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  • Column liquid chromatography  (1,216)
  • Springer  (1,216)
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  • 1
    Electronic Resource
    Electronic Resource
    The effect of pH on the high pH anion-exchange chromatography elution of monosaccharides (1999)
    Springer
    Chromatographia 49 (1999), S. 699-702 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange chromatography ; High ph elvents ; Monosaccharides ; Carbopac PA-100
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We have studied the elution behaviour of six common monosaccharides, fucose, galactosamine, glucosamine, galactose, glucose and mannose, on the CarboPac PA-100 column. The relative elution positions of galactose, glucose and mannose were dependent on the sodium hydroxide concentrations, a phenomenon which was likely to be the result of differential ionisation of the hydroxyl groups at ring positions two and four. The optimal resolution of the monosaccharides studied was achieved by elution with 30 mM sodium hydroxide with no appreciable loss in sensitivity at this low concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466915
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  • 2
    Electronic Resource
    Electronic Resource
    High performance liquid chromatography method for the determination of meropenem in human plasma (1999)
    Springer
    Chromatographia 49 (1999), S. 253-255 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Meropenem in human plasma ; Solid phase extraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper describes an HPLC method for the determination of meropenem in human plasma. The method uses solid phase extraction (SPE) of the samples and has good sensitivity, precision and accuracy. The limit of quantification in plasma samples is 0.02 μg mL−1. Calibration curves were linear over a large dynamic range, namely within 0.02–50 μg mL−1. The method was applied to the determination of meropenem levels in patients receiving meropenem, as a single dose or at steady state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467552
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  • 3
    Electronic Resource
    Electronic Resource
    FMOC-Cl as derivatizing agent for the analysis of amino acids and dipeptides by the absolute analysis method (1999)
    Springer
    Chromatographia 49 (1999), S. 317-320 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Amino acids ; FMOC derivatives ; Oligopeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary One classical method for quantitation of amino acids in proteins is hydrolysis of the proteins and determination of the free amino acids. Although the drastic experimental conditions necessary for complete hydrolysis always cause degradation of some of the amino acids, if mild hydrolysis conditions are used, a mixture of amino acids and oligopeptides is obtained. If these conditions are adequately tuned, the oligopeptides are almost exclusively dipeptides. For this reason we have initiated a study to find a derivatizing agent suitable for the analysis of amino acids and dipeptides by an absolute method of quantitation already tested for amino acids. FMOC-Cl was found to be a suitable derivatizing agent for this purpose.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467563
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  • 4
    Electronic Resource
    Electronic Resource
    Potentiometric detection of monovalent anions separated by ion chromatography using all solid-state contact PVC matrix membrane electrode (1999)
    Springer
    Chromatographia 49 (1999), S. 338-342 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion chromatography ; Monovalent anions determination ; Potentiometric detection ; Ion selective PVC-matrix electrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An all solid-state contact tubular PVC-matrix membrane electrode has been applied for potentiometric detection of inorganic and organic monovalent anions using phosphate and hydrogen phosphate eluents at low concentrations. This is a “monovalent detection method” as the selectivity of the electrode towards monovalent anions results in some other anions being undetected unless the concentration of those other anions is higher than 10−3 mol dm−3 in the sample solution injected. It takes only eight minutes to complete the separation with a good resolution. Theoretical and practical considerations are discussed, and in particular, sensitivity, linearity, detection limit and dynamic behaviour are presented. The use of an all solid-state contact bromide-selective electrode as a detector offers so far the best simultaneous sensitivity toward all anions when compared with other detection methods. Determination of Cl− and NO3 − ions in river, rain and drinking water samples without any further sample preconcentration has been successfully achieved. The detection limit is sub-ppb for most of anions in a 20 μL injection volume.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467567
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  • 5
    Electronic Resource
    Electronic Resource
    A system for predicting the retentions of O-alkyl, n-(1-methylthioethylideneamino) phosphoramidates on RP-HPLC (1999)
    Springer
    Chromatographia 49 (1999), S. 444-448 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; O-alkyl, O-(1-methylthioethylideneamino) phosphoramidates ; Quantitative structure-retention relationship (QSRR) ; Reversed-phase LC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary By using factor analysis, cluster analysis and multiple linear regression methods, two parameters, FHF and ECCR, were selected from eight solute-related structure parameters as showing the best correlation with retention data. The relationship between the retention data (k) and these two structure parameters were established for ten O-alkyl, O-(1-methylthioethylideneamino) phosphoramidate compounds under the experimental conditions studied. Retention data (k) for six other compounds that have a high correlation with structure parameters were predicted using these QSRR equations. The system was evaluated by comparing the experimentalk values with the predicted ones. Good agreement was obtained between the experimental and predictedk values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467621
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of flupoxam residues in soil by high performance liquid chromatography (1999)
    Springer
    Chromatographia 49 (1999), S. 535-538 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Herbicides in soil ; Flupoxam
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-performance liquid chromatography with UV detection was used to determine the residues of flupoxam (a new herbicide) in soils. Soil samples were extracted with aqueous methanol. The soil extracts were cleaned up and concentrated using two solid phase extraction columns: a polymeric stationary phase based on a polystyrene-divinylbenzene resin (Lichrolut EN) and alumina. Recovery experiments were performed at ppb levels in spiked soil samples. The recovery was 76±1.7% for flupoxam in the range 5–100 μg kg−1 of soil. Limit of determination was 3 μg kg−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467754
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of doxorubicin in cell culture media and human plasma using solid phase extraction and HPLC (1999)
    Springer
    Chromatographia 49 (1999), S. 557-561 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; Doxorubicin ; Cell culture media ; Human plasma ; Fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Doxorubicin is an antineoplastic antibiotic isolated fromStreptomyces peucetius var.cesius clinically used in the treatment of tumors such as lung or breast, Hodgkin's disease and various types of leukemias. The main goal of this study was to develop a simple and sensitive HPLC method with fluorescence detection for the quantitation of doxorubicin in cell culture media collected during an in vitro studies and in human plasma. Solid phase extraction (C2 silica) was applied. The experiment established five-point standard curve (1 ng mL−1 to 100 ng mL−1). The standard curves prepared in blank cell tissue media were linear over the range of doxorubicin assayed and had a mean correlation coefficient of 0.9973±9.43×10−4 and slope 0.02545±1.85×10−3. The standard curves prepared in human plasma were linear and had mean correlation coefficient of 0.997 and slope 0.01885±5.19×10−4. The limit of quantitation for doxorubicin in both specimens was arbitrarily established to be 1 ng mL−1. Intra-day variabilities were determined using 3–4 replicates of control solutions of doxorubicin (3 ng mL−1 and 30 ng mL−1) in blank plasma and cell culture media. Inter-day variabilities were determined over a four day period analyzing replicates of controls. All precision and accuracy values fell within the acceptable range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467759
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  • 8
    Electronic Resource
    Electronic Resource
    Indirect liquid chromatographic determination of malathion based on copper(II) dimethyldithiophosphate complex formation (1996)
    Springer
    Chromatographia 42 (1996), S. 680-682 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cu(II) dimethyldithiophosphate complex ; Malathion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic method has been developed for the quantitative determination of the organophosphorus pesticide malathion. The method is based on alkaline hydrolysis of malathion to dimthyldithiophosphate (DDTP) which is complexed with copper(II) and extracted in chlorofrom. The complex is injected onto a Hypersil ODS or Licrosorb sicolumn and eluted with acetonitrile:methanol:water (80∶10∶10 v:v:v) or chloroform. Detection is at 245 or 260 nm. A linear calibration curve was obtained for 24–240 μg ml−1 DDTP and a detection limit of 2.4–4.8 ng DDTP per injection. The method was applied to the analysis of malathion in commerical products after spraying on leaves. Extrction efficiency of malathion from leaves in acetone-water was also evlauted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267701
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  • 9
    Electronic Resource
    Electronic Resource
    LC-separation of derivatized DL-amino acids by aminopropylsilica-bonded Marfey's reagent and analog (1996)
    Springer
    Chromatographia 42 (1996), S. 683-689 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral stationary phase ; Enantionary phase ; Enantiomer separation ; Amino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two chiral stationary phases (CSP-1 and CSP-2)) were synthesized by covalent bonding of aminopropylsilica (APS) to (a) 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide (Marfey's reagent), followed by end-capping of underivatized amino groups of APS with trifluoroacetic anhydride (CSP-1), and (b) by reaction of APS with 1-fluoro-2,4-dinitrophenyl-5-L-phenylalaninetert. butyl ester, followed by cleavage of the tert. butyl ester by trifluoroacetic acid and end-capping of underivatized amino groups of APS withn-butyryl chloride (CSP-2). Both CSPs were found to be suitable for the chiral resolution of 2,4-dinitrophenyl and 3,5-dinitrobenzoyl-DL-amino acid esters by liquid chromatography using mixtures ofn-hexane andiso-propanol as eluents. Racemic 2,2,2-trifluoro-1-(9-anthryl)ethanol was also resolved on CSP-2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02267702
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  • 10
    Electronic Resource
    Electronic Resource
    Gas and liquid chromatography and enzyme linked immuno sorbent assay in pesticide monitoring of surface water from the western mediterranean (Comunidad Valenciana, Spain) (1996)
    Springer
    Chromatographia 42 (1996), S. 151-158 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; Pesticide residues ; Surface water analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A monitoring programme based on gas chromatography (NPD, ECD) using MSD for confirmatory purposes and coupled-column liquid chromatography was applied to the analysis of pesticide residues in surface water from a predominantly agricultural area of Spain (Comunidad Valenciana). Samples analysed by means of enzyme-linked immunosorbent assay gave similar results to those obtained by GC (MSD) for the determination of total triazines. The test employed had the advantages of a simple test procedure, short analysis time and high confirmatory value. Nevertheless, the multiresidue character, accuracy and unequivocal identification of individual pesticide residues of GC (MSD) make this technique the most appropriate for environmental monitoring programmes. In this monitoring programme about 200 samples were analysed between 1993–1994. 27 different pesticides were detected in 91 of these samples. The pesticides more frequently detected were dimethoate, methidathion, endosulfan A and B, endosulfan sulphate and pirimicarb. The highest concentrations found were 39.9 μg L−1 of dimethoate, 10.6 of pirimicarb and 10.6 of methidathion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269645
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  • 11
    Electronic Resource
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    Cross validation of capillary electrophoresis and high-performance liquid chromatography for cefotaxime and related impurities (1996)
    Springer
    Chromatographia 42 (1996), S. 159-164 
    Details
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Column liquid chromatography ; Cefotaxime impurities ; Cross validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A micellar electrokinetic chromatography method is presented which permits separation of cefotaxime and its major related impurities. Separation was carried out at 15 kV, using 30 mM sodium dihydrogen phosphate adjusted to pH 7.2 with 5 M NaOH and which contained 165 mM sodium dodecylsulfate as electrolyte. Results obtained by capillary electrophoresis were in good agreement with those of high-performance liquid chromatography with respect to the level of the major known impurities, total impurity content and cefotaxime purity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269646
