Showing papers on "Elution published in 1993"
TL;DR: The kinetics of binding and dissociation between a soluble analyte and an immobilized ligand on or near a surface are described numerically by an iterative computer model applied to a microflow chamber used for surface plasmon resonance measurements.
380 citations
TL;DR: A method for the identification of secondary aromatic lichen substances using high-performance liquid chromatography (HPLC) with reversed phase columns, gradient elution and benzoic and solorinic acids as standards has been developed as discussed by the authors.
256 citations
TL;DR: Good sensitivity for phosphopeptide detection was achieved using standard trifluoroacetic acid containing mobile phases for reversed-phase high-performance liquid chromatography.
239 citations
TL;DR: In this article, the authors compared the elution of atrazine and metolachlor residues from a long-contaminated soil under saturated flow to elution from freshly-injected compounds from the same soil.
Abstract: Elution of atrazine and metolachlor residues from a longcontaminated soil under saturated flow was compared to elution of freshly-injected compounds from the same soil. The mobility of the injected herbicide was far greater than the native. A two-compartment diffusion sorption model-having a fast compartment S 1 in rapid exchange with water and a slow compartment S 2 with erchange by radial diffusion kinetics-gave good simultaneous fits to native and injected elution curves and predicted flow rate effects and postleaching soil herbicide profiles. An analogous model with first-order kinetics was less successful
217 citations
TL;DR: An HPLC method using a normal-phase silica column and a gradient of dichloromethane-methanol-formic acid water mixtures as the eluent was developed to separate procyanidins on a molecular mass basis, without derivatization.
178 citations
TL;DR: The pH-zone refining countercurrent chromatography (pH-ZRC) as discussed by the authors is a countercurrent method that utilizes two immiscible solvent phases, one being acidic and one being basic, to partition solutes in contiguous, well-resolved, rectangularly shaped peaks in order of their partition coefficients.
150 citations
TL;DR: In this article, the authors suggest that analyte anions and their countercations combine to make ''ion-pairing-like'' forms and are separated by the simultaneous electrostatic attraction and repulsion interactions between the zwitterionic charged stationary phase, anion, and its countercation.
Abstract: Ion chromatography using «strong/strong» charged zwitterionic micellar-coated stationary phase with pure water as the mobile phase has been investigated for the separation of inorganic solutes and organic zwitterionic solutes. Retention mechanisms of the zwitterionic charged stationary phase in ion chromatography have also been investigated using a conductivity detector. For inorganic analytes, anions and their countercations are always eluted together. The retention times of inorganic solutes are only dependent on the anions. According to experimental results, we suggest that analyte anions and their countercations combine to make «ion-pairing-like» forms and are separated by the simultaneous electrostatic attraction and repulsion interactions between the zwitterionic charged stationary phase, analyte anion, and its countercation
117 citations
Book•
01 Apr 1993
TL;DR: Liquid Chromatography as a Research Tool Developing the Separation Considerations for Proper Operation of a Liquid Chromatograph Gradient Elution Chromatography Experiment 1.
Abstract: Liquid Chromatography as a Research Tool The Chromatogram and What Contributes to It Approaching the Problem Developing the Separation Considerations for Proper Operation of a Liquid Chromatograph Gradient Elution Chromatography Experiment 1: Demonstrating the Fundamentals Experiment 2: Normal-Phase Chromatography Experiment 3: Effect of Column Length and Recycle Experiment 4: Gel Permeation Chromatography Using Dual Detectors (UV and RI) Experiment 5: Developing a Reverse Phase Chromatographic Separation Experiment 6: Quantitation Experiment 7: Monitoring Kinetics Experiment 8: Preparative Liquid Chromatography Experiment 9: Analysis of Essential Oils (Steam Distillates) Experiment 10: Gradient Elution Index.
108 citations
TL;DR: In this article, a method for the simultaneous determination of mercury species at sub-ng l-1 levels in natural waters is described, where methyl, ethyl and inorganic mercury are first preconcentrated on a dithiocarbamate resin packed in a miniature 60 µl column incorporated in a closed and semi-automated flow injection system.
