of breakthrough curves is better than 1% and that the maximum surface coverage qexp,max/qS is at least equal to 20%.

  14. Random sequential adsorption on fractals.

    PubMed

    Ciesla, Michal; Barbasz, Jakub

    2012-07-28

    Irreversible adsorption of spheres on flat collectors having dimension d < 2 is studied. Molecules are adsorbed on Sierpinski's triangle and carpet-like fractals (1 < d < 2), and on general Cantor set (d < 1). Adsorption process is modeled numerically using random sequential adsorption (RSA) algorithm. The paper concentrates on measurement of fundamental properties of coverages, i.e., maximal random coverage ratio and density autocorrelation function, as well as RSA kinetics. Obtained results allow to improve phenomenological relation between maximal random coverage ratio and collector dimension. Moreover, simulations show that, in general, most of known dimensional properties of adsorbed monolayers are valid for non-integer dimensions.

  15. [A novel multiple-channel apparatus for packing capillary chromatographic column and its application].

    PubMed

    Lü, Yayao; Hao, Feiran; Wang, Huanhuan; Fu, Bin; Qian, Xiaohong; Zhang, Yangjun

    2015-11-01

    A novel multiple-channel apparatus for packing capillary chromatographic column was designed and manufactured for packing six capillary chromatographic columns with close column efficiency at the same time. Briefly, it consists of a magnetic stirrer, a liquid chromatographic pump and a multiple-channel can. The reagents used for preparing ODS (C18) slurry and stirring condition of the magnetic stirrer were optimized in the study. Two batches of capillary chromatographic columns were packed under the optimum condition, and these packed capillary chromatographic columns were evaluated in the terms of peak capacity, sequence coverage, retention times of three peptide ions and column pressure using the tryptic digest of a bovine serum albumin (BSA) and detected by LC-MS in electrospray ionization (ESI) mode. The experimental results showed that the six capillary chromatographic columns packed at the same time had close column efficiencies, however, the column efficiencies of twelve capillary chromatographic columns packed at two times were significantly different. In addition, there was no significant column efficiency difference when packing one or six capillary chromatographic columns at the same time. The multiple-channel apparatus designed by us is simple, time-saving, and can be applied to pack capillary chromatographic columns with similar column efficiencies, thus it is of evident advantage over traditional one-channel apparatus.

  16. Protein Adsorption in Three Dimensions

    PubMed Central

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  17. Multi-objective optimization of chromatographic rare earth element separation.

    PubMed

    Knutson, Hans-Kristian; Holmqvist, Anders; Nilsson, Bernt

    2015-10-16

    The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium. PMID:26375205

  18. [Chromatographic separation of plasmid DNA by anion-exchange cryogel].

    PubMed

    Guo, Yantao; Shen, Shaochuan; Yun, Junxian; Yao, Kejian

    2012-08-01

    Plasmid DNA (pDNA) is used as an important vector for gene therapy, and its wide application is restricted by the purity and yield. To obtain high-purity pDNA, a chromatographic method based on anion-exchange supermacroporous cryogel was explored. The anion-exchange cryogel was prepared by grafting diethylaminoethyl-dextran to the epoxide groups of polyacrylamide-based matrix and pUC19 plasmid was used as a target to test the method. The plasmid was transferred into Escherichia coli DH5alpha, cultivated, harvested and lysed. The obtained culture was centrifuged and the supernatant was used as the plasmid feedstock, which was loaded into the anion-exchange cryogel bed for chromatographic separation. By optimizing the pH of running buffer and the elution conditions, high-purity pDNA was obtained by elution with 0.5 mol/L sodium chloride solution at pH 6.6. Compared to the traditional methods for purification of pDNA, animal source enzymes and toxic reagents were not involved in the present separation process, ensuring the safety of both the purification operations and the obtained pDNA.

  19. Gas chromatographic characterization of vegetable oil deodorization distillate.

    PubMed

    Verleyen, T; Verhe, R; Garcia, L; Dewettinck, K; Huyghebaert, A; De Greyt, W

    2001-07-01

    Because of its complex nature, the analysis of deodorizer distillate is a challenging problem. Deodorizer distillate obtained from the deodorization process of vegetable oils consists of many components including free fatty acids, tocopherols, sterols, squalene and neutral oil. A gas chromatographic method for the analysis of deodorizer distillate without saponification of the sample is described. After a concise sample preparation including derivatization and silylation, distillate samples were injected on column at 60 degrees C followed by a gradual increase of the oven temperature towards 340 degrees C. The temperature profile of the oven was optimized in order to obtain a baseline separation of the different distillate components including free fatty acids, tocopherols, sterols, squalene and neutral oil. Good recoveries for delta-tocopherol, alpha-tocopherol, stigmasterol and cholesteryl palmitate of 97, 94.4, 95.6 and 92%, respectively were obtained. Repeatability of the described gas chromatographic method was evaluated by analyzing five replicates of a soybean distillate. Tocopherols and sterols had low relative standard deviations ranging between 1.67 and 2.25%. Squalene, mono- and diacylglycerides had higher relative standard deviations ranging between 3.33 and 4.12%. Several industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower and soybean have been analyzed for their composition.

  20. Influence of barometric pressure on the results of chromatographic analysis

    SciTech Connect

    Sivchenko, V.Ya.; Mal'tsev, E.K.; Voloshina, I.V.; Simonov, V.M.

    1986-07-01

    Changes in barometric pressure introduce an additional error to the results obtained with different types of gas analyzers. These errors can be reduced or eliminated by technical steps or by the application of corrections to the results obtained. In this paper, the authors present the results of their determinations of correction coefficients for gases measured by the Poisk chromatograph in the range of barometric pressures from 80 to 120 kPa (from 600 to 900 mm Hg). The authors designed their investigations to simulate increased and reduced barometric pressures with respect to the calibration pressure simultaneously at the outlet from the chromatographic columns (carrier gas discarding tube) and in the dosed volume. A head in the dosing volume and in the carrier gas outlets from the columns, simulating an increase in atmospheric pressure, was created by using compressed gas from a cylinder and a regulating valve; dilution, corresponding to a decrease in atmospheric pressure, was created by a flow rate stimulator and a regulating valve. A storage capacity eliminated fluctuations of the reduced or excess pressure.

  1. Nanodiamond-Decorated Silica Spheres as a Chromatographic Material.

    PubMed

    Xue, Zuqin; Vinci, John C; Colón, Luis A

    2016-02-17

    Nanodiamond (ND) particles (∼5 nm), obtained from detonation soot, were oxidized and/or thermally hydrogenated. Both, the non-hydrogenated and hydrogenated ND particles were successfully coupled to the surface of micrometer-size organo-silica particles. A thin layer of nanodiamonds (NDs) decorating the surface of the organo-silica particles was visible on transmission electron microscopy (TEM) images. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) were used to characterize the NDs prior to coupling and to confirm attachment onto the organo-silica particles. Both, ultraviolet (UV) radiation and a chemical initiator were proved to be effective radical initiators for the ND-silica coupling reaction, although for scale-up purposes the chemical initiation was more advantageous to produce the ND-silica composite. Commercially available nanodiamond primary particles were also coupled to the surface of silica particles. The ND-containing silica particles were packed into chromatographic columns to study their initial feasibility as adsorbent material for liquid chromatography. The organo-silica particles decorated with hydrogenated NDs were shown to possess reversed phase type (i.e., hydrophobic) behavior toward the probe compounds, whereas silica particles decorated with the non-hydrogenated NDs showed polar (i.e., hydrophilic) interactions, both under liquid chromatographic conditions. PMID:26790050

  2. Multi-objective optimization of chromatographic rare earth element separation.

    PubMed

    Knutson, Hans-Kristian; Holmqvist, Anders; Nilsson, Bernt

    2015-10-16

    The importance of rare earth elements in modern technological industry grows, and as a result the interest for developing separation processes increases. This work is a part of developing chromatography as a rare earth element processing method. Process optimization is an important step in process development, and there are several competing objectives that need to be considered in a chromatographic separation process. Most studies are limited to evaluating the two competing objectives productivity and yield, and studies of scenarios with tri-objective optimizations are scarce. Tri-objective optimizations are much needed when evaluating the chromatographic separation of rare earth elements due to the importance of product pool concentration along with productivity and yield as process objectives. In this work, a multi-objective optimization strategy considering productivity, yield and pool concentration is proposed. This was carried out in the frame of a model based optimization study on a batch chromatography separation of the rare earth elements samarium, europium and gadolinium. The findings from the multi-objective optimization were used to provide with a general strategy for achieving desirable operation points, resulting in a productivity ranging between 0.61 and 0.75 kgEu/mcolumn(3), h(-1) and a pool concentration between 0.52 and 0.79 kgEu/m(3), while maintaining a purity above 99% and never falling below an 80% yield for the main target component europium.

  3. Liquid chromatographic determination of vitamin B-6 in foods.

    PubMed

    Vanderslice, J T; Brownlee, S R; Cortissoz, M E

    1984-01-01

    Chromatographic analysis for vitamin B-6 in complex samples imposes certain requirements on the analyst, who must extract completely the bound, unstable vitamers without loss, remove interfering compounds, and provide clean extracts for analysis. The analyst also has to contend with the problems inherent in all methods, such as sample collection, storage, preparation, and homogenization. However, chromatography provides a means of identifying and quantitating all forms of the vitamin, and thus provides the possibility of addressing the problem of the bioavailability of specific vitamers. It also allows automation, which is absolutely essential in coping with the large numbers of samples that are generated in areas such as quality control. These factors are all addressed here, and chromatographic results for various meat and other food products are presented to illustrate the variations in vitamin content that occur from sample to sample, the agreement with microbiological results, and that liquid chromatography (LC) has come of age in dealing with complex biological samples, such as food and food products.

  4. Gas chromatographic characterization of vegetable oil deodorization distillate.

    PubMed

    Verleyen, T; Verhe, R; Garcia, L; Dewettinck, K; Huyghebaert, A; De Greyt, W

    2001-07-01

    Because of its complex nature, the analysis of deodorizer distillate is a challenging problem. Deodorizer distillate obtained from the deodorization process of vegetable oils consists of many components including free fatty acids, tocopherols, sterols, squalene and neutral oil. A gas chromatographic method for the analysis of deodorizer distillate without saponification of the sample is described. After a concise sample preparation including derivatization and silylation, distillate samples were injected on column at 60 degrees C followed by a gradual increase of the oven temperature towards 340 degrees C. The temperature profile of the oven was optimized in order to obtain a baseline separation of the different distillate components including free fatty acids, tocopherols, sterols, squalene and neutral oil. Good recoveries for delta-tocopherol, alpha-tocopherol, stigmasterol and cholesteryl palmitate of 97, 94.4, 95.6 and 92%, respectively were obtained. Repeatability of the described gas chromatographic method was evaluated by analyzing five replicates of a soybean distillate. Tocopherols and sterols had low relative standard deviations ranging between 1.67 and 2.25%. Squalene, mono- and diacylglycerides had higher relative standard deviations ranging between 3.33 and 4.12%. Several industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower and soybean have been analyzed for their composition. PMID:11471811

  5. Chromatographic methods for the bioanalysis of antiviral agents.

    PubMed

    Riley, C M; Ault, J M; Klutman, N E

    1990-10-12

    The present review has concentrated on chromatographic techniques for the quantitative determination of antiviral drugs in biological samples. Special attention has been paid to the elements of chromatographic assays that are essential to ensure selectivity, sensitivity, accuracy and precision of the various methods. Wherever possible, attempts have been made to determine the suitability of the methods for application to investigations in pharmacokinetics in man and experimental animals, biopharmaceutics, therapeutic drug monitoring, metabolism and pharmacology. Because of the serious consequences of infection from material contaminated with viruses, special consideration has been given to the handling of contaminated samples. It was convenient to divide the antiviral drugs for the purpose of this review into two groups, the nucleoside and the non-nucleoside antiviral drugs. The nucleosides discussed are vidarabine, cytarabine, ribavirin, riboxamide, acyclovir, ganciclovir, desciclovir, carbovir, 2',3'-dideoxyadenosine, 2',3'-dideoxycytidine, zidovudine, 2',3'-dideoxyinosine, 2',3'-didehydro-3'-deoxythymidine, idoxuridine, 5-(2-bromovinyl)-2'-deoxyuridine, 2'-fluoro-5-iodoaracytidine and 5-iodo-2'-deoxycytidine. The non-nucleoside antiviral drugs discussed are arildone, amantidine, rimantidine, moroxydine, enviroxime, foscarnet and ampligen. PMID:2258420

  6. [Chromatographic separation of plasmid DNA by anion-exchange cryogel].

    PubMed

    Guo, Yantao; Shen, Shaochuan; Yun, Junxian; Yao, Kejian

    2012-08-01

    Plasmid DNA (pDNA) is used as an important vector for gene therapy, and its wide application is restricted by the purity and yield. To obtain high-purity pDNA, a chromatographic method based on anion-exchange supermacroporous cryogel was explored. The anion-exchange cryogel was prepared by grafting diethylaminoethyl-dextran to the epoxide groups of polyacrylamide-based matrix and pUC19 plasmid was used as a target to test the method. The plasmid was transferred into Escherichia coli DH5alpha, cultivated, harvested and lysed. The obtained culture was centrifuged and the supernatant was used as the plasmid feedstock, which was loaded into the anion-exchange cryogel bed for chromatographic separation. By optimizing the pH of running buffer and the elution conditions, high-purity pDNA was obtained by elution with 0.5 mol/L sodium chloride solution at pH 6.6. Compared to the traditional methods for purification of pDNA, animal source enzymes and toxic reagents were not involved in the present separation process, ensuring the safety of both the purification operations and the obtained pDNA. PMID:23185899

  7. Centrifugal Adsorption Cartridge System

    NASA Technical Reports Server (NTRS)

    Gonda, Steve R.; Tsao, Yow-Min D.; Lee, Wenshan

    2004-01-01

    The centrifugal adsorption cartridge system (CACS) is an apparatus that recovers one or more bioproduct(s) from a dilute aqueous solution or suspension flowing from a bioreactor. The CACS can be used both on Earth in unit gravity and in space in low gravity. The CACS can be connected downstream from the bioreactor; alternatively, it can be connected into a flow loop that includes the bioreactor so that the liquid can be recycled. A centrifugal adsorption cartridge in the CACS (see figure) includes two concentric cylinders with a spiral ramp between them. The volume between the inner and outer cylinders, and between the turns of the spiral ramp is packed with an adsorbent material. The inner cylinder is a sieve tube covered with a gas-permeable, hydrophobic membrane. During operation, the liquid effluent from the bioreactor is introduced at one end of the spiral ramp, which then constrains the liquid to flow along the spiral path through the adsorbent material. The spiral ramp also makes the flow more nearly uniform than it would otherwise be, and it minimizes any channeling other than that of the spiral flow itself. The adsorbent material is formulated to selectively capture the bioproduct(s) of interest. The bioproduct(s) can then be stored in bound form in the cartridge or else eluted from the cartridge. The centrifugal effect of the spiral flow is utilized to remove gas bubbles from the liquid. The centrifugal effect forces the bubbles radially inward, toward and through the membrane of the inner cylinder. The gas-permeable, hydrophobic membrane allows the bubbles to enter the inner cylinder while keeping the liquid out. The bubbles that thus enter the cylinder are vented to the atmosphere. The spacing between the ramps determines rate of flow along the spiral, and thereby affects the air-bubble-removal efficiency. The spacing between the ramps also determines the length of the fluid path through the cartridge adsorbent, and thus affects the bioproduct

  8. Improving stability of virus-like particles by ion-exchange chromatographic supports with large pore size: advantages of gigaporous media beyond enhanced binding capacity.

    PubMed

    Yu, Mengran; Li, Yan; Zhang, Songping; Li, Xiunan; Yang, Yanli; Chen, Yi; Ma, Guanghui; Su, Zhiguo

    2014-02-28

    Limited binding capacity and low recovery of large size multi-subunits virus-like particles (VLPs) in conventional agarose-gel based chromatographic supports with small pores have long been a bottleneck limiting the large scale purification and application of VLPs. In this study, four anion exchange media including DEAE-Sepharose FF (DEAE-FF), DEAE-Capto, gigaporous DEAE-AP-120nm and DEAE-AP-280nm with average pore diameters of 32nm, 20nm, 120nm and 280nm, respectively, were applied for purification of hepatitis B virus surface antigen (HBsAg) VLPs. Pore size effects of media on the VLPs adsorption equilibrium, adsorption kinetics, dynamic binding capacity (DBC), and recovery were investigated in detail. According to the confocal laser scanning microscopy observation, adsorption of the VLPs in DEAE-FF and DEAE-Capto was mostly confined to a thin shell on the outer surface of the beads, leaving the underlying pore space and the binding sites inaccessibly, while the large pores in gigaporous media enabled the VLPs to access to the interior pore spaces by diffusion transport efficiently. Compared to the most widely used DEAE-FF, gigaporous media DEAE-AP-280nm gained about 12.9 times increase in static adsorption capacity, 8.0 times increase in DBC, and 11.4 times increase in effective pore diffusivity. Beyond increasing the binding capacity and enhancing the mass transfer, the gigaporous structure also significantly improved the stability of the VLPs during intensive adsorption-desorption process by lowing the multi-point interaction between the VLPs and binding sites in the pores. At 2.0mg/mL-media loading quantity, about 85.5% VLPs were correctly self-assembled after the chromatography with DEAE-AP-280nm media; oppositely about 85.2% VLPs lost their normal assembly with DEAE-FF due to irreversible disassembly. Comparative investigation was made to study the purifying performance of these four chromatographic media for actual VLPs purification from recombinant

  9. Improving stability of virus-like particles by ion-exchange chromatographic supports with large pore size: advantages of gigaporous media beyond enhanced binding capacity.

    PubMed

    Yu, Mengran; Li, Yan; Zhang, Songping; Li, Xiunan; Yang, Yanli; Chen, Yi; Ma, Guanghui; Su, Zhiguo

    2014-02-28

    Limited binding capacity and low recovery of large size multi-subunits virus-like particles (VLPs) in conventional agarose-gel based chromatographic supports with small pores have long been a bottleneck limiting the large scale purification and application of VLPs. In this study, four anion exchange media including DEAE-Sepharose FF (DEAE-FF), DEAE-Capto, gigaporous DEAE-AP-120nm and DEAE-AP-280nm with average pore diameters of 32nm, 20nm, 120nm and 280nm, respectively, were applied for purification of hepatitis B virus surface antigen (HBsAg) VLPs. Pore size effects of media on the VLPs adsorption equilibrium, adsorption kinetics, dynamic binding capacity (DBC), and recovery were investigated in detail. According to the confocal laser scanning microscopy observation, adsorption of the VLPs in DEAE-FF and DEAE-Capto was mostly confined to a thin shell on the outer surface of the beads, leaving the underlying pore space and the binding sites inaccessibly, while the large pores in gigaporous media enabled the VLPs to access to the interior pore spaces by diffusion transport efficiently. Compared to the most widely used DEAE-FF, gigaporous media DEAE-AP-280nm gained about 12.9 times increase in static adsorption capacity, 8.0 times increase in DBC, and 11.4 times increase in effective pore diffusivity. Beyond increasing the binding capacity and enhancing the mass transfer, the gigaporous structure also significantly improved the stability of the VLPs during intensive adsorption-desorption process by lowing the multi-point interaction between the VLPs and binding sites in the pores. At 2.0mg/mL-media loading quantity, about 85.5% VLPs were correctly self-assembled after the chromatography with DEAE-AP-280nm media; oppositely about 85.2% VLPs lost their normal assembly with DEAE-FF due to irreversible disassembly. Comparative investigation was made to study the purifying performance of these four chromatographic media for actual VLPs purification from recombinant

  10. Chemical and morphological changes in hydrochars derived from microcrystalline cellulose and investigated by chromatographic, spectroscopic and adsorption techniques.

    PubMed

    Diakité, Mamadou; Paul, Andrea; Jäger, Christian; Pielert, Judith; Mumme, Jan

    2013-12-01

    Hydrothermal carbonization (HTC) can be used for converting the biomass into a carbon-rich material, whose application as a fuel requires higher heating value, whereas soil amendment needs stable carbon. This work was focused on the characterization of hydrochars derived from microcrystalline cellulose. The chars were investigated using elemental analysis, Brunauer-Emmett-Teller technique, nuclear magnetic resonance spectroscopy, Raman, Fourier transform infrared, and electron spin resonance spectroscopy. Severity in temperature between 230 and 270°C with reaction times between 2 and 10 h only affect the carbon content moderately. The results show that aromatization of HTC chars correlates well with temperature, which was further supported by the increase of organic radicals with decreasing g values at higher temperatures. Based on these results, the energetic use of chars favors mild HTC (T<230°C and t≤6 h), while the soil amendement favors serve conditions (T≥230°C, and t>6 h).

  11. Short-Cycle Adsorption Refrigerator

    NASA Technical Reports Server (NTRS)

    Chan, C. K.

    1988-01-01

    Modular adsorption/Joule-Thomson-effect refrigerator offers fast regeneration; adsorption/desorption cycle time expected to be 1 minute. Pressurized hydrogen generated by bank of compressor modules during heating phase passes through system of check valves and expands in Joule-Thomson junction as it enters refrigeration chamber. Hydrogen absorbs heat from load before it is sucked out by another bank of compressor modules in cooling phase.

  12. Surfactant adsorption kinetics in microfluidics

    PubMed Central

    Riechers, Birte; Maes, Florine; Akoury, Elias; Semin, Benoît; Gruner, Philipp; Baret, Jean-Christophe

    2016-01-01

    Emulsions are metastable dispersions. Their lifetimes are directly related to the dynamics of surfactants. We design a microfluidic method to measure the kinetics of adsorption of surfactants to the droplet interface, a key process involved in foaming, emulsification, and droplet coarsening. The method is based on the pH decay in the droplet as a direct measurement of the adsorption of a carboxylic acid surfactant to the interface. From the kinetic measurement of the bulk equilibration of the pH, we fully determine the adsorption process of the surfactant. The small droplet size and the convection during the droplet flow ensure that the transport of surfactant through the bulk is not limiting the kinetics of adsorption. To validate our measurements, we show that the adsorption process determines the timescale required to stabilize droplets against coalescence, and we show that the interface should be covered at more than 90% to prevent coalescence. We therefore quantitatively link the process of adsorption/desorption, the stabilization of emulsions, and the kinetics of solute partitioning—here through ion exchange—unraveling the timescales governing these processes. Our method can be further generalized to other surfactants, including nonionic surfactants, by making use of fluorophore–surfactant interactions. PMID:27688765

  13. PDMS compound adsorption in context.

    PubMed

    Li, Nianzhen; Schwartz, Michael; Ionescu-Zanetti, Cristian

    2009-02-01

    Soft lithography of polydimethylsiloxane (PDMS), an elastomeric polymer, has enabled rapid and inexpensive fabrication of microfluidic devices for various biotechnology applications. However, concerns remain about adsorption of compounds on PDMS surfaces because of its porosity and hydrophobicity. Here, the adsorption of 2 small fluorescent dyes of different hydrophobicity (calcein and 5- (and 6-)carboxytetramethylrhodamine (TMR)) on PDMS surface has been systematically characterized, and PDMS adsorption has been compared with 2 traditional substrates: glass and polystyrene. To characterize adsorption in a regimen that is more relevant to microfluidic applications, the adsorption and desorption of the 2 compounds in PDMS microfluidic channels under flow conditions were also studied. Results showed that there was minimal adsorption of the hydrophilic compound calcein on PDMS, whereas the more hydrophobic TMR adsorbed on PDMS up to 4 times of that on glass or polystyrene. Under flow conditions, the desorption profiles and times needed to drop desorbed compound concentrations to negligible levels (desorption time constant, 10-42 s) were characterized. In the worst case scenario, after a 4-min exposure to TMR, 4 min of continuous wash resulted in compound concentrations in the microchannels to drop to values below 2 x 10(- 5) of the initial concentration.

  14. Statistical learning of peptide retention behavior in chromatographic separations: a new kernel-based approach for computational proteomics

    PubMed Central

    Pfeifer, Nico; Leinenbach, Andreas; Huber, Christian G; Kohlbacher, Oliver

    2007-01-01

    Background High-throughput peptide and protein identification technologies have benefited tremendously from strategies based on tandem mass spectrometry (MS/MS) in combination with database searching algorithms. A major problem with existing methods lies within the significant number of false positive and false negative annotations. So far, standard algorithms for protein identification do not use the information gained from separation processes usually involved in peptide analysis, such as retention time information, which are readily available from chromatographic separation of the sample. Identification can thus be improved by comparing measured retention times to predicted retention times. Current prediction models are derived from a set of measured test analytes but they usually require large amounts of training data. Results We introduce a new kernel function which can be applied in combination with support vector machines to a wide range of computational proteomics problems. We show the performance of this new approach by applying it to the prediction of peptide adsorption/elution behavior in strong anion-exchange solid-phase extraction (SAX-SPE) and ion-pair reversed-phase high-performance liquid chromatography (IP-RP-HPLC). Furthermore, the predicted retention times are used to improve spectrum identifications by a p-value-based filtering approach. The approach was tested on a number of different datasets and shows excellent performance while requiring only very small training sets (about 40 peptides instead of thousands). Using the retention time predictor in our retention time filter improves the fraction of correctly identified peptide mass spectra significantly. Conclusion The proposed kernel function is well-suited for the prediction of chromatographic separation in computational proteomics and requires only a limited amount of training data. The performance of this new method is demonstrated by applying it to peptide retention time prediction in IP

  15. Protein Adsorption in Three Dimensions

    PubMed Central

    Vogler, Erwin A.

    2011-01-01

    Recent experimental and theoretical work clarifying the physical chemistry of blood-protein adsorption from aqueous-buffer solution to various kinds of surfaces is reviewed and interpreted within the context of biomaterial applications, especially toward development of cardiovascular biomaterials. The importance of this subject in biomaterials surface science is emphasized by reducing the “protein-adsorption problem” to three core questions that require quantitative answer. An overview of the protein-adsorption literature identifies some of the sources of inconsistency among many investigators participating in more than five decades of focused research. A tutorial on the fundamental biophysical chemistry of protein adsorption sets the stage for a detailed discussion of the kinetics and thermodynamics of protein adsorption, including adsorption competition between two proteins for the same adsorbent immersed in a binary-protein mixture. Both kinetics and steady-state adsorption can be rationalized using a single interpretive paradigm asserting that protein molecules partition from solution into a three-dimensional (3D) interphase separating bulk solution from the physical-adsorbent surface. Adsorbed protein collects in one-or-more adsorbed layers, depending on protein size, solution concentration, and adsorbent surface energy (water wettability). The adsorption process begins with the hydration of an adsorbent surface brought into contact with an aqueous-protein solution. Surface hydration reactions instantaneously form a thin, pseudo-2D interface between the adsorbent and protein solution. Protein molecules rapidly diffuse into this newly-formed interface, creating a truly 3D interphase that inflates with arriving proteins and fills to capacity within milliseconds at mg/mL bulk-solution concentrations CB. This inflated interphase subsequently undergoes time-dependent (minutes-to-hours) decrease in volume VI by expulsion of either-or-both interphase water and

  16. Adsorption and removal kinetics of phosphonate from water using natural adsorbents.

    PubMed

    Kumar, R Anil; Velayudhan, K T; Ramachandran, V; Bhai, R Susheela; Unnikrishnan, G; Vasu, K

    2010-01-01

    The removal of phosphonate from water was studied using some natural adsorbents. Potassium phosphonate is a fungicide used for the control of Phytophthora capsici, which is prevalent in black pepper (Piper nigrum L.). Batch adsorption kinetic experiments were conducted on the adsorption of phosphonate onto the adsorbents. The concentration of phosphonate was measured on a high-performance liquid chromatograph fitted with a conductivity detector. The percentage removal of phosphonate by powdered laterite stone (PLS) from water was 40.4%, within a residence time of 15 minutes. The mechanisms of the rate of adsorption were analyzed and compared using the pseudo-second-order, Elovich, and intraparticle diffusion models. The experimental data was found to correlate well with the pseudo-second-order kinetic model, indicating adsorption as a chemisorption process. A possible reaction in the phosphonate-PLS system also has been proposed. The PLS can be used as a low-cost natural adsorbent for phosphonate removal from water. PMID:20112539

  17. Adsorption properties and preparative separation of phenylethanoid glycosides from Cistanche deserticola by use of macroporous resins.

    PubMed

    Liu, Boyan; Ouyang, Jie; Yuan, Xiaofan; Wang, Liwei; Zhao, Bing

    2013-10-15

    A simple and efficient chromatographic method for large-scale preparative separation of phenylethanoid glycosides (mainly contain echinacoside and acteoside) from Cistanche deserticola was developed. The adsorption properties of eight macroporous resins were evaluated. Three selected resins were further screened depending on the adsorption kinetics curves, in which HPD300 resin showed the best separation efficiency. The adsorption isotherm data on HPD300 resin were fitted to the Freundlich equation in certain concentration range. The dynamic adsorption and desorption experiments were carried out on columns packed with HPD300 resin to optimize the separation process. The breakthrough curves showed that acteoside had a higher affinity to the resin than echinacoside. The contents of echinacoside and acteoside in the product increased from 1.79% and 1.43% in the crude extracts to 16.66% and 15.17%, with recovery yields of 80.41% and 90.17%, respectively. The purity of total phenylethanoid glycosides in the product was 76.58%. PMID:24022055

  18. Gas chromatograph-mass spectrometer (GC/MS) system for quantitative analysis of reactive chemical compounds

    DOEpatents

    Grindstaff, Quirinus G.

    1992-01-01

    Described is a new gas chromatograph-mass spectrometer (GC/MS) system and method for quantitative analysis of reactive chemical compounds. All components of such a GC/MS system external to the oven of the gas chromatograph are programmably temperature controlled to operate at a volatilization temperature specific to the compound(s) sought to be separated and measured.

  19. Chromatographic resolution of altered forms of protein kinase C

    SciTech Connect

    Ashendel, C.L.; Minor, P.L.; Baudoin, P.A.; Carlos, M.

    1987-05-01

    Rapid chromatographic resolution of protein kinase C (PKC) in extracts of rat brain on DEAE-cellulose yielded two major peaks of activity. These fractions bound phorbol esters with identical affinity and specificity and had similar ratios of PKC to phorbol ester-binding activities. Chicken egg yolk antibodies raised to PKC in the first fraction reacted with 74 to 76 kilodalton peptides in the second fraction. Chromatography of each fraction on hydroxylapatite yielded similar distributions of three PKC isozymes. Rechromatography of the DEAE-cellulose fractions on DEAE-cellulose confirmed that these forms of PKC were not rapidly interconvertible. Results of experiments in which extracts or fractions were incubated with MgATP and phosphatase inhibitors were consistent with elution of dephospho-PKC in the first fraction while the second fraction contained phospho-PKC. If confirmed, this suggests that a substantial fraction of PKC in rat and mouse tissues exists in the phosphorylated form.

  20. Gas chromatographic determination of cyclohexanone leached from hemodialysis tubing.

    PubMed

    Snell, R P

    1993-01-01

    A capillary gas chromatographic procedure is described for the determination of cyclohexanone leached from hemodialysis tubing by water. Recoveries were 100% at 2.0 mg/100 mL (20 ppm), 99.0% at 500 microg/100 mL (5 ppm), and 106% at 1.0 microg/100 mL (10 ppb). Reproducibility of the system was 0.152% for 3.0 microL injections of a solution containing cyclohexanone at 5.58 microg/mL. Correlation coefficients were 0.9983 for 0.3672-3.672 ng and 1.0000 for 3.672-367.2 ng. Twenty hemodialysis tubing sets from 4 manufacturers were examined. The leachable cyclohexanone ranged from 1.02 to 43.7 ppm per set. Rinsing the tubing with 1 L 0.9% sodium chloride solution did not remove significant amounts (P = 0.05) of leachable cyclohexanone.

  1. Liquid chromatographic determination of carminic acid in yogurt.

    PubMed

    Jalón, M; Peña, M J; Rivas, J C

    1989-01-01

    A reverse-phase liquid chromatographic method is described for the determination of carminic acid in yogurt. A C18 column is used with acetonitrile-1.19M formic acid (19 + 81) as mobile phase and diode array detection. Sample preparation includes deproteinization with papain and purification in a polyamide column. The relative standard deviation for repeated determinations of carminic acid in a commercial strawberry-flavored yogurt was 3.0%. Recoveries of carminic acid added to a natural-flavored yogurt ranged from 87.2 to 95.3% with a mean of 90.2%. The method permits measurement of amounts as low as 0.10 mg/kg. PMID:2708269

  2. The gas chromatographic resolution of DL-isovaline

    NASA Technical Reports Server (NTRS)

    Flores, J. J.; Bonner, W. A.; Van Dort, M. A.

    1977-01-01

    Isovaline is of cosmological interest because it is one of the 12 non-protein amino acids which have been isolated from the Murchison meteorite, and unlike the other chiral amino acids in this meteorite, it has no alpha-hydrogen at its asymmetric center and hence cannot racemize by the customary alpha-hydrogen-dependent mechanisms which engender racemization in ordinary amino acids. Experiments were conducted in which a .01 M solution of N-TFA-DL-isovalyl-L-leucine isopropyl ester in nitromethane was injected into the capillary column of a gas chromatograph coupled to a digital electronic integrator-recorder. Efflux times and integrated peak area percents are shown next to each diastereometer peak.

  3. Liquid Chromatographic Determination of Amnesic Shellfish Poison in Mussels

    NASA Astrophysics Data System (ADS)

    Duxbury, Mark

    2000-10-01

    A simple, rapid, high-performance liquid chromatographic experiment suitable for undergraduate students is described for determining amnesic shellfish poison in mussels. The poison itself is an unusual naturally occurring amino acid, domoic acid, that has been found in seafood, particularly shellfish, worldwide. The symptoms of poisoning include amnesia (memory loss), loss of balance, mental confusion, nausea, vomiting, diarrhea, coma, and in extreme cases death. The domoic acid is extracted from homogenized mussel tissue by boiling in water for 5 minutes. The homogenate is cooled and centrifuged, and an aliquot of the supernatant is diluted and analyzed by isocratic HPLC using a C18 column and an acetonitrile-water mobile phase at pH 2.5 with UV detection at 242 nm.