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  • 12
    Electronic Resource
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    Supported liquid membrane work-up in combination with liquid chromatography and electrochemical detection for the determination of chlorinated phenols in natural water samples (1996)
    Springer
    Chromatographia 42 (1996), S. 165-170 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Liquid membrane extraction ; Chlorinated phenols ; Natural water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sample preparation method has been developed for the determination of chlorinated phenols in water. The method is based on a supported liquid membrane extraction system connected on-line to liquid chromatography with electrochemical detection. The supported liquid membrane technique utilizes a porous PTFE membrane. The membrane is impregnated with an organic solvent which forms a barrier between two aqueous phases and enables selective extraction. The technique can easily be coupled in a flow system. In this investigation five chlorinated phenols (1–5 chlorine atoms) were extracted from natural water samples. Extraction for 30 minutes resulted in detection limits of approximately 25 ng L−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269647
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  • 13
    Electronic Resource
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    Calcium phosphate hydroxyapatite and lead phosphate hydroxyapatite for separation by liquid chromatography (1996)
    Springer
    Chromatographia 42 (1996), S. 177-180 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calcium and lead phosphate hydroxyapatite ; Globular proteins ; Colecalciferol (Vitamin D3) and related compounds ; Organophosphorus insecticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A qualitative study using two new stationary phases (spherical aggregates of calcium phosphate hydroxy-apatite and lead phosphate hydroxyapatite) as adsorbents in high performance liquid chromatography has achieved the separation of: a standard mixture of globular proteins; colecalciferol and related compounds (produced by irradiation and heating of provitamin D3); and a mixture of organophosphorus insecticides used in agriculture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269649
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  • 14
    Electronic Resource
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    Detection of cow's milk in ewe's or goat's milk by HPLC (1996)
    Springer
    Chromatographia 42 (1996), S. 181-184 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ewe's milk ; Whey proteins ; Goat's milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High-pressure liquid chromatography (HPLC) was used to detect added cows' milk in goat and ewe's milk. Analysis of the whey proteins enabled detection of mixtures in proportions of less than 1%. The method does not distinguish between goat and ewe's milk.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269650
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  • 15
    Electronic Resource
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    Chracterization of polyaniline using chromatographic studies (1996)
    Springer
    Chromatographia 42 (1996), S. 191-198 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polymer-coated silica phase ; Polyaniline ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of polyaniline as a chromatographic stationary phase has been examined. In the course of this work the column packing material was prepared by coating silica particles with polyaniline chloride. The aniline monomer was polymerised directly on the surface of the silica particles using a chemical method and was characterised using elemental analysis. A series of standard test compounds were employed for chromatographic characterization. The studies revealed information on the practical utility as well as the molecular interactions that took place on the stationary phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269652
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  • 16
    Electronic Resource
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    Sample size and retention values in gradient liquid chromatography of synthetic polymers (1996)
    Springer
    Chromatographia 42 (1996), S. 185-190 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gradient elution of synthetic polymers ; Polystyrene and various styrene copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention times in gradient liquid chromatography of synthetic polymers are often dependent on sample size. They increase with column load if the separation mechanism is governed by a solution process but decrease with increasing load if the mechanism is governed by adsorption. Since retention times independent of sample size are a prerequisite for peak identification as well as for the correct measurement of elution bands of samples with a broad distribution, measures to counteract sample-size effects deserve attention. Usually both solubility and adsorption are effective in gradient liquid chromatography of synthetic polymers. An appropriate balance of both effects is suitable for diminishing the influence of sample size on retention time of synthetic polymers. Ternary gradients allowing independent control of solubility and adsorption are promising.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269651
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  • 17
    Electronic Resource
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    Supercritical fluid extraction of carbamate pesticides from soils and cereals (1996)
    Springer
    Chromatographia 42 (1996), S. 206-212 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Supercritical fluid extraction ; Carbamate pesticides ; Soils ; Cereal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the supercritical fluid extraction of carbamate pesticides (propoxur, aminocarb, carbaryl and methiocarb) from soil and cereal samples using CO2 is proposed. Extractions were at 378 bar and 54 °C. Analytes were determined in the extracts by HPLC with fluorescence detection after post-column derivatization. Recoveries from spiked soil ranged between 39.6 and 91.7%, depending on analyte and soil components. Lowest recoveries were from sandy soils. Aminocarb could not be recovered from any soil using CO2. Recovery of aminocarb from diatomaceous earth was improved by adding methanol to the extraction cell prior to SFE, but the effect was not observed in soil samples. Recoveries for propoxur and aminocarb from spiked wheat were about 75%, and only between 30–50% for aminocarb from corn and oats, and carbaryl from wheat. Fat was coextracted using CO2 and retained in the trap together with the analytes, however, appropriate rinsing solvent allowed on-line clean-up of the extract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02269654
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  • 18
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    Analysis of contact allergenic compounds in oxidizedd-limonene (1996)
    Springer
    Chromatographia 42 (1996), S. 199-205 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Negative ion CI mass spectrometry ; Oxidizedd-limonene ; Contact allergenic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A detailed chemical analysis and quantification of oxygen-containing monoterpenes in auto-oxidizedd-limonene was performed. Some of these, e.g. the cis- and trans-isomers of limonene-2-hydroperoxide, have previously been shown to exhibit strong contact allergenic properties. GC-MS with chemical ionization in negative ion mode was shown to be a successful method for the identification and determination of the molecular weight of chemically unstable limonene hydroperoxides. An HPLC method for isolation of individual compounds in auto-oxidizedd-limonene is presented. Two different stationary phases were used in normal phase mode, cyanopropyl- and diamino-modified silica. The method described can be used for the isolation of individual contact allergens in sensitization experiment vehicles, such as petrolatum and olive oil. This makes it possible to study whether test compounds, such as hydroperoxides, are chemically stable during a sensitization experiment.
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    URL: http://dx.doi.org/10.1007/BF02269653
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  • 19
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    Native and modified alumina, titania and zirconia in normal and reversed-phase high-performance liquid chromatography (1996)
    Springer
    Chromatographia 42 (1996), S. 217-222 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phases ; TiO2 ZrO2 AlO3 ; Separation of basic compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Chromatographic properties of silica, alumina, titania and zirconia have been investigated in normal phase mode in the separation of test mixtures of basic, neutral and acidic compounds. In contrast to silica the chromatographic behaviour revealed the basic properties of the alumina, titania and zirconia surfaces. Therefore, separation of basic compounds on these packings seems very promising. Lypophilic packings have been synthesized by modification of titania, zirconia and alumina with organosilanes and polymers and tested for the separation of basic compounds and proteins. High hydrolytic stability of the modified packings was observed during separations with strong alkali and acidic eluents.
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    URL: http://dx.doi.org/10.1007/BF02269656
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  • 20
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    Validation of a strategic approach to high-performance liquid chromatographic method selection (1994)
    Springer
    Chromatographia 39 (1994), S. 339-345 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; First-guess ; Retention optimization ; Validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A recently reported chromatographic method selection strategy has been validated using fifteen drug formulations selected randomly from the Belgium Compendium, 1992. On the basis of the hydrophobic and the acidic — basic properties of the sample components, reversed-phase was recommended as the first choice mode for all formulations. For two multicomponent formulations the range of analyte polarity dictated the need for gradient elution. The commerical software DryLab G/plus® was used for selection of optimum gradient conditions. The results obtained by both isocratic and gradient chromatography are discussed, as is the usefulness of a tailing suppressor in both modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274523
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  • 21
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    A chromatographic comparison of the pore structure of zirconia high performance liquid chromatographic materials made by the polymerization induced colloidal aggregation and the Oil Emulsion methods (1996)
    Springer
    Chromatographia 42 (1996), S. 273-282 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Size exclusion chromatography ; Pore structure ; Nitrogen sorptometry ; Zirconium oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The pore structures of zirconium oxide particles prepared by two different methods (PICA and Oil Emulsion processes) are compared. Nitrogen sorptometry and size exclusion chromatography are used to characterize the two different types of particles. Significant and unexpected differences were found in the accessible pore volumes and the bed packing densities of the two materials. The PICA material was found to have a higher totally included and totally excluded volume than would be normally expected. The chromatographic method provides results which are more useful for the application of these materials to separation sciences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290309
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  • 22
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    Analysis of oligonucleotides using coupled high performance liquid chromatography-electrospray mass spectrometry (1994)
    Springer
    Chromatographia 39 (1994), S. 405-408 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrospray mass spectrometry ; Oligonucleotides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Improved HPLC and ESMS conditions have been established, allowing the separation and analysis of oligodesoxyribonucleotides by coupled HPLC-ESMS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02278754
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  • 23
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    Salt effects in anion exchange displacement chromatography: Comparison of pentosan polysulfate and dextran sulfate displacers (1994)
    Springer
    Chromatographia 39 (1994), S. 409-418 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exchange chromatography ; Protein purification ; Pentosan polysulfate displacers ; Dextran sulfate displacers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Experimental studies were carried out to investigate the utility of pentosan polysulfate as a low molecular weight polyelectrolyte displacer for the purification of proteins in anion-exchange displacement systems. In addition, the influence of mobile phase salt concentration on displacer efficacy, protein-protein resolution, and displacement development were studied for several anionic displacers. It was found that while large polyelectrolytes (50 kd dextran sulfate) were efficient displacers for a wide range of salt concentrations, relatively small polyelectrolytes (3 kd pentosan polysulfate) were seen to act as an efficient displacer only under conditions of high salt micro-environments. In addition, for proteins exhibiting similar affinities, zone mixing at the protein-protein boundary was found to be quite sensitive to the salt concentration. Finally, displacement chromatography was successfully implemented for the separation of proteins from milk whey.
