Showing papers in "Journal of Liquid Chromatography & Related Technologies in 1983"
TL;DR: In this article, a repeating sequence of three potentials electrochemically cleans the electrode surface of oxidation products and other interfering species, such as disaccharides and alcohols.
Abstract: Carbohydrates such as sugar alcohols, monosaccharides, disaccharides, and other oligosaccharides are separated as anions by ion exchange chromatography with a sodium hydroxide eluent. Retention time and selectivity are controlled by varying eluent strength and column temperature. The carbohydrates are detected by oxidation at a gold electrode. A repeating sequence of three potentials electrochemically cleans the electrode surface of oxidation products and other interfering species. Detection limits are as low as 30 ppb for sugar alcohols and monosaccharides, and about 100 ppb for oligosaccharides. Other species containing CHOH groups can also be detected, such as alcohols and glycols.
426 citations
TL;DR: In this article, the preparation of HPLC carbons is reviewed in detail and the results which have been obtained are assessed in terms of their kinetic and thermodynamic performance, and applications are reviewed.
Abstract: Early work on use of carbons for liquid chromatography shows that special carbons must be developed if carbon is to be useful in HPLC. The processes used to make carbons, the properties of such carbons and the requirements for HPLC carbons are discussed. The preparation of HPLC carbons is reviewed in detail and the results which have been obtained are assessed in terms of their kinetic and thermodynamic performance. Applications are reviewed.
93 citations
TL;DR: In this article, a pulsedpotential waveform applied at a frequency of ca. 1 Hz is demonstrated to provide direct amperometric detection of adsorbed amino acids at a Pt electrode.
Abstract: It is the general experience that most organic compounds including amino acids do not produce reversible or even quasi-reversible anodic waves at a Pt electrode under conditions of conventional cyclic voltammetry. Furthermore, amperometric detection of these compounds at a constant electrode potential is not successful because of the accumulation of adsorbed reaction products and/or an oxide film at the electrode surface. However, it is observed that a Pt electrode surface is cleaned quite effectively of adsorbed organic molecles and radicals simultanaeously with the anodic formation of the oxide layer. This oxidation of adsorbed organic species is concluded to be electrocatalyzed by PtOH formed as the first step in the production of the oxide layer (PtO). A pulsed-potential waveform applied at a frequency of ca. 1 Hz is demonstrated to provide direct amperometric detection of adsorbed amino acids at a Pt electrode. Satisfactory analytical precision (i.e., < 3% rel. std. dev.) results because the...
78 citations
TL;DR: In this paper, a trifluoroacetic acid/2-propanol mobile phase system was used for HPLC of proteins on reversed-phase columns of varying n-alkyl chain length.
Abstract: High-performance liquid chromatography (HPLC) of proteins on reversed-phase columns of varying n-alkyl chain length (C2 to C22 was studied using a trifluoroacetic acid/2-propanol mobile phase system. Protein resolution was influenced by chain length but retention times for proteins, unlike those of small molecules, were relatively constant, independent of chain length or carbon loading. Loading capacities were found to be affected by chain length, and aspects of protein interaction with stationary phase are discussed.
56 citations
TL;DR: In this article, the use of Sephadex G 10 (which allows a rapid sample purification for 11 compounds) appeared an attractive alternative when direct injection techniques cannot be applied, and various aspects of the routine use of the electrochemical detector at a sensitive setting are discussed.
Abstract: Analysis of catecholamines and related metabolites is often based on direct injection on the HPLC column of supernatants of centrifuged brain homogenates. In this study we have investigated to what extent direct injection techniques are also useful for analysis in the picogram-range. The use of Sephadex G 10 (which allows a rapid sample purification for 11 compounds) appeared an attractive alternative when direct injection techniques cannot be applied. Various aspects of the routine use of the electrochemical detector at a sensitive setting are discussed. Finally the identity of small peaks in the chromatogram is addressed.