  4. Evaluation of chemometric techniques to select orthogonal chromatographic systems.

    PubMed

    Van Gyseghem, E; Dejaegher, B; Put, R; Forlay-Frick, P; Elkihel, A; Daszykowski, M; Héberger, K; Massart, D L; Heyden, Y Vander

    2006-04-11

    Several chemometric techniques were compared for their performance to determine the orthogonality and similarity between chromatographic systems. Pearson's correlation coefficient (r) based color maps earlier were used to indicate selectivity differences between systems. These maps, in which the systems were ranked according to decreasing or increasing dissimilarities observed in the weighted-average-linkage dendrogram, were now applied as reference method. A number of chemometric techniques were evaluated as potential alternative (visualization) methods for the same purpose. They include hierarchical clustering techniques (single, complete, unweighted-average-linkage, centroid and Ward's method), the Kennard and Stone algorithm, auto-associative multivariate regression trees (AAMRT), and the generalized pairwise correlation method (GPCM) with McNemar's statistical test. After all, the reference method remained our preferred technique to select orthogonal and identify similar systems.

  5. Flight contaminant trace analyser. Phase 1: Chromatographic input system

    NASA Technical Reports Server (NTRS)

    1975-01-01

    The development of a chromatographic column capable of resolving compounds associated with spacecraft atmospheres is presented. Consideration is given to sampling techniques, column parameters and operation, and column interface with a mass spectrometer. A capillary column coated with a mixture of polyalkylene glycols is found to provide the best selectivity for resolving multicomponent mixtures found in spacecraft atmospheres. Temperature programming and isothermal operation of the column are evaluated and it is found that temperature programming has a shorter analysis time for a given carrier gas flow rate and overall superior resolution. It is observed that hydrogen provides a 15% savings in analysis time over helium. Following the optimization of column operational parameters, a mixed phase Ucon capillary is prepared for evaluation during the column test period in which the test sample is automatically analyzed. Analysis of the multicomponent test mixture is completed within 45 minutes provided temperature programming is used. All but two of the test compounds are well resolved.

  6. Fatty acids determination in Bronte pistachios by gas chromatographic method.

    PubMed

    Pantano, Licia; Lo Cascio, Giovanni; Alongi, Angelina; Cammilleri, Gaetano; Vella, Antonio; Macaluso, Andrea; Cicero, Nicola; Migliazzo, Aldo; Ferrantelli, Vincenzo

    2016-10-01

    A gas chromatographic with flame ionization detector (GC-MS FID) method for the identification and quantification of fatty acids based on the extraction of lipids and derivatisation of free acids to form methyl esters was developed and validated. The proposed method was evaluated to a number of standard FAs, and Bronte pistachios samples were used for that purpose and to demonstrate the applicability of the proposed method. In this regard, repeatability, mean and standard deviation of the analytical procedure were calculated. The results obtained have demonstrated oleic acid as the main component of Bronte pistachios (72.2%) followed by linoleic acid (13.4%) and showed some differences in composition with respect to Tunisian, Turkish and Iranian pistachios.

  7. RAPID MEASUREMENTS OF NEPTUNIUM OXIDATION STATES USING CHROMATOGRAPHIC RESINS

    SciTech Connect

    Diprete, D; C Diprete, C; Mira Malek, M; Eddie Kyser, E

    2009-03-24

    The Savannah River Site's (SRS) H-Canyon facility uses ceric ammonium nitrate (CAN) to separate impure neptunium (Np) from a high sulfate feed stream. The material is processed using a two-pass solvent extraction purification which relies on CAN to oxidize neptunium to Np(VI) during the first pass prior to extraction. Spectrophotometric oxidation-state analyses normally used to validate successful oxidation to Np(VI) prior to extraction were compromised by this feed stream matrix. Therefore, a rapid chromatographic method to validate successful Np oxidation was developed using Eichrom Industries TRU and TEVA{reg_sign} resins. The method was validated and subsequently transferred to existing operations in the process analytical laboratories.

  8. Improved Chromatographic Separation of Sitagliptin Phosphate and Metformin Hydrochloride.

    PubMed

    Hendy, Moataz S

    2015-12-01

    New UPLC method was developed for determination of sitagliptin and metformin using Symmetry C18 column (100 mm × 2.1 mm, 2.2 μm) and isocratic elution (methanol 20%), pH (3.5) as a mobile phase. The ultraviolet detector was operated at 220 nm and the column temperature was 50°C. Linearity parameters were acceptable over the concentration ranges of 2-12 μgml(-1) and 5-35 μgml(-1) for sitagliptin and metformin, respectively. The variables were premeditated to adjust the chromatographic conditions using design of experiment. The proposed method was proved to be accurate for the quality control of the mentioned drugs in their pharmaceutical dosage form. PMID:26759536

  9. A Duffing oscillator algorithm to detect the weak chromatographic signal.

    PubMed

    Zhang, Wei; Xiang, Bing-Ren

    2007-02-28

    Based on the Duffing equation, a Duffing oscillator algorithm (DOA) to improve the signal-to-noise ratio (SNR) was presented. By simulated and experimental data sets, it was proven that the signal-to-noise ratio (SNR) of the weak signal could be greatly enhanced by this method. Using signal enhancement by DOA, this method extends the SNR of low concentrations of methylbenzene from 2.662 to 29.90 and the method can be used for quantitative analysis of methylbenzene, which are lower than detection limit of an analytical system. The Duffing oscillator algorithm (DOA) might be a promising tool to extend instrumental linear range and to improve the accuracy of trace analysis. The research enlarged the application scope of Duffing equation to chromatographic signal processing.

  10. Extraction, chromatographic and mass spectrometric methods for lipid analysis.

    PubMed

    Pati, Sumitra; Nie, Ben; Arnold, Robert D; Cummings, Brian S

    2016-05-01

    Lipids make up a diverse subset of biomolecules that are responsible for mediating a variety of structural and functional properties as well as modulating cellular functions such as trafficking, regulation of membrane proteins and subcellular compartmentalization. In particular, phospholipids are the main constituents of biological membranes and play major roles in cellular processes like transmembrane signaling and structural dynamics. The chemical and structural variety of lipids makes analysis using a single experimental approach quite challenging. Research in the field relies on the use of multiple techniques to detect and quantify components of cellular lipidomes as well as determine structural features and cellular organization. Understanding these features can allow researchers to elucidate the biochemical mechanisms by which lipid-lipid and/or lipid-protein interactions take place within the conditions of study. Herein, we provide an overview of essential methods for the examination of lipids, including extraction methods, chromatographic techniques and approaches for mass spectrometric analysis.

  11. Fatty acids determination in Bronte pistachios by gas chromatographic method.

    PubMed

    Pantano, Licia; Lo Cascio, Giovanni; Alongi, Angelina; Cammilleri, Gaetano; Vella, Antonio; Macaluso, Andrea; Cicero, Nicola; Migliazzo, Aldo; Ferrantelli, Vincenzo

    2016-10-01

    A gas chromatographic with flame ionization detector (GC-MS FID) method for the identification and quantification of fatty acids based on the extraction of lipids and derivatisation of free acids to form methyl esters was developed and validated. The proposed method was evaluated to a number of standard FAs, and Bronte pistachios samples were used for that purpose and to demonstrate the applicability of the proposed method. In this regard, repeatability, mean and standard deviation of the analytical procedure were calculated. The results obtained have demonstrated oleic acid as the main component of Bronte pistachios (72.2%) followed by linoleic acid (13.4%) and showed some differences in composition with respect to Tunisian, Turkish and Iranian pistachios. PMID:27265004

  12. Ecdysteroid glycosides: identification, chromatographic properties, and biological significance.

    PubMed

    Maria, Annick; Girault, Jean-Pierre; Saatov, Ziyadilla; Harmatha, Juraj; Dinan, Laurence; Lafont, René

    2005-03-01

    Ecdysteroid glycosides are found in both animals and plants. The chromatographic behavior of these molecules is characteristic, as they appear much more polar than their corresponding free aglycones when analyzed by normal-phase high-performance liquid chromatography (HPLC), whereas the presence of glycosidic moieties has a very limited (if any) impact on polarity when using reversed-phase HPLC. Biological activity is greatly reduced because the presence of this bulky substituent probably impairs the interaction with ecdysteroid receptor(s). 2-Deoxy-20-hydroxyecdysone 22-O-beta-D-glucopyranoside, which has been isolated from the dried aerial parts of Silene nutans (Caryophyllaceae), is used as a model compound to describe the rationale of ecdysteroid glycoside purification and identification.

  13. Measurement uncertainty of liquid chromatographic analyses visualized by Ishikawa diagrams.

    PubMed

    Meyer, Veronika R

    2003-09-01

    Ishikawa, or cause-and-effect diagrams, help to visualize the parameters that influence a chromatographic analysis. Therefore, they facilitate the set up of the uncertainty budget of the analysis, which can then be expressed in mathematical form. If the uncertainty is calculated as the Gaussian sum of all uncertainty parameters, it is necessary to quantitate them all, a task that is usually not practical. The other possible approach is to use the intermediate precision as a base for the uncertainty calculation. In this case, it is at least necessary to consider the uncertainty of the purity of the reference material in addition to the precision data. The Ishikawa diagram is then very simple, and so is the uncertainty calculation. This advantage is given by the loss of information about the parameters that influence the measurement uncertainty.

  14. Chemical characterization of Brickellia cavanillesii (Asteraceae) using gas chromatographic methods.

    PubMed

    Eshiet, Etetor R; Zhu, Jinqiu; Anderson, Todd A; Smith, Ernest E

    2014-03-01

    A methanol extract of lyophilized Brickellia cavanillesii was quantitatively analyzed using gas chromatographic (GC) techniques. The chromatographic methods employed were (i) GC-flame ionization detector (GC-FID), (ii) GC-mass spectrometry (GC-MS), and (iii) purge and trap GC-MS (P&T GC-MS). Thirteen compounds were identified with a quality match of 90% and above using GC-MS. The compounds were (1) Cyclohexene, 6-ethenyl-6-methyl-1-(1-methylethyl)-3-(1-methylethylidene)-, (S)-; (2) Bicylo (2.2.1) heptan-2-one, 1, 7, 7-trimethyl-(1S, 4S)-; (3) Phenol, 2-methoxy-4-(1-propenyl)-; (4) Benzene, 1-(1, 5-dimethyl-4-hexenyl)-4-methyl-; (5) Naphthalene, 1, 2, 3, 5, 6, 8a-hexahydro4, 7-dimethyl-1-1-(1-methylethyl)-, (1S-cis)-; (6) Phenol, 2-methoxy-; (7) Benzaldehyde, 3-hydroxy-4-methoxy-; (8) 11, 13-Eicosadienoic acid, methyl ester; (9) 2-Furancarboxaldehyde, 5-methyl-; (10) Maltol; (11) Phenol; (12) Hydroquinone; (13) 1H-Indene, 1-ethylideneoctahydro-7a-methyl-, (1E, 3a.alpha, 7a.beta.). Other compounds (14) 3-methyl butanal; (15) (D)-Limonene; (16) 1-methyl-4-(1-methyl ethyl) benzene; (17) Butanoic acid methyl ester; (18) 2-methyl propanal; (19) 2-butanone; (20) 2-pentanone; and (21) 2-methyl butane were also identified when P&T GC-MS was performed. Of the 21 compounds identified, 12 were validated using chemical standards. The identified compounds were found to be terpenes, derivatives of terpenes, esters, ketones, aldehydes, and phenol-derived aromatic compounds; these are the primary constituents of the essential oils of many plants and flowers. PMID:24804069

  15. Combined liquid and gas chromatographic characterisation of polyglycerol fatty acid esters.

    PubMed

    De Meulenaer, B; Van Royen, G; Vanhoutte, B; Huyghebaert, A

    2000-10-27

    In the present study a combined liquid and gas chromatographic technique is described for the analysis of polyglycerol fatty acid esters. Liquid chromatographic fractionation of samples resulted in pure standards of monoesters of di- and triglycerols and diesters of di- and triglycerols. Confirmation of their identity was achieved by LC-MS analysis. Moreover, a chromatographic identification of the mono- and diesters of cyclic diglycerol was proposed. From the isolation of pure esters and their gas chromatographic analysis, it was revealed that co-elution of several compounds occurred. Thus it was shown that prefractionation of the sample using a simplified liquid chromatographic separation, was necessary in order to characterise the esters correctly. In combination with some other chemical analyses, a complete profile of the chemical composition of polyglycerol fatty acid esters can be obtained.

  16. Evaluation of chromatographic descriptors for the prediction of gastro-intestinal absorption of drugs.

    PubMed

    Deconinck, E; Ates, H; Callebaut, N; Van Gyseghem, E; Vander Heyden, Y

    2007-01-01

    The use of chromatographic descriptors in QSAR was evaluated. Therefore, retentions were measured on an immobilized artificial membrane system, 2 micellar liquid chromatography systems and 17 orthogonal or disimilar reversed-phase liquid chromatographic systems. It was investigated whether it was possible to model gastro-intestinal absorption as a function of chromatographic retentions applying two linear and one non-linear multivariate modeling technique. In a second step it was evaluated if models built with theoretical descriptors could be improved by adding the measured retention factors to the data set of descriptive variables. It was seen that gastro-intestinal absorption could be modelled in function of chromatographic retention using the non-linear modeling technique multivariate adaptive regression splines (MARS). The best models were obtained using a combination of theoretical and chromatographic descriptors with MARS as modeling technique.

  17. [Advancement of colloidal gold chromatographic technique in screening of ochratoxin A].

    PubMed

    Zhou, Wei-lu; Wang, Yu-ting; Kong, Wei-jun; Yang, Mei-hua; Zhao, Ming; Ou-Yang, Zhen

    2015-08-01

    Ochratoxin A (OTA) is a toxic secondary metabolite mainly produced by Aspergillus and Penicillium species, existing in a variety of foodstuffs and Chinese medicines. OTA is difficult to be detected in practice because of the characteristics such as trace amounts, toxicity, existing in complex matrices. In the numerous detection technologies, colloidal gold chromatographic techniques are highly sensitive, specific, cost-effective and user-friendly, and are being used increasingly for OTA screening. Recently, with the development of aptamer technology and its application in chromatographic technique, a newly colloidal gold aptamer chromatographic technique has been developed. This review elaborates the structures and principles of both traditional and newly colloidal gold chromatographic techniques, focuses on newly colloidal gold aptamer chromatographic technique, summarizes and compares their use in rapid detection of OTA. Finally, in order to provide a reference for better research of related work, the development trends of this novel technique are prospected.

  18. Metal adsorption on mosses: Toward a universal adsorption model.

    PubMed

    González, A G; Pokrovsky, O S

    2014-02-01

    This study quantifies the adsorption of heavy metals on 4 typical moss species used for environmental monitoring in the moss bag technique. The adsorption of Cu(2+), Cd(2+), Ni(2+), Pb(2+) and Zn(2+) onto Hypnum sp., Sphagnum sp., Pseudoscleropodium purum and Brachytecium rutabulum has been investigated using a batch reactor in a wide range of pH (1.3-11.0) and metal concentrations in solution (1.6μM-3.8mM). A Linear Programming Model (LPM) was applied for the experimental data to derive equilibrium constants and the number of surface binding sites. The surface acid-base titration performed for 4 mosses at a pH range of 3-10 in 0.1M NaNO3 demonstrated that Sphagnum sp. is the most efficient adsorbent as it has the maximal number of proton-binding sites on the surface (0.65mmol g(-1)). The pKa computed for all the moss species suggested the presence of 5 major functional groups: phosphodiester, carboxyl, phosphoryl, amine and polyphenols. The results of pH-edge experiments demonstrated that B. rutabulum exhibits the highest percentage of metal adsorption and has the highest number of available sites for most of the metals studied. However, according to the results of the constant pH "Langmuirian" isotherm, Sphagnum sp. can be considered as the strongest adsorbent, although the relative difference from other mosses is within 20%. The LPM was found to satisfactorily fit the experimental data in the full range of the studied solution parameters. The results of this study demonstrate a rather similar pattern of five metal adsorptions on mosses, both as a function of pH and as a metal concentration, which is further corroborated by similar values of adsorption constants. Therefore, despite the species and geographic differences between the mosses, a universal adsorption edge and constant pH adsorption isotherm can be recommended for 4 studied mosses. The quantitative comparison of metal adsorption with other common natural organic and inorganic materials demonstrates

  19. Gas chromatographic determination of polycyclic aromatic hydrocarbons in water and smoked rice samples after solid-phase microextraction using multiwalled carbon nanotube loaded hollow fiber.

    PubMed

    Matin, Amir Abbas; Biparva, Pourya; Gheshlaghi, Mohammad

    2014-12-29

    A novel solid-phase microextraction fiber was prepared based on multiwalled carbon nanotubes (MWCNTs) loaded on hollow fiber membrane pores. Stainless steel wire was used as unbreakable support. The major advantages of the proposed fiber are its (a) high reproducibility due to the uniform structure of the hollow fiber membranes, (b) high extraction capacity related to the porous structure of the hollow fiber and outstanding adsorptive characteristics of MWCNTs. The proposed fiber was applied for the microextraction of five representative polycyclic aromatic hydrocarbons (PAHs) from aqueous media (river and hubble-bubble water) and smoked rice samples followed by gas chromatographic determination. Analytical merits of the method, including high correlation coefficients [(0.9963-0.9992) and (0.9982-0.9999)] and low detection limits [(9.0-13.0ngL(-1)) and (40.0-150.0ngkg(-1))] for water and rice samples, respectively, made the proposed method suitable for the ultra-trace determination of PAHs.

  20. Comparison of nutshell granular activated carbons to commercial adsorbents for the purge-and-trap gas chromatographic analysis of volatile organic compounds.

    PubMed

    Wartelle, L H; Marshall, W E; Toles, C A; Johns, M M

    2000-05-26

    Granular activated carbons (GACs) made from agricultural by-products were investigated as adsorbents for short path thermal desorption gas chromatographic analysis of selected polar and nonpolar organic compounds. GACs made from macadamia nut, black walnut and hazelnut shells were compared to four commercially available adsorbents, namely, Tenax TA, Carboxen 569, Carbosieve SIII and coconut charcoal for their properties in purge-and-trap analysis. Adsorption values and breakthrough volumes were calculated for compounds from C3 and C6-C10. GACs derived from macadamia nut shells were found to adsorb and desorb between 80% (benzene) and 277% (ethylbenzene) more acetone (C3), benzene (C6), toluene (C7), ethyl- (C8), n-propyl- (C9), or sec.-butylbenzenes (C10) purged from water at the 100 ppb level than the commercial adsorbents tested. PMID:10893033

  1. Fractional Statistical Theory of Adsorption of Polyatomics

    NASA Astrophysics Data System (ADS)

    Riccardo, J. L.; Ramirez-Pastor, A. J.; Romá, F.

    2004-10-01

    A new theoretical description of fractional statistical theory of adsorption (FSTA) phenomena is presented based on Haldane’s statistics. Thermodynamic functions for adsorption of polyatomics are analytically developed. The entropy is characterized by an exclusion parameter g, which relates to the configuration of the admolecules and surface geometry. FSTA provides a simple framework to address a large class of complex adsorption systems. Comparisons of theoretical adsorption isotherms with experiments and simulations indicate that adsorption configuration and adsorption energy can accurately be assessed from this theory.

  2. Fractional statistical theory of adsorption of polyatomics.

    PubMed

    Riccardo, J L; Ramirez-Pastor, A J; Romá, F

    2004-10-29

    A new theoretical description of fractional statistical theory of adsorption (FSTA) phenomena is presented based on Haldane's statistics. Thermodynamic functions for adsorption of polyatomics are analytically developed. The entropy is characterized by an exclusion parameter g, which relates to the configuration of the admolecules and surface geometry. FSTA provides a simple framework to address a large class of complex adsorption systems. Comparisons of theoretical adsorption isotherms with experiments and simulations indicate that adsorption configuration and adsorption energy can accurately be assessed from this theory. PMID:15525184

  3. Host receptors for bacteriophage adsorption.

    PubMed

    Bertozzi Silva, Juliano; Storms, Zachary; Sauvageau, Dominic

    2016-02-01

    The adsorption of bacteriophages (phages) onto host cells is, in all but a few rare cases, a sine qua non condition for the onset of the infection process. Understanding the mechanisms involved and the factors affecting it is, thus, crucial for the investigation of host-phage interactions. This review provides a survey of the phage host receptors involved in recognition and adsorption and their interactions during attachment. Comprehension of the whole infection process, starting with the adsorption step, can enable and accelerate our understanding of phage ecology and the development of phage-based technologies. To assist in this effort, we have established an open-access resource--the Phage Receptor Database (PhReD)--to serve as a repository for information on known and newly identified phage receptors. PMID:26755501

  4. Adsorption-induced colloidal aggregation

    NASA Astrophysics Data System (ADS)

    Law, B. M.; Petit, J.-M.; Beysens, D.

    1998-03-01

    Reversible colloidal aggregation in binary liquid mixtures has been studied for a number of years. As the phase separation temperature of the liquid mixture is approached the thickness of an adsorption layer around the colloidal particles increases. Beysens and coworkers have demonstrated experimentally that this adsorption layer is intimately connected with the aggregation of the colloidal particles, however, no definitive theory has been available which can explain all of the experimental observations. In this contribution we describe an extension of the Derjaguin, Landau, Verwey, and Overbeek theory of colloidal aggregation which takes into account the presence of the adsorption layer and which more realistically models the attractive dispersion interactions. This modified theory can quantitatively account for many of the observed experimental features such as the characteristics of the aggregated state, the general shape of the aggregation line, and the temperature dependence of the second virial coefficient for a lutidine-water mixture containing a small volume fraction of silica colloidal particles.

  5. Synthesis of metronidazole-imprinted molecularly imprinted polymers by distillation precipitation polymerization and their use as a solid-phase adsorbent and chromatographic filler.

    PubMed

    Liu, Jiang; Zhang, Lu; Li Han Song, Le; Liu, Yuan; Tang, Hui; Li, Yingchun

    2015-04-01

    Metronidazole-imprinted polymers with superior recognition properties were prepared by a novel strategy called distillation-precipitation polymerization. The as-obtained polymers were characterized by Fourier-transform infrared spectroscopy, laser particle size determination and scanning electron microscopy, and their binding performances were evaluated in detail by static, kinetic and dynamic rebinding tests, and Scatchard analysis. The results showed that when the fraction of the monomers was 5 vol% in the whole reaction system, the prepared polymers afforded good morphology, monodispersity, and high adsorption capacity and excellent selectivity to the target molecule, metronidazole. The optimal binding performance is 12.41 mg/g for metronidazole just before leakage occurred and 38.51 mg/g at saturation in dynamic rebinding tests. Metronidazole-imprinted polymers were further applied as packing agents in solid-phase extraction and as chromatographic filler, both of which served for the detection of metronidazole in fish tissue. The results illustrated the recoveries of spiked samples ranged from 82.97 to 87.83% by using molecularly imprinted solid-phase extraction combined with a C18 commercial column and 93.7 to 101.2% by directly using the polymer-packed chromatographic column. The relative standard deviation of both methods was less than 6%. PMID:25594306

  6. Multivariate curve resolution based chromatographic peak alignment combined with parallel factor analysis to exploit second-order advantage in complex chromatographic measurements.

    PubMed

    Parastar, Hadi; Akvan, Nadia

    2014-03-13

    In the present contribution, a new combination of multivariate curve resolution-correlation optimized warping (MCR-COW) with trilinear parallel factor analysis (PARAFAC) is developed to exploit second-order advantage in complex chromatographic measurements. In MCR-COW, the complexity of the chromatographic data is reduced by arranging the data in a column-wise augmented matrix, analyzing using MCR bilinear model and aligning the resolved elution profiles using COW in a component-wise manner. The aligned chromatographic data is then decomposed using trilinear model of PARAFAC in order to exploit pure chromatographic and spectroscopic information. The performance of this strategy is evaluated using simulated and real high-performance liquid chromatography-diode array detection (HPLC-DAD) datasets. The obtained results showed that the MCR-COW can efficiently correct elution time shifts of target compounds that are completely overlapped by coeluted interferences in complex chromatographic data. In addition, the PARAFAC analysis of aligned chromatographic data has the advantage of unique decomposition of overlapped chromatographic peaks to identify and quantify the target compounds in the presence of interferences. Finally, to confirm the reliability of the proposed strategy, the performance of the MCR-COW-PARAFAC is compared with the frequently used methods of PARAFAC, COW-PARAFAC, multivariate curve resolution-alternating least squares (MCR-ALS), and MCR-COW-MCR. In general, in most of the cases the MCR-COW-PARAFAC showed an improvement in terms of lack of fit (LOF), relative error (RE) and spectral correlation coefficients in comparison to the PARAFAC, COW-PARAFAC, MCR-ALS and MCR-COW-MCR results.

  7. Adsorption on a stepped substrate

    NASA Astrophysics Data System (ADS)

    Merikoski, J.; Timonen, J.; Kaski, K.

    1994-09-01

    The effect of substrate steps on the adsorption of particles is considered. The problem is formulated as a lattice-gas model with nearest neighbor interactions and it is studied by a numerical transfer-matrix method. In particular, the influence of the substrate-induced row potential on adsorbed monolayers is discussed. It is found that strong row-transition-like features appear in the presence of a row potential and it is suggested that these may be seen in adsorption on vicinal faces.

  8. Fractional statistical theory of adsorption applied to protein adsorption.

    PubMed

    Quiroga, E; Centres, P M; Ochoa, N A; Ramirez-Pastor, A J

    2013-01-15

    Experimental adsorption isotherms of bovine serum albumin (BSA) adsorbed on sulfonated microspheres were described by means of two analytical models: the first is the well-known Langmuir-Freundlich model (LF), and the second, called fractional statistical theory of adsorption (FSTA), is a statistical thermodynamics model developed recently by Ramirez-Pastor et al. [Phys. Rev. Lett. 93 (2004) 186101]. The experimental data, obtained by Hu et al. [Biochem. Eng. J. 23 (2005) 259] for different concentrations of sulfonate group on the surface of the microspheres, were correlated by using a fitting algorithm based on least-squares statistics. The combination of LF and FSTA models, along with the choice of an adequate fitting procedure, allowed us to obtain several conclusions: (i) as previously reported in the literature, the maximum amount adsorbed increases as the amount of sulfonate group increases; (ii) the equilibrium constant does not appear as a sensitive parameter to the amount of sulfonate group on the surface of the microspheres; and (iii) the values of the fitting parameters obtained from FSTA may be indicative of a mismatch between the equilibrium separation of the intermolecular interaction and the distance between the adsorption sites. The exhaustive study presented here has shown that FSTA model is a good one considering the complexity of the physical situation, which is intended to be described and could be more useful in interpreting experimental data of adsorption of molecules with different sizes and shapes. PMID:23084559

  9. Chromatographic and computational assessment of lipophilicity using sum of ranking differences and generalized pair-correlation.

    PubMed

    Andrić, Filip; Héberger, Károly

    2015-02-01

    Lipophilicity (logP) represents one of the most studied and most frequently used fundamental physicochemical properties. At present there are several possibilities for its quantitative expression and many of them stems from chromatographic experiments. Numerous attempts have been made to compare different computational methods, chromatographic methods vs. computational approaches, as well as chromatographic methods and direct shake-flask procedure without definite results or these findings are not accepted generally. In the present work numerous chromatographically derived lipophilicity measures in combination with diverse computational methods were ranked and clustered using the novel variable discrimination and ranking approaches based on the sum of ranking differences and the generalized pair correlation method. Available literature logP data measured on HILIC, and classical reversed-phase combining different classes of compounds have been compared with most frequently used multivariate data analysis techniques (principal component and hierarchical cluster analysis) as well as with the conclusions in the original sources. Chromatographic lipophilicity measures obtained under typical reversed-phase conditions outperform the majority of computationally estimated logPs. Oppositely, in the case of HILIC none of the many proposed chromatographic indices overcomes any of the computationally assessed logPs. Only two of them (logkmin and kmin) may be selected as recommended chromatographic lipophilicity measures. Both ranking approaches, sum of ranking differences and generalized pair correlation method, although based on different backgrounds, provides highly similar variable ordering and grouping leading to the same conclusions.

  10. Preparative separation and purification of fumigaclavine C from fermented mycelia of Aspergillus fumigatus CY018 by macroporous adsorption resin.

    PubMed

    Yao, Ling-Yun; Zhu, Yi-Xiang; Liu, Chang-Qing; Jiao, Rui-Hua; Lu, Yan-Hua; Tan, Ren-Xiang

    2015-05-01

    In this work, the separation and purification of fumigaclavine C (FC), an ergot alkaloid with strong anti-inflammatory activity from fermented mycelia of Aspergillus fumigatus was systematically evaluated. Among the eight tested resins, the non-polar resin D101 displayed the best adsorption and desorption based on of static adsorption and desorption tests. Adsorption isotherms were constructed on D101 resin and fitted well to the Freundlich model. Dynamic adsorption and desorption tests on a column packed with D101 resin have been investigated for optimization of chromatographic parameters. Under optimized conditions, the contents of FC increased from 7.32% (w/w) in the crude extract to 67.54% in the final product with a recovery yield of 90.35% (w/w) via one run. Furthermore, a lab scale-up separation was carried out, in which the FC content and recovery yield were 65.83% and 90.13%, respectively. These results demonstrated that this adsorption-desorption strategy by using D101 resin was simple and efficient, thus showing potential for large scale purification and preparation of FC in the future.

  11. Preparative separation and purification of fumigaclavine C from fermented mycelia of Aspergillus fumigatus CY018 by macroporous adsorption resin.

    PubMed

    Yao, Ling-Yun; Zhu, Yi-Xiang; Liu, Chang-Qing; Jiao, Rui-Hua; Lu, Yan-Hua; Tan, Ren-Xiang

    2015-05-01

    In this work, the separation and purification of fumigaclavine C (FC), an ergot alkaloid with strong anti-inflammatory activity from fermented mycelia of Aspergillus fumigatus was systematically evaluated. Among the eight tested resins, the non-polar resin D101 displayed the best adsorption and desorption based on of static adsorption and desorption tests. Adsorption isotherms were constructed on D101 resin and fitted well to the Freundlich model. Dynamic adsorption and desorption tests on a column packed with D101 resin have been investigated for optimization of chromatographic parameters. Under optimized conditions, the contents of FC increased from 7.32% (w/w) in the crude extract to 67.54% in the final product with a recovery yield of 90.35% (w/w) via one run. Furthermore, a lab scale-up separation was carried out, in which the FC content and recovery yield were 65.83% and 90.13%, respectively. These results demonstrated that this adsorption-desorption strategy by using D101 resin was simple and efficient, thus showing potential for large scale purification and preparation of FC in the future. PMID:25817261

  12. The Huygens Gas Chromatograph Mass Spectrometer Investigation Of Titan

    NASA Astrophysics Data System (ADS)

    Atreya, Sushil; Harpold, Dan; Owen, Tobias

    2015-04-01

    A decade ago, on 14 January 2005, the Huygens probe of the Cassini-Huygens mission descended through the smog filled atmosphere of Titan and landed on the surface, revealing for the first time the extraordinary nature of Saturn's largest moon. One of the six payload instruments, the gas chromatograph mass spectrometer (GCMS), was crucial for measuring the composition of the atmosphere and the surface of Titan [1,2]. Most of the GCMS findings were "firsts", including the first direct identification of molecular nitrogen as the bulk constituent of the atmosphere, first vertical profile of Titan's second most abundant volatile, methane, first determination of primordial and radiogenic argon, first quantification of a number of stable gas isotopes, and the first measurements of the make-up of Titan's surface. These data are key to understanding why Titan is so unique amongst planetary moons in possessing a massive atmosphere [3], how Titan maintains a cycle of methane complete with surface reservoirs, evaporation and condensation like the hydrological cycle on earth [3,4,5], and what is responsible for the photochemical smog on Titan that plays a central role in the very existence of an atmosphere on Titan [3]. This presentation will discuss the GCMS investigation and how it helped shape our current view of Titan. [website for downloading pdf's of relevant papers: www.umich.edu/~atreya] [1] Niemann, H. B. et al., The abundances of constituents of Titan's atmosphere from the GCMS instrument on the Huygens probe, Nature 438, 779-784, 2005. [2] Niemann, H. B. et al., The composition of Titan's lower atmosphere and simple surface volatiles as measured by the Cassini-Huygens probe gas chromatograph mass spectrometer experiment, J. Geophys. Res. (Planets) 115, 12006, 2010. [3] Atreya S. K., R. D. Lorenz and J. H. Waite, Volatile origin and cycles: Nitrogen and methane, in Titan from Cassini-Huygens, R. H. Brown, J. P. Lebreton and J. Waite, (eds.), Springer Dordrecht

  13. Adsorption of Organics from Domestic Water Supplies.

    ERIC Educational Resources Information Center

    McGuire, Michael J.; Suffet, Irwin H.

    1978-01-01

    This article discusses the current state of the art of organics removal by adsorption. Various theoretical explanations of the adsorption process are given, along with practical results from laboratory, pilot-scale, and full-scale applications. (CS)

  14. CONTAMINANT ADSORPTION AND OXIDATION VIA FENTON REACTION

    EPA Science Inventory

    A ground water treatment process is proposed involving two cgemical processes: adsorption and oxidation. Adsorption of an organic compound onto granulated activated carbon (GAC) containing iron conveniently results in immobilizing and concentrating contaminants from the ground w...

  15. Chromatographic separation and concentration of quercetin and (+)-catechin using mesoporous composites based on MCM-41

    NASA Astrophysics Data System (ADS)

    Karpov, S. I.; Belanova, N. A.; Korabel'nikova, E. O.; Nedosekina, I. V.; Roessner, F.; Selemenev, V. F.

    2015-05-01

    Data on chromatographic separation of quercetin and (+)-catechin-flavonoids with similar physicochemical (including sorption) properties—are presented. The highest efficiency of chromatographic process at high sorption capacity of the material with respect to quercetin and slightly lower capacity for (+)-catechin were observed when silylated composites of ordered MCM-41 type materials were used. The application of acetonitrile as a solvent increased the sorption capacity of the material and can be recommended for separation of related polyphenol substances and their determination using ordered MCM-41 modified with trimethylchlorosilane as a stationary phase in a chromatographic column.