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    URL: http://dx.doi.org/10.1007/BF02278755
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  • 24
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    Chemical analysis of microcystins RR and LR in cyanobacterium using a prepacked cyano cartridge (1994)
    Springer
    Chromatographia 39 (1994), S. 427-430 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Microcystins RR and LR ; Solid phase extraction ; Cyano cartridges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method for the determination of microcystins PR and LR in cyanobacterium was developed using cyano-type prepacked cartridges. The microcystins were extracted with 10% acetic acid and the extract applied to a Baker 10 cyano cartridge. After elution from the cartridge with 0.5M acetic acid-acetonitrile (1∶9) the microcystins were determined by HPLC. Better recoveries and chromatograms were observed than with ODS cartridges.
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    URL: http://dx.doi.org/10.1007/BF02278757
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    Isocratic high-performance liquid chromatographic determination of plasma adenosine (1996)
    Springer
    Chromatographia 42 (1996), S. 318-322 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine in blood ; Isocratic elution ; Stop-solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Due to manifold physiological and cardioprotective actions of adenosine, the demand for a simple but accurate method to determine its concentration in plasma is increasing. The aim of this study was firstly to develop a simple isocratic method instead of the gradient elution or peak-shifting techniques used earlier and secondly to check conflicting data on the composition of “stop-solution”, added to the sample in order to prevent changes in adenosine concentration. Isocratic elution improved signal to noise ratio and concentrations of 100 μmol L−1 dipyridamole and 2.5 μmol L−1 erythro-9(2-hydroxy-3-nonyl)adenine in the blood sample effectively prevented both adenosine formation and degradation, even without the use of a 5′-ecto-nucleotidase inhibitor. Lowering the concentration of dipyridamole to 25 μmol L−1 caused more than a tenfold increase of adenosine concentration in two out of five cases and even 100 μmol L−1 dipyridamole alone is not sufficient to inhibit adenosine deaminase in blood samples.
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    URL: http://dx.doi.org/10.1007/BF02290317
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    HPLC study of the binding of sulfinpyrazone to serum albumin (1996)
    Springer
    Chromatographia 42 (1996), S. 401-404 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hummel Dreyer method ; Sulfinpyrazone ; Bovine serum albumin ; Scatchard-Rosenthal plot
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hummel-Dreyer method was used to study the binding of sulfinpyrazone to bovine serum albumin. The technique involves our newly developed internal calibration method with the elution pattern consisting of two positive peaks and with the integrator to evaluate the area of second peak. From the area of the second peak the numerical value ofL b (the amount of drug bound to protein) was calculated. Sctachard-Rosenthal plot was used to estimate the binding parametersn i (the number of binding sites) andk i (the binding constants). The results are compared with those obtained by equilibrium dialysis.
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    URL: http://dx.doi.org/10.1007/BF02272130
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    Determination of tacrolimus (FK 506) in whole blood using liquid chromatography and fluorescence detection (1994)
    Springer
    Chromatographia 39 (1994), S. 490-496 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precolumn derivatization ; Dansylhydrazine ; Fluorescence detection ; Tacrolimus (FK 506) in blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and selective liquid chromatographic method, using precolumn derivatization with dansylhydrazine followed by fluorescence detection, has been developed for the determination of tacrolimus (FK 506) in whole blood. After haemolysis, whole blood samples are extracted with diethyl ether and derivatized. After on-line removal of excess dansylhydrazine on a C18 precolumn, the derivative is loaded on to a C18 clean-up column, and a heart cut is subsequently transferred to a graphitized carbon column, where the final separation takes place. The method requires 1 ml of sample and has a limit of quantitation of 3 ng/ml. At the 15 ng/ml level the precision isca 10%, and the response is linear from the limit of quantitation toca 200 ng/ml of FK 506 in whole blood. The capacity of the method is 50 samples/day and about 1000 1-ml samples can be analyzed without changing either clean-up or separation column. Finally, the applicability of the method for therapeutic drug monitoring is shown.
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    URL: http://dx.doi.org/10.1007/BF02278767
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    Spectroscopic studies of butylphenyl, mono-ol and perfluorinated bonded phases (1994)
    Springer
    Chromatographia 39 (1994), S. 520-528 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; New bonded phases ; 13C and29Si CP-MAS NMR ; DRIFT ; ESCA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A variety of olefins were bonded to silaceous supports through a hydride modified substrate. The products were then examined by13C and29Si solid state-NMR with cross-polarization (CP) and magic angle spinning (MAS). Information about the surface was also obtained by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and the related photoelectron spectroscopic technique (ESCA). Carbon analysis on bonded silicas was carried out and surface coverage was calculated. Confirmation of the organic groups bound to the silica support was possible. The hydride intermediate is shown to be a versatile material for bonding a wide variety of organic moieties to silica surfaces.
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    URL: http://dx.doi.org/10.1007/BF02268274
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    Simultaneous determination of dexamethasone and betamethasone in pharmaceuticals by reversed-phase HPLC (1994)
    Springer
    Chromatographia 39 (1994), S. 539-542 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Glucocorticoids ; Betamethasone and dexamethasone ; Pharmaceuticals ; Tablet preparations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An HPLC method for the simultaneous determination of the glucocorticoids betamethasone and dexamethasone is described. The method based on the separation of these compounds using a binary watertetrahydrofuran mobile phase and a reversed-phase Hypersil C18 column, was applied to the determination of betamethasone and dexamethasone in tablets.
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    URL: http://dx.doi.org/10.1007/BF02268276
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    Control of adsorption and solubility in gradient high-performance liquid chromatography (1994)
    Springer
    Chromatographia 39 (1994), S. 557-563 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Copoly(styrene/methyl methacrylate) ; Gradient elution ; Precipitation chromatography of polymers ; Solubility of polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Copolymers from styrene and methyl methacrylate (MMA) were separated by both normal and reversedphase gradient chromatography. Both modes could be performed by sudden-transition gradients where the polymers were injected into a non-solvent whose polarity was either rather low (e.g.,n-heptane) or high (e.g., acetonitrile). Then the solvent strength of the starting eluent was rapidly increased to a given level by addition of dichloromethane. Under properly defined conditions, the sample components still remained on the column. Elution could be triggered off by the steady addition of another non-solvent whose polarity was opposite of that of the starting non-solvent. Thus, the mixture of five copolymers with MMA content ranging from 14 to 84% could be separated on a polar cyanopropyl column by injection inton-heptane and elution through acetonitrile (normal phase mode) and on a RP C18 column by injection into acetonitrile and elution throughn-heptane (reversed-phase mode), provided that in both modes about 30% dichloromethane was added to the starting non-solvent. The elution sequence in the reversed-phase mode was opposite to that in the normal-phase mode, obeying the approved polarity rules of chromatography in both cases.
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    URL: http://dx.doi.org/10.1007/BF02268279
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    HPLC determination of tryptophan enantiomers with photometric, fluorimetric and diode-laser polarimetric detection (1996)
    Springer
    Chromatographia 42 (1996), S. 494-498 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tryptophan ; Chiral separations ; Diode-laser polarimetric detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The combined utilization of photometric, fluorimetric and polarimetric detection liquid chromatography detectors in series for the identification and quantification of D-tryptophan and L-tryptophan was evaluated. Detection limits of about 1 μg were established with the range of linearity extending to about 100 μg. The relative standard deviation of the D-form and L-form tryptophan were 7.32 and 4.22%, respectively. The amount unknown of tryptophan enantiomers in the different mixtures was determined with an accuracy of 1.58% at the 40 μg injection level.
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    Separation and characterisation of hop bitter acids by HPLC-1H NMR coupling (1996)
    Springer
    Chromatographia 42 (1996), S. 499-505 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hop bitter acids ; Supercritical fluid extraction ; On-line-1H NMR coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A supercritical carbon dioxide hop extract has been analysed using on-line coupling of high performance liquid chromatography (HPLC) with1H nuclear magnetic resonance (NMR) spectroscopy. For the first time high quality NMR spectra of the six major hop bitter acids were recorded by employing the stopped-flow detection mode. The resolution of the spectra obtained is similar to that of conventionally recorded spectra. All data are in agreement with the known structures.
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    URL: http://dx.doi.org/10.1007/BF02290283
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    1,1′-[Ethenylidenebis(sulfonyl)]bis-benzene: A useful pre-chromatographic derivatization reagent for HPLC analysis of thiol drugs (1996)
    Springer
    Chromatographia 42 (1996), S. 515-520 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thiol drugs ; Pre-chromatographic derivatization ; 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 1,1′-[ethenylidenebis(sulfonyl)]bis-benzene as a pre-chromatographic reagent for LC analysis of thiol drugs is proposed. The reagent reacts rapidly (2 min) under mild conditions (pH 7.5, ambient) with thiol drugs and the resulting adducts can be chromatographed under reversed-phase conditions (C-18 column). Excess reagent can be removed from the reaction mixture by simple liquid-liquid extraction with chloroform. The HPLC method using UV detection was successfully applied to the analysis of reduced glutathione (GSH), N-acetylcysteine, N-2-mercaptopropionylglycine and captopril in their commercial formulations.