55 citations
TL;DR: In this paper, a method for determining a-tocopherol in liver and other biological specimens is described, where hexane extracts of saponified samples are acid-washed and then injected onto a reversed phase column using hexane:propan-2-ol (99:1 v/v) for elution, and fluorimetry at 210 nm excitation for detection.
Abstract: A method is described for determining a-tocopherol in liver and other biological specimens. Hexane extracts of saponified samples are acid-washed and then injected onto a reversed phase column using hexane:propan-2-ol (99:1 v/v) for elution, and fluorimetry at 210 nm excitation for detection.
54 citations
TL;DR: In this article, the amount of saturated phospholipid in a zone on a thin layer chromatogram (TLC) can be calculated by the difference in reactivity.
Abstract: Cupric acetate (3% in 8% phosphoric acid) as a charring agent reacts only with unsaturated phospholipids while cupric sulfate (10% in 8% phosphoric acid) reacts with both saturated and unsaturated phospholipids. Thus, the amount of saturated phospholipid in a zone on a thin layer chromatogram (TLC) can be calculated by the difference in reactivity. An evaluation of methods shows that direct application of biological samples to TLC for separation and quantitation of phospholipids is reproducible. The use of these techniques for a number of different samples is described.
53 citations
TL;DR: In this article, a detector made full use of the advantages offered by chemiluminiscence has been constructed for light measurement with modern electronic equipment using photon counting and the system was tested using dansyl derivatives of adrenaline, noradrenaline and of some amino acids.
Abstract: A detector making full use of the advantages offered by chemiluminiscence has been constructed. Light measurement was performed with modern electronic equipment using photon counting and the system was tested using dansyl derivatives of adrenaline, noradrenaline and of some amino acids. The detection limits for the two catecholamines were 6 and 16 fmol, respectively, and less than 0.5 fmol for the amino acids. To reach these low levels all reagents were purified or selected for ultra-high purity. The effects of reagent contaminants and of various optical filters have been studied using adrenaline as the test substance.
52 citations
TL;DR: In this paper, the Kel-F-graphite (Kelgraf) electrode was shown to possess a signal-to-noise (S/N) advantage compared to continuous electrodes such as glassy carbon when used for detection of analytes in flowing streams.
Abstract: Results obtained in this laboratory and elsewhere suggest that carbon composite electrodes may possess a signal-to-noise (S/N) advantage compared to continuous electrodes such as glassy carbon when used for detection of analytes in flowing streams. One succomposite electrode which appears partic- ularly attractive in this regard is the Kel-F-graphite (Kelgraf) electrode, compression molded from Kel-F and powdered graphite and containing 5 to 30% graphite by weight. Studies of the electrode surface by scanning electron microscopy and X-ray photoelectron spectroscopy in conjunction with electrochemical investigations employing chronoamperometry, cyclic voltammetry, and capacitance measurements have led us to view the electrode surface as an ensemble of rnicroelectrodes, the dimensions of which can be varied by changes in particle size and/or ratio of Kel-F to graphite in the composite. The S/N advantage of the composite electrode apparently arises from a signal (current) enhanced by radial diffusio...
49 citations
TL;DR: Reverse-phase, ion exchange, and reverse-phase ionpairing were evaluated as liquid chromatographic modes for the isocratic separation of cysteine, cystine, glutathione (reduced and oxidized), homocysteine and penicillamine (Reduced and Oxified).
Abstract: Reverse-phase, ion-exchange, and reverse-phase ion-pairing were evaluated as liquid chromatographic modes for the isocratic separation of cysteine, cystine, glutathione (reduced and oxidized), homocysteine, and penicillamine (reduced and oxidized). A series dual Hg/Au amperometric detector was used to detect both thiols and disulfides. Reverse-phase ion-pairing was determined to provide the most satisfactory performance for a liquid chromatographic separation of the compounds of interest.
44 citations
TL;DR: In this paper, a method for the determination of formaldehyde and other aldehydes has been developed based on the reaction of the aldehyde species with 2-diphenylacetyl-1,3-indandione-1-hydrazone to form fluorescent azine derivatives.