  16. Optimisation of n-Hexyl Acetate Synthesis in a Chromatographic Reactor

    NASA Astrophysics Data System (ADS)

    Patel, Dipesh; Saha, Basudeb; Wakeman, Richard

    Laboratory scale batch chromatographic reactor experiments were carried for the esterification of acetic acid with n-hexanol to synthesise a value added ester, namely n-hexyl acetate in the presence of an ion exchange resin catalyst, Purolite CT-124. The effect of various parameters such as solvent flow rates in the regeneration step, amount of reactants in the reaction step and reaction step time was studied for optimisation of the reaction condition in a batch chromatographic reactor. This information would be useful for the design, operation and optimisation of n-hexyl acetate synthesis in a continuous chromatographic reactor.

  17. Multilayer adsorption by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Molina-Mateo, J.; Salmerón Sánchez, M.; Monleón Pradas, M.; Torregrosa Cabanilles, C.

    2012-10-01

    Adsorption phenomena are characterized by models that include free parameters trying to reproduce experimental results. In order to understand the relationship between the model parameters and the material properties, the adsorption of small molecules on a crystalline plane surface has been simulated using the bond fluctuation model. A direct comparison between the Guggenheim-Anderson-de Boer (GAB) model for multilayer adsorption and computer simulations allowed us to establish correlations between the adsorption model parameters and the simulated interaction potentials.

  18. Adsorption and excess fission xenon

    NASA Technical Reports Server (NTRS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    1982-01-01

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  19. ADSORPTIVE MEDIA TECHNOLOGIES: MEDIA SELECTION

    EPA Science Inventory

    The presentation provides information on six items to be considered when selecting an adsorptive media for removing arsenic from drinking water; performance, EBCT, pre-treatment, regeneration, residuals, and cost. Each item is discussed in general and data and photographs from th...

  20. Interfacial adsorption in ternary alloys

    SciTech Connect

    Huang, C.; Cruz, M.O. de la; Voorhees, P.W.

    1999-11-26

    Interfaces of A-B-C ternary alloys decomposed into two and three phases are studied. The effect of the gradient energy coefficients {bar {kappa}}{sub II}, I = A, B, C, on the interface composition profiles of ternary alloys is examined. The adsorption of component C in ternary alloys is obtained numerically by finding steady-state solutions of the nonlinear Cahn-Hilliard equations and by solving the two Euler-Lagrange equations resulting from minimizing the interfacial energy, and analytically near the critical point. It is found that the solutions from both numerical methods are identical for a two-phase system. In symmetric ternary systems (equal interaction energy between each pair of components) with a minority component C, the gradient energy coefficient of C, {bar {kappa}}{sub CC}, can have a very strong influence on the degree of adsorption. In the {alpha} and {beta} two-phase regions, where {alpha} and {beta} are the phases rich in the majority components A and B, respectively, as {bar {kappa}}{sub CC} increases, the adsorption of the minority component C in the {alpha} and {beta} interfaces decreases. Near a critical point, however, the degree of adsorption of minority component C is independent of the gradient energy coefficient.

  1. ADSORPTION OF SURFACTANT ON CLAYS

    EPA Science Inventory

    Surfactants used to enhance remediation of soils by soil washing are often lost in the process. Neither the amount nor the cause of this loss is known. It is assumed that clays present in the soil are responsible for the loss of the surfactant. In this papere, adsorption prope...

  2. Capillary gas chromatographic analysis of pans with luminol chemilumnescent detection

    SciTech Connect

    Gaffney, J.; Bornick, R.; Chen, Yu-Harn; Marley, N.

    1996-12-31

    Peroxyacyl nitrates (PANs) are important air pollutants in tropospheric chemistry. PANs are known to be potent phytotoxins at low ppb concentrations and are lachrymators. They can also transport the more reactive nitrogen dioxide long distances, because they are in equilibrium with that NO{sub x} species. Since PANs are trapped peroxyradicals, they are a direct measure of the peroxyradical levels and the of {open_quotes}photochemical age{close_quotes} of an air parcel. The PANs are typically measured in the atmosphere by using electron capture detection methods. These methods suffer from large background signals and detector responses to oxygen and water vapor. This paper describes the combination of a capillary gas chromatographic column with a modified luminol chemiluminescent nitrogen dioxide detector (Scintrex, Luminox) for rapid and sensitive detection of nitrogen dioxide, peroxyacetyl nitrate, peroxypropionyl nitrate, and peroxybutyryl nitrate. Detection limits for this approach in the low tens of parts per trillion have been observed with total analysis times of less than three minutes. We will discuss the potential application of this method to other compounds, particularly, organonitrates, in a pyrolysis system and/or with ozone addition to the sampling streams.

  3. Gas chromatographic analysis of volatiles in fluid and gas inclusions.

    PubMed

    Andrawes, F; Holzer, G; Roedder, E; Gibson, E K; Oro, J

    1984-01-01

    Most geological samples and some synthetic materials contain fluid inclusions. These inclusions preserve for us tiny samples of the liquid and/or the gas phase that was present during formation, although in some cases they may have undergone significant changes from the original material. Studies of the current composition of the inclusions provide data on both the original composition and the change since trapping. These conclusions are seldom larger than 1 millimeter in diameter. The composition varies from a single major compound (e.g., water) in a single phase to a very complex mixture in one or more phases. The concentration of some of the compounds present may be at trace levels. We present here some analyses of inclusion on a variety of geological samples, including diamonds. We used a sample crusher and a gas chromatography-mass spectrometry (GC-MS) system to analyze for organic and inorganic volatiles present as major to trace constituents in inclusions. The crusher is a hardened stainless-steel piston cylinder apparatus with tungsten carbide crushing surfaces, and is operated in a pure helium atmosphere at a controlled temperature. Samples ranging from 1 mg to 1 g were crushed and the released volatiles were analyzed using multi-chromatographic columns and detectors, including the sensitive helium ionization detector. Identification of the GC peaks was carried out by GC-MS. This combination of procedures has been shown to provide geochemically useful information on the processes involved in the history of the samples analyzed. PMID:11541990

  4. Authenticity analysis of pear juice employing chromatographic fingerprinting.

    PubMed

    Willems, Jamie L; Low, Nicholas H

    2014-12-01

    Pear juice is predominately composed of carbohydrates/polyols (>95% of the total soluble solids), making it susceptible to adulteration by the addition of less expensive commercial sweeteners. In this research, the major carbohydrate and polyol (fructose, glucose, sucrose, and sorbitol) content of 32 pure pear juices representing five world producing regions and three years of production was determined. Additionally, methods employing oligosaccharide profiling to detect the debasing of these samples with four commercial sweeteners (HFCS 55 and 90, TIS, and HIS) were developed using capillary gas chromatography with flame ionization detection (CGC-FID) and high-performance liquid chromatography with pulsed amperometric detection (HPAE-PAD). Detection limits for the four commercial sweeteners ranged from 0.5 to 5.0% (v/v). In addition, the developed CGC-FID method could be used to (a) detect the addition of pear to apple juice via arbutin detection and (b) determine if a pear juice was produced using enzymatic liquefaction via the presence of O-β-d-glucopyranosyl-(1→4)-d-glucopyranose (cellobiose), all within a single chromatographic analysis.

  5. Liquid chromatographic determination of amphotericin B in different pharmaceuticals.

    PubMed

    Lue, Louis P; Hadman, Susan T; Vancura, Ales

    2002-01-01

    Amphotericin B (AmB) is one of the most potent antifungal agents and the drug of choice in the treatment of serious fungal infections. A liquid chromatographic (LC) method was developed to determine AmB in pharmaceutical formulations for injection, tissue culture, cream, and lotion. pBondapak C18 reversed-phase column and a simple mobile phase consisting of acetonitrile-water-acetic acid (40 + 54 + 6, v/v) was used. The flow rate was 1.8 mL/min and the effluent was monitored at 405 nm. The developed LC method uses piroxicam as an internal standard and has a limit of detection of 10 ng/mL, a limit of quantitation of 30 ng/mL, and the assay is linear from 0.01 to 100 microg/mL. AmB and piroxicam elute with retention times of 12.4 and 4.0 min, respectively, and the resolution between AmB and piroxicam was 10.6. In comparison with the official United States Pharmacopeia microbial assay for AmB, this LC method is more rapid, selective, sensitive, and offers positive identification.

  6. Characterisation of wax works of art by gas chromatographic procedures.

    PubMed

    Regert, M; Langlois, J; Colinart, S

    2005-10-14

    To identify the various natural and synthetic substances used by sculptors at the end of the 19th century, several contemporary reference samples were investigated by high temperature gas chromatography (HT GC) and HT GC-MS. Using specific chromatographic conditions and minimising sample preparation, we could separate, detect and identify a wide range of biomolecular markers covering a great variety of molecular weights and volatilities, with a minimum amount of sample, in a single run. Beeswax, spermaceti, carnauba, candellila and Japan waxes as well as pine resin derivatives, animal fats, paraffin, ozokerite and stearin, used as additives in wax works of art, were chemically investigated. In the case of low volatile compounds, transbutylation was performed. The structure of long-chain esters of spermaceti was elucidated for the first time by HT GC-MS analysis. Such a method was then carried out on 10 samples collected on a statuette of Junon by Antoine-Louis Barye (Louvre Museum, Paris, France) and on a sculpture by Aimé-Jules Dalou (Musée de la Révolution Française, Vizille, France). The analytical results obtained provide new data on the complex recipes elaborated by sculptors at the end of the 19th century.

  7. Gas chromatographic analysis of volatiles in fluid and gas inclusions

    USGS Publications Warehouse

    Andrawes, F.; Holzer, G.; Roedder, E.; Gibson, E.K.; Oro, J.

    1984-01-01

    Most geological samples and some synthetic materials contain fluid inclusions. These inclusions preserve for us tiny samples of the liquid and/or the gas phase that was present during formation, although in some cases they may have undergone significant changes from the original material. Studies of the current composition of the inclusions provide data on both the original composition and the change since trapping. These inclusions are seldom larger than 1 millimeter in diameter. The composition varies from a single major compound (e.g., water) in a single phase to a very complex mixture in one or more phases. The concentration of some of the compounds present may be at trace levels. We present here some analyses of inclusions in a variety of geological samples, including diamonds. We used a sample crusher and a gas chromatography-mass spectrometry (GC-MS) system to analyze for organic and inorganic volatiles present as major to trace constituents in inclusions. The crusher is a hardened stainless-steel piston cylinder apparatus with tungsten carbide crusing surfaces, and is operated in a pure helium atmosphere at a controlled temperature. Samples ranging from 1 mg to 1 g were crushed and the released volatiles were analyzed using multi-chromatographic columns and detectors, including the sensitive helium ionization detector. Identification of the GC peaks was carried out by GC-MS. This combination of procedures has been shown to provide geochemically useful information on the process involved in the history of the samples analyzed. ?? 1984.

  8. Authenticity analysis of pear juice employing chromatographic fingerprinting.

    PubMed

    Willems, Jamie L; Low, Nicholas H

    2014-12-01

    Pear juice is predominately composed of carbohydrates/polyols (>95% of the total soluble solids), making it susceptible to adulteration by the addition of less expensive commercial sweeteners. In this research, the major carbohydrate and polyol (fructose, glucose, sucrose, and sorbitol) content of 32 pure pear juices representing five world producing regions and three years of production was determined. Additionally, methods employing oligosaccharide profiling to detect the debasing of these samples with four commercial sweeteners (HFCS 55 and 90, TIS, and HIS) were developed using capillary gas chromatography with flame ionization detection (CGC-FID) and high-performance liquid chromatography with pulsed amperometric detection (HPAE-PAD). Detection limits for the four commercial sweeteners ranged from 0.5 to 5.0% (v/v). In addition, the developed CGC-FID method could be used to (a) detect the addition of pear to apple juice via arbutin detection and (b) determine if a pear juice was produced using enzymatic liquefaction via the presence of O-β-d-glucopyranosyl-(1→4)-d-glucopyranose (cellobiose), all within a single chromatographic analysis. PMID:25384245

  9. Micro-miniature gas chromatograph column disposed in silicon wafers

    DOEpatents

    Yu, Conrad M.

    2000-01-01

    A micro-miniature gas chromatograph column is fabricated by forming matching halves of a circular cross-section spiral microcapillary in two silicon wafers and then bonding the two wafers together using visual or physical alignment methods. Heating wires are deposited on the outside surfaces of each wafer in a spiral or serpentine pattern large enough in area to cover the whole microcapillary area inside the joined wafers. The visual alignment method includes etching through an alignment window in one wafer and a precision-matching alignment target in the other wafer. The two wafers are then bonded together using the window and target. The physical alignment methods include etching through vertical alignment holes in both wafers and then using pins or posts through corresponding vertical alignment holes to force precision alignment during bonding. The pins or posts may be withdrawn after curing of the bond. Once the wafers are bonded together, a solid phase of very pure silicone is injected in a solution of very pure chloroform into one end of the microcapillary. The chloroform lowers the viscosity of the silicone enough that a high pressure hypodermic needle with a thumbscrew plunger can force the solution into the whole length of the spiral microcapillary. The chloroform is then evaporated out slowly to leave the silicone behind in a deposit.

  10. Sensitive gas chromatographic--mass spectrometric screening of acetylated benzodiazepines.

    PubMed

    Borrey, D; Meyer, E; Lambert, W; Van Calenbergh, S; Van Peteghem, C; De Leenheer, A P

    2001-02-23

    GC-MS screening conditions were developed for 15 low-dosed benzodiazepines, covering alprazolam, flunitrazepam, flurazepam, ketazolam, lorazepam and triazolam, and the corresponding metabolites alpha-hydroxyalprazolam, 4-hydroxyalprazolam; 7-aminoflunitrazepam, desmethylflunitrazepam, 7-aminodesmethylflunitrazepam; hydroxyethylflurazepam, N-desalkylflurazepam; oxazepam and alpha-hydroxytriazolam, respectively. Benzodiazepines are analyzed on a polydimethylsiloxane column in both the scan and the multiple ion monitoring modes using on-column injection to attain maximal sensitivity. The reactive compounds are acetylated with pyridine and acetic anhydride for 20 min. The derivatives are stable for at least 4 days. The relative standard deviation observed with standard compounds at the low nanogram-level ranged from 1.13 to 4.87% within-day and from 1.12 to 4.94% between-day. Unequivocal identification potential, high chromatographic resolution and sensitivity are combined with minimal thermal degradation. The presented screening conditions provide the basis for a unique routine screening method for low-dosed benzodiazepines with a broad polarity range.

  11. Comparison of three advanced chromatographic techniques for cannabis identification.

    PubMed

    Debruyne, D; Albessard, F; Bigot, M C; Moulin, M

    1994-01-01

    The development of chromatography technology, with the increasing availability of easier-to-use mass spectrometers combined with gas chromatography (GC), the use of diode-array or programmable variable-wavelength ultraviolet absorption detectors in conjunction with high-performance liquid chromatography (HPLC), and the availability of scanners capable of reading thin-layer chromatography (TLC) plates in the ultraviolet and visible regions, has made for easier, quicker and more positive identification of cannabis samples that standard analytical laboratories are occasionally required to undertake in the effort to combat drug addiction. At laboratories that do not possess the technique of GC combined with mass spectrometry, which provides an irrefutable identification, the following procedure involving HPLC or TLC techniques may be used: identification of the chromatographic peaks corresponding to each of the three main cannabis constituents-cannabidiol (CBD), delta-9-tetrahydrocannabinol (delta-9-THC) and cannabinol (CBN)-by comparison with published data in conjunction with a specific absorption spectrum for each of those constituents obtained between 200 and 300 nm. The collection of the fractions corresponding to the three major cannabinoids at the HPLC system outlet and the cross-checking of their identity in the GC process with flame ionization detection can further corroborate the identification and minimize possible errors due to interference.

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

    PubMed

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

    1987-01-01

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

  13. Fluoroalkyl chloroformates in treating amino acids for gas chromatographic analysis.

    PubMed

    Husek, Petr; Simek, Petr; Hartvich, Petr; Zahradnícková, Helena

    2008-04-01

    Novel fluoroalkyl chloroformates with three and four carbon atoms were investigated for the immediate conversion of amino acids into hydrophobic derivatives in water-containing media. Derivatization conditions were extensively studied and optimized sample preparation protocols elaborated. More than 30 amino acids were treated with the particular reagent in isooctane by simply vortexing the reactive organic phase with a slightly basified aqueous medium containing pyridine or 3-picoline as a catalyst. Outstanding separation of nearly all components on 5% phenylmethylsilicone phase in gas chromatographic (GC) analysis with mass spectrometric (MS) or flame ionization detection (FID) required <10 min. Quantitation characteristics involving linearity in the range of 0.1-100 nmol, regression coefficients of 0.999-0.953 (histidine), MS limit of detection (LOD) reaching 0.03 pmol at proline to nearly 20 pmol at glutamic acid, plus electron impact (EI) spectra and diagnostic SIM fragment ions of the derivatives are reported. The novel method is simple, robust and rapid, enabling to treat amino acids in aqueous environment and to analyze them in <15 min. PMID:18242622

  14. Recent Advances in Water Analysis with Gas Chromatograph Mass Spectrometers

    NASA Technical Reports Server (NTRS)

    MacAskill, John A.; Tsikata, Edem

    2014-01-01

    We report on progress made in developing a water sampling system for detection and analysis of volatile organic compounds in water with a gas chromatograph mass spectrometer (GCMS). Two approaches are described herein. The first approach uses a custom water pre-concentrator for performing trap and purge of VOCs from water. The second approach uses a custom micro-volume, split-splitless injector that is compatible with air and water. These water sampling systems will enable a single GC-based instrument to analyze air and water samples for VOC content. As reduced mass, volume, and power is crucial for long-duration, manned space-exploration, these water sampling systems will demonstrate the ability of a GCMS to monitor both air and water quality of the astronaut environment, thereby reducing the amount of required instrumentation for long duration habitation. Laboratory prototypes of these water sampling systems have been constructed and tested with a quadrupole ion trap mass spectrometer as well as a thermal conductivity detector. Presented herein are details of these water sampling system with preliminary test results.

  15. Comprehensive two-dimensional liquid chromatographic analysis of poloxamers.

    PubMed

    Malik, Muhammad Imran; Lee, Sanghoon; Chang, Taihyun

    2016-04-15

    Poloxamers are low molar mass triblock copolymers of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), having number of applications as non-ionic surfactants. Comprehensive one and two-dimensional liquid chromatographic (LC) analysis of these materials is proposed in this study. The separation of oligomers of both types (PEO and PPO) is demonstrated for several commercial poloxamers. This is accomplished at the critical conditions for one of the block while interaction for the other block. Reversed phase LC at CAP of PEO allowed for oligomeric separation of triblock copolymers with regard to PPO block whereas normal phase LC at CAP of PPO renders oligomeric separation with respect to PEO block. The oligomeric separation with regard to PEO and PPO are coupled online (comprehensive 2D-LC) to reveal two-dimensional contour plots by unconventional 2D IC×IC (interaction chromatography) coupling. The study provides chemical composition mapping of both PEO and PPO, equivalent to combined molar mass and chemical composition mapping for several commercial poloxamers.

  16. Protein adsorption to poly(ethylenimine)-modified Sepharose FF: V. Complicated effects of counterions.

    PubMed

    Liu, Na; Yu, Linling; Sun, Yan

    2015-07-24

    results indicate that protein adsorption and chromatographic performance with PEI-Sepharose can be improved by proper counterions. For the four counterions tested, SO4(2-) was the most favorable for providing the best adsorption and elution outcomes with FF-PEI-L680. PMID:26054560

  17. Protein adsorption to poly(ethylenimine)-modified Sepharose FF: V. Complicated effects of counterions.

    PubMed

    Liu, Na; Yu, Linling; Sun, Yan

    2015-07-24

    results indicate that protein adsorption and chromatographic performance with PEI-Sepharose can be improved by proper counterions. For the four counterions tested, SO4(2-) was the most favorable for providing the best adsorption and elution outcomes with FF-PEI-L680.

  18. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents, ion exchagne resins, and ion papers) intended for use in ion exchange chromatography, a procedure in which...

  19. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents, ion exchagne resins, and ion papers) intended for use in ion exchange chromatography, a procedure in which...

  20. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents, ion exchagne resins, and ion papers) intended for use in ion exchange chromatography, a procedure in which...

  1. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents, ion exchagne resins, and ion papers) intended for use in ion exchange chromatography, a procedure in which...

  2. 21 CFR 862.2230 - Chromatographic separation material for clinical use.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... chromatographic separation material for clinical use is a device accessory (e.g., ion exchange absorbents, ion exchagne resins, and ion papers) intended for use in ion exchange chromatography, a procedure in which...

  3. Miniaturized gas chromatograph-Paul ion trap system: applications to environmental monitoring

    NASA Technical Reports Server (NTRS)

    Shortt, B. J.; Darrach, M. R.; Holland, Paul M.; Chutjian, A.

    2004-01-01

    A miniature gas chromatograph (GC) and miniature Paul ion trap (PT) mass spectrometer system has been developed for identifying and quantifying chemical species present in closed environments having a complex mixture of gases.

  4. DEVELOPMENT AND VALIDATION OF AN ION CHROMATOGRAPHIC METHOD FOR DETERMINING PERCHLORATE IN FERTILIZERS

    EPA Science Inventory

    A method has been developed for the determination of perchlorate in fertilizers. Materials are leached with deionized water to dissolve any soluble perchlorate compounds. Ion chromatographic separation is followed by suppressed conductivity for detection. Perchlorate is retained ...

  5. Oxygen carrier for gas chromatographic analysis of inert gases in propellants

    NASA Technical Reports Server (NTRS)

    Cannon, W. A.

    1972-01-01

    Gas chromatographic determination of small quantities of inert gases in reactive propellants is discussed. Operating conditions used for specific analyses of helium in diborane and nitrogen in oxygen difluoride are presented in tabular form.

  6. Gas chromatographic analysis of simmondsins and simmondsin ferulates in jojoba meal.

    PubMed

    Van Boven, M; Holser, R; Cokelaere, M; Flo, G; Decuypere, E

    2000-09-01

    A capillary gas chromatographic method was developed for the simultaneous determination of simmondsins and simmondsin ferulates in jojoba meal, in detoxified jojoba meal, in jojoba meal extracts, and in animal food mixtures.

  7. Fluorescence investigation of the chromatographic interactions of nitrogen heterocycles with deactivated silica

    SciTech Connect

    Burrell, G.J.; Hurtubise, R.J.

    1988-10-15

    Solid-surface fluorescence spectroscopy was used to study the chromatographic interactions of benzo(f)quinoline (B(f)Q) and benzo(h)quinoline (B(h)Q) with water-deactivated silica gel. The results indicated that some of the water was adsorbed on sites in silica that were incapable of proton donation to B(h)Q in the excited singlet state. It was also found that solute localization became more important on the water-deactivated silica. By combination of the luminescence data and the chromatographic data, the mass balance was calculated for three B(h)Q species responsible for the chromatographic bands. Spectral evidence was also obtained that supported a displacement-type of chromatographic mechanism for the systems investigated.

  8. HIGH PERFORMANCE LIQUID CHROMATOGRAPHIC SEPARATION OF THE ENANTIOMERS OF ORGANOPHOSPHORUS PESTICIDES ON POLYSACCHARIDE CHIRAL STATIONARY PHASES

    EPA Science Inventory

    High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiph...

  9. Extraction and chromatographic elution behavior of endohedral metallofullerenes: Inferences regarding effective dipole moments

    SciTech Connect

    Fuchs, D.; Rietschel, H.; Michel, R.H.; Fischer, A.; Weis, P.; Kappes, M.M.

    1996-01-11

    Chromatographic retention relationships between Ce-, Gd-, La-, and Y- containing endohedral metallofullerenes and a [2-(1-pyrenyl)ethyl]silyl-silica stationary phase were studied using toluene as eluent. Measurements are discussed in comparison to those of empty fullerenes. Both the extraction and chromatographic elution behaviour of the metallofullerenes reflect their polar nature and allow inferences regarding the presence of a dipole moment in M@C{sub 82}. 55 refs., 4 figs.

  10. Chromatographic extraction with di(2-ethylhexyl)orthophosphoric acid for production and purification of promethium-147

    DOEpatents

    Boll, Rose A [Knoxville, TN

    2008-10-14

    A method of producing and purifying promethium-147 including the steps of: irradiating a target material including neodymium-146 with neutrons to produce promethium-147 within the irradiated target material; dissolving the irradiated target material to form an acidic solution; loading the acidic solution onto a chromatographic separation apparatus containing HDEHP; and eluting the apparatus to chromatographically separate the promethium-147 from the neodymium-146.

  11. Adsorption of organic chemicals in soils.

    PubMed Central

    Calvet, R

    1989-01-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described. PMID:2695323

  12. Phosphate adsorption on lanthanum loaded biochar.

    PubMed

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC. PMID:26871732

  13. Adsorption of organic chemicals in soils.

    PubMed

    Calvet, R

    1989-11-01

    This paper presents a review on adsorption of organic chemicals on soils sediments and their constituents. The first part of this review deals with adsorption from gas and liquid phases and gives a discussion on the physical meaning of the shape of adsorption isotherms. Results show that no general rules can be proposed to describe univocally the relation between the shape of isotherms and the nature of adsorbate-adsorbent system. Kinetics of adsorption is discussed through the description of various models. Theoretical developments exist both for the thermodynamics and the kinetics of adsorption, but there is a strong need for experimental results. Possible adsorption mechanisms are ion exchange, interaction with metallic cations, hydrogen bonds, charge transfers, and London-van der Waals dispersion forces/hydrophobic effect. However, direct proofs of a given mechanism are rare. Several factors influence adsorption behavior. Electronic structure of adsorbed molecules, properties of adsorbents, and characteristics of the liquid phase are discussed in relation to adsorption. Such properties as water solubility, organic carbon content of adsorbing materials, and the composition of the liquid phase are particularly important. Evaluation of adsorption can be obtained through either laboratory measurements or use of several correlations. Adsorption measurements must be interpreted, taking into account treatment of adsorbent materials, experimental conditions, and secondary phenomena such as degradations. Correlations between adsorption coefficients and water-octanol partition coefficient or water solubility are numerous. They may be useful tools for prediction purposes. Relations with transport, bioavailability, and degradation are described.

  14. Adsorption Behavior of Nonplanar Phthalocyanines: Competition of Different Adsorption Conformations

    PubMed Central

    2016-01-01

    Using density functional theory augmented with state-of-the-art van der Waals corrections, we studied the geometric and electronic properties of nonplanar chlorogallium-phthalocyanine GaClPc molecules adsorbed on Cu(111). Comparing these results with published experimental data for adsorption heights, we found indications for breaking of the metal–halogen bond when the molecule is heated during or after the deposition process. Interestingly, the work-function change induced by this dissociated geometry is the same as that computed for an intact adsorbate layer in the “Cl-down” configuration, with both agreeing well with the experimental photoemission data. This is unexpected, as the chemical natures of the adsorbates and the adsorption distances are markedly different in the two cases. The observation is explained as a consequence of Fermi-level pinning due to fractional charge transfer at the interface. Our results show that rationalizing the adsorption configurations on the basis of electronic interface properties alone can be ambiguous and that additional insight from dispersion-corrected DFT simulations is desirable. PMID:27066160

  15. Separation of chiral nanotubes with an opposite handedness by chiral oligopeptide adsorption: A molecular dynamics study.

    PubMed

    Raffaini, Giuseppina; Ganazzoli, Fabio

    2015-12-18

    The separation of enantiomeric chiral nanotubes that can form non-covalent complexes with an unlike stability upon adsorption of chiral molecules is a process of potential interest in different fields and applications. Using fully atomistic molecular dynamics simulations, we report in this paper a theoretical study of the adsorption and denaturation of an oligopeptide formed by 16 chiral amino acids having a helical structure in the native state on both the inner and the outer surface of the chiral (10, 20) and (20, 10) single-walled carbon nanotubes having an opposite handedness, and of the armchair (16, 16) nanotube with a similar diameter for comparison. In the final adsorbed state, the oligopeptide loses in all cases its native helical conformation, assuming elongated geometries that maximize its contact with the surface through all the 16 amino acids. We find that the complexes formed by the two chiral nanotubes and the chosen oligopeptide have a strongly unlike stability both when adsorption takes place on the outer convex surface of the nanotube, and when it occurs on the inner concave surface. Thus, our molecular simulations indicate that separation of chiral, enantiomeric carbon nanotubes for instance by chromatographic methods can indeed be carried out using oligopeptides of a sufficient length.

  16. Chromatographic and related reactors. Final report, 1 October 1983-30 September 1987

    SciTech Connect

    Langer, S.H.

    1988-01-07

    Several variations of gas- and liquid-column chromatographic reactors were investigated. In connection with this, new information on the kinetics and course of the base-catalyzed esterification reaction of tetrachloroterephthaloyl chloride and its derivatives was obtained with /sup 13/C Nuclear Magnetic Resonance. The operation and conversion in a reverse-phase liquid chromatographic reactor could be analyzed on a quantitative basis when consideration was given to the associative interaction between the stationary phase and elements of the mobile phase. Furthermore, the composition and models for the stationary phase could be examined on the basis of the kinetics of reaction of the tetrachloroterephthaloyl derivatives. A related procedure for determining the phase ratio was developed. Mass-transfer limitations for chromatographic reactions were also analyzed. Incorporation of a void column between two packed liquid-chromatographic columns made it possible to decouple esterification-rate constants for both the mobile and stationary phase. The stopped-flow liquid chromatographic reactor was found to be viable for conversions and operation but not amenable to quantitive analysis because of ionic-strength effects with the systems. Operation of a version of the stopped-flow-gas chromatographic reactor was successful and applications to studies of catalytic reactions were demonstrated. The rate of the CO methanation reaction even could be measured at room temperature on supported nickel, ruthenium, and cobalt catalysts.

  17. Five-descriptor model to predict the chromatographic sequence of natural compounds.

    PubMed

    Hou, Shuying; Wang, Jinhua; Li, Zhangming; Wang, Yang; Wang, Ying; Yang, Songling; Xu, Jia; Zhu, Wenliang

    2016-03-01

    Despite the recent introduction of mass detection techniques, ultraviolet detection is still widely applied in the field of the chromatographic analysis of natural medicines. Here, a neural network cascade model consisting of nine small artificial neural network units was innovatively developed to predict the chromatographic sequence of natural compounds by integrating five molecular descriptors as the input. A total of 117 compounds of known structure were collected for model building. The order of appearance of each compound was determined in gradient chromatography. Strong linear correlation was found between the predicted and actual chromatographic position orders (Spearman's rho = 0.883, p < 0.0001). Application of the model to the external validation set of nine natural compounds was shown to dramatically increase the prediction accuracy of the real chromatographic order of multiple compounds. A case study shows that chromatographic sequence prediction based on a neural network cascade facilitated compound identification in the chromatographic fingerprint of Radix Salvia miltiorrhiza. For natural medicines of known compound composition, our method provides a feasible means for identifying the constituents of interest when only ultraviolet detection is available.

  18. Mars Solar Balloon Landed Gas Chromatograph Mass Spectrometer

    NASA Technical Reports Server (NTRS)

    Mahaffy, P.; Harpold, D.; Niemann, H.; Atreya, S.; Gorevan, S.; Israel, G.; Bertaux, J. L.; Jones, J.; Owen, T.; Raulin, F.

    1999-01-01

    A Mars surface lander Gas Chromatograph Mass Spectrometer (GCMS) is described to measure the chemical composition of abundant and trace volatile species and isotope ratios for noble gases and other elements. These measurements are relevant to the study of atmospheric evolution and past climatic conditions. A Micromission plan is under study where a surface package including a miniaturized GCMS would be delivered to the surface by a solar heated hot air balloon based system. The balloon system would be deployed about 8 km above the surface of Mars, wherein it would rapidly fill with Martian atmosphere and be heated quickly by the sun. The combined buoyancy and parachuting effects of the solar balloon result in a surface package impact of about 5 m/sec. After delivery of the package to the surface, the balloon would ascend to about 4 km altitude, with imaging and magnetometry data being taken for the remainder of the daylight hours as the balloon is blown with the Martian winds. Total atmospheric entry mass of this mission is estimated to be approximately 50 kg, and it can fit as an Ariane 5 piggyback payload. The GCMS would obtain samples directly from the atmosphere at the surface and also from gases evolved from solid phase material collected from well below the surface with a Sample Acquisition and Transport Mechanism (SATM). The experiment envisioned in the Mars Micromission described would obtain samples from a much greater depth of up to one meter below the surface, and would search for organic molecules trapped in ancient stratified layers well below the oxidized surface. Insitu instruments on upcoming NASA missions working in concert with remote sensing measurement techniques have the potential to provide a more detailed investigation of mineralogy and the extent of simple volatiles such as CO2 and H2O in surface and subsurface solid phase materials. Within the context of subsequent mission opportunities such as those provided by the Ariane 5 piggyback

  19. The use of silica nanoparticles for gas chromatographic separation.

    PubMed

    Na, Na; Cui, Xianglan; De Beer, Thomas; Liu, Tingting; Tang, Tingting; Sajid, Muhammad; Ouyang, Jin

    2011-07-15

    A new IL-dispersed silica nanoparticles (IL-SNs) capillary column, combining properties of silica nanoparticles and ionic liquid (IL), was used for gas chromatographic separation. By dispersing silica nanoparticles in a conventional IL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BuMIm][BF6]), a layer of homogeneous interconnected particulate silica networks (thickness: 0.4-0.6 μm) was formed on the inner surface of a capillary column. This coating integrates advantages of silica nanoparticles (high surface area, high dispersed behaviour) and IL (extended liquid-state temperature range, chemical stability), hence increasing interactions between stationary phase and analytes. It was demonstrated that mixtures of a wide range of organic compounds including alcohols, esters, alkanes, aromatic compounds, as well as isomers and non-polar compounds can be well separated using an IL-SNs capillary column. Comparing to traditional support coated open tubular columns, the IL-SNs capillary column displays retention behaviors of separating both polar and non-polar compounds. The much thinner coating film of IL-SNs capillary column, compared to the coating film of SNs capillary column, decreases the resistance to mass transfer, resulting a good column efficiency of 3030 theoretical plates per meter for n-butanol (which is about 5 times higher than for the SNs capillary column). Furthermore, the IL-SNs capillary column decreases the IL retention selectivity dominated by IL structures, and has a higher coating value than neat IL stationary phase. Moreover, the preparation is simple as no modification of ILs or adoption of additional reagents is needed in pretreatments. This manuscript is the first report on the use of silica nanoparticles for gas chromatography, which would expand the applicability of silica nanoparticles in analytical chemistry.