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    Improved separation of diastereoisomers in capillary electrophoresis using a mixture of β-cyclodextrin and sodium taurodeoxycholate (1994)
    Springer
    Chromatographia 39 (1994), S. 627-630 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar electrokinetic capillary electrophoresis ; Tetrahydrocarbazole derivatives ; β-Cyclodextrin ; Taurodeoxycholate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary 2,3,4,6-tetra-O-acetyl-β-D-glucopranosyl isothiocyanate derivatives of a number of basic compounds, containing one chiral center, have been prepared. The indirect resolution of enantiomers was achieved with a high separation efficiency by capillary electrophoresis, using a sodium taurodeoxycholate/β-cyclodextrin system. This methodology was found to be superior to the resolution of the same derivatives by reversed phase HPLC analysis. A possible mechanism for stereoselectivity is described.
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    Chroamtographic behaviour of un-sulphated and sulphated oligoethyleneglycol nonylphenyl ether surfactants in normal-phase liquid chromatographic systems containing water (1996)
    Springer
    Chromatographia 42 (1996), S. 539-546 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Un-sulphated and sulphated surfactants ; Oligoethyleneglycol nonylphenyl ethers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention behaviour of un-sulphated and sulphated, oligoethyleneglycol nonylphenyl ether, anionic surfactants was investigated in normal-phase LC systems with chemically bonded amino stationary phase in organic mobile phases containing water and cetyl trimethylammonium bromide (CTAB). Addition of water to the mobile phase improves efficiency of separation and linearity of the dependences of logk′ versus number of oxyethylene units in the sulphated oligomers, so that it is possible to describe simultaneous effects of this number and of the concentration of CTAB on retention by a simple equation. In this system, it is possible to separate lower sulphated and un-sulphated oligomers in a single run in 10–15 min under isocratic conditions.
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    URL: http://dx.doi.org/10.1007/BF02290288
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    Identification of vitamin B12 analogues by liquid chromatography with electrothermal atomic absorption detection (1996)
    Springer
    Chromatographia 42 (1996), S. 566-570 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrothermal atomic absorption spectrometry ; Vitamin B12 analogues ; Cobalamins and cobalt ; Meat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The coupling of liquid chromatography and electrothermal atomic absorption spectrometry (LC-ETAAS) lowers the detection limit for identification of vitamin B12 analogues. Cobalamins and aqueous cobalt (II) were separated by reversed-phase liquid chromatography using a linear gradient: 26∶74 (v/v) methanol:0.05 M phosphate buffer (pH 4.2) to 50∶50 mixture over 8 min. The vitamins were quantitatively determined in the column effluent by measuring total cobalt by ETAAS. The analysis of meat and liver extracts by LC-ETAAS showed that the matrix did not interfere with the determination of cobalt. Hence, recoveries of cobalt in spiked meat and liver samples were satisfactory.
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    URL: http://dx.doi.org/10.1007/BF02290293
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    Estimation of the pK a of the amine groups of benzhydrylamine resin and its lysyl derivative by measurement of swelling (1996)
    Springer
    Chromatographia 43 (1996), S. 82-84 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion-exchange chromatography ; Benzhydrylamine resin ; pK a
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary For better evaluation of the potential of benzhydrylamine resin (BHAR), used as a solid support for peptide synthesis, as a novel anion-exchange resin, the pK a of its amine group was estimated by microscopic measurement of the sizes of the dry and swollen beads. Using the volume of the bead occupied by the solvent (as a percentage) as the swelling parameter, a plot of the degree of swelling of BHAR loaded with 2.4 mmol g−1 amine groups against the pH of the medium produced a decreasing sigmoidal-type curve with increasing pH. By considering the point of inflection of the curve, a pK a value of approximately 7.5 was estimated for the amine group of the BHAR. The same approach was also applied to the lysyl derivative of the BHAR (Lys-BHAR) and pK a values around 6.5 and 10.0 were obtained for the α and ε amine groups, respectively.
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    Normal and reversed-phase HPLC for more complete evaluation of tocopherols, retinols, carotenes and sterols in dairy products (1996)
    Springer
    Chromatographia 43 (1996), S. 89-93 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sterols, tocopherols, retinols and carotenes ; Dairy products
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We have previously described a normal-phase HPLC method for the simultaneous determination of α, β, γ and δ tocopherol, thecis andtrans isomers of retinol, and total carotenes in different Italian cheeses and milk. In this paper we describe a reversed-phase HPLC method using solely methanol as the mobile phase for the determination of α-tocopherol, β-+γ-tocopherols, total retinols, cholesterol, β-sitosterol, campesterol and stigmasterol, and α- and β-carotene. The method developed has been applied to some new dairy products such as natural Quark, with olive, basil or banana and to processed cheese with tomato and the results have been compared with the corresponding results obtained by the normal-phase method. The conclusion is that more complete evaluation of the tocopherol, retinol, carotene and sterol content of dairy products, especially when vegetables and fruits are present, is necessary and can be obtained using both the normal- and reversed-phase HPLC methodologies.
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    URL: http://dx.doi.org/10.1007/BF02272829
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    Determination of tetramethylthiuram disulfide (Thiram) in river water by high-performance liquid chromatography: Micellar versus conventional reversed phase chromatography (1996)
    Springer
    Chromatographia 43 (1996), S. 607-611 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar vs. reversed phase separation ; Thiram in river water ; Dithiocarbamate fungicides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary After a comparative study of conventional reversed phase and micellar liquid chromatography a method is described for the determination of the fungicide thiram in river water based on the use of micelles of CTAB. The method involves the extraction/concentration of thiram with a C18 cartridge followed by separation on a C18 reversed-phase column with a mobile phase of 20% (v/v) acetonitrile/0.01 M CTAB in phosphate buffer (pH-6.3), and detection at 254 nm. The method allows the determination of thiram in the presence of other water-soluble dithiocarbamate fungicides (nabam, ziram and ferbam) with a limit of detection of 36 pg mL−1 for a typical 20-fold preconcentration.
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    Determination of pesticides by on-line trace enrichment-reversed-phase liquid chromatography-diode-array detection and confirmation by particle-beam mass spectrometry (1996)
    Springer
    Chromatographia 43 (1996), S. 592-598 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diode-array detection ; Particle beam mass spectrometric detection ; Pesticides in water ; On-line solid-phase extraction (SPE)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of pesticides has been determined by liquid chromatography with diode-array detection (DAD). The coupling of a particle-beam (PB) mass spectrometer to the outlet of the DAD enabled the identities of the pesticides to be confirmed from mass spectra obtained by electron impact ionization. On-line trace enrichment of 200 mL of sample with a PLRP-S precolumn enabled most pesticides to be determined in real samples at levels between 0.2 and 5 μg L−1 and with limits of detection (LOD) between 0.05 and 0.5 μg L−1. In the analysis of real samples, one of the pesticides studied was determined by DAD and its identity was confirmed by comparison of PB mass spectra. The use of PB-MS also enabled the detection of non-target compounds.
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    Hexamethyldisiloxane as a mobile phase component for normal phase liquid chromatography (1996)
    Springer
    Chromatographia 43 (1996), S. 647-653 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hexamethyldisiloxane ; Mobile phase component ; Silica column
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Hexamethyldisiloxane (HMDX) has been evaluated as a modifier solvent for the normal phase separation of substituted naphthalene componds as well as aromatics such as nitrobenzene, acetophenone, benzonitrile, and aniline. It is found to be a weaker eluting solvent than n-butyl ether and other commonly used normal phase solvents filling a niche in the eluotropic series. HMDX exhibited an unusual retention factor (k′) profile as a function of mobile phase composition in hexane. In a range from 0 to 40 %, thek′ values remained quite constant with increasing HMDX composition. As the concentration of HMDX progressed to 100 %, thek′ values actually increased in a generally linear fashion. This trend ink′ is due to longer solute retention not just a change in the retention time of the unretained component. Although slight silanization of the silica column may occur with initial use of HMDX, retention of these analytes on a commerical C-1 silica column is much lower with no positivek′ slope with increasing HMDX. The chromatographic data provide evidence that HMDX is likely adsorbed to the silica surface and a solute partitioning mechanism may be operative.
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    Thin-layer and column chromatography of sulfonamides on aminopropyl silica gel (1996)
    Springer
    Chromatographia 43 (1996), S. 654-658 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Ion-pairing ; Sulfonamides ; NH2-Modified stationary phase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Thin-layer and column high-performance liquid chromatography based on amino propyl-modified silica gel using aqueous and non-aqueous mobile phases containing organic modifier and cationic or anionic ion-pairing reagents were used for the determination ofR F andk values of some sulfonamides. The influence of the different organic modifiers and ion-pairing reagents on retention has been compared.
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    Polycyclic aromatic hydrocarbons in waste waters and sewage sludge: Extraction and clean-up for HPLC analysis with fluorescence detection (1996)
    Springer
    Chromatographia 43 (1996), S. 135-142 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Polycyclic aromatic hydrocarbons ; Waste waters ; Sewage sludge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified solid-phase extraction technique using sonication of the adsorbent material instead of the elution normally applied has been compared with two conventional liquid-liquid extraction procedures for the determination of the 16 EPA PAHs in municipal waste waters by means of HPLC coupled with fluorescence detection. Liquid-liquid extraction with cyclohexane proved to be the most efficient and simplest procedure. Clean-up of the waste-water extracts was not considered necessary, because of the high chromatographic resolution of the column and the selectivity of the fluorescence detector. Different organic solvents were also compared for ultrasonic extraction of PAHs from sewage sludge. The best results were obtained by use of acetonitrile. Clean-up of sewage-sludge extracts was not found necessary for accurate quantification of the major PAH components with fluorescence detection. The precision of the whole analytical procedure from extraction to the final determination of PAHs was satisfactory for both waste-water and sewage-sludge samples.