Abstract: A sensitive, uncomplicated, and rapid method for the determination of formaldehyde and other aldehydes has been developed. The method is based on the reaction of the aldehyde species with 2-diphenylacetyl-1,3-indandione-1-hydrazone to form fluorescent azine derivatives. The fluorescence excitation and emission spectra have been obtained for several derivatives. The method developed eliminates the lengthy recovery steps required in other methods by performing the sample collection and derivatization directly in midget impingers containing an acetonitrile solution of the reagent. High performance liquid chromatography with fluorescence detection is used to separate and quantitate the individual aldehydes. The detection limits for formaldehyde, acetaldehyde, acrolein, and benzaldehyde are 6 ppb, 4.5 ppb, 0.6 pb, and 0.15 ppb, respectively, in the exhaust gas. The analysis time for the method is about 10 minutes if only one or two aldehydes are of interest. This technique has been used to measure ald...
TL;DR: In this paper, a reversed-phase high performance liquid chromatography (HPC) was used to separate uroporphyrin I and III isomers by using ODS-Hypersil with ammonium acetate buffer-acetonitrile solvent systems.
Abstract: The separation of uroporphyrin I and III isomers by reversed-phase high performance liquid chromatography on ODS-Hypersil with ammonium acetate buffer-acetonitrile solvent systems is described. The effects of buffer concentration, pH, organic modifier proportion and different organic modifiers on the resolution are studied. The optimum conditions for the separation were 12–13% acetonitrile in 1M ammonium acetate buffer pH 5.10–5.20. The method also separated uroporphyrin I and III from the II isomers but the resolution of uroporphyrin III and IV isomers was not achieved.
TL;DR: In this paper, the authors present an online type derivatization-separation-detection or separation-derivatizationdetection method for high performance liquid chromatography (HPLC) analytes.
Abstract: As in all other forms of chromatography, high performance liquid chromatography (HPLC) has come to rely quite heavily on derivatization of individual analytes for improved qualitative and quantitative identifications (1–13). Virtually all of this work has involved the use of homogeneous type derivatizations, wherein the sample solution to be injected, in the pre-column approach, or the HPLC effluent, in the post-column approach, are fully mixed with the derivatization reagents in solution. Clearly, homogeneous type derivatizations can be done off-line or on-line, in either the pre-or post-column modes, but in general, pre-column methods have been done offline, and post-column approaches have been done both on-line and off-line. Online type derivatizations, in either the pre-or post-column modes, appear to offer some very significant advantages. Major among these is the ability to perform derivatization-separation-detection or separation-derivatization-detection following injection of the sample m...
TL;DR: The emergence of bacterial strains resistant to antibiotics is a matter of increasing concern to the medical profession and necessitates the continuing search for new antimicrobial agents and judicious therapy with the ones already in use.
Abstract: The discovery of penicillin and subsequently other antibiotics represents one of the great progresses in modern medicine Newer agents, such as the aminoglyco-sides and the cephalosporins, have also contributed significantly to man's struggle against bacterial and fungal infections, and antiviral agents are expected to emerge in the next decades The evergrowing number of antibiotics have, however, also given rise to several problems The emergence of bacterial strains resistant to antibiotics is a matter of increasing concern to the medical profession and necessitates the continuing search for new antimicrobial agents and judicious therapy with the ones already in use Many antibiotics exert undesired toxic side effects when given in excessive doses: examples are the oto-and nephrotoxicity of aminoglycosides, the bone-marrow depressant action of chloramphenicol and the nephrotoxic effects of some of the early cephalosporins Even a comparatively nontoxic drug such as penicillin causes coma and c
TL;DR: It is shown that the decline in oxidation current during the initial sampling period is due primarily to a decrease in ascorbic acid.
Abstract: A comparison is made of chronoamperometric data recorded from the striatum and chromatographic data obtained from extracellular striatal perfusate. Three specific cases are considered: the initial sampling period in which a decline in the observed oxidation current occurs; the effect of haloperidol, a dopamine receptor blocker; and the effect of amphetamine. The perfusate is analyzed for ascorbic acid (AA), the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), and the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA). Using the relative response of these compounds at a carbon epoxy or carbon paste electrode, and the relative concentration of each in the extracellular fluid, the expected changes in oxidation currents for the three cases mentioned above are calculated. It is shown that the decline in oxidation current during the initial sampling period is due primarily to a decrease in ascorbic acid. It is also shown that different electroactive components ...