  20. Chromatographic fingerprint similarity analysis for pollutant source identification.

    PubMed

    Xie, Juan-Ping; Ni, Hong-Gang

    2015-12-01

    In the present study, a similarity analysis method was proposed to evaluate the source-sink relationships among environmental media for polybrominated diphenyl ethers (PBDEs), which were taken as the representative contaminants. Chromatographic fingerprint analysis has been widely used in the fields of natural products chemistry and forensic chemistry, but its application to environmental science has been limited. We established a library of various sources of media containing contaminants (e.g., plastics), recognizing that the establishment of a more comprehensive library allows for a better understanding of the sources of contamination. We then compared an environmental complex mixture (e.g., sediment, soil) with the profiles in the library. These comparisons could be used as the first step in source tracking. The cosine similarities between plastic and soil or sediment ranged from 0.53 to 0.68, suggesting that plastic in electronic waste is an important source of PBDEs in the environment, but it is not the only source. A similarity analysis between soil and sediment indicated that they have a source-sink relationship. Generally, the similarity analysis method can encompass more relevant information of complex mixtures in the environment than a profile-based approach that only focuses on target pollutants. There is an inherent advantage to creating a data matrix containing all peaks and their relative levels after matching the peaks based on retention times and peak areas. This data matrix can be used for source identification via a similarity analysis without quantitative or qualitative analysis of all chemicals in a sample. PMID:26440782

  1. Chromatographic fingerprint similarity analysis for pollutant source identification.

    PubMed

    Xie, Juan-Ping; Ni, Hong-Gang

    2015-12-01

    In the present study, a similarity analysis method was proposed to evaluate the source-sink relationships among environmental media for polybrominated diphenyl ethers (PBDEs), which were taken as the representative contaminants. Chromatographic fingerprint analysis has been widely used in the fields of natural products chemistry and forensic chemistry, but its application to environmental science has been limited. We established a library of various sources of media containing contaminants (e.g., plastics), recognizing that the establishment of a more comprehensive library allows for a better understanding of the sources of contamination. We then compared an environmental complex mixture (e.g., sediment, soil) with the profiles in the library. These comparisons could be used as the first step in source tracking. The cosine similarities between plastic and soil or sediment ranged from 0.53 to 0.68, suggesting that plastic in electronic waste is an important source of PBDEs in the environment, but it is not the only source. A similarity analysis between soil and sediment indicated that they have a source-sink relationship. Generally, the similarity analysis method can encompass more relevant information of complex mixtures in the environment than a profile-based approach that only focuses on target pollutants. There is an inherent advantage to creating a data matrix containing all peaks and their relative levels after matching the peaks based on retention times and peak areas. This data matrix can be used for source identification via a similarity analysis without quantitative or qualitative analysis of all chemicals in a sample.

  2. Adsorption air cleaning from ozone.

    PubMed

    Baltrenas, Pranas; Paliulis, Dainius; Vasarevicius, Saulius; Simaitis, Ramutis

    2003-01-01

    Not much has been written about air cleaning from ozone. The aim of this paper was to demonstrate the possibility of adsorption air cleaning from ozone. The second aim was to investigate the dependence of the efficiency of ozone removal from the air on the height of the adsorber layer and on concentrations of ozone, and to obtain empirical formulas for calculating the efficiency of ozone treatment. Equipment for air cleaning from ozone and nitrogen and sulphur dioxides is suggested.

  3. Studies on Vapor Adsorption Systems

    NASA Technical Reports Server (NTRS)

    Shamsundar, N.; Ramotowski, M.

    1998-01-01

    The project consisted of performing experiments on single and dual bed vapor adsorption systems, thermodynamic cycle optimization, and thermal modeling. The work was described in a technical paper that appeared in conference proceedings and a Master's thesis, which were previously submitted to NASA. The present report describes some additional thermal modeling work done subsequently, and includes listings of computer codes developed during the project. Recommendations for future work are provided.

  4. Protein adsorption onto ceramic surfaces.

    PubMed

    Takami, Y; Yamane, S; Makinouchi, K; Otsuka, G; Glueck, J; Benkowski, R; Nosé, Y

    1998-04-01

    Ceramics seldom have been used as blood-contacting materials. However, alumina ceramic (Al2O3) and polyethylene are incorporated into the pivot bearings of the Gyro centrifugal blood pump. This material combination was chosen based on the high durability of the materials. Due to the stagnant flow that often occurs in a continuous flow condition inside a centrifugal pump, pivot bearing system is extremely critical. To evaluate the thombogenicity of pivot bearings in the Gyro pump, this study sought to investigate protein adsorption, particularly albumin, IgG, fibrinogen, and fibronectin onto ceramic surfaces. Al2O3 and silicon carbide ceramic (SiC) were compared with polyethylene (PE) and polyvinylchloride (PVC). Bicinchoninic acid (BCA) protein assay revealed that the amount of adsorbed proteins onto Al2O3 and SiC was significantly less than that on PVC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that numerous proteins adsorbed onto PVC compared to PE, Al2O3, and SiC. Identification of adsorbed proteins by Western immunoblotting revealed that the adsorption of albumin was similar on all four materials tested. Western immunoblotting also indicated lesser amounts of IgG, fibrinogen, and fibronectin on Al2O3 and SiC than on PE and PVC. In conclusion, ceramics (Al2O3 and SiC) are expected to be thromboresistant from the viewpoint of protein adsorption. PMID:9511095

  5. Ion chromatographic separation of inorganic ions using a combination of hydrophilic interaction chromatographic column and cation-exchange resin column.

    PubMed

    Arai, Kaori; Mori, Masanobu; Hironaga, Takahiro; Itabashi, Hideyuki; Tanaka, Kazuhiko

    2012-04-01

    A combination of hydrophilic interaction chromatographic (HILIC) column and a weakly acidic cation-exchange resin (WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography (IC). Firstly, the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions. The columns used were SeQuant ZIC-HILIC (ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase (ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase (HILIC-10). When using tartaric acid as the eluent, the HILIC columns indicated strong retentions for anions, based on ion-pair interaction. Especially, HILIC-10 could strongly retain anions compared with ZIC-HILIC. The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I(-) > NO3(-) > Br(-) > Cl(-) > H2PO4(-). However, since HILIC-10 could not separate analyte cations, a WCX column (TSKgel Super IC-A/C) was connected after the HILIC column in series. The combination column system of HILIC and WCX columns could successfully separate ten ions (Na+, NH4+, K+, Mg2+, Ca2+, H2PO4(-), Cl(-), Br(-), NO3(-) and I(-)) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6. The relative standard deviations (RSDs) of analyte ions by the system were in the ranges of 0.02% - 0.05% in retention times and 0.18% - 5.3% in peak areas through three-time successive injections. The limits of detection at signal-to-noise ratio of 3 were 0.24 - 0.30 micromol/L for the cations and 0.31 - 1.2 micromol/L for the anions. This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.

  6. Preparation and characterization of molecularly imprinted polymer for di(2-ethylhexyl) phthalate: application to sample clean-up prior to gas chromatographic determination.

    PubMed

    Shaikh, Huma; Memon, Najma; Khan, Hamayun; Bhanger, M I; Nizamani, S M

    2012-07-20

    The molecularly imprinted polymer (MIP) selective for di(2-ethylhexyl) phthalate (DEHP) an environmental endocrine disruptor was prepared by suspension polymerization using methacrylamide as functional monomer and N,N'-methylene-bis-acrylamide as cross-linker. The imprinted polymer was employed for solid-phase extraction of DEHP from water samples of environmental importance and characterized by FT-IR and SEM. The adsorption properties of the imprinted polymer were demonstrated by equilibrium rebinding experiments, Pseudo-second-order kinetic model, Sips isotherm and Scatchard analysis. The reusability of MIP was checked for at least six repeated batch adsorption cycles and the results showed almost no deterioration in the adsorption capacity. The competitive recognition studies were performed with DEHP and structurally similar compounds; dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP). The imprinting factor (IF) of DEHP was found to be 12.86 which was much higher than the imprinting factors (IF) of other phthalates. A method constituted by molecularly imprinted solid-phase extraction (MISPE) with GC-FID was developed for DEHP analysis in water samples under very simple conditions. Sample loading and desorption conditions were also optimized. The MISPE method's linearity ranged from 0.035 to 3.0 μg ml⁻¹ with r² = 0.9998. Intra-assay, interassay precision and accuracy ranged from 0.0168% to 1.017%, 1.130% to 4.799% and 94.98% to 99.35%, respectively. The LOD and LOQ were found to be 0.011 and 0.035 μg ml⁻¹, respectively. Synthesized MIP was employed in MISPE for cleaning up the spiked river water samples prior to gas chromatographic analysis. The river samples were found to contain DEHP in the range of 1.4 × 10⁻³ to 0.349 μg ml⁻¹. PMID:22673816

  7. Chromatographic metasomatism of the Arabian—Nubian lithosphere

    NASA Astrophysics Data System (ADS)

    Stein, Mordechai; Navon, Oded; Kessel, Ronit

    1997-11-01

    Trace elements and isotopic ratios of calc-alkaline and tholeiitic dikes from the very last stage of the late Proterozoic, Pan-African orogeny in the northern Arabian-Nubian Shield (ANS), and alkali basalts from the overlying Phanerozoic section are used to constrain the composition and model the evolution of the lithospheric mantle in this region. The dikes and basalts are interpreted as lithospheric melts formed during the post-orogenic (and post-subduction) history of the shield. While the mafic member of all suites share a primitive La/Th ratio, the Nb/Th and Ce/Pb are distinct for each suite. The (Nb/Th) PM (primitive mantle normalized) is ˜0.2 in the calc-alkaline dikes and 1.4 in the tholeiitic dikes and the Phanerozoic alkali basalts. The (Ce/Pb) PM ratios are low in the dikes (0.4 in the calc-alkaline and 0.3 in the tholeiitic) and high in the Phanerozoic basalts (2.8). We suggest that the variations in the trace element ratios reflect sampling of different zones in the lithospheric mantle, which were formed by subduction related metasomatism of the mantle wedge. We constructed a chromatographic model to explain this zonation. In this model a plume-derived oceanic lithosphere is subducted and dehydrates at depth. Fluids released from the dehydrating slab metasomatize the overlying wedge and form amphibole-rich channels. Nb is preferentially taken by the amphibole and is enriched only in the lower zones of the column. The other elements (U, Th, REE and especially Pb and Rb) behave incompatibly. They are enriched in the fluid and transported efficiently to the melting zone in the centre of the wedge. Dehydration of the base of the wedge as it descends below the amphibole stability field depletes this region in Pb and Rb. After the end of subduction, the wedge is fossilized and forms the lithospheric mantle. The zone above the Nb concentration front is sampled by the calc-alkaline magmas. The tholeiitic magmas sample the zone below the Nb front. The

  8. Chromatographic metasomatism of the Arabian-Nubian lithosphere

    NASA Astrophysics Data System (ADS)

    Kessel, R.; Navon, O.; Stein, M.

    1997-11-01

    Trace elements and isotopic ratios of calc-alkaline and tholeiitic dikes from the very last stage of the late Proterozoic, Pan-African orogeny in the northern Arabian-Nubian Shield (ANS), and alkali basalts from the overlying Phanerozoic section are used to constrain the composition and model the evolution of the lithospheric mantle in this region. The dikes and basalts are interpreted as lithospheric melts formed during the post-orogenic (and post-subduction) history of the shield. While the mafic member of all suites share a primitive La/Th ratio, the Nb/Th and Ce/Pb are distinct for each suite. The (Nb/Th)PM (primitive mantle normalized) is ~0.2 in the calc-alkaline dikes and 1.4 in the tholeiitic dikes and the Phanerozoic alkali basalts. The (Ce/Pb)PM ratios are low in the dikes (0.4 in the calc-alkaline and 0.3 in the tholeiitic) and high in the Phanerozoic basalts (2.8). We suggest that the variations in the trace element ratios reflect sampling of different zones in the lithospheric mantle, which were formed by subduction related metasomatism of the mantle wedge. We constructed a chromatographic model to explain this zonation. In this model a plume-derived oceanic lithosphere is subducted and dehydrates at depth. Fluids released from the dehydrating slab metasomatize the overlying wedge and form amphibole-rich channels. Nb is preferentially taken by the amphibole and is enriched only in the lower zones of the column. The other elements (U, Th, REE and especially Pb and Rb) behave incompatibly. They are enriched in the fluid and transported efficiently to the melting zone in the centre of the wedge. Dehydration of the base of the wedge as it descends below the amphibole stability field depletes this region in Pb and Rb. After the end of subduction, the wedge is fossilized and forms the lithospheric mantle. The zone above the Nb concentration front is sampled by the calc-alkaline magmas. The tholeiitic magmas sample the zone below the Nb front. The Phanerozoic

  9. Chromatographic removal and heat inactivation of hepatitis A virus during manufacture of human albumin.

    PubMed

    Adcock, W L; MacGregor, A; Davies, J R; Hattarki, M; Anderson, D A; Goss, N H

    1998-08-01

    CSL Limited, an Australian biopharmaceutical company, has recently converted its method of manufacture for human albumin from a traditional Cohn-ethanol fractionation method to a method employing chromatographic techniques. Studies were undertaken to determine the efficiency of the chromatographic and pasteurization steps used in the manufacture of Albumex(R) (CSL's trade name for albumin) in removing and inactivating the potential viral contaminant, hepatitis A virus (HAV). The manufacturing process for Albumex(R) includes three chromatographic steps, two of which are ion-exchange steps (DEAE-Sepharose(R) Fast Flow and CM-Sepharose(R) Fast Flow) and the third is a gel-filtration step (Sephacryl(R) S200 HR). The final stage of the Albumex(R) process involves a bulk pasteurization step where product is held at 60 degrees C for 10 h. HAV partitioning experiments on the DEAE-Sepharose(R) FF and CM-Sepharose(R) FF ion-exchange and Sephacryl(R) S200 HR gel-filtration columns were performed with scaled-down models of the production-scale chromatographic Albumex(R) process. Production samples collected before each of the chromatographic steps were spiked with HAV and processed through each of the scaled-down chromatographic columns. Samples collected during processing were assayed and the log10 reduction factors calculated. Inactivation kinetics of HAV were examined during the pasteurization of Albumex(R) 5 and 20 [5% and 20% (w/v) albumin solutions] held at 60 degrees C for 10 h. Log10 reductions for HAV through the DEAE-Sepharose(R) FF, CM-Sepharose(R) FF and Sephacryl(R) S200 HR chromatographic columns were 5.3, 1.5 and 4.2 respectively, whereas a 4.4 and a greater than 3.9 log10 reduction in HAV in Albumex(R) 5 and 20 respectively were achieved during pasteurization.

  10. High ionic strength narrows the population of sites participating in protein ion-exchange adsorption: A single-molecule study

    PubMed Central

    Kisley, Lydia; Chen, Jixin; Mansur, Andrea P.; Dominguez-Medina, Sergio; Kulla, Eliona; Kang, Marci; Shuang, Bo; Kourentzi, Katerina; Poongavanam, Mohan-Vivekanandan; Dhamane, Sagar; Willson, Richard C.; Landes, Christy F.

    2014-01-01

    The retention and elution of proteins in ion-exchange chromatography is routinely controlled by adjusting the mobile phase salt concentration. It has repeatedly been observed, as judged from adsorption isotherms, that the apparent heterogeneity of adsorption is lower at more-eluting, higher ionic strength. Here, we present an investigation into the mechanism of this phenomenon using a single-molecule, super-resolution imaging technique called motion-blur Points Accumulation for Imaging in Nanoscale Topography (mbPAINT). We observed that the number of functional adsorption sites was smaller at high ionic strength and that these sites had reduced desorption kinetic heterogeneity, and thus narrower predicted elution profiles, for the anion-exchange adsorption of α-lactalbumin on an agarose-supported, clustered-charge ligand stationary phase. Explanations for the narrowing of the functional population such as inter-protein interactions and protein or support structural changes were investigated through kinetic analysis, circular dichroism spectroscopy, and microscopy of agarose microbeads, respectively. The results suggest the reduction of heterogeneity is due to both electrostatic screening between the protein and ligand and tuning the steric availability within the agarose support. Overall, we have shown that single molecule spectroscopy can aid in understanding the influence of ionic strength on the population of functional adsorbent sites participating in the ion-exchange chromatographic separation of proteins. PMID:24751557

  11. Measuring and modeling the competitive adsorption of CO2, CH4, and N2 on a dry coal.

    PubMed

    Ottiger, Stefan; Pini, Ronny; Storti, Giuseppe; Mazzotti, Marco

    2008-09-01

    Data on the adsorption behavior of CO 2, CH 4, and N 2 on coal are needed to develop enhanced coalbed methane (ECBM) recovery processes, a technology where the recovery of CH 4 is enhanced by injection of a gas stream consisting of either pure CO 2, pure N 2, or a mixture of both. The pure, binary, and ternary adsorption of these gases on a dry coal from the Sulcis Coal Province in Italy has been measured at pressures up to 180 bar and temperatures of 45 and 70 degrees C for the pure gases and of 45 degrees C for the mixtures. The experiments were performed in a system consisting of a magnetic suspension balance using a gravimetric-chromatographic technique. The excess adsorption isotherms are successfully described using a lattice density functional theory model based on the Ono-Kondo equations exploiting information about the structure of the coal, the adsorbed gases, and the interaction between them. The results clearly show preferential adsorption of CO 2 over CH 4 and N 2, which therefore indicate that ECBM may be a viable option for the permanent storage of CO 2. PMID:18680385

  12. Adsorption of goethite onto quartz and kaolinite

    USGS Publications Warehouse

    Goldberg, M.C.; Weiner, Eugene R.; Boymel, P.M.

    1984-01-01

    The adsorption of colloidal goethite onto quartz and kaolinite substrates has been studied as a function of pH and NaCl concentration. Goethite adsorption was measured quantitatively by Fourier-transform infrared spectroscopy. The results indicate that adsorption onto both substrates is due primarily to coulombic forces; however, the pH dependence of adsorption is very different for the two substrates. This is explained by the fact that the surface charge on quartz is entirely pH-dependent, while kaolinite has surface faces which carry a permanent negative charge. Adsorption of goethite on to kaolinite increases markedly with increasing NaCl concentration, while adsorption onto quartz is relatively independent of NaCl concentration. This can be explained by the influence of NaCl concentration upon the development of surface charge on the substrates. A method is described for separating surface-bound goethite from free goethite.

  13. [Synthesis of two-organic complexes and characterization of their adsorption behaviour of ten polycyclic aromatic hydrocarbons].

    PubMed

    Meng, Jie; Sun, Yuxiu; Li, Yan

    2014-07-01

    Metal-organic frameworks (MOFs) are concerned mainly due to the unusual properties for diverse analytical applications, such as high surface area, good thermal stability, inpore functionally and outer-surface modification. Two metal-organic complexes were prepared by two methods of hydrothermal synthesis and room temperature synthesis, separately. The compositions, structures, thermal stability and adsorption properties of the two complexes were characterized by X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) method, which indicated that the two complexes have not only good thermal stability but also good adsorption for polycyclic aromatic hydrocarbons (PAHs). PAHs enter into environment leading to pollution by industrial and agricultural production and life, rooting in the incomplete combustion or pyrolysis of organism. PAHs are strongly carcinogenic and mutagenic. Some PAHs are considered as endocrine disruptors, and maybe have biological effects on human health. Regulations have thus been formulated for monitoring and controlling PAHs by the United States Environmental Protection Agency (U.S. EPA) and other government agencies. Adsorption kinetic of PAHs on the two complexes could be well described by the pseudo-second order kinetic model, and the adsorption behaviors of the two complexes on PAHs are in accord with Langmuir model. In addition, the adsorption capacities increase with the increasing adsorbent dosage. It is proved by the FT-IR data that pi-pi interactions between the PAHs and the framework terephthalic acid molecules. Ten PAHs were adsorbed well on the two complexes which have good adsorptive selectivity. By further optimizing of the two complex materials, it is promising to use them as chromatographic stationary phases.

  14. Ozone adsorption on carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Chassard, Guillaume; Gosselin, Sylvie; Visez, Nicolas; Petitprez, Denis

    2014-05-01

    Carbonaceous particles produced by incomplete combustion or thermal decomposition of hydrocarbons are ubiquitous in the atmosphere. On these particles are adsorbed hundreds of chemical species. Those of great concern to health are polycyclic aromatic hydrocarbons (PAHs). During atmospheric transport, particulate PAHs react with gaseous oxidants. The induced chemical transformations may change toxicity and hygroscopicity of these potentially inhalable particles. The interaction between ozone and carbon particles has been extensively investigated in literature. However ozone adsorption and surface reaction mechanisms are still ambiguous. Some studies described a fast catalytic decomposition of ozone initiated by an atomic oxygen chemisorption followed by a molecular oxygen release [1-3]. Others suggested a reversible ozone adsorption according to Langmuir-type behaviour [4,5]. The aim of this present study is a better understanding of ozone interaction with carbon surfaces. An aerosol of carbon nanoparticles was generated by flowing synthetic air in a glass tube containing pure carbon (primary particles < 50 nm), under magnetic stirring. The aerosol was then mixed with ozone in an aerosol flow tube. Ozone uptake experiments were performed with different particles concentrations with a fixed ozone concentration. The influence of several factors on kinetics was examined: initial ozone concentration, particle size (50 nm ≤ Dp ≤ 200 nm) and competitive adsorption (with probe molecule and water). The effect of initial ozone concentration was first studied. Accordingly to literature, it has been observed that the number of gas-phase ozone molecules lost per unit particle surface area tends towards a plateau for high ozone concentration suggesting a reversible ozone adsorption according to a Langmuir mechanism. We calculated the initial reaction probability between O3 and carbon particles.An initial uptake coefficient of 1.10-4 was obtained. Similar experiments were

  15. Adsorption thermodynamics of Methylene Blue onto bentonite.

    PubMed

    Hong, Song; Wen, Cheng; He, Jing; Gan, Fuxing; Ho, Yuh-Shan

    2009-08-15

    The effect of temperature on the equilibrium adsorption of Methylene Blue dye from aqueous solution using bentonite was investigated. The equilibrium adsorption data were analyzed using three widely applied isotherms: Langmuir, Freundlich, and Redlich-Peterson. A non-linear method was used for comparing the best fit of the isotherms. Best fit was found to be Redlich-Peterson isotherm. Thermodynamic parameters, such as DeltaG degrees, DeltaH degrees, and DeltaS degrees were calculated using adsorption equilibrium constant obtained from the Langmuir isotherm. Results suggested that the Methylene Blue adsorption on bentonite was a spontaneous and endothermic process.

  16. Adsorption of phenol on wood surfaces

    NASA Astrophysics Data System (ADS)

    Mamleeva, N. A.; Lunin, V. V.

    2016-03-01

    Adsorption of phenol on aspen and pine wood is investigated. It is shown that adsorption isotherms are described by the Langmuir model. The woods' specific surface areas and adsorption interaction constants are determined. It is found that the sorption of phenol on surfaces of aspen and pine is due to Van der Waals interactions ( S sp = 45 m2/godw for aspen and 85 m2/godw for pine). The difference between the adsorption characteristics is explained by properties of the wood samples' microstructures.

  17. Physical adsorption strength in open systems.

    PubMed

    Knippenberg, M Todd; Stuart, Steven J; Cooper, Alan C; Pez, G P; Cheng, Hansong

    2006-11-23

    For a physical adsorption system, the distances of adsorbates from the surface of a substrate can vary significantly, depending on particle loading and interatomic interactions. Although the total adsorption energy is quantified easily, the normalized, per-particle adsorption energies are more ambiguous if some of these particles are far away from the surface and are interacting only weakly with the substrate. A simple analytical procedure is proposed to characterize the distance dependence of the physisorption strength and effective adsorption capacity. As an example, the method is utilized to describe H2 physisorption in a finite bundle of single-walled carbon nanotubes. PMID:17107125

  18. Adsorption and isotopic fractionation of Xe

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.

    1986-01-01

    A theoretical description of the mechanisms of isotopic fractionation arising during adsorption of noble gases in a Henry's Law pressure regime is given. Experimental data on the isotopic composition of Xe adsorbed on activated charcoal in the temperature range 220 K to 350 K are presented. Both theoretical considerations and the experimental data indicate that equilibrium adsorption does not significantly alter the isotopic structure of adsorbed structure of adsorbed noble gases. Therefore, if adsorption is responsible for the elemental noble gas pattern in meteorites and the earth, the heavy noble gas isotopic fractionation between them must have been produced prior to and by a different process than equilibrium adsorption.

  19. Evaluation of two adsorbents for diffusive sampling and thermal desorption-gas chromatographic analysis of monoterpenes in air.

    PubMed

    Sunesson, A L; Sundgren, M; Levin, J O; Eriksson, K; Carlson, R

    1999-02-01

    Tube type samplers with two different adsorbents, Chromosorb 106 and Tenax TA, were evaluated by laboratory experiments and field tests for simultaneous diffusive sampling of alpha-pinene, beta-pinene and delta 3-carene and subsequent thermal desorption-gas chromatographic analysis. No statistically significant effects of exposure time, concentrations of monoterpenes or relative humidity were found for samplers with Chromosorb 106 when running a factorial design, with the exception of the adsorption of delta 3-carene, for which some weak effects were noted. Samplers with Tenax TA were affected by the sampling time as well as the concentration for all terpenes, with a strong interaction effect between these two factors. The terpenes showed good storage stability on both adsorbents. No effect of back-diffusion was noted when using Chromosorb 106, while Tenax TA showed some back-diffusion effects. The uptake rates, in ml min-1, for the terpenes on Chromosorb 106 were 0.36 for alpha-pinene, 0.36 for beta-pinene and 0.40 for delta 3-carene. The corresponding average values on Tenax TA were 0.30 for alpha-pinene, 0.32 for beta-pinene and 0.38 for delta 3-carene. The field validation proved that diffusive sampling on Chromosorb 106 agreed well with pumped sampling on charcoal for stationary samples, while the personal samples indicated a discrepancy of 25% between Chromosorb 106 and charcoal samples. Tenax TA generally gave lower results than Chromosorb 106 in all field samples. Samplers packed with Chromosorb 106 could be used to monitor terpene levels in workplaces such as sawmills. The major advantages with this method are the sampling procedure, which is simple to perform compared to other techniques, the easily automated analysis procedure and the possibility to reuse the samplers.

  20. Charcoal/Nitrogen Adsorption Cryocooler

    NASA Technical Reports Server (NTRS)

    Bard, Steven

    1987-01-01

    Refrigerator with no wear-related moving parts produces 0.5 W of cooling at 118 K. When fully developed, refrigerator needs no electrical power, and life expectancy of more than 10 yr, operates unattended to cool sensitive infrared detectors for long periods. Only moving parts in adsorption cryocooler are check valves. As charcoal is cooled in canister, gas pressure drops, allowing inlet check valve to open and admit more nitrogen. When canister is heated, pressure rises, closing inlet valve and eventually opening outlet valve.

  1. Moisture adsorption in optical coatings

    NASA Technical Reports Server (NTRS)

    Macleod, H. Angus

    1988-01-01

    The thin film filter is a very large aperture component which is exceedingly useful because of its small size, flexibility and ease of mounting. Thin film components, however, do have defects of performance and especially of stability which can cause problems in systems, particularly where long-term measurements are being made. Of all of the problems, those associated with moisture absorption are the most serious. Moisture absorption occurs in the pore-shaped voids inherent in the columnar structure of the layers. Ion-assisted deposition is a promising technique for substantially reducing moisture adsorption effects in thin film structures.

  2. Surfactant adsorption to soil components and soils.

    PubMed

    Ishiguro, Munehide; Koopal, Luuk K

    2016-05-01

    Soils are complex and widely varying mixtures of organic matter and inorganic materials; adsorption of surfactants to soils is therefore related to the soil composition. We first discuss the properties of surfactants, including the critical micelle concentration (CMC) and surfactant adsorption on water/air interfaces, the latter gives an impression of surfactant adsorption to a hydrophobic surface and illustrates the importance of the CMC for the adsorption process. Then attention is paid to the most important types of soil particles: humic and fulvic acids, silica, metal oxides and layered aluminosilicates. Information is provided on their structure, surface properties and primary (proton) charge characteristics, which are all important for surfactant binding. Subsequently, the adsorption of different types of surfactants on these individual soil components is discussed in detail, based on mainly experimental results and considering the specific (chemical) and electrostatic interactions, with hydrophobic attraction as an important component of the specific interactions. Adsorption models that can describe the features semi-quantitatively are briefly discussed. In the last part of the paper some trends of surfactant adsorption on soils are briefly discussed together with some complications that may occur and finally the consequences of surfactant adsorption for soil colloidal stability and permeability are considered. When we seek to understand the fate of surfactants in soil and aqueous environments, the hydrophobicity and charge density of the soil or soil particles, must be considered together with the structure, hydrophobicity and charge of the surfactants, because these factors affect the adsorption. The pH and ionic strength are important parameters with respect to the charge density of the particles. As surfactant adsorption influences soil structure and permeability, insight in surfactant adsorption to soil particles is useful for good soil management. PMID

  3. [Use of LKhM-80 chromatograph in the analysis of urinary steroids].

    PubMed

    Orlov, E N; Antipov, E M

    1995-01-01

    The paper describes a simple way of updating a Russian production-type LKaM-80 chromatograph in order to make a gas chromatographic analysis of urinary steroids for separation by using high performance capillary columns. To connect capillary columns, the units consisting of a gas heaving T-joint, a stream separating chamber, and a releasing restrictor were applied. To achieve satisfactory results, it is necessary to place a column through the tube connecting the union for attachment of the column and the flame-ionization detector so that the end of a capillary should be located at the detector as soon as closer. The updated chromatograph has been successfully used to obtain urinary steroidal profiles which are essential for the differential diagnosis of causes of hyperandrogyny in females, including pregnants.

  4. A linear modulation-based stochastic resonance algorithm applied to the detection of weak chromatographic peaks.

    PubMed

    Deng, Haishan; Xiang, Bingren; Liao, Xuewei; Xie, Shaofei

    2006-12-01

    A simple stochastic resonance algorithm based on linear modulation was developed to amplify and detect weak chromatographic peaks. The output chromatographic peak is often distorted when using the traditional stochastic resonance algorithm due to the presence of high levels of noise. In the new algorithm, a linear modulated double-well potential is introduced to correct for the distortion of the output peak. Method parameter selection is convenient and intuitive for linear modulation. In order to achieve a better signal-to-noise ratio for the output signal, the performance of two-layer stochastic resonance was evaluated by comparing it with wavelet-based stochastic resonance. The proposed algorithm was applied to the quantitative analysis of dimethyl sulfide and the determination of chloramphenicol residues in milk, and the good linearity of the method demonstrated that it is an effective tool for detecting weak chromatographic peaks.

  5. Chromatographic immunoassays: strategies and recent developments in the analysis of drugs and biological agents.

    PubMed

    Matsuda, Ryan; Rodriguez, Elliott; Suresh, Doddavenkatanna; Hage, David S

    2015-01-01

    A chromatographic immunoassay is a technique in which an antibody or antibody-related agent is used as part of a chromatographic system for the isolation or measurement of a specific target. Various binding agents, detection methods, supports and assay formats have been developed for this group of methods, and applications have been reported that range from drugs, hormones and herbicides to peptides, proteins and bacteria. This review discusses the general principles and applications of chromatographic immunoassays, with an emphasis being given to methods and formats that have been developed for the analysis of drugs and biological agents. The relative advantages or limitations of each format are discussed. Recent developments and research in this field, as well as possible future directions, are also considered.

  6. A "stripping" ligand tactic for use with the kinetic locking-on strategy: its use in the resolution and bioaffinity chromatographic purification of NAD(+)-dependent dehydrogenases.

    PubMed

    O'Flaherty, M; O'Carra, P; McMahon, M; Mulcahy, P

    1999-08-01

    The kinetic locking-on strategy utilizes soluble analogues of the target enzymes' specific substrate to promote selective adsorption of individual NAD(+)-dependent dehydrogenases on their complementary immobilized cofactor derivative. Application of this strategy to the purification of NAD(+)-dependent dehydrogenases from crude extracts has proven that it can yield bioaffinity systems capable of producing one-chromatographic-step purifications with yields approaching 100%. However, in some cases the purified enzyme preparation was found to be contaminated with other proteins weakly bound to the immobilized cofactor derivative through binary complex formation and/or nonspecific interactions, which continuously "dribbled" off the matrix during the chromatographic procedure. The fact that this problem can be overcome by including a short pulse of 5'-AMP (stripping ligand) in the irrigant a couple of column volumes prior to the discontinuation of the specific substrate analogue (locking-on ligand) is clear from the results presented in this report. The general effectiveness of this auxiliary tactic has been assessed using model studies and through incorporation into an actual purification from a crude cellular extract. The results confirm the usefulness of the stripping-ligand tactic for the resolution and purification of NAD(+)-dependent dehydrogenases when using the locking-on strategy. These studies have been carried out using bovine liver glutamate dehydrogenase (GDH, EC 1.4.1.3), yeast alcohol dehydrogenase (YADH, EC 1.1.1.1), porcine heart mitochondrial malate dehydrogenase (mMDH, EC 1.1.1.37), and bovine heart L-lactate dehydrogenase (l-LDH, EC 1.1.1.27).

  7. A "stripping" ligand tactic for use with the kinetic locking-on strategy: its use in the resolution and bioaffinity chromatographic purification of NAD(+)-dependent dehydrogenases.