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    Optimization of alkali-alkalkine earth cation separation on weak cation-exchangers (1996)
    Springer
    Chromatographia 43 (1996), S. 117-123 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-exchange chromatography ; Ion-exchange mechanism ; Optimization of alkali and alkaline earth separation ; Crown ether complexing reagents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The elution behavior of alkali and earth alkaline cations has been studied on a newly synthesized weak cationexchanger (WCX). Applying this stationary phase isocratic separation of these cations is possible. The dependence of retention on competing ion concentration is described via a simple model. The influence of crown ethers as well as organic eluent additives on selectivity and peak efficiency is demonstrated. With optimized separation such cations can be determined with detection limits of about 0.5 ppm using a conductivity detector without ion suppression.
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    Identification and determination of fumonisin FB1 and FB2 in corn and corn products by high-performance liquid chromatography-electrospray-ionization tandem mass spectrometry (HPLC-ESI-MS-MS) (1996)
    Springer
    Chromatographia 43 (1996), S. 124-128 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Tandem mass spectrometry ; Fumonisin in corn products ; Electrospray-ionization (ESI) ; Selected rection monitoring (SRM)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new method has been developed for qualitative and quantitative analysis of fumonisin FB1 and FB2 in corn and corn products. After extractive sample preparation followed by solid phase extraction using a strong anionexchanger, highest selectivity and sensitivity was achieved by high-performance liquid chromatography-electrospray-ionization, tandem mass spectrometry (HPLC-ESI-MS-MS) analysis combined with selected reaction monitoring (SRM). With deuterated fumonisin FB1-d6 as internal standard the routine quantitation limit for FB1 was set at 400 pg (0.8 ng g−1 sample) with a signal-to-noise ratio of 10∶1. Almost all corn grit and corn meal samples under study were found to be contaminated with fumonisin FB1 and FB2 in concentrations ranging from 1 to 200 ng g−1. Lower fumonisin levels were found in cornflakes, popcorn and baby food, while no fumonisins were detected in canned sweet corn.
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    Simultaneous separation and identification of hashish constituents by coupled liquid chromatography-mass spectrometry (HPLC-MS) (1996)
    Springer
    Chromatographia 43 (1996), S. 129-134 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; On-line liquid chromatography-mass spectrometry ; Neutral and acidic cannabinoids ; Hashish samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This paper reports the use of liquid chromatography for the separation and determination of the major cannabinoids extracted from hashish samples. The direct coupling to the mass spectrometer enables the selective identification both of neutral and acidic cannabinoids. The developed method does not require any preliminary derivatization and should, therefore, be of interest in forensic analysis for simple and unequivocal determination of hashish constituents.
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    Identification of the [(bpy)2Ru(Im)(H2O)]2+ complex as an reaction intermediate by reversed-phase high-performance liquid chromatography (1996)
    Springer
    Chromatographia 43 (1996), S. 322-326 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ruthenium diimine complexes ; Inorganic synthesis ; Kinetics monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of the complex [(bpy)2Ru(Im)2]2+ (bpy=2,2′-bipyridine; Im=imidazole) has been monitored by reversed-phase HPLC. The analytical results obtained during the reaction have shown that it is feasible to identify and isolate the [(bpy)2RuIm(H2O)]2+ complex as a reaction intermediate. The optimization of the synthetic procedures for these two species has been established and the compounds have been obtained in high purity. The use of HPLC has enabled complete analytical control of the synthesis of the [(bpy)2RuL2]2+ class of compounds, enabling the identification of reaction intermediates.
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    URL: http://dx.doi.org/10.1007/BF02271003
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    Assay of four stereoisomers of desacetyl diltiazem hydrochloride. Application toin vitro chiral inversion studies (1996)
    Springer
    Chromatographia 43 (1996), S. 413-418 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Desacetyl diltiazem hydrochloride stereoisomers ; Chiralcel OF ; Chiral inversion ; Epimerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Direct resolution of four stereoisomers of the related compound of diltiazem hydrochloride, namely desacetyl diltiazem hydrochloride, was studied by both normal and reversed-phase chiral HPLC. The four stereoisomers were completely resolved on a Chiralcel OF column. The technique developed was applied to a chiral inversion study of desacetyl diltiazem hydrochloride. This inversion was observed neither in the solid state, in aqueous solution at 100°C for 3 h nor under visible light for 10h, but was observed in aqueous solution under UV irradiation. The (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride degraded with a half-life of 1.9 h in aqueous solution under UV and epimerized to (+)-(2R, 3S)-trans-desacetyl diltiazem hydrochloride. Similarly, (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride degraded about three times faster than diltiazem hydrochloride. Reverse epimerization of (+)-(2R, 3S)-trans-desacetyl diltiazem hydrochloride to (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride was not observed. The overall degradation was the result of two competitive processes, the epimerization and the decomposition of the benzothiazepin ring. The degradation and epimerization rate of (+)-(2S, 3S)-cis-desacetyl diltiazem hydrochloride in solution under UV depended upon the solvent, the aqueous pH, and concentration.
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    URL: http://dx.doi.org/10.1007/BF02271021
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    High-performance liquid chromatography of some estrogens on chemically bonded phases (1996)
    Springer
    Chromatographia 43 (1996), S. 551-556 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded silica gel ; Mixed solvents ; Steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic behaviour of 30 estradiol and estrone derivatives has been studied on diol, amino- and cyanopropyl silica gel stationary phases with non-aqueous mobile phases. The slopes of linear relationships between the logarithm of the retention factor and logarithm of the volume fractions of the polar components of the binary eluents have been calculated and are discussed in relation to the characteristics of the solute, eluent and stationary phase. An equation for testing the separation efficiency of stationary phases has been derived.
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    URL: http://dx.doi.org/10.1007/BF02293009
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    Optimisation of chiral separation of omeprazole and one of its metabolites on immobilized α1-acid glycoprotein using chemometricsglycoprotein using chemometrics (1997)
    Springer
    Chromatographia 44 (1997), S. 10-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Experimental design ; Direct chiral resolution ; Omeprazole ; Hydroxy-omeprazole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A strategy for the optimisation of direct chiral separation of omeprazole and a metabolite, hydroxi-omeprazole, in reversed phase liquid chromatography is described. A factorial design was used, where mobile phase pH, concentration of a mobile phase modifier, ionic strength and column temperature were tested as the variables and enantioselective retention, column efficiency and asymmetry factor as the responses. The experimental results were evaluated with multivariate analyses, which demonstrated that the column temperature and content of mobile phase acetonitrile were by far the most important variables. The enantiomers of omeprazole and one of its metabolites were baseline resolved within 15 minutes. The optimised chromatographic system was used for a separation of the enantiomers of omeprazole and its main metabolite in a patient plasma sample.
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    Interactions between cisplatin derivatives and mobile phase during chromatographic separation (1997)
    Springer
    Chromatographia 44 (1997), S. 19-24 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cisplatin stability ; Cisplatin metabolites ; Platinum phosphato-derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Althoughcis-dichlorodiammineplatinum(II) (cisplatin or CDDP) is widely used for the treatment of several kinds of tumour, its stability and metabolism in biological fluids have not been completely elucidated. Conditions in which mobile phases of formic or phosphoric acids interact with platinum derivatives during chromatographic separation performed by high performance liquid chromatography on-line with inductively coupled plasma-mass spectrometry (ICPMS) are investigated. During chromatographic separation of CDDP the formic acid mobile phase does not interact with CDDP itself nor with its hydrolysis products. In contrast, the phosphoric acid mobile phase interacts, not with the CDDP itself, but with its hydrolysis products which are present only in an aged aqueous solution, to generate two platinum phosphato-derivatives. This study suggests that the phosphoric acid has greater affinity for the CDDP hydrated complexes than formic acid and the latter is more appropriate for the study of cisplatin behavior in aqueous and biological media.
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    Chemiluminescence determination of tiopronin and its metabolite 2-mercaptopropionic acid in human urine by HPLC coupled with flow injection (1997)
    Springer
    Chromatographia 44 (1997), S. 31-36 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemiluminescence detection ; Tiopronin ; Thiols
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In previous pharmacokinetic studies tiopronin, a drug used for effective treatment of cystinuria and rheumatoid arthritis, and its metabolite 2-mercaptopropionic acid were analysed by conventional liquid chromatography with pre- and post-column derivatization and UV detection. Now a novel HPLC-coupled chemiluminescence-flow-injection analysis (CL-FIA) method has been developed for the determination of tiopronin and 2-mercaptopropionic acid in urine. The method is based on chemiluminescence from a Ce(IV) oxidation system sensitized by quinine, as proposed earlier by this group, and flow-injection analysis. The method, which has the advantages of high sensitivity and selectivity, simple sample treatment and prompt production of results, has also been preliminarily adapted for pharmacokinetic study of tiopronin in urine.