Abstract: A method for the simultaneous determination of mercury species at sub-ng l–1 levels in natural waters is described. The detection limits are 0.05 ng l–1 for methyl- and ethylmercury and 0.15 ng l–1 for inorganic mercury. Methyl-, ethyl- and inorganic mercury are first preconcentrated on a dithiocarbamate resin packed in a miniature 60 µl column incorporated in a closed and semi-automated flow injection system. The mercury species, which are quantitatively enriched on the resin, are completely eluted with an acidic thiourea solution, extracted into toluene as diethyldithiocarbamate complexes and butylated with a Grignard reagent. The butylated forms (2–40 µl) are injected into a gas chromatograph equipped with a retention gap, linked to a non-polar analytical column, and detected at 253.7 nm with an atomic emission detector after excitation in a microwave-induced plasma.
96 citations
TL;DR: A multiresidue analytical method based on C18 solid-phase extraction and one-run HPLC determination has been developed for the analysis of eleven acidic, neutral and weak basic herbicides in drinking water.
88 citations
TL;DR: The simple mobile phase, the extremely sensitive detection limit, and the stability of the complex make this system applicable to routine clinical analysis with a small amount of tissue or biopsy sample.
Patent•
18 Jan 1993TL;DR: In this paper, a method of streamlining and lowering the cost of operation of ion chromatography as well as improving detection limits is disclosed, which includes chromatographic separating means through which a sample is eluted in an eluent solution including an electrolyte.
Abstract: A method of streamlining and lowering the cost of operation of ion chromatography as well as improving detection limits is disclosed. The apparatus includes chromatographic separating means through which a sample is eluted in an eluent solution including an electrolyte. The apparatus includes suppressor means having a chromatography effluent compartment means separated from a detector effluent compartment means by an ion exchange membrane, forming a chromatography effluent flow channel and a detector effluent channel, respectively. Electrode means are disposed in communication with both flow channels for passing an electric current transverse to the solution that is passing through them. The chromatography effluent flows through the chromatography effluent flow channel of the suppressor and through detector means which detects resolved ionic species therein. The effluent from the detector means is then recycled through the detector effluent flow channel and forms a sump for electrolyte ions passing across the chromatography effluent as well as supplying the water for the electrolysis reaction generating acid (or base) for suppression.
TL;DR: In this article, graphitized carbon black (GCB) is used to act as both a reversed phase and an anion exchanger for the extraction of acids from water, and a tetramethylammonium hyroxide-basified solvent mixture is the most effective eluent for the rapid elution from a GCB extraction of any kind of organic acid.
TL;DR: A solid-phase extraction procedure was developed for the isolation of heroin, 6-acetylmorphine, and morphine from blood, plasma, saliva, and urine with subsequent assay by gas chromatography/mass spectrometry to corroborate heroin use and to study the pharmacological effects of heroin and its metabolites.
Abstract: A solid-phase extraction procedure was developed for the isolation of heroin, 6-acetylmorphine, and morphine from blood, plasma, saliva, and urine with subsequent assay by gas chromatography/mass spectrometry. Aprotic solvents, mild elution conditions, and an enzyme inhibitor were used to ensure maximum analyte stability. Samples were extracted and the extract was divided into two equal portions. One portion was assayed directly for heroin; detector response was linear over a concentration range of 1.0 to 250 micrograms/L. The second part of the extract was reacted with N-methyl-bis-trifluoroacetamide and assayed for the trifluoroacetyl derivatives of 6-acetylmorphine and morphine; detector response was linear over a concentration range of 1.0 to 500 micrograms/L. The limit of sensitivity was 1.0 microgram/L for each analyte. Hydrolysis of heroin to 6-acetylmorphine during extraction and analysis was < 5%. The method can be used to corroborate heroin use and to study the pharmacological effects of heroin and its metabolites.