TL;DR: A variety of chromogenic and fluorogenic detection reagents were evaluated for detection and densitometric quantification of lipids and phospholipids on silica gel and chemically bonded octadecylsilane reversed phase thin layer plates.
Abstract: A variety of chromogenic and fluorogenic detection reagents were evaluated for detection and densitometric quantification of lipids and phospholipids on silica gel and chemically bonded octadecylsilane reversed phase thin layer plates. Phosphosphomolybdic acid (PMA) was found to be the most generally favorable reagent, followed by cupric acetate and ethanolic sulfuric acid. The quantification of lipids in blood serum by chemically bonded RP-TLC was demonstrated using PMA with direct sample application to preadsorbent plates.
TL;DR: Investigation of enzyme immunoassays based on chromatographic separation and amperometric detection of an enzyme generated product have been investigated, finding them to combine the selectivity of the antigen/antibody reaction with the high sensitivity of thin layer amperometry.
Abstract: Enzyme immunoassays based on chromatographic separation and amperometric detection of an enzyme generated product have been investigated. These assays combine the selectivity of the antigen/antibody reaction with the high sensitivity of thin layer amperometry. The feasibility of utilizing LCEC as a detection scheme was demonstrated using the Syva EMIT® kit for phenytoin. NADH production by glucose-6-phosphate dehydrogenase was monitored following a homogeneous procedure. Heterogeneous assays were developed for alkaline phosphatase labeled species which were based upon LCEC determination of phenol. Assays were designed for a common serum glycoprotein (orosomucoid) and a clinically important drug (digoxin). Detection limits approach the pg/mL level and as such may prove fruitful in the quantitation of numerous antigens of clinical interest.
TL;DR: In this article, it was shown that Cd, Co, Cu, Pb, Hg and Ni impurities can be simultaneously determined at concentrations less than or equal to 1 ppm using a combination of solvent extraction, high performance liquid chromatography and electrochemical or spectrophotometrie detection.
Abstract: The current efficiency (cost) of electrolytic production of high purity metallic zinc from zinc sulfate plant electrolyte is critically dependent on the concentration of a number of trace elements. The matrix, containing a very large concentration excess of zinc sulfate in concentrated sulfuric acid presents difficulties for determining low concentrations of other metals with many analytical methods. In this work it is shown that Cd, Co, Cu, Pb, Hg and Ni impurities may be simultaneously determined at concentrations less than or equal to 1 ppm using a combination of solvent extraction, high performance liquid chromatography and electrochemical or spectrophotometrie detection. Solvent extraction utilizes the formation of pyrrolidine dithiocarbamate complexes, which after removal of zinc complexes and excess ligand on an anion exchange column can be separated on a C-18 reverse phase chromatographic column and detected by UV/Visible spectrophotometrie or electrochemical detection. Other combinations...
TL;DR: In this paper, an HPLC method was described for rapid analysis of caffeine and seven of its metabolites in plasma, urine, milk and saliva in a single operation using a 5 μ C18 reverse phase column.
Abstract: An HPLC method is described for rapid analysis of caffeine and seven of its metabolites in plasma, urine, milk and saliva in a single operation using a 5 μ C18 reverse phase column. The metabolites are extracted with chloroform - iso-propanol (85:15) from 100 μL samples added to NH4HCO3. No interference from normal blood, urine, milk or saliva constituents was observed. The method is accurate and precise and separates 1,7-dimethylxanthine (paraxanthine) from 1,3-dimethylxanthine (theophylline). Sensitivity for most metabolites is in the range of 0.1 to 0.3 μg/mL and the detectability is at the nanogram level.