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    Determination of cortisol in guinea pig urine by high performance thin-layer chromatography, high performance liquid chromatography, and thin-layer chromatography/radioimmunoassay (1997)
    Springer
    Chromatographia 44 (1997), S. 50-54 
    Details
    ISSN: 1612-1112
    Keywords: Thin layer chromatography ; Column liquid chromatography ; Radioimmunoassay ; Cortisol ; Guinea pig ; Urine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to collect urinary samples from unrestrained guinea pigs, animals were kept in their familiar home cages with wood shavings for bedding. Cortisol was removed from shavings by a simple washing step, and an attempt was made to measure its concentrations by high performance thin-layer chromatography (HPTLC), high performance liquid chromatography (HPLC), or thin layer chromatography/radioimmunoassay (TLC-RIA). After intramuscular administration of 25 mg cortisol, cortisol excretion increased from about 20–30 μg/day to 400–500 μg/day (HPTLC: 531 μg/day, HPLC: 493 μg/day; TLC-RIA: 394 μg/day). Similarly, the treatment of the animals with 20 IU ACTH resulted in an augmented cortisol excretion, with mean values of 294 μg/day (HPTLC), 256 μg/day (HPLC) and 143 μg/day (TLC-RIA), respectively. The present study shows, for the first time, that cortisol excretion in unrestrained laboratory animals can be determined. Whilst the cortisol values measured by HPTLC and HPLC agree, the amounts measured by TLC-RIA were significantly lower. These differences are probably due to the presence of substances in urine or shavings which interfere with the radioimmunological determination. Hence, cortisol should be determined either by HPTLC or HPLC. Beside having a desirable specificity, these methods are more suited than TLC/RIA for steroid analysis since they confer the possibility of measuring additional steroids (e.g. precursors and/or metabolites of cortisol) in a single urine extract. This is especially the case for the HPTLC method since substances can be transformed into fluorescent derivatives.
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    Influence of mobile phase conditions on the clean-up effect of restricted-access media precolumns for plasma samples injected in a column-switching system (1997)
    Springer
    Chromatographia 44 (1997), S. 589-594 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column-switching systems ; Restricted-access media precolumns ; Mobile phase composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Various mobile phases including phosphate buffer, pure water and five kinds of biological buffers (pH around 7) were systematically studied in terms of their ability to clean-up plasma matrix on precolumns of restrictedaccess media in a column-switching system. The necessary washing time, buffer pH, type and content of organic modifier were evaluated with respect to plasma elution profiles on restricted-access media precolumns. The influence of different mobile phases on the recovery of plasma matrix from alkyl-diol silica precolumns was studied by means of a scanning spectrophotometer. Our results show that phosphate buffer near physiological pH with small amounts of 2-propanol or acetonitrile was prefereble for direct injection of large plasma volumes (500 μL). More than 93% of the proteins in a plasma matrix can be recovered within 3 min from the alkyl-diol silica C18 column (25 mx 4 mm I.D.) as measured at 280 nm for all selected mobile phases except for tris (hydroxymethyl) aminomethane buffer, from which only about 88% was obtained.
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    HPLC analysis of boldine in pharmaceuticals (1997)
    Springer
    Chromatographia 44 (1997), S. 619-622 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Boldine in pharmaceuticals
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is proposed for extraction, separation, identification and quantitative measurement of boldine (I) in pharmaceuticals. The extraction of (I) from the matrix (syrups, tablets, extracts) was realized with aqueous ammonium chloride (0.02 M, pH=3.0 with perchloric acid) and the clean-up of the extract was performed by solid-phase extraction by means of cartridges containing a strong cation-exchange sorbent, from which (I) was eluted with aqueous ammonium chloride (1 M, pH=10.0 with ammonia). The final eluate was examined by HPLC. Chromatography was performed on a C-8 column with a gradient elution from 15:85 to 30:70 of acetonitrile-water containing 0.1 M sodium perchlorate (pH=3.0), in 20 min. A diode array detector was used at 302 nm for detection. The method gives recovery values greater than 98% and the reproducibility is within 6.0%.
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    Chiral chromatography of amino- and hydroxy-acids on surface modified porous graphite (1995)
    Springer
    Chromatographia 40 (1995), S. 9-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphite ; Chiral stationary phase ; Copper complexation chromatography ; Amino acids ; Hydroxy acids ; Adsorbed stationary phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new type of chiral stationary phase has been prepared by coating porous graphite with a near-monolayer of an adsorbed enantiomeric modifier which then acts as an adsorbed stationary phase. The most effective modifiers are L- or D-isomers of N-(2-naphthalene-sulphonyl)-phenylalanine (NS-Phe). Conveniently 80% of monolayer coverages, corresponding to 1.2 μmol m−2, are achieved by adsorption of NS-Phe from methanolic solution. Enantiomeric separations by complexation with cupric ion show base-line resolution of α-amino and α-hydroxy acids with separation factors up to 2. Identical separations are achieved with chiral phases made from the L- and D-isomers of NS-Phe except that the elution orders of enantiomers are inverted. Reduced plate heights are around 5 and the adsorbed chiral phases are extremely stable, retention ratios being unchanged after passage of 7000 column volumes of eluent. A mechanism of retention is proposed, which fits the experimental observations.
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    Analysis of azines and diazines by HPLC on bonded alkyl stationary phases. Pyridine and quinoline in environmental samples (1997)
    Springer
    Chromatographia 44 (1997), S. 253-256 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Environmental samples ; Azines and diazines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Several heterocyclic compounds have been investigated by HPLC on RP-8 and RP-18 with methanol-water mixtures as mobile phase. The chromatographic systems developed showed good selectivity for determination of azines and diazines. Pyridine and quinoline have been determined in environmental samples and in food. Samples for analysis were preconcentrated by solid phase extraction on-column with octadecyl silane packing.
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    Enantiomeric resolution of anti-HIV agents on a cellulose derivative chiral stationary phase. Note II (1995)
    Springer
    Chromatographia 40 (1995), S. 39-41 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantioseparation ; ChiralcelR OJ ; Anti-HIV agents ; Thiazolo-benzimidazoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A series of enantiomeric 1H,3H-thiazolo[3,4-a] benzimidazoles with anti-HIV activity has been stereospecifically analyzed. The enantiomeric resolution has been carried out by means of an HPLC method using a column of cellulose tris-(4-methyl-phenylbenzoate) ester adsorbed on macroporous silica gel (ChiralcelR OJ).
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    Analysis of lignin degradation products by capillary electrophoresis (1995)
    Springer
    Chromatographia 40 (1995), S. 51-57 
    Details
    ISSN: 1612-1112
    Keywords: Column electrophoresis ; Column liquid chromatography ; Phenolic lignin degradation compounds ; Sugar degradation products ; Quantitative analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method for the quantitative analysis of phenolic lignin degradation products by capillary electrophoresis (CE) with on-column UV detection has been developed. The liquid biomass solutions contain low molecular hemicellulosic sugars and phenolic lignin degradation products with various degrees of polymerization. Special attention has been paid to the monomeric phenolic components of lignin degradation fragments, e.g. derivatives of phenolic acids, aldehydes, and alcohols. Uncoated fused silica capillaries and borate-phosphate buffer systems at moderate pH conditions were used in order to separate the compounds of interest. To provide validation of the method, the same samples were analyzed independently by HPLC using gradient elution on a RP-C18 column. As sugar degradation fragment, furan-2-carboxylic acid was detected.
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    Liquid chromatography of phenolic compounds in natural water using on-line trace enrichment (1995)
    Springer
    Chromatographia 40 (1995), S. 85-90 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Ion-pair solid phase extraction ; On-line trace enrichment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Two packing materials, C18 and PLRP-S, are studied for on-line trace enrichment of phenolic compounds in water. Various precolumns of different internal diameter are also tested and the addition of an ion-pair reagent to increase retention and thus, breakthrough volumes of phenolic compounds, is studied. Best results are obtained when a PLRP-S precolumn is coupled on-line with a C18 analytical column and DAD detector. Addition of TBA considerably increases breakthrough volumes. In contrast, when a C18 precolumn is used, breakthrough volumes are lower and it is impossible to determine TCP and PCP, under the experimental conditions used, because of interference of other nonpolar compounds in the samples. The performance of the system is evaluated with river and tap water and the preconcentration of 10 ml of sample in a PLRP-S precolumn involves a linear range between 1 μg 1−1 and 20 μl−1 and limits of determination between 0.5 μg l−1 and 1 μg l−1 are obtained.
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    Oxidation of acetophenone in a high temperature open-tubular capillary column liquid chromatographic system (1995)
    Springer
    Chromatographia 40 (1995), S. 99-101 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High temperature open-tubular columns ; Solvent make-up ; Acetophenone oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Acetophnone, a substance stable at room temperature, is readily oxidizes in a high temperature open tubular liquid chromatographic system by the residual oxygen in the mobile phase. The oxidation product is less UV absorptive and detection sensitivity decreases greatly. To prevent the oxidation, through degassing of the mobile phase is necessary.
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    Determination of D- and L-amino acid residues in peptides with fluorescent chiral tagging reagents by high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 645-651 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chiral resolution of amino acids ; Pre-column derivatization ; Fluorescent chiral tagging reagents ; Stereochemical purity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Derivatization of amino acid enantiomers with fluorescent chiral Edman-type reagents, 4-(3-isothiocyanatopyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole [R(−)- and S(+)-NBD-PyNCS] and 4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole [R(−)-and S(+)-DBD-PyNCS], yields corresponding diastereomers separable by reversed-phase HPLC on normal achiral columns. The resolved diastereomers were detected fluorometrically at 530 nm with excitation at 490 nm for the NBD-PyNCS derivatives and at 560 nm with excitation at 450 nm for those derived from DBD-PyNCS reagents. This HPLC-derivatization method was used for evaluation of stereochemical purity for some synthetic commercial peptides. The enantioanalysis was reliable down to 0.05% racemization of the amino acid residues and a quantity of 100 μg peptide sample was usually enough for the analysis. Two acid hydrolysis methods, i.e. the standard procedure with constant-boiling hydrochloric acid (HCl) and a rapid vapor-phase procedure with HCl-trifluoroacetic acid (TFA) mixture, were compared. The later was found to be unsuitable owing to increased racemization of the amino acid residues during the hydrolysis. Judging from the results obtained for proline and leucine residues, most of the tested peptides including biologically active peptides, such as neurotensin, [d-Ala2,d-Leu5]-enkepharin and morphine tolerance peptide, possessed stereochemical purities higher than 98%. Influence of structural features of the peptides on the racemization of the amino acid residues was found to be significant.