TL;DR: High-performance liquid chromatography was used for the characterization of sophorolipids, one of the most important types of glycolipid biosurfactants, and led to the identification of almost all significant compounds observed in HPLC, including several previously unreported sophorlipids.
TL;DR: The coupling of electrospray ionization mass spectrometry with gel permeation chromatography (GPC) has been used for the separation of a commercial polydisperse mixture of octylphenoxypoly(ethoxy)ethanol.
Abstract: The coupling of electrospray ionization mass spectrometry with gel permeation chromatography (GPC) has been used for the separation of a commercial polydisperse mixture of octylphenoxypoly(ethoxy)ethanol. Stable electrospray conditions are obtained upon using, as GPC solvent, tetrahydrofuran containing 10−5−10−4M sodium salt which also provides for the formation of intact molecular ions through cationization. Selected-ion chromatograms of sodiated species allow for the monitoring of the elution profiles of individual oligomers, and can be used for the calibration of the GPC.
TL;DR: In this paper, a model for the migration rate of polymers, based on the assumption that interstitial channels in a packed column can be represented by a bundle of capillary tubes, is compared with experimental elution data.
TL;DR: A semi-automated flow-injection system was developed for on-line sample preparation for the determination of mono-, di- and tributyl- and phenyltin compounds in water as discussed by the authors.
TL;DR: In this article, a combined capillary electrophoresis/mass spectrometry (CE/MS) method is described that provides an increase in the efficiency of analysis by decreasing the analyte elution rate into an electrospray ionization (ESI) interface.
Abstract: A combined capillary electrophoresis/mass spectrometry (CE/MS) method is described that provides an increase in the efficiency of analysis by decreasing the analyte elution rate into an electrospray ionization (ESI) interface. The method is readily implemented by instituting a step change in the CE electric field strength for desired periods of time during a separation. As a result, the m/z range or the number of times an m/z range can be scanned while a solute elutes is increased by a factor proportional to the decrease in CE electric field strength. In addition, the method is shown not to cause any significant loss in separation quality as demonstrated for mixtures of proteins and peptides, while providing an effective gain in sensitivity. This allows an enhancement in the quality of mass spectra recorded while scanning wide m/z ranges. Mass spectra for a set of standard proteins were obtained for injections of 60 femtomole/protein, while analysis of an albumin tryptic digest was obtained for injections corresponding to 40 femtomoles of protein.
TL;DR: In this paper, a model to describe the retention behavior of solutes in any mobile phase of surfactant and alcohol is proposed, which makes use of the elution data in five mobile phases with different amounts of alcohol.
TL;DR: Filtration membranes carrying strong cation- or anion-exchange groups on their surface were evaluated for their potential as membrane adsorber stationary phases in the high-performance liquid chromatography of proteins.
TL;DR: In this article, a method was developed to analyze 11 compounds, which may occur in fresh or fermented cucumbers, by a single injection onto a polymeric sulfonated styrene-divinylbenzene cation ion-exchange column.
Abstract: A method was developed to analyze 11 compounds, which may occur in fresh or fermented cucumbers, by a single injection onto a polymeric sulfonated styrene-divinylbenzene cation ion-exchange column. Isocratic elution with 1.6 mM heptafluorobutyric acid resulted in separation and elution of the following compounds in 28 min: glucose, fructose, glycerol, ethanol, 1-propanol, malic acid, succinic acid, lactic acid, acetic acid, propionic acid, and butyric acid. A conductivity detector for determination of organic acids and a pulsed amperometric detector for analysis of sugars and alcohols were connected in series to analyze these compounds without interferences
TL;DR: Reversed-phase high-performance liquid chromatography was adapted for the determination of trace concentrations of carbaryl and seven organophosphorus pesticides in drinking water and the preconcentration yields of the examined solutes obtained with the two types of precolumn are almost identical.