TL;DR: In this article, a C-18 reverse phase column packing was used for automated analysis of rat brain regional extracts for dopamine, dihydroxyphenyl acetic acid, homovanillic acid, serotonin, and 5-hydroxyindole acetic acids.
Abstract: Techniques have been developed to permit rapid and accurate automated analyses of rat brain regional extracts for dopamine, dihydroxyphenyl acetic acid, homovanillic acid, serotonin, and 5-hydroxyindole acetic acid. Separations on a C-18 reverse phase column packing were effected with the following mobile phases: one phase consisted of a solution of 1 mM EDTA pus 400 mM sodium acetate, at pH 4.0, mixed with 0.015 volume of methanol; the second phase consisted of 1 mM EDTA plus 500 mM sodium acetate, at pH 5.0. Chemical stability of the 5-hydroxyindole compounds was achieved by adding bisulfite to the perchloric acid homogenizing solution immediately prior to preparation of extracts. Time-related alterations in response of the electrochemical detector were monitored by repeated intermittent analysis of reference tissue extracts during an automated run; results obtained from analyses of the reference solutions permitted construction of detector response curves which were used to correct integrator ...
TL;DR: In this paper, the accuracy and precision of the method was evaluated using plasma samples spiked with ascorbic acid (10 μg/ml) and the results were also compared to the classical colorimetric procedure.
Abstract: Following the stabilization of the plasma samples with HClO4 and EDTA, the samples could be directly analyzed by HPLC using electrochemical detection and reversed-phase columns. The accuracy and precision of the method was evaluated using plasma samples spiked with ascorbic acid (10 μg/ml) and the results were also compared to the classical colorimetric procedure. Dehydroascorbic (5 μg/ml) was determined in plasma samples using UV detection following derivatization at room temperature for 45 minutes with o-phenylenediamine.
TL;DR: A method for mobile phase selection for optimal separation in reversed-phase high pressure liquid chromatography is presented based on a plot of solute retention time versus binary mobile phase composition.
Abstract: A method for mobile phase selection for optimal separation in reversed-phase high pressure liquid chromatography is presented. The system is based on a plot of solute retention time versus binary mobile phase composition. A total of five data points are required. The method is simple and does not require a computer for data analysis.
TL;DR: In this paper, an HPLC method was described for the extraction and analysis of iodine as iodide in milk, cocoa beans and milk chocolate, using an 8 mm 5μ C18 cartridge in a RCM-100 with detection of the iodide ion at 226 nm.
Abstract: An HPLC method is described for the extraction and analysis of iodine as iodide in milk, cocoa beans and milk chocolate. Prior to analysis samples are finely ground if necessary and combusted in a modified Shoeninger flask. The liberated halide is absorbed in a basic reducing medium which is concentrated and brought to volume with distilled water prior. HPLC analysis used an 8 mm 5μ C18 cartridge in a RCM-100 with detection of the iodide ion at 226 nm. The mobile phase consisted of an ion-pairing agent, buffer and acetonitrile. The method is accurate and precise showing reasonable agreement with a National Bureau of Standards spray dried milk sample.
TL;DR: In this paper, HPLC trace enrichment techniques were used to monitor the amount of organics in water stored in various types of containers, starting with initial, high purity water, it was shown that organics could be detected in as little as one hour after storage in plastic containers.
Abstract: Experimental results are presented which indicate that the quality of high purity water degrades with storage time. HPLC trace enrichment techniques were used to monitor the amount of organics in water stored in various types of containers. Starting with initial, high purity water, it was shown that organics could be detected in as little as one hour after storage in plastic containers. Organics could also be detected if the water was stored in glass.
TL;DR: The 3-phenylbenzopyrone is a natural plant constituent with a structure based on the aromatic heterocycle, which is ideally suited for analysis by HPLC as discussed by the authors.
Abstract: During the past ten years there has been a dramatic increase of interest in the field of flavonoid chemistry. This was mainly due to the application of HPLC to the study of flavonoids. These compounds, natural plant constituents with a structure based on the aromatic heterocycle, 3-phenylbenzopyrone, are ideally suited for analysis by HPLC. The basic complex structure can be varied by the number and position of hydroxyl substituents and other derivatives (sugars, methyl). These variations cause changes in the way the compounds react to solvents and columns commonly used in HPLC allowing separation and identification.