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    Effect of pH on the retention behaviour of some preservatives-antioxidants in reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 652-656 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preservatives-antioxidants ; Eluent pH ; Retention and separation factors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In this paper the dependence of eluent pH on the efficiency of separation in RP-HPLC is described. Preservatives-antioxidants, esters ofp-hydroxybenzoic acid (methyl, ethyl, propyl and butyl parabens), sorbic acid, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate (PG) and L-ascorbic acid (Vitamine C) were investigated by reversed-phase high-performance liquid chromatography, utilising isocratic elution with UV detection. The mobile phase composition (methanol-water v/v containing 1% acetic acid), was varied in order to obtain the best separation. For all substances analysed the pH, pKa and the fitted pKa values were calculated in different mixtures of mobile phases using the graphical method of Charlot and Trémillon [1]. The retention factors (k) and the separation factors (α) were also calculated.
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    Analysis of pyrithiones by reversed-phase high-performance liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 669-673 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Transchelation ; Zinc pyrithione and related compounds ; Antidandruff formulations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the determination of zinc pyrithione in antidandruff formulations. Zinc pyrithione was converted into a stable copper complex and then analysed by reversed-phase HPLC. The proposed method allows the separation of the analyte from related pyrithiones and therefore is able to verify the compliance of cosmetic preparations with current legislation.
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    HPLC-continuous-flow fast atom bombardment mass spectrometry (HPLC-CFFAB) — a convenient method for the analysis of bile acids in bile and serum (1995)
    Springer
    Chromatographia 40 (1995), S. 674-679 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mass spectrometric detection ; Fast atom bombardment ionization ; Serum bile acid ; Rat bile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to analyse bile acids in biological matrices, e.g. rat bile and human serum, high performance liquid chromatography (HPLC) was coupled to continuous-flow fast atom bombardment mass spectrometry (CFFAB-MS). A gradient elution system which had already proved to be well suited for the quantitative determination of conjugated bile acids in bile was modified to allow HPLC-CFFAB-MS-coupling. Due to the sensitivity of this coupling method it is possible to obtain more information about the biliary bile acid pattern and species-specific secondary bile acids. Furthermore, we were able to identify obviously unknown bile acid species in rat bile which most likely classify as mono-oxo and di-oxo-taurocholates (MW 513 Da, 511 Da) and mono-oxo-glycocholates (MW 463 Da). In the present study we show that using this system it is possible to determine both conjugated and unconjugated as well as sulfated bile acids, without time consuming group separation and derivatization, from rat bile and human serum. In addition, it is suggested that the method presented here should be considered for use in routine analysis.
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    Determination of sugars by liquid chromatography and amperometric detection with a cuprous oxide modified electrode (1995)
    Springer
    Chromatographia 40 (1995), S. 684-689 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sugars ; Amperometric detection ; Chemically modified electrodes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chemically modified electrode was applied as a working electrode for the amperometric detection of sugars in liquid chromatography. A mixture of cuprous oxide and conductive carbon cement was used as electrode material. Cuprous oxide acted as a catalyst for the oxidation of sugars. Cyclic voltammetry was used to examine the oxidation of the sugars at the electrode surface. The stability and sensitivity of a cuprous oxide/conductive carbon cement (20/80 %, w/w) electrode were tested in flow injection analysis experiments. For liquid chromatography, sugars were separated on an ion-exclusion column with 0.01 M H2SO4 as mobile phase. After the separation, 0.2 M NaOH was added post-column and the sugars were determined at 550 mV vs. Ag/AgCl. Calibration was linear in the range of 10−6·10−3 M with limits of detection of approximately 1·10−6M. The application of the modified electrode for the determination of sugars in fruit beverages and dairy products following chromatographic separation is shown.
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    Quantitative structure-retention relationships for the investigation of the retention mechanism in high performance liquid chromatography using apolar eluent with a very low content of polar modifiers (1995)
    Springer
    Chromatographia 40 (1995), S. 690-696 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Structure vs. retention ; Principal component analysis ; Multiple linear regression ; Molecular descriptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The mechanism of the retention in HPLC when using a non-polar solvent with a very low content of polar modifier as mobile phase is outside the scope of the classical interpretations. We have used quantitative structure-retention relationships (QSRR) to interpret the retention of a series of 36 compounds on 18 chromatographic systems (3 stationary phases and 6 mobile phases). Principal Component Analysis (PCA) was used to reduce the complexity of the data and to obtain the most significant axis; molecular modeling (molecular mechanics and molecular orbital calculations) was used to obtain structural information on the solutes, and multiple regression to correlate coordinates and descriptors. We have shown that the coordinates of the solutes on the first PCA axis are related to three molecular descriptors: the calculated logarithm of the partition coefficient in an octanol/water system (Log P), the polarisability (pol) and the energetic level of the highest occupied molecular orbital (HOMO). We have found the same equation with a similar coefficient for the three different stationary phases. These results prove the dominant role of the polar modifier in such chromatographic systems.
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    URL: http://dx.doi.org/10.1007/BF02315139
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    Isolation and purification of digalactosyldiacylglycerols (1995)
    Springer
    Chromatographia 40 (1995), S. 129-133 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Digalactosyldiacylglycerols ; Solid phase extraction ; Oats ; Experimental design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A convenient method for the isolation of digalactosyldiacylglycerols from plant material has been developed using solid phase extraction. Commerical cartridges were utilized to prepare 100 mg fractions of galactolipids containing more than 97% of digalactosyldiacylglycerol. The purity of the fractions was monitored by an isocratic normal phase analytical HPLC procedure, which was optimized using factorial design. The optimized system was successfully scaled up to a semi-preparative HPLC system with a capacity of about 10 mg/injection which was used to further purify the digalactosyldiacylglycerol fraction.
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    URL: http://dx.doi.org/10.1007/BF02272159
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    Application of micropellicular poly-styrene/divinylbenzene stationary phases for high-performance reversed-phase liquid chromatography electrospray-mass spectrometry of proteins and peptides (1997)
    Springer
    Chromatographia 44 (1997), S. 438-448 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Electrospray ionization mass spectrometry ; Micropellicular poly-styrene/divinylbenzene ; Peptides and proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Short columns packed with highly crosslinked 2.3 μm poly-styrene/divinylbenzene (PS/DVB) particles were used for rapid and efficient separation of proteins and peptides by reversed-phase high-performance liquid chromatography at elevated temperatures. Enhancement of the diffusivities of the sample components at elevated temperatures together with the short diffusion pathlength with the micropellicular polymeric stationary phases were responsible for high efficiency, high speed of analysis, and short column regeneration times. Underivatized PS/DVB beads as well as PS/DVB microspheres which have been modified with polyvinylalcohol or octadecyl chains on the surface were synthesized, employed, and compared to HY-TACH-C18, a commercially available micropellicular octadecyl-silica stationary phase, for the separation of proteins, octapeptides and tryptic protein digests. Highest performance was obtained with the silica- and PS/DVB-based octadecyl stationary phases, which exhibited similar column efficiencies but different selectivities for proteins and peptides. The minimum detectability at 214 nm and the maximum loading capacity for ribonuclease A using analytical 30×4.6 mm I.D. columns were 10 ng (0.6 pmol) and 1 μg, respectively. Finally, reversed-phase HPLC with a 60×2 mm I.D. narrow-bore column packed with micropellicular octadecyl PS/DVB was coupled successfully to electrospray mass spectrometry at a flow-rate of 0.15 mL min−1 and on-line full-scan mass spectra for molecular mass determination and identification of proteins in the lower picomol range were obtained.
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    URL: http://dx.doi.org/10.1007/BF02466324
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    A stability-indicating HPLC method for the determination of benzalkonium chloride in 0.5% tramadol ophthalmic solution (1995)
    Springer
    Chromatographia 40 (1995), S. 155-158 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Benzalkonium chloride ; Tramadol ; Ophthalmic solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high-performance liquid chromatographic procedure employing ultraviolet detection for the analysis of benzalkonium chloride in 0.5% Tramadol ophthalmic solution is reported. The method requires minimal sample pretreatment and is sensitive, accurate, and reproducible. The peak area versus BAK concentration is linear over the range of 50–150% of its label claim of 0.05 mg/mL. The mean absolute recovery of BAK using the described method is 100.2±1.2%, (mean ±SD, n=10). A stress study with heat, acid, base and UV radiation indicates that the method is stabilityindicating with no interference from drug or degradation products.
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    URL: http://dx.doi.org/10.1007/BF02272164
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    Fluorescence enhancement of dansylamino acids by bovine serum albumin as mobile phase additive in microcolumn liquid chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 159-162 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorescence enhancement ; Bovine serum albumin ; Dansylamino acids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effects of acetonitrile and bovine serum albumin (BSA) concentrations on the signal intensity and retention behavior of dansylamino acids have been examined by using γ-cyclodextrin-bonded silica gel as the stationary phase in microcolumn liquid chromatography. Fluorescence intensities of dansylamino acids were enhanced by BSA as a mobile phase additive, e.g., detection limits of dansyl derivatives of L-Ala and L-Phe were improved by a factor of 12–18.
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    URL: http://dx.doi.org/10.1007/BF02272165
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    An HPLC screening method for the detection of isonicotinic acid hydrazide in cattle milk (1995)
    Springer
    Chromatographia 40 (1995), S. 170-174 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isoniazid in milk ; SPE preconcentration ; Diode array UV spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simple, fast, accurate and highly sensitive (5 ng/ml) method for the detection of sionicotinic acid hydrazide (isoniazid) in cattle milk is described, based upon an RP-HPLC system, equipped with a C18 column and a UV detector. Milk was deproteinized with trichloroacetic acid and treated with cinnamaldehyde, before being injected into the HPLC system. Preconcentration of samples on an SPE phenyl cartridge allows the sensitivity of the method to be increased to 0.05 ng/ml using a UV detector. The presence of isoniazid can be confirmed at concentrations as low as 0.4 ng/ml, through a diode-array UV spectrum of isoniazid hydrazone. The analytical procedure here described is routinely applied to investigate the illegal administration of isoniazid to cattle, as it provides a means of screening that can be carried out in a very short time.