TL;DR: The changes in the Fl/HyFFF elution profiles indicate that the RBCs decrease in size but become partially aggregated in the presence of the dextran, and these changes were found to depend on polymer concentration and specific blood samples.
TL;DR: In this paper, a procedure for column calibration with vesicles is proposed, in order to obtain the selectivity curve of the TSK-G6000 PW gel; this appears to be the most convenient gel for sizing of liposomes.
TL;DR: In this article, the feasibility of employing peroxyoxalate chemiluminescence (PO-CL) detection in capillary electrophoresis (CE) was demonstrated using a two-step approach for the CE separation and dynamic elution (elution under pressure) of the analytes.
TL;DR: In this article, a rationalization is presented as to the possible origin of temperature-dependent enantioselectivity of chiral stationary phases, which is related to the nature and concentration of the polar modifier in the mobile phase and requires particular chiral phase analyte-mobile phase combinations.
Abstract: Typically, reduction of column temperature increases the enantioselectivity of a chiral stationary phase. An instance in which progressive reduction of temperature initially reduces enantioselectivity, then inverts the elution order of the enantiomers, and finally causes enantioselectivity to increase has been observed. This behavior is related to the nature and concentration of the polar modifier in the mobile phase, and requires particular chiral phase-analyte-mobile phase combinations. A rationalization is presented as to the possible origin of this behavior. This rationale may aid in finding other examples of this temperature-dependent elution order of enantiomers and ultimately increase our understanding of chiral recognition processes.
TL;DR: This study confirms that bandwidth measurements can be used as an integral experimental component to study the effect of the secondary structure of peptidic solutes on their RP-HPLC retention behavior and demonstrates the utility of RP- HPLC as a tool to examine peptide conformational dynamics at hydrophobic surfaces.
Abstract: The dynamics of several peptides in reversed-phase high-performance liquid chromatography (RP-HPLC) have been investigated on both n-octadecyl (C18) silica and n-butyl (C4) silica sorbents. In particular, the conformational interconversions and the relative rates of chromatographic relaxation of bombesin, glucagon, and beta-endorphin on both C18 and C4 n-alkylsilicas were monitored by examining changes in the experimental bandwidths of these peptides as a function of temperature and column residence time under linear gradient elution RP-HPLC conditions. The observed band-broadening trends were correlated with previously derived retention parameters and thermodynamic descriptors of the association process determined for bombesin, beta-endorphin, glucagon, and a control peptide, penta-L-phenylalanine. This study confirms that bandwidth measurements can be used as an integral experimental component to study the effect of the secondary structure of peptidic solutes on their RP-HPLC retention behavior. Further, the data demonstrate the utility of RP-HPLC as a tool to examine peptide conformational dynamics at hydrophobic surfaces. The relevance of these results to the general phenomenon of peptide-lipid interactions is discussed in terms of the associated evidence for lipid-induced changes in the conformation of these three bioactive peptides.
Book•
01 Jan 1993
TL;DR: The theory of chromatographic separations with reference to gas chromatography has been discussed in this article, where the development, technology and utilization of capillary columns for gas chromation are discussed.
Abstract: Introduction to the theory of chromatographic separations with reference to gas chromatography Gas chromatography instrumentation, operation, and experimental considerations The development, technology and utilization of capillary columns for gas chromatography Applications of packed and capillary GC Chemical derivatization in gas chromatography Gas chromatography in analytical toxicology - Principles and practice Gas chromatography in clinical chemistry Chrial separations by gas chromatography Environmental analysis using gas chromatography The role of gas chromatography in petroleum exploration Combined instrumental techniques using gas chromatography. Appendices.
Patent•
03 Aug 1993
TL;DR: An automated integrated system for programmably selectively extracting and purifying one or more particular solutes from a contaminated solution, then being recovered as a concentrated solution suitable for analysis is described in this article.
Abstract: An automated, integrated system for programmably selectively extracting and purifying one or more particular solutes from a contaminated solution, said purified solutes then being recovered as a concentrated solution suitable for analysis.