    PubMed

    O'Flaherty, M; O'Carra, P; McMahon, M; Mulcahy, P

    1999-08-01

    The kinetic locking-on strategy utilizes soluble analogues of the target enzymes' specific substrate to promote selective adsorption of individual NAD(+)-dependent dehydrogenases on their complementary immobilized cofactor derivative. Application of this strategy to the purification of NAD(+)-dependent dehydrogenases from crude extracts has proven that it can yield bioaffinity systems capable of producing one-chromatographic-step purifications with yields approaching 100%. However, in some cases the purified enzyme preparation was found to be contaminated with other proteins weakly bound to the immobilized cofactor derivative through binary complex formation and/or nonspecific interactions, which continuously "dribbled" off the matrix during the chromatographic procedure. The fact that this problem can be overcome by including a short pulse of 5'-AMP (stripping ligand) in the irrigant a couple of column volumes prior to the discontinuation of the specific substrate analogue (locking-on ligand) is clear from the results presented in this report. The general effectiveness of this auxiliary tactic has been assessed using model studies and through incorporation into an actual purification from a crude cellular extract. The results confirm the usefulness of the stripping-ligand tactic for the resolution and purification of NAD(+)-dependent dehydrogenases when using the locking-on strategy. These studies have been carried out using bovine liver glutamate dehydrogenase (GDH, EC 1.4.1.3), yeast alcohol dehydrogenase (YADH, EC 1.1.1.1), porcine heart mitochondrial malate dehydrogenase (mMDH, EC 1.1.1.37), and bovine heart L-lactate dehydrogenase (l-LDH, EC 1.1.1.27). PMID:10425164

  8. High-performance liquid chromatography of amino acids, peptides and proteins. CXXIX. Ceramic-based particles as chemically stable chromatographic supports.

    PubMed

    Wirth, H J; Eriksson, K O; Holt, P; Aguilar, M; Hearn, M T

    1993-08-27

    Porous zirconia based particles have been modified using different derivatisation procedures. The modified particles were characterised in terms of their accessible surface areas and degree of surface coverage of the bounded or physicoated phases utilising the strong and specific adsorption of phosphate ions to the zirconia surface. The hydroxyl group density was determined by a 1H NMR technique. The particles were modified by immobilising different silanes to introduce either hydrophobic ligands or reactive groups onto the zirconia surface. In the latter case, various ligands were then covalently attached to the activated supports. Using this type of modification, n-octadecyl- (C18), carbohydrate- and Cibacron Blue F3GA-modified zirconia particles were produced. Furthermore, polymeric coated particles were prepared either by using polybutadiene or by cross-linking the carbohydrate modified sorbents. The pH stability of the different sorbents were determined in batch experiments and under chromatographic conditions. The leakage of ligands was monitored by UV absorption and by employing radioactively labelled ligands. The performance of the C18 reversed-phase modified zirconia in packed columns was also used as an indicator of changes in the surface chemistry following pH stability tests. The experimental results indicate that the Cibacron Blue F3GA dye-modified sorbent was stable up to pH 10.5, the C18 reversed-phase packing up to pH 13 and the carbohydrate-bonded phase up to pH 12. These investigations substantiate the favourable chemical and physical characteristics anticipated for surface modified zirconias for potential use as chromatographic adsorbents. PMID:8408421

  9. Investigation into the phenomena affecting the retention behavior of basic analytes in chaotropic chromatography: Joint effects of the most relevant chromatographic factors and analytes' molecular properties.

    PubMed

    Čolović, Jelena; Kalinić, Marko; Vemić, Ana; Erić, Slavica; Malenović, Anđelija

    2015-12-18

    The aim of this study was to systematically investigate the phenomena affecting the retention behavior of structurally diverse basic drugs in ion-interaction chromatographic systems with chaotropic additives. To this end, the influence of three factors was studied: pH value of the aqueous phase, concentration of sodium hexafluorophosphate, and content of acetonitrile in the mobile phase. Mobile phase pH was found to affect the thermodynamic equilibria in the studied system beyond its effects on the analytes' ionization state. Specifically, increasing pH from 2 to 4 led to longer retention times, even with analytes which remain completely protonated. An explanation for this phenomenon was sought by studying the adsorption behavior of acetonitrile and chaotropic additive onto stationary phase. It was shown that the magnitude of the developed surface potential, which significantly affects retention - increases with pH, and that this can be attributed to the larger surface excess of acetonitrile. To study how analytes' structural properties influence their retention, quantitative structure-retention modeling was performed next. A support vector machine regression model was developed, relating mobile phase constituents and structural descriptors with retention data. While the ETA_EtaP_B_RC and XlogP can be considered as molecular descriptors which describe factors affecting retention in any RP-HPLC system, TDB9p and RDF45p are molecular descriptors which account for spatial arrangement of polarizable atoms and they can clearly relate to analytes' behavior on the stationary phase surface, where the electrostatic potential develops. Complementarity of analytes' structure with that of the electric double layer can be seen as a key factor influencing their retention behavior. Structural diversity of analytes and good predictive capabilities over a range of experimental conditions make the established model a useful tool in predicting retention behavior in the studied

  10. Adsorptive separation in bioprocess engineering

    SciTech Connect

    Huang, E.W.Y.

    1987-01-01

    The invention and development of an energy-efficient separation technique for recovery of desired chemicals from biomass conversion would greatly enhance the economic viability of this bioprocess. Adsorptive separation of several chemicals from aqueous solution was studied in this thesis. The desired species were recovered from the dilute aqueous solution by using crosslinked polyvinylpyridine resin to effect selective sorption. The sorbed chemicals were then removed from the resin by either thermal regeneration or elution with some appropriate desorbents. The effects of temperature, pH value, and solute concentration on resin swelling were investigated. The adsorption equilibrium isotherms, resin capacities and resin selectivities of methanol, ethanol, 1-propanol, isopropanol, glycerol, acetone, 1-butanol, tert-butanol, and 2,3-butanediol were determined to study the homologies. Furthermore, acetic acid, butyric acid, hydrochloric acid, lactic acid, and sulfuric acid were recovered from very dilute aqueous solutions. The concentration of the sorbed chemical in the stationary phase can be many times higher than in the mobile phase for some acids. Finally, different types of equilibrium isotherms were used to fit the experimental data. A mathematical model was developed by using the theory of interference to predict the breakthrough curves and the process efficiency to provide information for large-scale process design and development.

  11. Microstructure-based analysis and simulation of flow and mass transfer in chromatographic stationary phases

    NASA Astrophysics Data System (ADS)

    Koku, Harun

    Limitations of mass transfer in chromatographic bioseparations employing traditional packed particles have fuelled the inception and development of alternative stationary phases with improved performance characteristics. This work investigates case studies in two categories of these alternative media, namely polymer-modified packed particles and continuous monolithic phases, for insight into their enhanced properties. Specifically, high-resolution microscopy techniques and image-based analysis algorithms were implemented to extract morphology information for these materials, in an attempt to elucidate the relation between microstructure and performance. For the monolith, mesoscopic simulation methods were also employed for a more rigorous analysis of the flow and dispersion behavior. Scanning and transmission electron microscopy images of the commercial polymer-modified, agarose-based particle Sepharose XL were compared to those for its unmodified counterpart, Sepharose FF. Local regions in the composite dextran-agarose Sepharose XL particles were noted to exhibit a denser network of fibers and smaller pore sizes overall, compared to those in the traditional Sepharose FF particles. Images of particles equilibrated with high concentrations of protein revealed a significant difference in protein localization patterns, with the stained protein in XL occupying a markedly higher area fraction of the images. This suggests a higher volume available for adsorption and provides visual clues into how the consistently higher static capacity of these polymer-modified particles is manifested. Treatment of the XL particles with dextranase, an enzyme that breaks down dextran, resulted in a reduction of protein coverage, providing evidence that it is indeed the dextran that is responsible for the improved static capacity in this polymer-modified stationary phase. Imaging and image analysis techniques were also used to analyze the commercial CIM(TM) disk monolith. Two- and three

  12. Test plan for demonstrating plutonium extraction from 10-L solutions using EIChrom extraction chromatographic resins

    SciTech Connect

    Barney, G.S.

    1994-08-15

    Corrosive plutonium solutions stored in 10-L containers at the Plutonium Finishing Plant must be treated to convert the plutonium to a safe, solid form for storage and to remove the americium so that radiation exposure can be reduced. Extraction chromatographic resins will be tested for separating plutonium from these solutions in the laboratory. Separation parameters will be developed during the testing for large scale processing of the 10-L solutions and solutions of similar composition. Use of chromatographic resins will allow plutonium separation with minimum of chemical addition to the feed and without the need for plutonium valence adjustment. The separated plutonium will be calcined to plutonium oxide by direct solution calcination.

  13. Derivatization in gas chromatographic determination of phenol and aniline traces in aqueous media

    NASA Astrophysics Data System (ADS)

    Gruzdev, I. V.; Zenkevich, I. G.; Kondratenok, B. M.

    2015-06-01

    Substituted anilines and phenols are the most common hydrophilic organic environmental toxicants. The principles of gas chromatographic determination of trace amounts of these compounds in aqueous media at concentrations <=0.1 μg litre-1 based on synthesis of their derivatives (derivatization) directly in the aqueous phase are considered. Conversion of relatively hydrophilic analytes into more hydrophobic derivatives makes it possible to achieve such low detection limits and optimize the protocols of extractive preconcentration and selective chromatographic detection. Among the known reactions, this condition is best met by electrophilic halogenation of compounds at the aromatic moiety. The bibliography includes 177 references.

  14. Surfactant Modified/Mediated Thin-Layer Chromatographic Systems for the Analysis of Amino Acids

    PubMed Central

    Bhawani, Showkat A.; Albishri, Hassan M.; Mohamad Ibrahim, Mohamad N.; Mohammad, A.

    2013-01-01

    This review incorporates a large number of chromatographic systems modified by the surfactants. A large number of solvent systems and stationary phases are summarized in this paper. Three different kinds of surfactants (anionic, cationic, and nonionic) are used as modifiers for stationary phases as well as solvent systems. Surfactants are used at all the three different concentration levels (below, above, and at critical micelle concentration) where surfactants behave differently. Modifications of both stationary phases and solvent systems by surfactants produced a new generation of chromatographic systems. Microemulsion solvent systems are also incorporated in this paper. Microemulsion thin-layer chromatography is a new approach in the field of chromatography. PMID:24455427

  15. A comparative study of using in-line near-infrared spectra, ultraviolet spectra and fused spectra to monitor Panax notoginseng adsorption process.

    PubMed

    Jiang, Cheng; Qu, Haibin

    2015-01-01

    The step of enriching and purifying saponins by macroporous resin column chromatography is closely related to the safety and efficacy of Panax notoginseng products during their manufacturing processes. Adsorption process is one of the most critical unit operations within each chromatographic cycle. In order to understand the adsorption process directly, it is necessary to develop a rapid and precise method to monitor the adsorption process in real time. In this study, comparative evaluation of using near-infrared (NIR) spectra, ultraviolet (UV) spectra and fused spectra to monitor the adsorption process of P. notoginseng was conducted. The uninformative variable elimination by partial least squares (UVE-PLS) regression models were established for quantification of notoginsenoside R1, ginsenoside Rg1, ginsenoside Re, ginsenoside Rb1 and ginsenoside Rd in effluents based on different spectra. There was a significant improvement provided by the models based on fused spectra. The results in this work were conducive to solving the problems about real-time quantitative analysis of saponins during P. notoginseng adsorption. The fusion method of NIR and UV spectra combined with UVE-PLS regression could be a promising strategy to real-time analyze the components, which are difficult to be quantified by individual spectroscopic technique.

  16. Ion Exchange and Adsorption of Inorganic Contaminants

    EPA Science Inventory

    In the first part of the chapter, the fundamentals of ion exchange and adsorption processes are explained, with the goal of demonstrating how these principles influence process design for inorganic contaminant removal. In the second part, ion exchange and adsorption processes th...

  17. High-performance liquid chromatographic column packings with different particle sizes: chromatographic behavior for the quality analysis of HuanglianShangqing pill.

    PubMed

    Yang, Dongzhi; Li, Ying; Yang, Fangxiu; Du, Yan; Li, Yinjie; Zheng, Xiaoxiao; Tang, Daoquan

    2015-02-01

    The chromatographic separation of traditional Chinese medicines is still a highly challenging task in analytical science with respect to its hundreds and thousands of chemical compounds, while increase of separation efficiency can greatly improve the separation power of chromatographic column for traditional Chinese medicine. In this study, 13 bioactive components in HuanglianShangqing pill were selected as an index to optimize the separation conditions and evaluate the system suitability of three commercially available columns packed with 1.8, 3.5, and 5.0 μm particles. The chromatographic separations were obtained by the most appropriate Eclipse Plus C18 column (100 × 2.1 mm, 3.5 μm) within 45 min using gradient elution with aqueous-ammonium acetate (10 mmol/L, pH 5.0) and acetonitrile, at a flow rate of 0.3 mL/min and an operating temperature of 30°C. The quality of HuanglianShangqing pill was assessed through combining simultaneous quantification of 13 compounds with fingerprint analysis. For the qualitative analysis, mass spectrometry was used to confirm the 13 compounds. All the validation data conformed to the acceptable requirements. For the fingerprint analysis, 32 peaks were selected as the common peaks at 254 nm to evaluate the similarities among HuanglianShangqing pills obtained from ten manufacturers.

  18. Adsorption Hysteresis and its Effect on CO2 Sequestration and Enhanced Coalbed Methane Recovery

    NASA Astrophysics Data System (ADS)

    Seto, C. J.; Tang, G. T.; Jessen, K.; Kovscek, A. R.; Orr, F. M.

    2006-12-01

    CO2 sequestration in coal reservoirs is a promising technology for reducing atmospheric CO2 concentrations. Of the candidates for geological sequestration, the physics of transport and sequestration in coal is the least well understood. Adsorption hysteresis has been observed for pure gas adsorption on some coals. It is manifest as desorption curves where the loading of gas on coal surfaces is greater than sorption at the same pressure. Current simulation technology does not have the functionality to incorporate this phenomenon that has a potentially great effect on sequestration in coalbeds. Understanding the interplay between adsorption and desorption of gas species, phase behaviour and convection is paramount to designing safe and effective sequestration projects. Our work integrates experiments and theory development. Isotherms of CH4, N2 and CO2 were measured on a sample of coal from the Powder River Basin, WY, for adsorption and desorption paths. Hysteresis was observed for all gases. Likewise, the displacment of methane by various mixtures of N2 and CO2 was also measured. Simultaneously, a model was developed to solve for the dispersion-free limit of convective transport in multiphase systems with adsorption, including the effects of volume change as components transfer from vapour to liquid and solid phases. Analytical solutions were obtained using the method of characteristics. These solutions were compared against corresponding solutions without adsorption hysteresis. For pure gas injection, in which the amount of adsorbed injected gas increases monotonically and the amount of adsorbed initial gas decreases monotonically, hysteresis effects were not observed. For injection gas mixtures of N2-CO2 displacing CH4, CO2 and N2 separated chromatographically and hysteresis effected breakthrough and bank arrival times as well as shifted overall component concentrations as the displacement progressed. When injection gas mixtures were rich in N2, the structures

  19. Development of facile property calculation model for adsorption chillers based on equilibrium adsorption cycle

    NASA Astrophysics Data System (ADS)

    Yano, Masato; Hirose, Kenji; Yoshikawa, Minoru; Thermal management technology Team

    Facile property calculation model for adsorption chillers was developed based on equilibrium adsorption cycles. Adsorption chillers are one of promising systems that can use heat energy efficiently because adsorption chillers can generate cooling energy using relatively low temperature heat energy. Properties of adsorption chillers are determined by heat source temperatures, adsorption/desorption properties of adsorbent, and kinetics such as heat transfer rate and adsorption/desorption rate etc. In our model, dependence of adsorption chiller properties on heat source temperatures was represented using approximated equilibrium adsorption cycles instead of solving conventional time-dependent differential equations for temperature changes. In addition to equilibrium cycle calculations, we calculated time constants for temperature changes as functions of heat source temperatures, which represent differences between equilibrium cycles and real cycles that stemmed from kinetic adsorption processes. We found that the present approximated equilibrium model could calculate properties of adsorption chillers (driving energies, cooling energies, and COP etc.) under various driving conditions quickly and accurately within average errors of 6% compared to experimental data.

  20. Adsorption of xenon and krypton on shales

    NASA Technical Reports Server (NTRS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    1981-01-01

    A method that uses a mass spectrometer as a manometer is employed in the measurement of Xe and Kr adsorption parameters on shales and related samples, where gas partial pressures were lower than 10 to the -11th atm, corresponding adsorption coverages are only small fractions of a monolayer, and Henry's Law behavior is expected and observed. Results show heats of adsorption in the 2-7 kcal/mol range, and Henry constants at 0-25 C of 1 cu cm STP/g per atmosphere are extrapolated. Although the adsorption properties obtained are variable by sample, the range obtained suggests that shales may be capable of an equilibrium adsorption with modern air high enough to account for a significant fraction of the atmospheric inventory of Xe, and perhaps even of Kr. This effect will nevertheless not account for the factor-of-25 defficiency of atmospheric Xe, in comparison with the planetary gas patterns observed in meteorites.

  1. Adsorption kinetics of methyl violet onto perlite.

    PubMed

    Doğan, Mehmet; Alkan, Mahir

    2003-01-01

    This study examines adsorption kinetics and activation parameters of methyl violet on perlite. The effect of process parameters like contact time, concentration of dye, temperature and pH on the extent of methyl violet adsorption from solution has been investigated. Results of the kinetic studies show that the adsorption reaction is first order with respect to dye solution concentration with activation energy of 13.2 kJ mol(-1). This low activation energy value indicates that the adsorption reaction is diffusion controlled. The activation parameters using Arrhenius and Eyring equations have been calculated. Adsorption increases with increase of variables such as contact time, initial dye concentration, temperature and pH.

  2. Chromatographic background drift correction coupled with parallel factor analysis to resolve coelution problems in three-dimensional chromatographic data: quantification of eleven antibiotics in tap water samples by high-performance liquid chromatography coupled with a diode array detector.

    PubMed

    Yu, Yong-Jie; Wu, Hai-Long; Fu, Hai-Yan; Zhao, Juan; Li, Yuan-Na; Li, Shu-Fang; Kang, Chao; Yu, Ru-Qin

    2013-08-01

    Chromatographic background drift correction has been an important field of research in chromatographic analysis. In the present work, orthogonal spectral space projection for background drift correction of three-dimensional chromatographic data was described in detail and combined with parallel factor analysis (PARAFAC) to resolve overlapped chromatographic peaks and obtain the second-order advantage. This strategy was verified by simulated chromatographic data and afforded significant improvement in quantitative results. Finally, this strategy was successfully utilized to quantify eleven antibiotics in tap water samples. Compared with the traditional methodology of introducing excessive factors for the PARAFAC model to eliminate the effect of background drift, clear improvement in the quantitative performance of PARAFAC was observed after background drift correction by orthogonal spectral space projection.

  3. Isolation of high-purity anthocyanin mixtures and monomers from blueberries using combined chromatographic techniques.

    PubMed

    Wang, Erlei; Yin, Yongguang; Xu, Caina; Liu, Jingbo

    2014-01-31

    Research on the isolation and preparation of anthocyanins has intensified in recent years because of the requirements of quantitative and bioactive analyses. However, simple and effective methods for the scale purification of pure anthocyanins from natural products are rarely reported. In this study, high-purity anthocyanin mixtures and monomers were successfully isolated from wild blueberries using a combination of column chromatography and semi-preparative HPLC. We established an effective elution system to separate high-purity anthocyanin mixtures with aqueous ethanol containing 0.01% HCl first in an Amberlite XAD-7HP column (ethanol/H2O=35:65) and then in a Sephadex LH-20 column (ethanol/H2O=25:75). Crude anthocyanin extracts were isolated using the Amberlite column, and a purity of 32% was obtained based on UV-vis analysis. Three fractions of anthocyanin mixtures were isolated from the crude extracts using the Sephadex column with purities ranging from 59% to 68%. Three pure monomeric anthocyanins of malvidin-3-O-glucoside, petunidin-3-O-glucoside, and delphinidin-3-O-glucoside were also isolated by semi-preparative HPLC and identified by HPLC-DAD-ESI-MS/MS. The purities of these anthocyanins were determined by analytical HPLC and estimated to be 97.7%, 99.3%, and 95.4%, respectively. The results of this study may help promote the purification of anthocyanins from most blueberry varieties as well as from other plant materials.

  4. ENVIRONMENTAL TECHNOLOGY VERIFICATION REPORT, EXPLOSIVES DETECTION TECHNOLOGY, SRI INSTRUMENTS, MODEL 8610C, GAS CHROMATOGRAPH/THERMIONIC IONIZATION DETECTION

    EPA Science Inventory

    The SRI Model 86 1 OC gas chromatograph (GC) is a transportable instrument that can provide on-site analysis of soils for explosives. Coupling this transportable gas chromatograph with a thermionic ionization detector (TID) allows for the determination of explosives in soil matri...

  5. Characterization of Gas Chromatographic Liquid Phases Using McReynolds Constants. An Experiment for Instrumental Analysis Laboratory.

    ERIC Educational Resources Information Center

    Erskine, Steven R.; And Others

    1986-01-01

    Describes a laboratory experiment that is designed to aid in the understanding of the fundamental process involved in gas chromatographic separations. Introduces the Kovats retention index system for use by chemistry students to establish criteria for the optimal selection of gas chromatographic stationary phases. (TW)

  6. Temperature Swing Adsorption Compressor Development

    NASA Technical Reports Server (NTRS)

    Finn, John E.; Mulloth, Lila M.; Affleck, Dave L.

    2001-01-01

    Closing the oxygen loop in an air revitalization system based on four-bed molecular sieve and Sabatier reactor technology requires a vacuum pump-compressor that can take the low-pressure CO, from the 4BMS and compress and store for use by a Sabatier reactor. NASA Ames Research Center proposed a solid-state temperature-swing adsorption (TSA) compressor that appears to meet performance requirements, be quiet and reliable, and consume less power than a comparable mechanical compressor/accumulator combination. Under this task, TSA compressor technology is being advanced through development of a complete prototype system. A liquid-cooled TSA compressor has been partially tested, and the rest of the system is being fabricated. An air-cooled TSA compressor is also being designed.

  7. Using Aspen to Teach Chromatographic Bioprocessing: A Case Study in Weak Partitioning Chromatography for Biotechnology Applications

    ERIC Educational Resources Information Center

    Evans, Steven T.; Huang, Xinqun; Cramer, Steven M.

    2010-01-01

    The commercial simulator Aspen Chromatography was employed to study and optimize an important new industrial separation process, weak partitioning chromatography. This case study on antibody purification was implemented in a chromatographic separations course. Parametric simulations were performed to investigate the effect of operating parameters…

  8. [Use of electrodialysis in the technology of desalinization of chromatographic eluates of proteins].

    PubMed

    Vasil'ev, V N; Omel'chenko, Iu N; Gusarova, E N; Iarotskiĭ, S V

    1994-05-01

    In a model of recombinant protein as an intermediate in production of rRNA-origin insulin, electrodialysis was shown to be useful in demineralization of protein chromatographic eluates. The operation conditions were developed. It was demonstrated that the electrodialysis provided higher purity of the recombinant protein.

  9. An HPLC chromatographic reactor approach for investigating the hydrolytic stability of a pharmaceutical compound.

    PubMed

    Skrdla, Peter J; Abrahim, Ahmed; Wu, Yan

    2006-06-01

    The solution-phase hydrolysis kinetics of the Aprepitant (Emend) prodrug, Fosaprepitant Dimeglumine, were investigated using an HPLC chromatographic reactor approach. The term 'chromatographic reactor' refers to the use of an analytical-scale column as both a flow-through reactor and, simultaneously, as separation medium for the reactant(s) and product(s). Recently, we reported a novel mathematical treatment for the kinetic data obtained from chromatographic reactors, which we believe is superior to other treatments in terms of its accuracy, robustness and ease of implementation. In this work, we demonstrate that our treatment may be applied equally well to HPLC reactors, as previously we studied only GC reactors. It is found that the hydrolysis of Fosaprepitant Dimeglumine (FD) has an apparent activation energy of 107 kJ/mol when the reaction is investigated on-column, using the gradient elution conditions of the validated HPLC impurity profile method for this compound. For comparison, the activation energy determined for the same reaction occurring in a quiescent solution consisting of a fixed ratio of acetonitrile-0.1% v/v aqueous H3PO4 (50:50, v/v) is 91 kJ/mol, calculated using direct application of the Arrhenius equation. The data presented show that, when used as a screening tool, chromatographic reactors may be feasible for use in the pharmaceutical industry to quickly gauge the relative stabilities of various compounds with similar degradation pathways. PMID:16524680

  10. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  11. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  12. 40 CFR 1065.267 - Gas chromatograph with a flame ionization detector.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Gas chromatograph with a flame ionization detector. 1065.267 Section 1065.267 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Measurement Instruments Hydrocarbon...

  13. Thin-Layer Chromatographic Separation of Phenols: An Undergraduate Laboratory Experiment.

    ERIC Educational Resources Information Center

    Kurth, Mark J.

    1986-01-01

    Background information, procedures used, and equipment needed are provided for an experiment in which a series of readily available, inexpensive, and relatively nontoxic phenols are separated using thin-layer chromatographic techniques. The experiment permits a discussion of how relative Rf values may be rationalized by considering a molecule's…

  14. High Performance Liquid Chromatographic Analysis of Phytoplankton Pigments Using a C16-Amide Column

    EPA Science Inventory

    A reverse-phase high performance liquid chromatographic (RP-HPLC) method was developed to analyze in a single run, most polar and non-polar chlorophylls and carotenoids from marine phytoplankton. The method is based on a RP-C16-Amide column and a ternary gradient system consistin...

  15. [Resolution of overlapping chromatographic peaks by radial basis function neural network].

    PubMed

    Li, Y B; Huang, X Y; Sha, M; Meng, X S

    2001-03-01

    A new algorithm-resolution of overlapping chromatographic peaks by radial basis function neural network(RBFNN) is presented. A two-phase genetic algorithm(GA) which has robustness and random globe optimization is used to train RBFNN so that it has the ability on the resolution of overlapping chromatographic peaks. The two-phase genetic algorithm involves two procedures: training structure and optimizing parameter. The first procedure uses GA to train the architectures of RBFNN, the second procedure uses gradient descent to train the center(tR) and the width(sigma) of RBFNN. The alternate use of these two procedures makes the network having the ability to learn structure, therefore makes itself adaptable to resolution of the chromatographic peaks with unknown number of components. The method proposed here needs no artificial interference, not only has it robustness and globalism, but also the ability of accurate resolution to completely overlapped chromatographic peaks. The simulation experiments show that this method is more accurate than other methods. PMID:12541651

  16. High-performance liquid-chromatographic separation of subcomponents of antimycin-A

    USGS Publications Warehouse

    Abidi, S.L.

    1988-01-01

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

  17. Residual solvent testing: a review of gas-chromatographic and alternative techniques.

    PubMed

    B'Hymer, Clayton

    2003-03-01

    The purpose of this brief review is to describe and discuss some of the current analytic procedures including gas-chromatographic and alternative techniques for residual solvent testing. Residual solvents, or organic volatile impurities, are a potential toxic risk for pharmaceutic products and have been a concern of manufacturers for many years. Residual solvents have had official limits in the United States as set in USP XXV and by the FDA in 1997 and have been monitored by most pharmaceutical manufacturers extensively for more than two decades in both bulk and finished products. The chief method of analysis for residual solvents is gas chromatography, which is generally considered the preferred methodology. Sample introduction techniques include both static and dynamic headspace analysis, solid-phase microextraction, and direct injection of solution containing bulk drug substance or drug product into the gas chromatograph. Also, some alternative methodologies for residual solvent testing are discussed in this review. In conclusion, gas chromatograph-based procedures will continue to dominate residual solvent testing because of its specificity for identification of the solvent, but the use of alternative sample introduction techniques into a gas chromatograph will continue to expand in the near future.

  18. Estimation of the environmental properties of compounds from chromatographic measurements and the solvation parameter model.

    PubMed

    Poole, Colin F; Ariyasena, Thiloka C; Lenca, Nicole

    2013-11-22

    This article provides an overview of chromatographic methods as surrogate models for environmental processes and for the determination of descriptors for compounds of environmental interest. The solvation parameter model is the link to the identification of suitable chromatographic models for the estimation of environmental properties using a set of tools that allow screening of chromatographic databases for the selection of candidate systems. As an alternative approach, many transport and distribution properties of environmental interest can be described directly by the solvation parameter model. Environmental properties for compounds with known descriptors can then be predicted through these models. The central role chromatographic methods, together with liquid-liquid partition coefficients, occupy in the determination of the six descriptors used in the solvation parameter model is detailed. There is a current need to accelerate efforts to expand the coverage of environmental process models by incorporating more complex molecules of contemporary environmental interest. For many of these molecules descriptor values are unavailable and their determination should be prioritized.

  19. [Use of electrodialysis in the technology of desalinization of chromatographic eluates of proteins].

    PubMed

    Vasil'ev, V N; Omel'chenko, Iu N; Gusarova, E N; Iarotskiĭ, S V

    1994-05-01

    In a model of recombinant protein as an intermediate in production of rRNA-origin insulin, electrodialysis was shown to be useful in demineralization of protein chromatographic eluates. The operation conditions were developed. It was demonstrated that the electrodialysis provided higher purity of the recombinant protein. PMID:7857154

  20. Simple automatic strategy for background drift correction in chromatographic data analysis.

    PubMed

    Fu, Hai-Yan; Li, He-Dong; Yu, Yong-Jie; Wang, Bing; Lu, Peng; Cui, Hua-Peng; Liu, Ping-Ping; She, Yuan-Bin

    2016-06-01

    Chromatographic background drift correction, which influences peak detection and time shift alignment results, is a critical stage in chromatographic data analysis. In this study, an automatic background drift correction methodology was developed. Local minimum values in a chromatogram were initially detected and organized as a new baseline vector. Iterative optimization was then employed to recognize outliers, which belong to the chromatographic peaks, in this vector, and update the outliers in the baseline until convergence. The optimized baseline vector was finally expanded into the original chromatogram, and linear interpolation was employed to estimate background drift in the chromatogram. The principle underlying the proposed method was confirmed using a complex gas chromatographic dataset. Finally, the proposed approach was applied to eliminate background drift in liquid chromatography quadrupole time-of-flight samples used in the metabolic study of Escherichia coli samples. The proposed method was comparable with three classical techniques: morphological weighted penalized least squares, moving window minimum value strategy and background drift correction by orthogonal subspace projection. The proposed method allows almost automatic implementation of background drift correction, which is convenient for practical use.

  1. [Sample preparation methods for chromatographic analysis of organic components in atmospheric particulate matter].

    PubMed

    Hao, Liang; Wu, Dapeng; Guan, Yafeng

    2014-09-01

    The determination of organic composition in atmospheric particulate matter (PM) is of great importance in understanding how PM affects human health, environment, climate, and ecosystem. Organic components are also the scientific basis for emission source tracking, PM regulation and risk management. Therefore, the molecular characterization of the organic fraction of PM has become one of the priority research issues in the field of environmental analysis. Due to the extreme complexity of PM samples, chromatographic methods have been the chief selection. The common procedure for the analysis of organic components in PM includes several steps: sample collection on the fiber filters, sample preparation (transform the sample into a form suitable for chromatographic analysis), analysis by chromatographic methods. Among these steps, the sample preparation methods will largely determine the throughput and the data quality. Solvent extraction methods followed by sample pretreatment (e. g. pre-separation, derivatization, pre-concentration) have long been used for PM sample analysis, and thermal desorption methods have also mainly focused on the non-polar organic component analysis in PM. In this paper, the sample preparation methods prior to chromatographic analysis of organic components in PM are reviewed comprehensively, and the corresponding merits and limitations of each method are also briefly discussed.

  2. NEAR-CONTINUOUS MEASUREMENT OF HYDROGEN SULFIDE AND CARBONYL SULFIDE BY AN AUTOMATIC GAS CHROMATOGRAPH

    EPA Science Inventory

    An automatic gas chromatograph with a flame photometric detector that samples and analyzes hydrogen sulfide and carbonyl sulfide at 30-s intervals is described. Temperature programming was used to elute trace amounts of carbon disulfide present in each injection from a Supelpak-S...

  3. Modeling the adsorption of mixed gases based on pure gas adsorption properties

    NASA Astrophysics Data System (ADS)

    Tzabar, N.; Holland, H. J.; Vermeer, C. H.; ter Brake, H. J. M.

    2015-12-01

    Sorption-based Joule-Thomson (JT) cryocoolers usually operate with pure gases. A sorption-based compressor has many benefits; however, it is limited by the pressure ratios it can provide. Using a mixed-refrigerant (MR) instead of a pure refrigerant in JT cryocoolers allows working at much lower pressure ratios. Therefore, it is attractive using MRs in sorption- based cryocoolers in order to reduce one of its main limitations. The adsorption of mixed gases is usually investigated under steady-state conditions, mainly for storage and separation processes. However, the process in a sorption compressor goes through various temperatures, pressures and adsorption concentrations; therefore, it differs from the common mixed gases adsorption applications. In order to simulate the sorption process in a compressor a numerical analysis for mixed gases is developed, based on pure gas adsorption characteristics. The pure gas adsorption properties have been measured for four gases (nitrogen, methane, ethane, and propane) with Norit-RB2 activated carbon. A single adsorption model is desired to describe the adsorption of all four gases. This model is further developed to a mixed-gas adsorption model. In future work more adsorbents will be tested using these four gases and the adsorption model will be verified against experimental results of mixed-gas adsorption measurements.

  4. Arsenic Adsorption Equilibrium Concentration and Adsorption Rate of Activated Carbon Coated with Ferric-Aluminum Hydroxides

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Sugita, H.; Oguma, T.; Hara, J.; Takahashi, S.