TL;DR: In this paper, the fractionation of amino acid specific tRNAs by descending salt gradient on a reversed-phase high-performance liquid chromatography column is demonstrated, and the concentration of organic modifier to adjust elution profiles can be critical in terms of tRNA retention.
Abstract: Fractionation of amino acid specific tRNAs by descending salt gradient on a reversed-phase high-performance liquid chromatography column is demonstrated. Stationary phase variables such as n-alkyl chain length and silica type are discussed in terms of stability and selectivity. Mobile phase parameters including salt concentration, organic modifier, pH, and temperature are investigated. The concentration of organic modifier to adjust elution profiles can be critical in terms of tRNA retention.
TL;DR: A reverse phase high-performance liquid chromatographic method for the quantitative determination of α-amanitin in serum of poisoned patients is described and discussed in this paper, which is simple and rapid with a minimum of sample preparation steps required.
Abstract: A reverse-phase high-performance liquid chromatographic method for the quantitative determination of α-amanitin in serum of poisoned patients is described and discussed. The methodology developed is simple and rapid with a minimum of sample preparation steps required. Detection is very sensitive, allowing quantitation of 25 ng of α-amanitin/ml of serum. The technique described is a useful tool to determine the severity of Amanita phalloides intoxication during the first 24 h after ingestion of poisonous mushrooms.
TL;DR: In this paper, a liquid chromatographic method coupled with electrochemical detection was developed to measure plasma trazodone and its metabolite 1-m-chlorophenylpiperazine (m-CPP).
Abstract: A liquid chromatographic method coupled with electrochemical detection was developed to measure plasma trazodone and its metabolite 1-m-chlorophenylpiperazine (m-CPP). Following extraction from 1 ml of alkaline plasma with methyl-t-butyl ether, the extracts were chromatographed on a reversed phase trimethylsilyl bonded column using a 0.05 M phosphate buffer and acetonitrile (90:10) with n-nonylamine and sodium heptane sulfonate added to the mobile phase. The compounds were detected via a thin layer electrochemical transducer with glassy carbon electrodes at a potential of + 1.15V vs Ag/AgCl reference electrode. The recovery of trazodone ranged from 91–97% and the coefficient of variation was less than 5% for between run and within-run analyses. The recovery of m-CPP ranged from 82–86% and the coefficient of variation was less than 8% for between run and within-run analysis. Steady state plasma concentration data are presented from several patients.
TL;DR: In this paper, a two-dimensional TLC was used to separate anionic and nonionic surfactants using a special silica gel plate containing a 2.5 cm strip of reversed phase material along one edge.
Abstract: TLC is a potentially powerful technique for the separation of surfactants. Reversed phase thin layer chromatography (RPTLC) can be used to separate entire classes of surfactants (i.e., anionics from nonionics from cationics). Conversely, silica gel can be used to separate individual anionic or cationic surfactants from other similarly charged surfactants. RPTLC can also be used to separate individual nonionic surfactants. Using two dimensional TLC (with a special silica gel plate containing a 2.5 cm strip of reversed phase material along one edge) a complex mixture of surfactants was first fractionated into classes and then (using the second dimension) into individual components. Standard scanning densitometry was used for quantitation.
TL;DR: In this article, the separation of 19 amino acids was studied on reversed phase thin layers, including C18 chemically bonded silica gel, impregnated silica gels, and acetylated cellulose.
Abstract: The separation of 19 amino acids was studied on reversed phase thin layers, including C18 chemically bonded silica gel, impregnated silica gel, and acetylated cellulose. Normal aqueous-organic solvents, aqueous micellar solutions, and reversed micellar solutions were tested as mobile phases. The only practical system that provided a reversal in migration sequence compared to silica gel and cellulose included a C18 layer impregnated with HDBS, and this reversal was apparently due to an ion exchange mechanism.