    2015-12-01

    In some areas of developing countries, ground or well water contaminated with arsenic has been reluctantly used as drinking water. It is highly desirable that effective and inexpensive arsenic removal agents should be developed and provided to reduce the potential health risk. Previous studies demonstrated that activated carbon coated with ferric-aluminum hydroxides (Fe-Al-C) has high adsorptive potential for removal of arsenic. In this study, a series of experiments using Fe-Al-C were carried to discuss adsorption equilibrium time, adsorption equilibrium concentration and adsorption rate of arsenic for Fe-Al-C. Fe-Al-C used in this study was provided by Astec Co., Ltd. Powder reagent of disodium hydrogen arsenate heptahydrate was dissolved into ion-exchanged water. The solution was then further diluted with ion-exchanged water to be 1 and 10 mg/L as arsenic concentration. The pH of the solution was adjusted to be around 7 by adding HCl and/or NaOH. The solution was used as artificial arsenic contaminated water in two types of experiments (arsenic adsorption equilibrium and arsenic adsorption rate tests). The results of the arsenic equilibrium tests were showed that a time period of about 3 days to reach apparent adsorption equilibrium for arsenic. The apparent adsorption equilibrium concentration and adsorbed amount of arsenic on Fe-Al-C adsorbent could be estimated by application of various adsorption isotherms, but the distribution coefficient of arsenic between solid and liquid varies with experimental conditions such as initial concentration of arsenic and addition concentration of adsorbent. An adsorption rate equation that takes into account the reduction in the number of effective adsorption sites on the adsorbent caused by the arsenic adsorption reaction was derived based on the data obtained from the arsenic adsorption rate tests.

  5. Evaluation of selectivity in homologous multimodal chromatographic systems using in silico designed antibody fragment libraries.

    PubMed

    Karkov, Hanne Sophie; Woo, James; Krogh, Berit Olsen; Ahmadian, Haleh; Cramer, Steven M

    2015-12-24

    This study describes the in silico design, surface property analyses, production and chromatographic evaluations of a diverse set of antibody Fab fragment variants. Based on previous findings, we hypothesized that the complementarity-determining regions (CDRs) constitute important binding sites for multimodal chromatographic ligands. Given that antibodies are highly diversified molecules and in particular the CDRs, we set out to examine the generality of this result. For this purpose, four different Fab fragments with different CDRs and/or framework regions of the variable domains were identified and related variants were designed in silico. The four Fab variant libraries were subsequently generated by site-directed mutagenesis and produced by recombinant expression and affinity purification to enable examination of their chromatographic retention behavior. The effects of geometric re-arrangement of the functional moieties on the multimodal resin ligands were also investigated with respect to Fab variant retention profiles by comparing two commercially available multimodal cation-exchange ligands, Capto MMC and Nuvia cPrime, and two novel multimodal ligand prototypes. Interestingly, the chromatographic data demonstrated distinct selectivity trends between the four Fab variant libraries. For three of the Fab libraries, the CDR regions appeared as major binding sites for all multimodal ligands. In contrast, the fourth Fab library displayed a distinctly different chromatographic behavior, where Nuvia cPrime and related multimodal ligand prototypes provided markedly improved selectivity over Capto MMC. Clearly, the results illustrate that the discriminating power of multimodal ligands differs between different Fab fragments. The results are promising indications that multimodal chromatography using the appropriate multimodal ligands can be employed in downstream bioprocessing for challenging selective separation of product related variants. PMID:26654254

  6. Evaluation of selectivity in homologous multimodal chromatographic systems using in silico designed antibody fragment libraries.

    PubMed

    Karkov, Hanne Sophie; Woo, James; Krogh, Berit Olsen; Ahmadian, Haleh; Cramer, Steven M

    2015-12-24

    This study describes the in silico design, surface property analyses, production and chromatographic evaluations of a diverse set of antibody Fab fragment variants. Based on previous findings, we hypothesized that the complementarity-determining regions (CDRs) constitute important binding sites for multimodal chromatographic ligands. Given that antibodies are highly diversified molecules and in particular the CDRs, we set out to examine the generality of this result. For this purpose, four different Fab fragments with different CDRs and/or framework regions of the variable domains were identified and related variants were designed in silico. The four Fab variant libraries were subsequently generated by site-directed mutagenesis and produced by recombinant expression and affinity purification to enable examination of their chromatographic retention behavior. The effects of geometric re-arrangement of the functional moieties on the multimodal resin ligands were also investigated with respect to Fab variant retention profiles by comparing two commercially available multimodal cation-exchange ligands, Capto MMC and Nuvia cPrime, and two novel multimodal ligand prototypes. Interestingly, the chromatographic data demonstrated distinct selectivity trends between the four Fab variant libraries. For three of the Fab libraries, the CDR regions appeared as major binding sites for all multimodal ligands. In contrast, the fourth Fab library displayed a distinctly different chromatographic behavior, where Nuvia cPrime and related multimodal ligand prototypes provided markedly improved selectivity over Capto MMC. Clearly, the results illustrate that the discriminating power of multimodal ligands differs between different Fab fragments. The results are promising indications that multimodal chromatography using the appropriate multimodal ligands can be employed in downstream bioprocessing for challenging selective separation of product related variants.

  7. Adsorption of lead over graphite oxide.

    PubMed

    Olanipekun, Opeyemi; Oyefusi, Adebola; Neelgund, Gururaj M; Oki, Aderemi

    2014-01-24

    The adsorption efficiency and kinetics of removal of lead in presence of graphite oxide (GO) was determined using the Atomic Absorption Spectrophotometer (AAS). The GO was prepared by the chemical oxidation of graphite and characterized using FTIR, SEM, TGA and XRD. The adsorption efficiency of GO for the solution containing 50, 100 and 150 ppm of Pb(2+) was found to be 98%, 91% and 71% respectively. The adsorption ability of GO was found to be higher than graphite. Therefore, the oxidation of activated carbon in removal of heavy metals may be a viable option to reduce pollution in portable water.

  8. Random sequential adsorption of trimers and hexamers.

    PubMed

    Cieśla, Michał; Barbasz, Jakub

    2013-12-01

    Adsorption of trimers and hexamers built of identical spheres was studied numerically using the random sequential adsorption (RSA) algorithm. Particles were adsorbed on a two-dimensional, flat and homogeneous surface. Numerical simulations allowed us to determine the maximal random coverage ratio, RSA kinetics as well as the available surface function (ASF), which is crucial for determining the kinetics of the adsorption process obtained experimentally. Additionally, the density autocorrelation function was measured. All the results were compared with previous results obtained for spheres, dimers and tetramers.

  9. Thermodynamics of binary gas adsorption in nanopores.

    PubMed

    Dutta, Sujeet; Lefort, Ronan; Morineau, Denis; Mhanna, Ramona; Merdrignac-Conanec, Odile; Saint-Jalmes, Arnaud; Leclercq, Théo

    2016-09-21

    MCM-41 nanoporous silicas show a very high selectivity for monoalcohols over aprotic molecules during adsorption of a binary mixture in the gas phase. We present here an original use of gravimetric vapour sorption isotherms to characterize the role played by the alcohol hydrogen-bonding network in the adsorption process. Beyond simple selectivity, vapour sorption isotherms measured for various compositions help to completely unravel at the molecular level the step by step adsorption mechanism of the binary system in the nanoporous solid, from the first monolayers to the complete liquid condensation. PMID:27532892

  10. Adsorption in sparse networks. 2: Silica aerogels

    SciTech Connect

    Scherer, G.W.; Calas, S.; Sempere, R.

    1998-06-15

    The model developed in Part 1 is applied to nitrogen adsorption isotherms obtained for a series of silica aerogels whose densities are varied by partial sintering. The isotherms are adequately described by a cubic network model, with all of the pores falling in the mesopore range; the adsorption and desorption branches are fit by the same pore size distribution. For the least dense gels, a substantial portion of the pore volume is not detected by condensation. The model attributes this effect to the shape of the adsorbate/adsorptive interface, which can adopt zero curvature even in mesopores, because of the shape of the network.

  11. Adsorption affinity of anions on metal oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.

    2013-03-01

    The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO{4/3-}, CO{3/2-} > C2O{4/2-}, C(OH)(CH2)2(COO){3/3-}, (CHOH)2(COO){2/2-} > CrO{4/2-} ≫ SO{4/2-}.

  12. Albumin (BSA) Adsorption over Graphene in Aqueous Environment: Influence of Orientation, Adsorption Protocol, and Solvent Treatment.

    PubMed

    Vilhena, J G; Rubio-Pereda, Pamela; Vellosillo, Perceval; Serena, P A; Pérez, Rubén

    2016-02-23

    We report 150 ns explicit solvent MD simulations of the adsorption on graphene of albumin (BSA) in two orientations and using two different adsorption protocols, i.e., free and forced adsorption. Our results show that free adsorption occurs with little structural rearrangements. Even taking adsorption to an extreme, by forcing it with a 5 nN downward force applied during the initial 20 ns, we show that along a particular orientation BSA is able to preserve the structural properties of the majority of its binding sites. Furthermore, in all the cases considered in this work, the ibuprofen binding site has shown a strong resilience to structural changes. Finally, we compare these results with implicit solvent simulations and find that the latter predicts an extreme protein unfolding upon adsorption. The origin of this discrepancy is attributed to a poor description of the water entropic forces at interfaces in the implicit solvent methods.

  13. Albumin (BSA) Adsorption over Graphene in Aqueous Environment: Influence of Orientation, Adsorption Protocol, and Solvent Treatment.

    PubMed

    Vilhena, J G; Rubio-Pereda, Pamela; Vellosillo, Perceval; Serena, P A; Pérez, Rubén

    2016-02-23

    We report 150 ns explicit solvent MD simulations of the adsorption on graphene of albumin (BSA) in two orientations and using two different adsorption protocols, i.e., free and forced adsorption. Our results show that free adsorption occurs with little structural rearrangements. Even taking adsorption to an extreme, by forcing it with a 5 nN downward force applied during the initial 20 ns, we show that along a particular orientation BSA is able to preserve the structural properties of the majority of its binding sites. Furthermore, in all the cases considered in this work, the ibuprofen binding site has shown a strong resilience to structural changes. Finally, we compare these results with implicit solvent simulations and find that the latter predicts an extreme protein unfolding upon adsorption. The origin of this discrepancy is attributed to a poor description of the water entropic forces at interfaces in the implicit solvent methods. PMID:26799950

  14. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test

    SciTech Connect

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-15

    Highlights: • Equilibrium test was attempted to evaluate adsorption characteristics of siloxane. • L2 had higher removal efficiency in carbon compared to noncarbon adsorbents. • Total adsorption capacity of siloxane was 300 mg/g by coal activated carbon. • Adsorption characteristics rely on size of siloxane molecule and adsorbent pore. • Conversion of siloxane was caused by adsorption of noncarbon adsorbents. - Abstract: Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  15. Adsorption of Organic Compounds to Diesel Soot: Frontal Analysis and Polyparameter Linear Free-Energy Relationship.

    PubMed

    Lu, Zhijiang; MacFarlane, John K; Gschwend, Philip M

    2016-01-01

    Black carbons (BCs) dominate the sorption of many hydrophobic organic compounds (HOCs) in soils and sediments, thereby reducing the HOCs' mobilities and bioavailabilities. However, we do not have data for diverse HOCs' sorption to BC because it is time-consuming and labor-intensive to obtain isotherms on soot and other BCs. In this study, we developed a frontal analysis chromatographic method to investigate the adsorption of 21 organic compounds with diverse functional groups to NIST diesel soot. This method was precise and time-efficient, typically taking only a few hours to obtain an isotherm. Based on 102 soot-carbon normalized sorption coefficients (KsootC) acquired at different sorbate concentrations, a sorbate-activity-dependent polyparameter linear free-energy relationship was established: logKsootC = (3.74 ± 0.11)V + ((-0.35 ± 0.02)log ai)E + (-0.62 ± 0.10)A + (-3.35 ± 0.11)B + (-1.45 ± 0.09); (N = 102, R(2) = 0.96, SE = 0.18), where V, E, A, and B are the sorbate's McGowan's characteristic volume, excess molar refraction, and hydrogen acidity and basicity, respectively; and ai is the sorbate's aqueous activity reflecting the system's approach to saturation. The difference in dispersive interactions with the soot versus with the water was the dominant factor encouraging adsorption, and H-bonding interactions discouraged this process. Using this relationship, soot-water and sediment-water or soil-water adsorption coefficients of HOCs of interest (PAHs and PCBs) were estimated and compared with the results reported in the literature. PMID:26587648

  16. Adsorption Isotherms and Surface Reaction Kinetics

    ERIC Educational Resources Information Center

    Lobo, L. S.; Bernardo, C. A.

    1974-01-01

    Explains an error that occurs in calculating the conditions for a maximum value of a rate expression for a bimolecular reaction. The rate expression is derived using the Langmuir adsorption isotherm to relate gas pressures and corresponding surface coverages. (GS)

  17. Adsorption of nisin and pediocin on nanoclays.

    PubMed

    Meira, Stela Maris Meister; Jardim, Arthur Izé; Brandelli, Adriano

    2015-12-01

    Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) were studied as potential carriers for the antimicrobial peptides nisin and pediocin. Adsorption occurred from peptide solutions in contact with nanoclays at room temperature. Higher adsorption of nisin and pediocin was obtained on bentonite. The antimicrobial activity of the resultant bacteriocin-nanoclay systems was analyzed using skimmed milk agar as food simulant and the largest inhibition zones were observed against Gram-positive bacteria for halloysite samples. Bacteriocins were intercalated into the interlayer space of montmorillonites as deduced from the increase of the basal spacing measured by X-ray diffraction (XRD) assay. Infrared spectroscopy suggested non-electrostatic interactions, such as hydrogen bonding between siloxane groups from clays and peptide molecules. Transmission electron microscopy did not show any alteration in morphologies after adsorption of antimicrobial peptides on bentonite and halloysite. These results indicate that nanoclays, especially halloysite, are suitable nanocarriers for nisin and pediocin adsorption.

  18. Adsorption of nisin and pediocin on nanoclays.

    PubMed

    Meira, Stela Maris Meister; Jardim, Arthur Izé; Brandelli, Adriano

    2015-12-01

    Three different nanoclays (bentonite, octadecylamine-modified montmorillonite and halloysite) were studied as potential carriers for the antimicrobial peptides nisin and pediocin. Adsorption occurred from peptide solutions in contact with nanoclays at room temperature. Higher adsorption of nisin and pediocin was obtained on bentonite. The antimicrobial activity of the resultant bacteriocin-nanoclay systems was analyzed using skimmed milk agar as food simulant and the largest inhibition zones were observed against Gram-positive bacteria for halloysite samples. Bacteriocins were intercalated into the interlayer space of montmorillonites as deduced from the increase of the basal spacing measured by X-ray diffraction (XRD) assay. Infrared spectroscopy suggested non-electrostatic interactions, such as hydrogen bonding between siloxane groups from clays and peptide molecules. Transmission electron microscopy did not show any alteration in morphologies after adsorption of antimicrobial peptides on bentonite and halloysite. These results indicate that nanoclays, especially halloysite, are suitable nanocarriers for nisin and pediocin adsorption. PMID:26041178

  19. Argon adsorption and the lunar atmosphere

    NASA Technical Reports Server (NTRS)

    Bernatowicz, T. J.; Podosek, F. A.

    1991-01-01

    The results of Ar adsorption experiments on a terrestrial labradorite and lunar rock 15415 crushed in vacuo are reported. The experiments were designed to test lunar atmosphere simulation models for the behavior of Ar on the lunar surface, as determined from the Apollo 17 mass spectrometer results. These models (Hodges, 1980, 1982) used a single adsorption potential to characterize the surfaces of lunar soil grains, with the result that high (6-7 kcal/mol) heats of adsorption were inferred. The present experimental results show that very high adsorption potentials are indeed associated with fresh mineral surfaces, but that these energetic surfaces occupy only small fractions of the total surface area. Nonetheless, these small fractions of surface, if they can be maintained in the lunar regolith in steady-state condition, could be sufficient to account for the Apollo 17 mass spectrometer observations.

  20. H2O Adsorption Kinetics on Smectites

    NASA Technical Reports Server (NTRS)

    Zent, Aaron P.; Howard, J.; Quinn, R. C.

    2000-01-01

    The adsorptive equilibration of H2O with montomorillonite has been measured. At low temperatures and pressures equilibration can require many hours, effectively preventing smectites at the martian surface from responding to diurnal pressure and temperature variations.

  1. Fluorocarbon Adsorption in Hierarchical Porous Frameworks

    SciTech Connect

    Motkuri, Radha K.; Annapureddy, Harsha V.; Vijayakumar, M.; Schaef, Herbert T.; Martin, P F.; McGrail, B. Peter; Dang, Liem X.; Krishna, Rajamani; Thallapally, Praveen K.

    2014-07-09

    The adsorption behavior of a series of fluorocarbon derivatives was examined on a set of microporous metal organic framework (MOF) sorbents and another set of hierarchical mesoporous MOFs. The microporous M-DOBDC (M = Ni, Co) showed a saturation uptake capacity for R12 of over 4 mmol/g at a very low relative saturation pressure (P/Po) of 0.02. In contrast, the mesoporous MOF MIL-101 showed an exceptionally high uptake capacity reaching over 14 mmol/g at P/Po of 0.4. Adsorption affinity in terms of mass loading and isosteric heats of adsorption were found to generally correlate with the polarizability of the refrigerant with R12 > R22 > R13 > R14 > methane. These results suggest the possibility of exploiting MOFs for separation of azeotropic mixtures of fluorocarbons and use in eco-friendly fluorocarbon-based adsorption cooling and refrigeration applications.

  2. Krypton based adsorption type cryogenic refrigerator

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor); Schember, Helene R. (Inventor)

    1989-01-01

    Krypton and a monolithic porous carbon such as Saran carbon are used respectively as the sorbate and sorbent of an adsorption type refrigerator to improve refrigeration efficiency and operational longevity.

  3. Microcalorimetric study of adsorption and disassembling of virus-like particles on anion exchange chromatography media.

    PubMed

    Yu, Mengran; Zhang, Songping; Zhang, Yan; Yang, Yanli; Ma, Guanghui; Su, Zhiguo

    2015-04-01

    Chromatographic purification of virus-like particles (VLPs) is important to the development of modern vaccines. However, disassembly of the VLPs on the solid-liquid interface during chromatography process could be a serious problem. In this study, isothermal titration calorimetric (ITC) measurements, together with chromatography experiments, were performed on the adsorption and disassembling of multi-subunits hepatitis B virus surface antigen virus-like particles (HB-VLPs). Two gigaporous ion-exchange chromatography (IEC) media, DEAE-AP-280 nm and DEAE-POROS, were used. The application of gigaporous media with high ligand density led to significantly increased irreversible disassembling of HB-VLPs and consequently low antigen activity recovery during IEC process. To elucidate the thermodynamic mechanism of the effect of ligand density on the adsorption and conformational change of VLPs, a thermodynamic model was proposed. With this model, one can obtain the intrinsic molar enthalpy changes related to the binding of VLPs and the accompanying conformational change on the liquid-solid interface during its adsorption. This model assumes that, when intact HB-VLPs interact with the IEC media, the total adsorbed proteins contain two states, the intact formation and the disassembled formation; accordingly, the apparent adsorption enthalpy, ΔappH, which can be directly measured from ITC experiments, presents the sum of three terms: (1) the intrinsic molar enthalpy change associated to the binding of intact HB-VLPs (ΔbindHintact), (2) the intrinsic molar enthalpy change associated to the binding of HB-VLPs disassembled formation (ΔbindHdis), and (3) the enthalpy change accompanying the disassembling of HB-VLPs (ΔconfHdis). The intrinsic binding of intact HB-VLPs and the disassembled HB-VLPs to both kinds of gigaporous media (each of which has three different ligand densities), were all observed to be entropically driven as indicated by positive values of

  4. Microcalorimetric study of adsorption and disassembling of virus-like particles on anion exchange chromatography media.

    PubMed

    Yu, Mengran; Zhang, Songping; Zhang, Yan; Yang, Yanli; Ma, Guanghui; Su, Zhiguo

    2015-04-01

    Chromatographic purification of virus-like particles (VLPs) is important to the development of modern vaccines. However, disassembly of the VLPs on the solid-liquid interface during chromatography process could be a serious problem. In this study, isothermal titration calorimetric (ITC) measurements, together with chromatography experiments, were performed on the adsorption and disassembling of multi-subunits hepatitis B virus surface antigen virus-like particles (HB-VLPs). Two gigaporous ion-exchange chromatography (IEC) media, DEAE-AP-280 nm and DEAE-POROS, were used. The application of gigaporous media with high ligand density led to significantly increased irreversible disassembling of HB-VLPs and consequently low antigen activity recovery during IEC process. To elucidate the thermodynamic mechanism of the effect of ligand density on the adsorption and conformational change of VLPs, a thermodynamic model was proposed. With this model, one can obtain the intrinsic molar enthalpy changes related to the binding of VLPs and the accompanying conformational change on the liquid-solid interface during its adsorption. This model assumes that, when intact HB-VLPs interact with the IEC media, the total adsorbed proteins contain two states, the intact formation and the disassembled formation; accordingly, the apparent adsorption enthalpy, ΔappH, which can be directly measured from ITC experiments, presents the sum of three terms: (1) the intrinsic molar enthalpy change associated to the binding of intact HB-VLPs (ΔbindHintact), (2) the intrinsic molar enthalpy change associated to the binding of HB-VLPs disassembled formation (ΔbindHdis), and (3) the enthalpy change accompanying the disassembling of HB-VLPs (ΔconfHdis). The intrinsic binding of intact HB-VLPs and the disassembled HB-VLPs to both kinds of gigaporous media (each of which has three different ligand densities), were all observed to be entropically driven as indicated by positive values of

  5. Evaluation of the potassium adsorption capacity of a potassium adsorption filter during rapid blood transfusion.

    PubMed

    Matsuura, H; Akatsuka, Y; Muramatsu, C; Isogai, S; Sugiura, Y; Arakawa, S; Murayama, M; Kurahashi, M; Takasuga, H; Oshige, T; Yuba, T; Mizuta, S; Emi, N

    2015-05-01

    The concentration of extracellular potassium in red blood cell concentrates (RCCs) increases during storage, leading to risk of hyperkalemia. A potassium adsorption filter (PAF) can eliminate the potassium at normal blood transfusion. This study aimed to investigate the potassium adsorption capacity of a PAF during rapid blood transfusion. We tested several different potassium concentrations under a rapid transfusion condition using a pressure bag. The adsorption rates of the 70-mEq/l model were 76·8%. The PAF showed good potassium adsorption capacity, suggesting that this filter may provide a convenient method to prevent hyperkalemia during rapid blood transfusion.

  6. Gas chromatographic determination of polycyclic aromatic hydrocarbons in water and smoked rice samples after solid-phase microextraction using multiwalled carbon nanotube loaded hollow fiber.

    PubMed

    Matin, Amir Abbas; Biparva, Pourya; Gheshlaghi, Mohammad

    2014-12-29

    A novel solid-phase microextraction fiber was prepared based on multiwalled carbon nanotubes (MWCNTs) loaded on hollow fiber membrane pores. Stainless steel wire was used as unbreakable support. The major advantages of the proposed fiber are its (a) high reproducibility due to the uniform structure of the hollow fiber membranes, (b) high extraction capacity related to the porous structure of the hollow fiber and outstanding adsorptive characteristics of MWCNTs. The proposed fiber was applied for the microextraction of five representative polycyclic aromatic hydrocarbons (PAHs) from aqueous media (river and hubble-bubble water) and smoked rice samples followed by gas chromatographic determination. Analytical merits of the method, including high correlation coefficients [(0.9963-0.9992) and (0.9982-0.9999)] and low detection limits [(9.0-13.0ngL(-1)) and (40.0-150.0ngkg(-1))] for water and rice samples, respectively, made the proposed method suitable for the ultra-trace determination of PAHs. PMID:25476686

  7. Characterization and optimization of a chromatographic process based on ethylenediamine-N,N,N',N'-tetra(methylphosphonic) acid-modified zirconia particles.

    PubMed

    Sarkar, Sabyasachi; Carr, Peter W; McNeff, Clayton V; Subramanian, Anu

    2003-06-25

    The primary objective of work was to characterize, optimize and model a chromatographic process based on ethylenediamine-N,N,N',N'-tetra(methylphosphonic) acid (EDTPA)-modified zirconia particles. Zirconia particles were produced by spray-drying colloidal zirconia. Zirconia spheres produced were further classified, calcined and modified with EDTPA to yield a solid-phase support for use in bio-chromatography (r_PEZ). Specifically, the ability of r_PEZ to selectively bind and enrich IgG, IgA, and IgM from biological fluids was evaluated and demonstrated. To better understand the force of interaction between the IgG and the r_PEZ, the equilibrium disassociation constant (K(d)) was determined by static binding isotherms, as a function of temperature and by frontal analysis at different linear velocities. The maximum static binding capacity (Q(max)) was found to be in the range 55-65 mg IgG per ml of beads, and unaffected by temperature. The maximum dynamic binding capacity (Q(x)) was found to be in the range 20-12 mg IgG per ml of beads. The adsorption rate constant (k(a)) was determined by a split-peak approach to be between 982 and 3242 l mol(-1) s(-1) depending on the linear velocity. The standard enthalpy and entropy values were estimated for this interaction of IgG with this novel support. PMID:12767327

  8. Protein Adsorption on Surfaces with Grafted Polymers

    PubMed Central

    Szleifer, I.

    1997-01-01

    A general theoretical framework for studying the adsorption of protein molecules on surfaces with grafted polymers is presented. The approach is a generalization of the single-chain mean-field theory, in which the grafted polymer-protein-solvent layer is assumed to be inhomogeneous in the direction perpendicular to the grafting surface. The theory enables the calculation of the adsorption isotherms of the protein as a function of the surface coverage of grafted polymers, concentration of protein in bulk, and type of solvent molecules. The potentials of mean force of the protein with the surface are calculated as a function of polymer surface coverage and amount of protein adsorbed. The theory is applied to model lysozyme on surfaces with grafted polyethylene oxide. The protein is modeled as spherical in solution, and it is assumed that the protein-polymer, protein-solvent, and polymer-solvent attractive interactions are all equal. Therefore, the interactions determining the structure of the layer (beyond the bare polymer-surface and protein-surface interactions) are purely repulsive. The bare surface-protein interaction is taken from atomistic calculations by Lee and Park. For surfaces that do not have preferential attractions with the grafted polymer segments, the adsorption isotherms of lysozyme are independent of the polymer length for chains with more than 50 ethylene oxide units. However, the potentials of mean force show strong variations with grafted polymer molecular weight. The competition between different conformations of the adsorbed protein is studied in detail. The adsorption isotherms change qualitatively for surfaces with attractive interactions with ethylene oxide monomers. The protein adsorption is a function of chain length—the longer the polymer the more effective it is in preventing protein adsorption. The structure of the layer and its deformation upon protein adsorption are very important in determining the adsorption isotherms and the

  9. Gas adsorption capacity of wood pellets

    DOE PAGES

    Yazdanpanah, F.; Sokhansanj, Shahabaddine; Lim, C. Jim; Lau, A.; Bi, X. T.

    2016-02-03

    In this paper, temperature-programmed desorption (TPD) analysis was used to measure and analyze the adsorption of off-gases and oxygen by wood pellets during storage. Such information on how these gases interact with the material helps in the understanding of the purging/stripping behavior of off-gases to develop effective ventilation strategies for wood pellets. Steam-exploded pellets showed the lowest carbon dioxide (CO2) uptake compared to the regular and torrefied pellets. The high CO2 adsorption capacity of the torrefied pellets could be attributed to their porous structure and therefore greater available surface area. Quantifying the uptake of carbon monoxide by pellets was challengingmore » due to chemical adsorption, which formed a strong bond between the material and carbon monoxide. The estimated energy of desorption for CO (97.8 kJ/mol) was very high relative to that for CO2 (7.24 kJ/mol), demonstrating the mechanism of chemical adsorption and physical adsorption for CO and CO2, respectively. As for oxygen, the strong bonds that formed between the material and oxygen verified the existence of chemical adsorption and formation of an intermediate material.« less

  10. Defluoridation of drinking water using adsorption processes.

    PubMed

    Loganathan, Paripurnanda; Vigneswaran, Saravanamuthu; Kandasamy, Jaya; Naidu, Ravi

    2013-03-15

    Excessive intake of fluoride (F), mainly through drinking water, is a serious health hazard affecting humans worldwide. There are several methods used for the defluoridation of drinking water, of which adsorption processes are generally considered attractive because of their effectiveness, convenience, ease of operation, simplicity of design, and for economic and environmental reasons. In this paper, we present a comprehensive and a critical literature review on various adsorbents used for defluoridation, their relative effectiveness, mechanisms and thermodynamics of adsorption, and suggestions are made on choice of adsorbents for various circumstances. Effects of pH, temperature, kinetics and co-existing anions on F adsorption are also reviewed. Because the adsorption is very weak in extremely low or high pHs, depending on the adsorbent, acids or alkalis are used to desorb F and regenerate the adsorbents. However, adsorption capacity generally decreases with repeated use of the regenerated adsorbent. Future research needs to explore highly efficient, low cost adsorbents that can be easily regenerated for reuse over several cycles of operations without significant loss of adsorptive capacity and which have good hydraulic conductivity to prevent filter clogging during the fixed-bed treatment process.

  11. Adsorption of ferrous ions onto montmorillonites

    NASA Astrophysics Data System (ADS)

    Qin, Dawei; Niu, Xia; Qiao, Min; Liu, Gang; Li, Hongxin; Meng, Zhenxiao

    2015-04-01

    The adsorption of Fe (II) onto montmorillonites was investigated through initial concentration, contact time, pH and temperature. During the whole adsorption process, the ascorbic acid (Vitamin C) was added as a kind of antioxidant, at the same time, deionized water (after boiling) and nitrogen protection were also used to avoid oxidation. The Fe2+/Fetotal ratio of the iron exists in the Fe-montmorillonites was found more than 95%. Two kinetic models, including pseudo-first-order and pseudo-second-order model, were used to analyze the adsorption process of Fe (II) on montmorillonites. The results of our study showed that adsorption process fitted with pseudo-second-order well. Adsorption isotherms showed that Langmuir model was better than Freundlich model. The thermodynamic parameters ΔG0 and ΔH0 were 3.696 kJ/mol and 6.689 kJ/mol (we just gave the values at 298 K), respectively. The positive values at different temperatures showed that the adsorption process was non-spontaneous and endothermic. The characteristics of materials were determined by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Surface area and porosity analyzer, Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC) and Zeta potential distribution.

  12. ADSORPTION METHOD FOR SEPARATING METAL CATIONS

    DOEpatents

    Khym, J.X.

    1959-03-10

    The chromatographic separation of fission product cations is discussed. By use of this method a mixture of metal cations containing Zr, Cb, Ce, Y, Ba, and Sr may be separated from one another. Mentioned as preferred exchange adsorbents are resins containing free sulfonic acid groups. Various eluants, such as tartaric acid, HCl, and citric acid, used at various acidities, are employed to effect the selective elution and separation of the various fission product cations.

  13. The special features of protein adsorption isotherms on silica adsorbents

    NASA Astrophysics Data System (ADS)

    Chukhrai, E. S.; Atyaksheva, L. F.; Pilipenko, O. S.

    2011-05-01

    The adsorption isotherms of hemoglobin, peroxidase, and β-galactosidase on silochrome and mesoporous and biporous silicas were comparatively studied. Adsorption developed in two stages, including fast "reversible" protein adsorption (equilibrium was reached in t ≤ 1-2 h) and a "slow stage" of irreversible binding in t ≫ 24 h (multipoint adsorption). The corresponding equilibrium constants were determined. The mechanism of unlimited linear association of peroxidase in the adsorption layer on the surface of silochrome was established.

  14. A chromatographic estimate of the degree of heterogeneity of RPLC packing materials. 1. Non-endcapped polymeric C30-bonded stationary phase

    SciTech Connect

    Gritti, Fabrice; Guiochon, Georges A

    2006-01-01

    A new chromatographic method estimating the degree of heterogeneity of RPLC packing materials is based on the results of systematic measurements of the adsorption data in a wide concentration range for selected probe compounds. These data are acquired by frontal analysis (FA), modeled, and used for the calculation of the adsorption energy distribution (AED). Four compounds were used, two neutral compounds of different molecular sizes (caffeine and phenol) and two ionizable compounds of opposite charges, 2-naphthalene sulfonate, an anion, and propranololium, a cation. This work was done on a C{sub 30}-bonded silica stationary phase (Prontosil-C{sub 30}), using the same aqueous mobile phase (30% methanol, v/v) for all compounds, except that sodium chloride (25 mM) was added to elute the ionizable compounds. All four adsorption isotherms have Langmuirian behavior. The AEDs are tri-modal for phenol, quadri-modal for caffeine. The total saturation capacity of the stationary phase is four-fold lower for caffeine than for phenol, due in part to its larger molecular size. The equilibrium constants on the low-energy sites of types 1 and 2 are eight-fold larger. These two types of sites characterize the heterogeneity of the bonded layer itself. The density of the high-energy sites of types 3 and 4 is higher for caffeine, suggesting that caffeine molecules can be accommodated in some hydrophobic cages into which smaller molecules like phenol cannot. These high-energy types of sites characterize the heterogeneity of the whole stationary phase (silica support included). The ionizable compounds have larger molecules than the neutral ones and, accordingly, a lower relative density of sites of type 2 to sites of type 1. A tri-modal and a quadri-modal energy distributions were observed for the 2-naphthalene sulfonate anion and the propranololium cation, respectively. The fourth types of sites measured and its unusually high equilibrium constant are most probably due to ion

  15. Adsorption of aqueous copper on peanut hulls

    NASA Astrophysics Data System (ADS)

    Davis, Kanika Octavia

    A method was established for measuring the adsorption of Cu(II) from aqueous solution to unmodified and modified peanut hulls at constant temperature and pH. Modification of the hulls was performed by oxidation with alkaline hydrogen peroxide. During the modification process, the hydrogen peroxide solubilizes the lignin component, making the surface more porous which increases the availability of binding sites, while simultaneously oxidizing the cellulose. The oxidation of alcohol groups creates more binding sites by creating functional groups such as COO-, which increases chelation to metal ions. Fourier transform infrared spectroscopy confirms delignification of the peanut hulls by the disappearance of carboxyl peaks of the modified hulls, which were originally produced from the lignin content. Although, oxidation is not fully confirmed, it is not ruled out because the expected carboxylate peak (1680 cm-1) maybe overshadowed by a broad peak due to OH bending of water adsorbed to the hulls. Hulls adsorbed copper from solutions in the concentration range of 50-1000 ppm of CuCl2. Concentrations of pre- and post-adsorption solutions were determined using inductively coupled plasma optical emission spectroscopy. The adsorption isotherms were fit to known two and three-parameter models, evaluated and the binding mechanism was inferred. Maximum surface coverage was 3.5 +/- 0.6 mg Cu2+ /g hull for unmodified hulls and 11 +/- 1 mg Cu2+/g hull for modified hulls. The adsorption for the hulls is best described by the Langmuir model, suggesting monolayer, homogeneous adsorption. With a free energy of adsorption of 10.5 +/- 0.9 kJ/mol for unmodified hulls and 14.5 +/-0.4 kJ/mol for modified hulls, the process is categorized as chemisorption for both types of hulls. The adsorption for both hulls is also described by the Redlich-Peterson model, giving beta nearer to 1 than 0, which further suggests homogeneous adsorption described by the Langmuir model. After rinsing the hulls

  16. Assessing the Adsorption Properties of Shales

    NASA Astrophysics Data System (ADS)

    Pini, R.

    2014-12-01

    Fine-grained rocks, such as shales, contain a significant amount of nanopores that can significantly contribute to their storage capacity through the mechanism of adsorption. The current ability to extract natural gas that is adsorbed in the rock's matrix is limited and current technology focuses primarily on the free gas in the fractures, thus leading to very low recovery efficiencies. Shales constitute also a great portion of so-called caprocks above potential CO2 sequestration sites; hereby, the adsorption process may limit the CO2 mobility within the cap-rock, thus minimizing leakage phenomena. Whether it is a reservoir or a caprock, understanding and quantifying the mechanisms of adsorption in these natural materials is key to improve the engineering design of subsurface operations. Results will be presented from a laboratory study that combines conventional techniques for the measurement of adsorption isotherms with novel methods that allows for the imaging of adsorption using x-rays. Various nanoporous materials are considered, thus including rocks, such as shales and coals, pure clay minerals and engineered adsorbents with well-defined nanopore structures, such as zeolites. Supercritical CO2 adsorption isotherms have been measured with a Rubotherm Magnetic Suspension balance by covering the pressure range 0.1-20~MPa. A medical x-ray CT scanner has been used to identify three-dimensional patterns of the adsorption properties of a packed-bed of adsorbent, thus enabling to assess the spatial variability of the adsorption isotherm. The data are analyzed by using thermodynamically rigorous measures of adsorption and a graphical method is applied for their interpretation. The density of the adsorbed phase is estimated and compared to data reported in the literature; the latter is key to disclose gas-reserves and/or potential storage capacity estimates. When evaluated against classic adsorbent materials, the adsorption mechanism in shales is further complicated by

  17. Measuring and modeling the competitive adsorption of CO{sub 2}, CH{sub 4}, and N{sub 2} on a dry coal

    SciTech Connect

    Ottiger, S.; Pini, R.; Storti, G.; Mazzotti, M.

    2008-09-15

    Data on the adsorption behavior of CO{sub 2}, CH{sub 4}, and N{sub 2} on coal are needed to develop enhanced coalbed methane (ECBM) recovery processes, a technology where the recovery of CH{sub 4} is enhanced by injection of a gas stream consisting of either pure CO{sub 2}, pure N{sub 2}, or a mixture of both. The pure, binary, and ternary adsorption of these gases on a dry coal from the Sulcis Coal Province in Italy has been measured at pressures up to 180 bar and temperatures of 45 and 70{sup o}C for the pure gases and of 45{sup o}C for the mixtures. The experiments were performed in a system consisting of a magnetic suspension balance using a gravimetric-chromatographic technique. The excess adsorption isotherms are successfully described using a lattice density functional theory model based on the Ono-Kondo equations exploiting information about the structure of the coal, the adsorbed gases, and the interaction between them. The results clearly show preferential adsorption of CO{sub 2} over CH{sub 4} and N{sub 2}, which therefore indicate that ECBM may be a viable option for the permanent storage of CO{sub 2}.

  18. Liquid chromatographic determination of beta-cyclodextrin derivatives based on fluorescence enhancement after inclusion complexation.

    PubMed

    Reeuwijk, H J; Irth, H; Tjaden, U R; Merkus, F W; van der Greef, J

    1993-04-21

    A liquid chromatographic method using fluorescence detection for the determination of beta-cyclodextrin (beta CD) and its derivatives is presented. The chromatographic system is based on size-exclusion chromatography with the addition of the fluorophoric compound 1-naphthol to the mobile phase. Detection is based on fluorescence enhancement caused by the formation of inclusion complexes. By incorporating 10(-4) M 1-naphthol in the mobile phase, detection limits of 90, 27, 370 and 37 pmol were obtained for beta CD, hydroxypropyl-beta CD, trimethyl-beta CD and dimethyl-beta CD, respectively. The method was applied to the determination of dimethyl-beta CD in urine: the minimum detectable concentration was 0.2 microgram/ml after preconcentration of 10 ml of urine.

  19. Optimization of an improved single-column chromatographic process for the separation of enantiomers.

    PubMed

    Kazi, Monzure-Khoda; Medi, Bijan; Amanullah, Mohammad

    2012-03-30

    This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process. PMID:22364669

  20. Liquid chromatographic determination of benzo(a)pyrene in total particulate matter of cigarette smoke

    SciTech Connect

    Tomkins, B.A.; Jenkins, R.A.; Griest, W.H.; Reagan, R.R.; Holladay, S.K.

    1985-09-01

    The benzo(a)pyrene (BaP) delivery of reference and commercially available tobacco cigarettes, as well as reference and placebo marijuana cigarettes, is determined using a sequential liquid chromatographic/liquid chromatographic procedure. The total particulate matter of sample cigarette smoke is collected using a Cambridge filter pad, which is ultrasonically extracted with acetone. The resulting extract is filtered, then fractionated using semipreparative-scale normal phase liquid chromatography (LC). Quantitative determination is achieved using analytical-scale reverse phase LC equipped with a fluorescence detector. The method is precise (+/- 10-15% relative standard deviation) and yields 85% or better BaP recovery at the ng/cig. level. A single pad may be analyzed in 8 person-hours, while a more typical lot of 12 pads (6 pads each for 2 cigarette brands) may be analyzed in 10 person-days.

  1. Development of gas chromatographic system for dissolved organic carbon analysis in seawater. Annual progress report

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO{sub 2}.

  2. Development of gas chromatographic system for dissolved organic carbon analysis in seawater

    SciTech Connect

    Chipman, D.W.; Takahashi, T.

    1992-12-01

    During the first six months of this two-year grant, we have completed the construction of the analytical portion of a prototype gas chromatograph-based system for the analysis of dissolved organic carbon in seawater. We also have begun testing the procedures to be used to cryogenically concentrate and transfer carbon dioxide from the oxidizing atmosphere of the high-temperature furnace into the reducing hydrogen carrier gas of the gas chromatograph. During the second half of the first year, we will construct the high-temperature catalytic oxidation furnace and test the entire system on laboratory-prepared aqueous solutions of various organic compounds. Also during this period, we will take part in an initial scoping study within the Cape Hatteras field area on board the R/V Gyre. This study will involve both the collection of samples of seawater for organic and inorganic carbon analysis and the measurement of surface-water pCO[sub 2].

  3. Superheated water as chromatographic eluent for parabens separation on octadecyl coated zirconia stationary phase.

    PubMed

    Dugo, Paola; Buonasera, Katia; Crupi, Maria Lucia; Cacciola, Francesco; Dugo, Giovanni; Mondello, Luigi

    2007-05-01

    In this study, the use of pure water at superheated temperatures, between 100 and 200 degrees C, as a mobile phase for RP separation is explored. Instrumental parameters, such as temperature, flow rate, preheating and cooling, have shown significant effects on the quality of the chromatographic peaks. The properties of superheated water as an eluent were investigated by observing the chromatographic behaviour of four parabens on a carbon-clad zirconia (ZR) phase with covalently bonded octadecyl groups. Results were compared with those obtained at 30 degrees C on a silica-based phase with octadecyl groups, using water and ACN as mobile phase. The optimized method was finally applied to analyse parabens in a commercial body cream. PMID:17595947

  4. Optimization of an improved single-column chromatographic process for the separation of enantiomers.

    PubMed

    Kazi, Monzure-Khoda; Medi, Bijan; Amanullah, Mohammad

    2012-03-30

    This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process.

  5. Chromatographic separation of germanium and arsenic for the production of high purity (77)As.

    PubMed

    Gott, Matthew D; DeGraffenreid, Anthony J; Feng, Yutian; Phipps, Michael D; Wycoff, Donald E; Embree, Mary F; Cutler, Cathy S; Ketring, Alan R; Jurisson, Silvia S

    2016-04-01

    A simple column chromatographic method was developed to isolate (77)As (94±6% (EtOH/HCl); 74±11 (MeOH)) from germanium for potential use in radioimmunotherapy. The separation of arsenic from germanium was based on their relative affinities for different chromatographic materials in aqueous and organic environments. Using an organic or mixed mobile phase, germanium was selectively retained on a silica gel column as germanate, while arsenic was eluted from the column as arsenate. Subsequently, enriched (76)Ge (98±2) was recovered for reuse by elution with aqueous solution (neutral to basic). Greater than 98% radiolabeling yield of a (77)As-trithiol was observed from methanol separated [(77)As]arsenate [17].

  6. A review of the extraction and chromatographic determination methods for the analysis of parabens.

    PubMed

    Piao, Chunying; Chen, Ligang; Wang, Yu

    2014-10-15

    Parabens are a family of most widely used antimicrobial preservatives in food ingredients, cosmetic consumer products and pharmaceutical preparations. But several recent studies have cautioned that exposure to parabens may have more harmful consequences on animal and human health than what we realized previously, which made the analysis of parabens necessary. In this paper, we reviewed main sample preparation methods and chromatographic analysis methods proposed in formerly published works dealing with the analysis of parabens in different matrices. The sample preparation methods included ultrasonic assisted extraction, supercritical fluid extraction, pressurized liquid extraction, solid phase extraction, solid phase microextraction, liquid phase microextraction, dispersive liquid-liquid microextraction, stir bar sorptive extraction and matrix solid phase dispersion. The chromatographic analysis methods involved liquid chromatography, gas chromatography, and capillary electrophoresis.

  7. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test.

    PubMed

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-01

    Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane.

  8. Heavy metal adsorption changes of EAF steel slag after phosphorus adsorption.

    PubMed

    Song, Guanling; Cao, Lijing; Chen, Xiao; Hou, Wenhua; Wang, Qunhui

    2012-01-01

    A kind of electric arc furnace (EAF) steel slag was phosphated, and its isothermal and dynamic adsorptions of copper, cadmium, and lead ions were measured to determine if heavy metal adsorption changes after phosphorus adsorption. The surface area increased greatly after the slag was phosphated. Isothermal adsorption experiments showed that the theoretical Q(max) of the EAF steel slag on Cu(2+), Cd(2+), and Pb(2+) improved 59, 50, and 89% respectively after it was phosphated. Dynamic adsorption results showed that the greatest adsorption capacities of unit volume of Cu(2+), Cd(2+), and Pb(2+) were 2.2, 1.8, and 1.8 times that of the column packed with original EAF steel slag when the column was packed with phosphate EAF steel slag at the same heavy metal ion concentration. The breakthrough time, the exhaustion time and elution efficiency of the column also increased when the column was packed with phosphated EAF steel slag compared with that packed with original EAF steel slag. Phosphorus adsorption could further improve the heavy metal ion adsorption of the EAF steel slag.

  9. Adsorption characteristics of siloxanes in landfill gas by the adsorption equilibrium test.

    PubMed

    Nam, Sangchul; Namkoong, Wan; Kang, Jeong-Hee; Park, Jin-Kyu; Lee, Namhoon

    2013-10-01

    Due to the increase in energy cost by constantly high oil prices and the obligation to reduce greenhouse effect gases, landfill gas is frequently used as an alternative energy source for producing heat and electricity. Most of landfill gas utility facilities, however, are experiencing problems controlling siloxanes from landfill gas as their catalytic oxidizers are becoming fouled by silicon dioxide dust. To evaluate adsorption characteristics of siloxanes, an adsorption equilibrium test was conducted and parameters in the Freundlich and Langmuir isotherms were analyzed. Coconut activated carbon (CA1), coal activated carbon (CA2), impregnated activated carbon (CA3), silicagel (NCA1), and activated alumina (NCA2) were used for the adsorption of the mixed siloxane which contained hexamethyldisiloxane (L2), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). L2 had higher removal efficiency in noncarbon adsorbents compared to carbon adsorbents. The application of Langmuir and Freundlich adsorption isotherm demonstrated that coconut based CA1 and CA3 provided higher adsorption capacity on L2. And CA2 and NCA1 provided higher adsorption capacity on D4 and D5. Based on the experimental results, L2, D4, and D5 were converted by adsorption and desorption in noncarbon adsorbents. Adsorption affinity of siloxane is considered to be affect by the pore size distribution of the adsorbents and by the molecular size of each siloxane. PMID:23684695

  10. Gas chromatographic analysis of synthetic glycidol esters, mono-, di- and triglycerides.

    PubMed

    Engbersen, J A; van Stijn, F

    1976-03-01

    The gas chromatographic analysis of glycidol esters and mono-, di-,and triglycerides of palmitic-, stearic-, and oleic acid mixtures is described. The composition of the products was determined by gas chromatography on OV-17 after trimethylsilylation. Base-line separations between 1- and 2-monoglycerides and between 1,2- and 1,3-diglycerides were obtained. Isomerisation of the trimethylsilyl ethers of monoglycerides was not observed, contrary to published work.

  11. Chemometric approach for development, optimization, and validation of different chromatographic methods for separation of opium alkaloids.

    PubMed

    Acevska, J; Stefkov, G; Petkovska, R; Kulevanova, S; Dimitrovska, A

    2012-05-01

    The excessive and continuously growing interest in the simultaneous determination of poppy alkaloids imposes the development and optimization of convenient high-throughput methods for the assessment of the qualitative and quantitative profile of alkaloids in poppy straw. Systematic optimization of two chromatographic methods (gas chromatography (GC)/flame ionization detector (FID)/mass spectrometry (MS) and reversed-phase (RP)-high-performance liquid chromatography (HPLC)/diode array detector (DAD)) for the separation of alkaloids from Papaver somniferum L. (Papaveraceae) was carried out. The effects of various conditions on the predefined chromatographic descriptors were investigated using chemometrics. A full factorial linear design of experiments for determining the relationship between chromatographic conditions and the retention behavior of the analytes was used. Central composite circumscribed design was utilized for the final method optimization. By conducting the optimization of the methods in very rational manner, a great deal of excessive and unproductive laboratory research work was avoided. The developed chromatographic methods were validated and compared in line with the resolving power, sensitivity, accuracy, speed, cost, ecological aspects, and compatibility with the poppy straw extraction procedure. The separation of the opium alkaloids using the GC/FID/MS method was achieved within 10 min, avoiding any derivatization step. This method has a stronger resolving power, shorter analysis time, better cost/effectiveness factor than the RP-HPLC/DAD method and is in line with the "green trend" of the analysis. The RP-HPLC/DAD method on the other hand displayed better sensitivity for all tested alkaloids. The proposed methods provide both fast screening and an accurate content assessment of the six alkaloids in the poppy samples obtained from the selection program of Papaver strains.

  12. Development of and fabrication of high resolution gas chromatographic capillary columns

    NASA Technical Reports Server (NTRS)

    Zlatkis, A.

    1982-01-01

    Gas chromatographic columns which are used in the trace gas analyzer (TGA) for the space shuttle are coated with a polyoxyethylene lauryl ether. This stationary phase is of medium polarity and has a temperature limit of 160 C. A polymer for this application which has an improved thermal stability is investigated. The use of fused silica capillary columns with specially bonded phases as well as an introduction system (on column) was also studied.

  13. Inverse gas chromatography and other chromatographic techniques in the examination of engine oils.

    PubMed

    Fall, Jacek; Voelkel, Adam

    2002-09-01

    The emerging market of engine oils consists of a number of products from different viscosity and quality classes. Determination of the base oil used in manufacturing of the final product (engine oil) as well as estimation of mutual miscibility of oils and their solubility could be crucial problems. Inverse gas chromatography and other chromatographic techniques are presented as an interesting and fruitful extension of normalised standard analytical methods used in the oil industry. PMID:12385390

  14. Chromatographic fingerprinting: An innovative approach for food 'identitation' and food authentication - A tutorial.

    PubMed

    Cuadros-Rodríguez, Luis; Ruiz-Samblás, Cristina; Valverde-Som, Lucia; Pérez-Castaño, Estefanía; González-Casado, Antonio

    2016-02-25

    Fingerprinting methods describe a variety of analytical methods that provide analytical signals related to the composition of foodstuffs in a non-selective way such as by collecting a spectrum or a chromatogram. Mathematical processing of the information in such fingerprints may allow the characterisation and/or authentication of foodstuffs. In this context, the particular meaning of 'fingerprinting', in conjunction with 'profiling', is different from the original meanings used in metabolomics. This fact has produced some confusion with the use of these terms in analytical papers. Researchers coming from the metabolomic field could use 'profiling' or 'fingerprinting' on a different way to researchers who are devoted to food science. The arrival of an eclectic discipline, named 'foodomics' has not been enough to allay this terminological problem, since the authors keep on using the terms with both meanings. Thus, a first goal of this tutorial is to clarify the difference between both terms. In addition, the chemical approaches for food authentication, i.e., chemical markers, component profiling and instrumental fingerprinting, have been described. A new term, designated as 'food identitation', has been introduced in order to complete the life cycle of the chemical-based food authentication process. Chromatographic fingerprinting has been explained in detail and some strategies which could be applied has been clarified and discussed. Particularly, the strategies for chromatographic signals acquisition and chromatographic data handling are unified in a single framework. Finally, an overview about the applications of chromatographic (GC and LC) fingerprints in food authentication using different chemometric techniques has been included.

  15. How Much Can We Learn from a Single Chromatographic Experiment? A Bayesian Perspective.

    PubMed

    Wiczling, Paweł; Kaliszan, Roman

    2016-01-01

    In this work, we proposed and investigated a Bayesian inference procedure to find the desired chromatographic conditions based on known analyte properties (lipophilicity, pKa, and polar surface area) using one preliminary experiment. A previously developed nonlinear mixed effect model was used to specify the prior information about a new analyte with known physicochemical properties. Further, the prior (no preliminary data) and posterior predictive distribution (prior + one experiment) were determined sequentially to search towards the desired separation. The following isocratic high-performance reversed-phase liquid chromatographic conditions were sought: (1) retention time of a single analyte within the range of 4-6 min and (2) baseline separation of two analytes with retention times within the range of 4-10 min. The empirical posterior Bayesian distribution of parameters was estimated using the "slice sampling" Markov Chain Monte Carlo (MCMC) algorithm implemented in Matlab. The simulations with artificial analytes and experimental data of ketoprofen and papaverine were used to test the proposed methodology. The simulation experiment showed that for a single and two randomly selected analytes, there is 97% and 74% probability of obtaining a successful chromatogram using none or one preliminary experiment. The desired separation for ketoprofen and papaverine was established based on a single experiment. It was confirmed that the search for a desired separation rarely requires a large number of chromatographic analyses at least for a simple optimization problem. The proposed Bayesian-based optimization scheme is a powerful method of finding a desired chromatographic separation based on a small number of preliminary experiments. PMID:26607659

  16. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed. PMID:26290053

  17. Portable gas chromatograph mass spectrometer for on-site chemical analyses

    DOEpatents

    Haas, Jeffrey S.; Bushman, John F.; Howard, Douglas E.; Wong, James L.; Eckels, Joel D.

    2002-01-01

    A portable, lightweight (approximately 25 kg) gas chromatograph mass spectrometer, including the entire vacuum system, can perform qualitative and quantitative analyses of all sample types in the field. The GC/MS has a conveniently configured layout of components for ease of serviceability and maintenance. The GC/MS system can be transported under operating or near-operating conditions (i.e., under vacuum and at elevated temperature) to reduce the downtime before samples can be analyzed on-site.

  18. Chromatographic methods for the isolation, separation and characterisation of dissolved organic matter.

    PubMed

    Sandron, Sara; Rojas, Alfonso; Wilson, Richard; Davies, Noel W; Haddad, Paul R; Shellie, Robert A; Nesterenko, Pavel N; Kelleher, Brian P; Paull, Brett

    2015-09-01

    This review presents an overview of the separation techniques applied to the complex challenge of dissolved organic matter characterisation. The review discusses methods for isolation of dissolved organic matter from natural waters, and the range of separation techniques used to further fractionate this complex material. The review covers both liquid and gas chromatographic techniques, in their various modes, and electrophoretic based approaches. For each, the challenges that the separation and fractionation of such an immensely complex sample poses is critically reviewed.

  19. Evaluation of the suitability of chromatographic systems to predict human skin permeation of neutral compounds.

    PubMed

    Hidalgo-Rodríguez, Marta; Soriano-Meseguer, Sara; Fuguet, Elisabet; Ràfols, Clara; Rosés, Martí

    2013-12-18

    Several chromatographic systems (three systems of high-performance liquid chromatography and two micellar electrokinetic chromatography systems) besides the reference octanol-water partition system are evaluated by a systematic procedure previously proposed in order to know their ability to model human skin permeation. The precision achieved when skin-water permeability coefficients are correlated against chromatographic retention factors is predicted within the framework of the solvation parameter model. It consists in estimating the contribution of error due to the biological and chromatographic data, as well as the error coming from the dissimilarity between the human skin permeation and the chromatographic systems. Both predictions and experimental tests show that all correlations are greatly affected by the considerable uncertainty of the skin permeability data and the error associated to the dissimilarity between the systems. Correlations with much better predictive abilities are achieved when the volume of the solute is used as additional variable, which illustrates the main roles of both lipophilicity and size of the solute to penetrate through the skin. In this way, the considered systems are able to give precise estimations of human skin permeability coefficients. In particular, the HPLC systems with common C18 columns provide the best performances in emulating the permeation of neutral compounds from aqueous solution through the human skin. As a result, a methodology based on easy, fast, and economical HPLC measurements in a common C18 column has been developed. After a validation based on training and test sets, the method has been applied with good results to the estimation of skin permeation of several hormones and pesticides.

  20. Evaluation of coverage, retention patterns, and selectivity of seven liquid chromatographic methods for metabolomics.

    PubMed

    Wernisch, Stefanie; Pennathur, Subramaniam

    2016-09-01

    Liquid chromatography-mass spectrometry-based metabolomics studies require highly selective and efficient chromatographic techniques. Typically employed reversed-phase (RP) methods fail to target polar metabolites, but the introduction of hydrophilic interaction liquid chromatography (HILIC) is slow due to perceived issues of reproducibility and ruggedness and a limited understanding of the complex retention mechanisms. In this study, we present a comparison of the chromatographic performance of a traditional RP-C18 column with zwitterionic, amide-, alkyl diol-, and aminoalkyl-based HILIC and mixed-mode columns. Our metabolite library represents one of the largest analyte sets available and consists of 764 authentic metabolite standards, including amino acids, nucleotides, sugars, and other metabolites, representing all major biological pathways and commonly observed exogenous metabolites (drugs). The coverage, retention patterns, and selectivity of the individual methods are highly diverse even between conceptually related HILIC methods. Furthermore, we show that HILIC sorbents having highly orthogonal selectivity and specificity enhance the coverage of major metabolite groups in (semi-) targeted applications compared to RP. Finally, we discuss issues encountered in the analysis of biological samples based on the results obtained with human plasma extracts. Our results demonstrate that fast and highly reproducible separations on zwitterionic columns are feasible, but knowledge of analyte properties is essential to avoid chromatographic bias and exclusion of key analytes in metabolomics studies. Graphical Abstract The chromatographic parameters of 764 authentic metabolite standards provide the basis for a comparison of coverage, selectivity and orthogonality of 7 reversed-phase (RP), mixed-mode (MM) and hydrophilic interaction liquid chromatography (HILIC) methods.

  1. A Comparative Study of Chromatographic Behavior and Lipophilicity of Selected Imidazoline Derivatives.

    PubMed

    Filipic, Slavica; Antic, Aleksandra; Vujovic, Milena; Nikolic, Katarina; Agbaba, Danica

    2016-08-01

    Chromatographic behavior and lipophilicity of 20 selected imidazoline derivatives were examined by thin-layer chromatography using CN, RP-2, RP-8 and RP-18 as the stationary phases and a mixture of methanol, water and ammonia as the mobile phase. In all examined chromatographic systems, linear relationships were established between retention parameters and the volume fraction of methanol in the mobile phase (r > 0.985, 0.978, 0.981, 0.988 for the CN, RP-2, RP-8 and RP-18, respectively). The highest correlation between the obtained [Formula: see text] values was observed for RP-2 and RP-8 stationary phases. The experimental lipophilicity indices ([Formula: see text], m and C0) obtained from the retention data were used in correlation study with the calculated logP values. Experimentally determined [Formula: see text] values for all investigated chromatographic systems exhibited the highest correlation with the calculated ClogP values (r: 0.880, 0.872, 0.897 and 0.889 for the CN, RP-2, RP-8 and RP-18 stationary phases, respectively). In addition, principal component analysis enables new information about similarity and differences between tested compounds as well as experimental lipophilicity indices and calculated logP values. Performed QSRR analysis showed that the frequency of C-C at topological distance 1 and CATS2D Lipophilic-Lipophilic at lag 01 were important descriptors with influence on the [Formula: see text] values in all the examined chromatographic systems, while the differences in the retention behavior of compounds on the examined stationary phases can be distinguished based on their specific geometrical, electronic and constitutional properties.

  2. Chromatographic behaviour of steroidal saponins studied by high-performance liquid chromatography-mass spectrometry.

    PubMed

    Kite, Geoffrey C; Porter, Elaine A; Simmonds, Monique S J

    2007-05-01

    The chromatographic behaviour of steroidal saponins found in Anemarrhena asphodeloides, Asparagus officinalis, Convallaria majalis, Digitalis purpurea and Ruscus aculeatus was studied by HPLC-MS using a C-18 reversed-phase column and aqueous acetonitrile or aqueous methanol mobile phase gradients, with or without the addition of 1% acetic acid. The behaviour was compared to that of triterpene saponins found in Aesculus hippocastanum, Centella asiatica, Panax notoginseng and Potentilla tormentilla. Inclusion of methanol in the mobile phase under acidic conditions was found to cause furostanol saponins hydroxylated at C-22 to chromatograph as broad peaks, whereas the peak shapes of the spirostanol saponins and triterpene saponins studied remained acceptable. In aqueous methanol mobile phases without the addition of acid, furostanol saponins chromatographed with good peak shape, but each C-22 hydroxylated furostanol saponin was accompanied by a second chromatographic peak identified as its C-22 methyl ether. Methanolic extracts analysed in non-acidified aqueous acetonitrile mobile phases also resolved pairs of C-22 hydroxy and C-22 methoxy furostanol saponins. The C-22 methyl ether of deglucoruscoside was found to convert to deglucoruscoside during chromatography in acidified aqueous acetonitrile, or by dissolving in water. Poor chromatography of furostanol saponins in acidified aqueous methanol is due to the interconversion of the C-22 hydroxy and C-22 methoxy forms. It is recommended that initial analysis of saponins by HPLC-MS using a C-18 stationary phase is performed using acidified aqueous acetonitrile mobile phase gradients. The existence of naturally-occurring furostanol saponins methoxylated at C-22 can be investigated with aqueous acetonitrile mobile phases and avoiding methanol in the extraction solvent. PMID:17391684

  3. The application of atomic emission spectroscopy to chromatographic analyses for element-selective detection

    SciTech Connect

    Seeley, J.A.

    1992-01-01

    The goal of this work was to investigate the properties of existing atomic emission systems which are useful for element-selective detection of chromatographic effluent. A microwave induced plasma (MIP) system has been optimized for the selective detection of boron in the effluent of a gas chromatograph. A method was developed for the analysis of total boron present in several lubrication oil additives and in several formulated lubrication oils. Values obtained by this method compare favorably with those obtained by other atomic emission spectroscopic (AES) methods. A direct current plasma (DCP) system has been optimized for the selective detection of boron in flowing organic liquid streams. A method was developed for the analysis of total boron present in several lubrication oil additives by flow injection analysis (FIA). A method was also developed for the qualitative separation [open quotes]speciation[close quotes] of these additives by size exclusion chromatography-DCP. Values obtained through this method compare favorably with values obtained through other AES methods. The MIP system was optimized for the selective detection of titanium in the effluent of the gas chromatograph. This system was used to analyze a group of reaction mixtures containing novel titanium chelates and organo-metallic compounds, as well as several organo-titanium-boron compounds. The MIP system was optimized for the selective detection of several of the group VA and group VIA elements in the effluent of the gas chromatograph. This system was used to characterize a series of coal standards (the Argonne Premium Coal Standards) by pyrolysis-GC-AES. Volatile compounds containing nitrogen, oxygen and sulfur were detected. The Py-GC-AES method was used to characterize several other coal, sedimentary and kerogen samples. Volatile phosphorous, arsenic, and selenium compounds were detected, as were compounds of nitrogen, oxygen and sulfur.

  4. Poliovirus Adsorption by 34 Minerals and Soils

    PubMed Central

    Moore, Rebecca S.; Taylor, Dene H.; Sturman, Lawrence S.; Reddy, Michael M.; Fuhs, G. Wolfgang

    1981-01-01

    The adsorption of radiolabeled infectious poliovirus type 2 by 34 well-defined soils and mineral substrates was analyzed in a synthetic freshwater medium containing 1 mM CaCl2 and 1.25 mM NaHCO3 at pH 7. In a model system, adsorption of poliovirus by Ottawa sand was rapid and reached equilibrium within 1 h at 4°C. Near saturation, the adsorption could be described by the Langmuir equation; the apparent surface saturation was 2.5 × 106 plaque-forming units of poliovirus per mg of Ottawa sand. At low surface coverage, adsorption was described by the Freundlich equation. The soils and minerals used ranged from acidic to basic and from high in organic content to organic free. The available negative surface charge on each substrate was measured by the adsorption of a cationic polyelectrolyte, polydiallyldimethylammonium chloride. Most of the substrates adsorbed more than 95% of the virus. In general, soils, in comparison with minerals, were weak adsorbents. Among the soils, muck and Genesee silt loam were the poorest adsorbents; among the minerals, montmorillonite, glauconite, and bituminous shale were the least effective. The most effective adsorbents were magnetite sand and hematite, which are predominantly oxides of iron. Correlation coefficients for substrate properties and virus adsorption revealed that the elemental composition of the adsorbents had little effect on poliovirus uptake. Substrate surface area and pH, by themselves, were not significantly correlated with poliovirus uptake. A strong negative correlation was found between poliovirus adsorption and both the contents of organic matter and the available negative surface charge on the substrates as determined by their capacities for adsorbing the cationic polyelectrolyte, polydiallyldimethylammonium chloride. PMID:6274259

  5. Modeling adsorption: Investigating adsorbate and adsorbent properties

    NASA Astrophysics Data System (ADS)

    Webster, Charles Edwin

    1999-12-01

    Surface catalyzed reactions play a major role in current chemical production technology. Currently, 90% of all chemicals are produced by heterogeneously catalyzed reactions. Most of these catalyzed reactions involve adsorption, concentrating the substrate(s) (the adsorbate) on the surface of the solid (the adsorbent). Pore volumes, accessible surface areas, and the thermodynamics of adsorption are essential in the understanding of solid surface characteristics fundamental to catalyst and adsorbent screening and selection. Molecular properties such as molecular volumes and projected molecular areas are needed in order to convert moles adsorbed to surface volumes and areas. Generally, these molecular properties have been estimated from bulk properties, but many assumptions are required. As a result, different literature values are employed for these essential molecular properties. Calculated molar volumes and excluded molecular areas are determined and tabulated for a variety of molecules. Molecular dimensions of molecules are important in the understanding of molecular exclusion as well as size and shape selectivity, diffusion, and adsorbent selection. Molecular dimensions can also be used in the determination of the effective catalytic pore size of a catalyst. Adsorption isotherms, on zeolites, (crystalline mineral oxides) and amorphous solids, can be analyzed with the Multiple Equilibrium Analysis (MEA) description of adsorption. The MEA produces equilibrium constants (Ki), capacities (ni), and thermodynamic parameters (enthalpies, ΔHi, and entropies, ΔSi) of adsorption for each process. Pore volumes and accessible surface areas are calculated from the process capacities. Adsorption isotherms can also be predicted for existing and new adsorbate-adsorbent systems with the MEA. The results show that MEA has the potential of becoming a standard characterization method for microporous solids that will lead to an increased understanding of their behavior in gas

  6. Adding adsorption to a geothermal simulator

    SciTech Connect

    Holt, R.; Pingol, A.

    1992-01-01

    Physical adsorption of steam has increasingly become recognized as an important storage mechanism in vapor dominated geothermal reservoirs. A method has been developed which allows the effects of adsorption to be modeled using TETRAD, a commercially available geothermal simulator. The method consists of replacing the standard steam table with a new steam table which has been derived to include adsorptive effects. The TETRAD simulator, when run with the pseudo steam table, approximately matches the pressure, production, and saturation behavior of a desorbing geothermal system. Adsorption can be described as the existence of an immobile layer of liquid on the surfaces within a porous medium. The presence of an adsorbed liquid water layer in rocks has been shown experimentally to cause the vapor pressure of steam to be lower than its flat surface vapor pressure for a particular The pseudo steam table accounts for this vapor pressure lowering effect. A test run was made with TETRAD using the pseudo steam table and a low porosity, low permeability reservoir matrix. This test run was compared to an equivalent run made with Stanford Geothermal Program's simulator, ADSORB. The program ADSORB is a one dimensional simulator which has adsorption effects built into its difference equations. The comparison of these runs shows that the pseudo steam table allows TETRAD to match the behavior of the ADSORB simulator. Injection was not investigated in this study. A convenient method of modeling adsorption with TETRAD is to use standard steam tables while allowing for the vapor pressure lowering effect of adsorption. This will require modifications of the equations in the code that describe the partial pressure of the steam phase.

  7. Influence of oxygenated contaminants on the separation of C{sub 8} aromatics by adsorption of faujasite zeolites

    SciTech Connect

    Methivier, A.

    1998-02-01

    The influence of the formation of oxygenated compounds on the adsorption properties of a Y zeolite were investigated. A procedure was developed which allows the zeolite to age under a flow of toluene or p-xylene containing dissolved oxygen. The separation properties of the sieve were tested by a chromatographic method involving the separation of p-xylene and m-xylene. It was found that aging in the presence of oxygen leads to a dramatic decrease in both the capacity and selectivity of the sieve, while aging in a clean feed leads to stable separation properties. Together with the evolution of the sieve, impurities which are mainly benzaldehyde and water are produced in the feed. Heavy aromatic compounds also occur during aging. The oxidation of toluene to benzaldehyde and the subsequent formation of water may be responsible for the decreased performance of the sieve in the separation of p-xylene from C8 aromatics.

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

    PubMed

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

    2014-07-25

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

  9. Application of Sigmoidal Transformation Functions in Optimization of Micellar Liquid Chromatographic Separation of Six Quinolone Antibiotics.

    PubMed

    Hadjmohammadi, Mohammadreza; Salary, Mina

    2016-03-01

    A chemometrics approach has been used to optimize the separation of six quinolone compounds by micellar liquid chromatography (MLC). A Derringer's desirability function, a multicriteria decision-making (MCDM) method, was tested for evaluation of two different measures of chromatographic performance (resolution and analysis time). The effect of three experimental parameters on a chromatographic response function (CRF) expressed as a product of two sigmoidal desirability functions was investigated. The sigmoidal functions were used to transform the optimization criteria, resolution and analysis time into the desirability values. The factors studied were the concentration of sodium dodecyl sulfate, butanol content and pH of the mobile phase. The experiments were done according to the face-centered cube central composite design, and the calculated CRF values were fitted to a polynomial model to correlate the CRF values with the variables and their interactions. The developed regression model showed good descriptive and predictive ability (R(2) = 0.815, F = 6.919, SE = 0.038, [Formula: see text]) and used, by a grid search algorithm, to optimize the chromatographic conditions for the separation of the mixture. The efficiency of prediction of polynomial model was confirmed by performing the experiment under the optimal conditions.

  10. Band target entropy minimization for retrieving the information of individual components from overlapping chromatographic data.

    PubMed

    Xia, Zhenzhen; Liu, Yan; Cai, Wensheng; Shao, Xueguang

    2015-09-11

    Band target entropy minimization (BTEM) is a self-modeling curve resolution (SMCR) approach relying on non-negative criterion and minimization of Shannon entropy. In this study, BTEM algorithm was applied to retrieving the information of individual components from overlapping gas chromatography-mass spectrometry (GC-MS) data. The algorithm starts with dividing the whole data into bands along the retention time. In each band, singular value decomposition (SVD) is used to decompose the data into scores and loadings. Because the pure chromatographic signal possesses the lowest Shannon entropy, the chromatographic signal of each component can be constructed by optimizing the combination of the loadings with minimal Shannon entropy under non-negative criterion. To show the efficiency of the algorithm, a simulated four-component overlapping GC-MS data and an experimental GC-MS data of 18 organophosphorus pesticide mixture are investigated. The results show that both the chromatographic profiles and mass spectra of the components can be successfully extracted from the overlapping signals.

  11. Estimations of temperature deviations in chromatographic columns using isenthalpic plots. I. Theory for isocratic systems.

    PubMed

    Tarafder, Abhijit; Iraneta, Pamela; Guiochon, Georges; Kaczmarski, Krzysztof; Poe, Donald P

    2014-10-31

    We propose to use constant enthalpy or isenthalpic diagrams as a tool to estimate the extent of the temperature variations caused by the mobile phase pressure drop along a chromatographic column, e.g. of its cooling in supercritical fluid and its heating in ultra-performance liquid chromatography. Temperature strongly affects chromatographic phenomena. Any of its variations inside the column, whether intended or not, can lead to significant changes in separation performance. Although instruments use column ovens in order to keep constant the column temperature, operating conditions leading to a high pressure drop may cause significant variations of the column temperature, both in the axial and the radial directions, from the set value. Different ways of measuring these temperature variations are available but they are too inconvenient to be employed in many practical situations. In contrast, the thermodynamic plot-based method that we describe here can easily be used with only a ruler and a pencil. They should be helpful in developing methods or in analyzing results in analytical laboratories. Although the most effective application area for this approach should be SFC (supercritical fluid chromatography), it can be applied to any chromatographic conditions in which temperature variations take place along the column due to the pressure drop, e.g. in ultra-high pressure liquid chromatography (UHPLC). The method proposed here is applicable to isocractic conditions only.

  12. Improving the gas-chromatographic determination of the composition of the gas liberated from a battery

    SciTech Connect

    Dmitriev, V.V.; Zubov, M.S.; Baulov, V.I.; Toguzov, B.M.

    1992-07-10

    Normally, gas chromatography is used for analyzing the gas composition that is liberated when batteries operate. Earlier work describes a gas-chromatographic technique for determining the composition of gas liberated from a battery. According to this reference, the gas is collected in an inverted burette over water. The gas is either sampled with a batching valve or with a medical syringe, which pierces the connecting vacuum hoses. The gas sample is injected into the chromatographic evaporator, and is separated on the chromatographic column into its individual components, each of which is analyzed on the detector. The method described was used to study gas liberation during the storage of charged nickel-zinc batteries. In the method described above, a high proportion of the gas specimen that accumulates and is collected in the measuring system occurs in the dead space volume. In this situation, it is very difficult to determine the liberated gas composition with a high degree of accuracy when the gas is liberated at low rates. Moreover, this method does not provide reliable system air tightness during long term operation of the batteries. 5 refs., 2 figs., 1 tab.

  13. Determining orthogonal chromatographic systems prior to the development of methods to characterise impurities in drug substances.

    PubMed

    Van Gyseghem, E; Van Hemelryck, S; Daszykowski, M; Questier, F; Massart, D L; Vander Heyden, Y

    2003-02-21

    To define starting conditions for the development of methods to separate impurities from the active substance and from each other in drugs with an unknown impurity profile, the parallel application of generic orthogonal chromatographic systems could be useful. The possibilities to define orthogonal chromatographic systems were examined by calculation of the correlation coefficients between retention factors k for a set of 68 drugs on 11 systems, by visual evaluation of the selectivity differences, by using principal component analysis, by drawing color maps and evaluating dendrograms. A zirconia-based stationary phase coated with a polybutadiene (PBD) polymer and three silica-based phases (base-deactivated, polar-embedded and monolithic) were used. Besides the stationary phase, the influence of pH and of organic modifier, on the selectivity of a system were evaluated. The dendrograms of hierarchical clusters were found good aids to assess orthogonality of chromatographic systems. The PBD-zirconia phase/methanol/pH 2.5 system is found most orthogonal towards several silica-based systems, e.g. a base-deactivated C16 -amide silica/methanol/pH 2.5 system. The orthogonality was validated using cross-validation, and two other validation sets, i.e. a set of non-ionizable solutes and a mixture of a drug and its impurities.

  14. Dissimilar or orthogonal reversed-phase chromatographic systems: A comparison of selection techniques.

    PubMed

    Dumarey, M; Put, R; Van Gyseghem, E; Vander Heyden, Y

    2008-02-25

    Developing an analytical separation procedure for an unknown mixture is a challenging issue. An important example is the separation and quantification of a new drug and its impurities. One approach to start method development is the screening of the mixture on dissimilar chromatographic systems, i.e. systems with large selectivity differences. After screening, the most suited system is retained for further method development. In a step prior to such strategy dissimilar chromatographic systems need to be selected. In this paper the performance of different chemometric selection approaches, described in the literature, was visually evaluated and compared. Additionally, orthogonal projection approach (OPA) was tested as another potential selection method. All techniques, including the OPA method, were able to select (a set of) dissimilar chromatographic systems and many similarities between the selections were observed. However, the Kennard and Stone algorithm performed best in selecting the most dissimilar systems in the earliest steps of the selection procedure. The generalized pairwise correlation method (GPCM) and the auto-associative multivariate regression trees (AAMRT) were also performing well. OPA and weighted pair group method using arithmetic averages (WPGMA) are less preferable.

  15. Separation of substrates and closely related glucuronide metabolites using various chromatographic modes.

    PubMed

    Romand, Stéphanie; Rudaz, Serge; Guillarme, Davy

    2016-02-26

    The aim of this study was to assess the retention and selectivity of a cocktail of 10 substrates of uridine diphosphate glucuronosyltransferase enzymes (UGTs) and their respective glucuronides using four chromatographic approaches. For this purpose, seven different stationary phases were employed in reversed phase liquid chromatography (RPLC), two in hydrophilic interaction liquid chromatography (HILIC), one in aqueous normal phase chromatography (ANPC) and four in subcritical fluid chromatography (SFC). Highly orthogonal separations were achieved with these chromatographic modes. Hydrophobic interactions mainly governed the retention of the substrates and their polar glucuronides in RPLC despite the use of different chemical stationary phase bonding, involving additional possible interactions. In ANPC, atypical separations and poor peak shapes were observed with the selected compounds. In HILIC and SFC conditions, the metabolites were more retained than the substrates because of the polarity increase related to the glucuronic acid moiety. For the latter, a very high proportion of organic solvent (up to 80%) was required to elute the glucuronides that often displayed poor peak shapes. Finally, the selectivity of nine chromatographic systems was compared for the separation of isomeric and diastereoisomeric compounds. The stationary phases used in RPLC mode were more selective towards the two positional isomers of morphine glucuronides since they possess distinct lipophilicity. HILIC and SFC columns were found to be promising for the separation of a critical diastereoisomers pair, namely epitestosterone-glucuronide and testosterone-glucuronide. PMID:26818236

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

    PubMed

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

    2013-09-01

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

  17. From molecular model to sparse representation of chromatographic signals with an unknown number of peaks.

    PubMed

    Bertholon, F; Harant, O; Foan, L; Vignoud, S; Jutten, C; Grangeat, P

    2015-08-01

    Analysis of a fluid mixture using a chromatographic system is a standard technique for many biomedical applications such as in-vitro diagnostic of body fluids or air and water quality assessment. The analysis is often dedicated towards a set of molecules or biomarkers. However, due to the fluid complexity, the number of mixture components is often larger than the list of targeted molecules. In order to get an analysis as exhaustive as possible and also to take into account possible interferences, it is important to identify and to quantify all the components that are included in the chromatographic signal. Thus the signal processing aims to reconstruct a list of an unknown number of components and their relative concentrations. We address this question as a problem of sparse representation of a chromatographic signal. The innovative representation is based on a stochastic forward model describing the transport of elementary molecules in the chromatography column as a molecular random walk. We investigate three methods: two probabilistic Bayesian approaches, one parametric and one non-parametric, and a determinist approach based on a parsimonious decomposition on a dictionary basis. We examine the performances of these 3 approaches on an experimental case dedicated to the analysis of mixtures of the micro-pollutants Polycyclic Aromatic Hydrocarbons (PAH) in a methanol solution in two cases of high and low signal to noise ratio (SNR).

  18. Introduction to time-of-flight secondary ion mass spectrometry application in chromatographic analysis.

    PubMed

    Orinák, Andrej; Arlinghaus, Heinrich F; Vering, Guido; Orináková, Renáta; Hellweg, Sebastian

    2005-08-19

    New on-line analytical system coupling thin layer chromatography (TLC) and high selective identification unit-time of flight secondary ion mass spectrometry (TOF-SIMS) is introduced in this article. Chromatographic mixture separation and analyte surface deposition followed with surface TOF-SIMS analysis on-line allows to identify the analytes at trace and ultratrace levels. The selected analytes with different detectability and identification possibility were analysed in this hyphenated unit (Methyl Red indicator, Terpinolen and Giberrelic acid). Here, the chromatographic thin layer plays a universal role: separation unit, analyte depositing surface and TOF-SIMS interface, finally. Two depositing substrates and TOF-SIMS compatible interfaces were tested in above-mentioned interfacing unit: modified aluminium backed chromatographic thin layer and monolithic silica thin layer. The sets of positive and negative ions TOF-SIMS spectra obtained from different SIMS modes of analysis were used for analyte identification purposes. SIMS enables analyte detection with high mass resolution at the concentration level that is not achieved by other methods. PMID:16114244

  19. Evaluation of traditional medicines I: identification of PHELA using different chromatographic techniques.

    PubMed

    Lekhooa, Makhotso; Walubo, Andrew; Du Plessis, Jan J B; Matsabisa, Motlalepula C; Molefe, Duduzile

    2012-01-01

    PHELA is a herbal mixture of four African traditional medicinal plants that has been used for decades in wasting conditions and is now being developed by the Medical Research Council (MRC) as an immune booster for patients with compromised immune system. A chromatographic fingerprint of PHELA was needed for quality control purposes. Here, a comprehensive method for fingerprinting of PHELA using different chromatographic techniques is described. It involved extraction of the PHELA by either acidic or a simple 'salting-out' method, followed by Thin Layer Chromatography (TLC) analysis and/or preparative Column Chromatography (CC). The products were thereafter analyzed by High Performance Liquid Chromatography with UV-detector (HPLC-UV), HPLC with fluorescence-detector (HPLC-FL) and Gas-Chromatography with a Mass Selective Detector spectrometer (GC-MSD). The fingerprints were successfully used to differentiate PHELA from another common herbal product made from Hypericum perforatum (St. John's Wort), thereby illustrating its high potential for use in fingerprinting of PHELA and in differentiating it from other herbal medicines. By validating the different chromatographic techniques on the standardized extraction methods, this approach will enable wide application in quality control of PHELA using acceptable procedures, thereby promoting effective monitoring of the finished product in all countries where it will be used.

  20. Method and apparatus for thermal swing adsorption and thermally-enhanced pressure swing adsorption

    DOEpatents

    Wegeng, Robert S.; Rassat, Scot D.; TeGrotenhuis, Ward E.; Drost, Kevin; Vishwanathan, Vilayanur V.

    2004-06-08

    The present invention provides compact adsorption systems that are capable of rapid temperature swings and rapid cycling. Novel methods of thermal swing adsorption and thermally-enhanced pressure swing adsorption are also described. In some aspects of the invention, a gas is passed through the adsorbent thus allowing heat exchangers to be very close to all portions of the adsorbent and utilize less space. In another aspect, the adsorption media is selectively heated, thus reducing energy costs. Methods and systems for gas adsorption/desorption having improved energy efficiency with capability of short cycle times are also described. In another aspect, the apparatus or methods utilize heat exchange channels of varying lengths that have volumes controlled to provide equal heat fluxes. Methods of fuel cell startup are also described. Advantages of the invention include the ability to use (typically) 30-100 times less adsorbent compared to conventional systems.

  1. Method for thermal swing adsorption and thermally-enhanced pressure swing adsorption

    DOEpatents

    Wegeng, Robert S.; Rassat, Scot D.; Stenkamp, Victoria S.; TeGrotenhuis, Ward E.; Matson, Dean W.; Drost, M. Kevin; Viswanathan, Vilayanur V.

    2003-10-07

    The present invention provides compact adsorption systems that are capable of rapid temperature swings and rapid cycling. Novel methods of thermal swing adsorption and thermally-enhanced pressure swing adsorption are also described. In some aspects of the invention, a gas is passed through the adsorbent thus allowing heat exchangers to be very close to all portions of the adsorbent and utilize less space. In another aspect, the adsorption media is selectively heated, thus reducing energy costs. Methods and systems for gas adsorption/desorption having improved energy efficiency with capability of short cycle times are also described. Advantages of the invention include the ability to use (typically) 30-100 times less adsorbent compared to conventional systems.

  2. Apparatus for thermal swing adsorption and thermally-enhanced pressure swing adsorption

    DOEpatents

    Wegeng, Robert S.; Rassat, Scot D.; Stenkamp, Victoria S.; TeGrotenhuis, Ward E.; Matson, Dean W.; Drost, M. Kevin; Viswanathan, Vilayanur V.

    2005-12-13

    The present invention provides compact adsorption systems that are capable of rapid temperature swings and rapid cycling. Novel methods of thermal swing adsorption and thermally-enhanced pressure swing adsorption are also described. In some aspects of the invention, a gas is passed through the adsorbent thus allowing heat exchangers to be very close to all portions of the adsorbent and utilize less space. In another aspect, the adsorption media is selectively heated, thus reducing energy costs. Methods and systems for gas adsorption/desorption having improved energy efficiency with capability of short cycle times are also described. Advantages of the invention include the ability to use (typically) 30-100 times less adsorbent compared to conventional systems.

  3. ION-EXCLUSION CHROMATOGRAPHIC DETERMINATION OF CARBOXYLIC ACIDS USED TO SUPPORT THE MICROBIALLY MEDIATED REDUCTIVE DECHLORINATION OF TETRACHLOROETHENE

    EPA Science Inventory

    An analytical method was developed for the determination of lactic acid, formic acid, acetic acid, propionic acid, and butyric acid in environmental microcosm samples using ion-exclusion chromatography. The chromatographic behavior of various eluents was studied to determine the ...

  4. CHROMATOGRAPHIC ALTERATION OF A NONIONIC SURFACTANT MIXTURE DURING TRANSPORT IN DENSE NONAQUEOUS PHASE LIQUID CONTAMINATED SEDIMENT (R826650)

    EPA Science Inventory

    Chromatographic alteration of a nonionic surfactant mixture during transport through DNAPL-contaminated aquifer sediment may occur due to differential loss of oligomers to sediment and to dense nonaqueous phase liquid (DNAPL). These losses may significantly alter the solubilizing...

  5. Adsorption of phenolic compound by aged-refuse.

    PubMed

    Xiaoli, Chai; Youcai, Zhao

    2006-09-01

    The adsorption of phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol by aged-refuse has been studied. Adsorption isotherms have been determined for phenol, 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol and the data fits well to the Freundlich equation. The chlorinated phenols are absorbed more strongly than the phenol and the adsorption capacity has an oblivious relationship with the numbers and the position of chlorine subsistent. The experiment data suggests that both the partition function and the chemical adsorption involve in the adsorption process. Pseudo-first-order and pseudo-second-order model were applied to investigate the kinetics of the adsorption and the results show that it fit the pseudo-second-order model. More than one step involves in the adsorption process and the overall rate of the adsorption process appears to be controlled by the chemical reaction. The thermodynamic analysis indicates that the adsorption is spontaneous and endothermic.

  6. Neptunium(V) adsorption to calcite

    NASA Astrophysics Data System (ADS)

    Heberling, Frank; Brendebach, Boris; Bosbach, Dirk

    2008-12-01

    The migration behavior of the actinyl ions U(VI)O 22+, Np(V)O 2+ and Pu(V,VI)O 2(+,2+) in the geosphere is to a large extend controlled by sorption reactions (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) with minerals. Here NpO 2+ adsorption onto calcite is studied in batch type experiments over a wide range of pH (6.0-9.4) and concentration (0.4 μM-40 μM) conditions. pH is adjusted by variation of CO 2 partial pressure. Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH. pH dependence of adsorption decreases with increasing Np(V) concentration. EXAFS data of neptunyl adsorbed to calcite and neptunyl in the supernatant shows differences in the Np(V)-O-yl distance, 1.85 ± 0.01 Å for the adsorbed and 1.82 ± 0.01 Å for the solution species. The equatorial environment of the neptunyl in solution shows about 5 oxygen neighbours at 2.45 ± 0.02 Å. For adsorbed neptunyl there are also about 5 oxygen neighbours at 2.46 ± 0.01 Å. An additional feature in the adsorbed species' R-space spectrum can be related to carbonate neighbours, 3 to 6 carbon backscatterers (C-eq) at 3.05 ± 0.03 Å and 3 to 6 oxygen backscatterers (O-eq2) at 3.31 ± 0.02 Å. The differences in the Np(V)-O-yl distance and the C-eq and O-eq2 backscatterers which are only present for the adsorbed species indicate inner-sphere bonding of the adsorbed neptunyl species to the calcite surface. Experiments on adsorption kinetics indicate that after a fast surface adsorption process a continuous slow uptake occurs which may be explained by incorporation via surface dissolution and reprecipitation processes. This is also indicated by the part irreversibility of the adsorption as shown by increased KD values after desorption compared to adsorption.

  7. Adsorption of gases on carbon molecular sieves

    SciTech Connect

    Vyas, S.N.; Patwardhan, S.R.; Vijayalakshmi, S. . Dept. of Chemical Engineering); Ganesh, K.S. )

    1994-12-01

    Adsorption on carbon molecular sieves (CMS) prepared by coke deposition has become an interesting area of adsorption due to its microporous nature and favorable separation factor on size and shape selectivity basis for many gaseous systems. In the present work CMS was synthesized from coconut shell through three major steps, namely, carbonization, activation, and coke deposition by hydrocarbon cracking. The crushed, washed, and sieved granules of coconut shell (particle size 2--3 mm) were pretreated with sodium silicate solution and oven-dried at 150 C to create the inorganic sites necessary for coke deposition. Carbonization and activation of the dried granules were carried out at 800 C, for 30 min each. The activated char thus produced was subjected to hydrocarbon cracking at 600 C for periods varying from 30 to 180 min. The product samples were characterized in terms of adsorption isotherm, kinetic adsorption curve, surface area, pore volume, pore size distribution, and characteristic energy for adsorption by using O[sub 2], N[sub 2], C[sub 2]H[sub 2], CO[sub 2], C[sub 3]H[sub 6], and CH[sub 4].

  8. Adsorption behavior of heavy metals on biomaterials.

    PubMed

    Minamisawa, Mayumi; Minamisawa, Hiroaki; Yoshida, Shoichiro; Takai, Nobuharu

    2004-09-01

    We have investigated adsorption of Cd(II) and Pb(II) at pH 2-6.7 onto the biomaterials chitosan, coffee, green tea, tea, yuzu, aloe, and Japanese coarse tea, and onto the inorganic adsorbents, activated carbon and zeolite. High adsorptive capabilities were observed for all of the biomaterials at pH 4 and 6.7. In the adsorption of Cd(II), blend coffee, tea, green tea, and coarse tea have comparable loading capacities to activated carbon and zeolite. Although activated carbon, zeolite, and chitosan are utilized in a variety of fields such as wastewater treatment, chemical and metallurgical engineering, and analytical chemistry, these adsorbents are costly. On the other hand, processing of the test biomaterials was inexpensive, and all the biomaterials except for chitosan were able to adsorb large amounts of Pb(II) and Cd(II) ions after a convenient pretreatment of washing with water followed by drying. The high adsorption capability of the biomaterials prepared from plant materials is promising in the development of a novel, low-cost adsorbent. From these results, it is concluded that heavy metal removal using biomaterials would be an effective method for the economic treatment of wastewater. The proposed adsorption method was applied to the determination of amounts of Cd(II) and Pb(II) in water samples.

  9. Adsorption of small organic molecules on graphene.

    PubMed

    Lazar, Petr; Karlický, František; Jurečka, Petr; Kocman, Mikuláš; Otyepková, Eva; Šafářová, Klára; Otyepka, Michal

    2013-04-24

    We present a combined experimental and theoretical quantification of the adsorption enthalpies of seven organic molecules (acetone, acetonitrile, dichloromethane, ethanol, ethyl acetate, hexane, and toluene) on graphene. Adsorption enthalpies were measured by inverse gas chromatography and ranged from -5.9 kcal/mol for dichloromethane to -13.5 kcal/mol for toluene. The strength of interaction between graphene and the organic molecules was estimated by density functional theory (PBE, B97D, M06-2X, and optB88-vdW), wave function theory (MP2, SCS(MI)-MP2, MP2.5, MP2.X, and CCSD(T)), and empirical calculations (OPLS-AA) using two graphene models: coronene and infinite graphene. Symmetry-adapted perturbation theory calculations indicated that the interactions were governed by London dispersive forces (amounting to ∼60% of attractive interactions), even for the polar molecules. The results also showed that the adsorption enthalpies were largely controlled by the interaction energy. Adsorption enthalpies obtained from ab initio molecular dynamics employing non-local optB88-vdW functional were in excellent agreement with the experimental data, indicating that the functional can cover physical phenomena behind adsorption of organic molecules on graphene sufficiently well.

  10. Adsorption in sparse networks. 1: Cylinder model

    SciTech Connect

    Scherer, G.W.

    1998-06-15

    Materials with very low density, such as aerogels, are networks with polymers or chains of particles joined at nodes, where the spacing of the nodes is large compared to the thickness of the chains. In such a material, most of the solid surface has positive curvature, so condensation of an adsorbate is more difficult than condensation in a body containing cavities whose surfaces have negative curvature. A model is presented in which the network is represented by straight cylinders joined at nodes with coordination numbers 4, 6, or 12. The shape of the adsorbate/adsorptive interface is obtained for each network by minimizing its surface area. The adsorption behavior is found to depend on the ratio of the node separation, l, to the radius of the cylinders, a: if l/a exceeds a critical value (which depends on the coordination of the node), then the curvature of the adsorbate/adsorptive interface approaches zero while the adsorbate occupies a small fraction of the pore volume; if l/a is less than the critical value, then condensation occurs. Even in the latter case, interpretation of the adsorption isotherm in terms of cylindrical pores (as in the BJH model) yields apparent pore sizes much greater than the actual spacing of the nodes. In a companion paper, this model is applied to silica aerogels and found to give a good fit to both the adsorption and desorption curves with a single distribution of node spacings.

  11. Adsorption of reovirus by minerals and soils.

    PubMed Central

    Moore, R S; Taylor, D H; Reddy, M M; Sturman, L S

    1982-01-01

    Adsorption of [35S]methionine-labeled reovirus by 30 dry soils, minerals, and finely ground rocks suspended in synthetic freshwater at pH 7 was investigated to determine the conditions necessary for optimum virus removal during land application of wastewaters. All of the minerals and soils studied were excellent adsorbents of reovirus, with greater than 99% of the virus adsorbed after 1 h at 4 degrees C. Thereafter, virus remaining in suspension was significantly inactivated, and within 24 h a three to five log10 reduction in titer occurred. The presence of divalent cations, i.e., Ca2+ and Mg2+, in synthetic freshwater enhanced removal, whereas soluble organic matter decreased the amount of virus adsorbed in secondary effluent. The amount of virus adsorbed by these substrates was inversely correlated with the amount of organic matter, capacity to adsorb cationic polyelectrolyte, and electrophoretic mobility. Adsorption increased with increasing available surface area, as suspended infectivity was reduced further by the more finely divided substrates. However, the organic content of the soils reduced the level of infectious virus adsorbed below that expected from surface area measurements alone. The inverse correlation between virus adsorption and substrate capacity for cationic polyelectrolyte indicates that the adsorption of infectious reovirus particles is predominately a charged colloidal particle-charged surface interaction. Thus, adsorption of polyelectrolyte may be useful in predicting the fate of viruses during land application of sewage effluents and sludges. PMID:7149717

  12. Membrane Potential Generated by Ion Adsorption

    PubMed Central

    Tamagawa, Hirohisa; Morita, Sachi

    2014-01-01

    It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK) equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic solutions. The GHK equation describes that: variation of membrane permeability to ion in accordance with ion species results in the variation of the membrane potential. However, nonzero potential was observed even across the impermeable membrane (or separator) separating two electrolytic solutions. It gave rise to a question concerning the validity of the GHK equation for explaining the membrane potential generation. In this work, an alternative theory was proposed. It is the adsorption theory. The adsorption theory attributes the membrane potential generation to the ion adsorption onto the membrane (or separator) surface not to the ion passage through the membrane (or separator). The computationally obtained potential behavior based on the adsorption theory was in good agreement with the experimentally observed potential whether the membrane (or separator) was permeable to ions or not. It was strongly speculated that the membrane potential origin could lie primarily in the ion adsorption on the membrane (or separator) rather than the membrane permeability to ions. It might be necessary to reconsider the origin of membrane potential which has been so far believed explicable by the GHK equation. PMID:24957176

  13. Gas chromatographic determination of glutaraldehyde in the workplace atmosphere after derivatization with 0-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine on a solid-phase microextraction fibre.

    PubMed

    Pieraccini, Giuseppe; Bartolucci, Gianluca; Pacenti, Marco; Dugheri, Stefano; Boccalon, Pierpaolo; Focardi, Leonardo

    2002-04-26

    Glutaraldehyde is used primarily in hospital environments for the disinfection of various instruments (e.g., endoscopes). We describe in this paper the measurement of glutaraldehyde in a hospital environment using solid-phase microextraction. The method includes, prior to sampling, the adsorption of O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine on to the fibre (with polydimethylsiloxane-divinylbenzene). The fibre is then exposed to air, after which desorption is performed in the GC injection port. This process results in the formation of a stable derivative of the glutaraldehyde that is suitable for chromatographic purposes and detectable with classical detection methods, such as flame ionisation and electron-capture detection. We demonstrate that the procedure of adsorption, thermal desorption and derivatization is robust and reproducible. We were able to detect concentrations of 60 microg/m3 (10 s sampling) or 6 microg/m3 (120 s sampling) by electron-capture detection, and 80 microg/m3 (120 s sampling) by flame ionisation detection. We compared our method to currently existing methods of glutaraldehyde measurement and highlighted several important advantages of the method.

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

    PubMed

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

    2016-08-01

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

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

    PubMed

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

    2016-08-01

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

  16. Application of gas chromatographic method in simultaneous measurements of helium, argon and neon concentration in groundwaters

    NASA Astrophysics Data System (ADS)

    Najman, J.; Bielewski, J.; Sliwka, I.

    2012-04-01

    Helium concentration in groundwater is a fine indicator in water dating in a range from a hundred to tens of thousands of years. Gas chromatography (GC) measurements of helium can be used as an alternative to mass spectrometry (MS) determinations of 4He for groundwater dating [1]. Argon and neon concentrations mainly serve for determining the temperature of recharge and the air excess which is needed to correct measured values of helium concentration [2] . A chromatographic measurement system of helium, argon and neon concentration in groundwater is presented [3]. Water samples are taken from groundwater with a precise procedure without contamination with air in a special stainless steel vessels of volume equal to 2900 cm3. Helium is extracted from water samples using the head-space method. After enrichment by cryotrap method helium is analyzed in the gas chromatograph equipped with the thermal conductivity detector (TCD) with detection limit of about 2.8 ng He. The helium limit of detection of presented method is 1,2·10-8 cm3STP/gH2O [4]. We are currently working on adapting the method of cryogenic enrichment of helium concentration for simultaneous measurements of the concentration of helium, argon and neon using single sample of groundwater. Neon will be measured with the thermal conductivity detector and capillary column filled with molecular sieve 5A. Argon will be analyzed also with the thermal conductivity detector and packed column filled with molecular sieve 5A. This work was supported by grant No. N N525 3488 38 from the polish National Science Centre. [1] A. Zuber, W. Ciężkowski, K. Różański (red.), Tracer methods in hydrogeological studies - a methodological guide. Wroclaw University of Technology Publishing House, Wroclaw, 2007 (in polish). [2] P. Mochalski, Chromatographic method for the determination of Ar, Ne and N2 in water, Ph.D. thesis, Institute of Nuclear Physics Polish Academy of Sciences in Krakow, 2003 (in polish). [3] A. Żurek, P

  17. Preliminary Report on Monosodium Titanate Adsorption Kinetics

    SciTech Connect

    Hobbs, D.T.

    1998-12-11

    The Salt Disposition Systems Engineering Team identified the adsorption kinetics of actinides and strontium onto monosodium titanate (MST) as a technical risk for several of the processing alternatives selected for additional evaluation in Phase III of their effort. The Flow Sheet Team requested that the Savannah River Technology Center (SRTC) examine the adsorption kinetics of MST for several process alternatives.This study consisted of a statistically designed set of tests to determine the rate of adsorption of strontium, uranium, neptunium and plutonium as a function of temperature, MST concentration, and concentrations of sodium, strontium, uranium, neptunium and plutonium. Additional tests incorporated into the design assess the effects of mixing as well as the influence from the presence of sludge solids and sodium tetraphenylborate.

  18. GENERAL: Cluster Growth Through Monomer Adsorption Processes

    NASA Astrophysics Data System (ADS)

    Ke, Jian-Hong; Lin, Zhen-Quan; Chen, Xiao-Shuang

    2010-02-01

    We propose a monomer adsorption model, in which only the monomers are allowed to diffuse and adsorb onto other clusters. By means of the generalized rate equation we investigate the kinetic behavior of the system with a special rate kernel. For the system without monomer input, the concentration aj(t) of the Aj clusters (j > 1) asymptotically retains a nonzero quantity, while for the system with monomer input, it decays with time and vanishes finally. We also investigate the kinetics of an interesting model with fixed-rate monomer adsorption. For the case without monomer source, the evolution of the system will halt at a finite time; while the system evolves infinitely in time in the case with monomer source. Finally, we also suggest a connection between the fixed-rate monomer adsorption systems and growing networks.

  19. Novel nano bearings constructed by physical adsorption

    NASA Astrophysics Data System (ADS)

    Zhang, Yongbin

    2015-09-01

    The paper proposes a novel nano bearing formed by the physical adsorption of the confined fluid to the solid wall. The bearing is formed between two parallel smooth solid plane walls sliding against one another, where conventional hydrodynamic lubrication theory predicted no lubricating effect. In this bearing, the stationary solid wall is divided into two subzones which respectively have different interaction strengths with the lubricating fluid. It leads to different physical adsorption and slip properties of the lubricating fluid at the stationary solid wall respectively in these two subzones. It was found that a significant load-carrying capacity of the bearing can be generated for low lubricating film thicknesses, because of the strong physical adsorption and non-continuum effects of the lubricating film.

  20. Adsorption of hydroxyacetone on pure ice surfaces.

    PubMed

    Petitjean, Mélanie; Darvas, Maria; Picaud, Sylvain; Jedlovszky, Pál; Le Calvé, Stéphane

    2010-12-17

    The adsorption of hydroxyacetone molecules at the surface of ice is investigated by means of flow-tube reactor measurements in the temperature range: 213-253 K. The number of molecules adsorbed per surface unit is conventionally plotted as a function of the absolute gas concentration of hydroxyacetone and is compared to that previously obtained for acetone and ethanol. The enthalpy of adsorption and the monolayer capacity at the ice surface are determined. In addition, molecular dynamics simulations are performed to support the experimental results. However, it is shown that the available interaction potential between hydroxyacetone and ice is not accurate enough to allow a robust detailed analysis of the adsorption process. Finally, a rapid estimation of the hydroxyacetone partitioning between the gas phase and ice shows that in the densest ice clouds, up to 29% of hydroxyacetone could be adsorbed on pure ice surfaces at 203 K.