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    URL: http://dx.doi.org/10.1007/BF02272167
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    A statistical study of the correlation between k′ or log k′ and log Pow for a group of benzene and naphthalene derivatives in micellar liquid chromatography using a C-18 column (1995)
    Springer
    Chromatographia 40 (1995), S. 185-192 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micellar liquid phases ; Octanol-water partition coefficient ; Benzene and naphthalene derivatives
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is shown that the logarithm of the capacity factor (log k′) for fifteen benzene and naphthalene derivatives in micellar liquid chromatography with forty nine different mobile phases generally correlates better with the logarithm of the octanol-water partition coefficient (log Pow) than the capacity factor (k′). Optimum conditions are established to obtain the best linear correlations of log k′-log Pow.
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    Thermodynamic behavior of mixed benzodiazepines by a new liquid chromatographic method (1995)
    Springer
    Chromatographia 40 (1995), S. 193-196 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemometric methodology ; Elution order ; Simplex optimization ; Benzodiazepines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using a rapid chemometric methodology to determine the separation factor, α, at different temperatures, Gibbs Helmholtz parameters (Δ (ΔH), Δ (ΔS), Δ (ΔG)) of two adjacent benodiazepines on a chromatogram were obtained from ln α versus T−1 plots. A temperature dependent reversal of the elution order was studied and the mobile phase composition and column temperature were optimized to obtain the best separation. A flow rate of 0.80 ml min−1 with 52.6% methanol in the methanol-water mixture and a column temperature of 48°C gave the most efficient separation of ten benzodiazepines.
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    A stability-indicating HPLC method for the determination of 17β-estradiol-3-phosphate in an ophthalmic solution (1995)
    Springer
    Chromatographia 40 (1995), S. 204-206 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stability-indicating method ; 17β-Estradiol-3-phosphate ; Ophthalmic solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed-phase high-performance liquid chromatographic (HPLC) procedure using ultra-violet (UV) detection for the analysis of 17β-estradiol-3-phosphate in an ophthalmic solution is reported. The method is selective, accurate, and reproducible. The peak area versus 17β-estradiol-3-phosphate concentration is linear over the range of 50–150% of its label claim of 1.0 mg/mL, with a detection limit of 20 ng/mL. The mean absolute recovery of 17β-estradiol-3-phosphate using the described method is 99.8±0.6% (mean ±SD, n=10). A stress study with heat, acid, base and UV radiation indicates that the method is stability-indicating with no interference from excipients or degradation products.
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    URL: http://dx.doi.org/10.1007/BF02272172
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    Improvement of selectivity of electrochemical detection for the determination of compounds with chloro aromatic rings (1995)
    Springer
    Chromatographia 40 (1995), S. 247-252 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Photolysis ; Electrochemical detection ; Drugs with chlorinated aromatic rings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Pharmaceuticals containing a thiazide ring or chlorinated aromatic ring were investigated with respect to enhanced selectivity in determination. Oxidative electrochemical detection coupled with HPLC was used to study the influence of the pH of the mobile phase under conditions of photolysis. To cover a pH range 3.9–12, the employment of a polymer column stable in alkaline media was necessary. The method offers the great advantage of derivatization without chemicals at low operating potentials, thereby providing high selectivity.
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    Mixed-mode liquid chromatography of aliphatic anionic surfactants with a naphthalenetrisulfonate mobile phase (1995)
    Springer
    Chromatographia 40 (1995), S. 237-246 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mixed mode stationary phases ; Indirect photometric and fluorometric detection ; Conductimetric detection ; Alkyl-sulphates, and sulphonat-phosphates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Separation of three classes of anionic surfactants (alkyl sulfates, alkanesulfonates, and alkyl phosphates) are achieved on a mixed-mode reversed phase (RP) phenyl/-anion exchange column using a naphthalenetrisulfonate (NTS)-acetonitrile (ACN) mobile phase via indirect photometric, indirect fluorometric, direct or indirect conductivity detection. Mixtures of C5−C18 sulfates, C6−C18 sulfonates, and C1−C4 phosphates (mono- and di-ester) can be separated in less than 20, 24, and 20 min respectively. Although hydrophobic effects are more pronounced in mixed-mode chromatography, equivalent-per-equivalent exchange of analysis and eluent ion is still required for sensitive indirect photometric, fluorometric, or conductivity detection. The detection limits of alkyl sulfates and alkanesulfonates are in the range of 3–15 pmoles which are at least an order of magnitude better than suppressed conductivity detection. The determination of surfactants in a variety of real samples is also presented.
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    A potential application for large diameter pellicular supports in the reversed phase study of ultra high molecular mass polystyrenes (1995)
    Springer
    Chromatographia 40 (1995), S. 307-312 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Reversed phase ; Polystyrene ; Pellicular ; Ultra high molecular mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ultra high molecular mass (〉 7 million dalton) polystyrenes are prone to degradation in size exclusion chromatography. In gradient elution reversed phase HPLC they do not elute visibly on small particle size porous supports. However, large diameter C18 pellicular particles were successfully employed for reversed phase study of ultra high molecular mass (15 million dalton) polystyrenes without polymer degradation during elution. Although retention for the lower molecular mass polystyrenes was lower than on small diameter porous particles, the medium high molecular mass polystyrenes (0.5–1 million dalton) showed similar retention. The addition of small diameter porous particles in small quantities, to the large diameter pellicular particles, increased the amount of retention of the low molecular mass polystyrenes without affecting the higher molecular mass polystyrenes.
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    URL: http://dx.doi.org/10.1007/BF02290362
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    Retention in liquid chromatography with multicomponent mobile phases: Relationship with binary systems (1995)
    Springer
    Chromatographia 40 (1995), S. 321-328 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Multicomponent mobile phases ; Retention prediction ; Binary and multicomponent phases, comparison
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Using the concept of an effective concentration a method is proposed for predicting retention in liquid chromatography with multicomponent mobile phases based on experiments with corresponding binary ones. The method is verified for normal and reversed-phase systems with ternary mobile phases and agrees closely with experimental data.
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    High performance liquid chromatographic determination of methyl ethyl ketone in urine as its 3-methyl-2-benzothiazolinone hydrazone derivative (1995)
    Springer
    Chromatographia 40 (1995), S. 336-340 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Methyl ethyl ketone in urine ; Derivatization ; 3-Methyl-2-benzothiazolinone hydrazone ; Comparison with GC-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A HPLC method for the determination of methyl ethyl ketone (MEK) in urine after derivatization with 3-methyl-2-benzothiazolinone hydrazone is proposed. The calibration curve for the ketone was linear, ranging between 0.23–10 mg/L, with a detection limit of 0.025 mg/L. The results were compared to those obtained by GC-MS, coupled to the headspace technique. MEK derivatization and the derivative purification processes were verified with respect to the main variables such as reaction temperature, reagent concentration, probable interferences and enrichment phase. The method is simple and reliable and shows a good sensitivity.
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    URL: http://dx.doi.org/10.1007/BF02290366
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    Indirect photometric detection of inorganic anions by microcolumn liquid chromatography using anthraquinone-disulfonate as visualization agent (1995)
    Springer
    Chromatographia 40 (1995), S. 379-381 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Indirect photometric detection ; Anthraquinone-disulfonate ion ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Disodium salts of several anthraquinone-disulfonic acids, which possess large molar absorptivity, were employed as the visualization agent for microcolumn ion chromatography with indirect photometric detection. Detection limits of inorganic anions were improved, e.g., concentration detection limits of chloride, nitrate and sulfate were 0.91–1.6 μmol L−1 at S/N=3, corresponding to mass detection limits of 18–32 fmol. The present system was applied to the determination of inorganic anions in tap water.
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    URL: http://dx.doi.org/10.1007/BF02269898
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    Liquid chromatographic analysis of sulfornamides in foods (1995)
    Springer
    Chromatographia 40 (1995), S. 382-386 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sulfonamides in foodstuffs ; Honey ; Milk ; Eggs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A procedure for the simultaneous determination of several sulfonamides in different foods, such as honey, milk and eggs is proposed. The analysis is carried out using reversed phase liquid chromatography with spectrophotometric detection. Optimization of the mobile phase led to good separation and a short analysis time when an initial isocratic step with a 3∶97 acetonitrile: water mixture was used for 5 minutes, followed by a linear gradient up to a 40∶60 mixture over 15 min. The proposed method is suitable for routine quality control analysis to ensure the absence of sulfonamides in foods. Recovery studies yielded good results for all food samples because there were no interferences from the matrices.
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    URL: http://dx.doi.org/10.1007/BF02269899
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    Use of high speed liquid chromatography (HSLC) in the pharmaceutical industry. Practical aspects and limitations (1995)
    Springer
    Chromatographia 40 (1995), S. 394-398 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High speed LC ; Pharmaceutical drugs ; Routine analysis ; Fast HPLC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary High performance liquid chromatography (HPLC) is widely used in drug development and quality control. The main objective is to obtain dependable results in the shortest time in order to reduce the time taken to develop drugs and to ensure better quality of the final compound. High speed liquid chromatography (HSLC) helps us to reach this objective. In this paper pratical aspects of HSLC are discussed mainly in terms of instrument requirements and the practical needs of users. Comparison between HPLC and HSLC separations of pharmaceutical preparations are given and discussed. The contribution of HSLC to decrease solvent consumption and consequently analysis cost and its role in reducing environmental pollution, are also mentioned.
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    URL: http://dx.doi.org/10.1007/BF02269901
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    Retention parameters of some isomeric 2-benzoylbenzoic acids in reversed-phase ion-pair high performance thin-layer and column chromatography (1995)
    Springer
    Chromatographia 40 (1995), S. 453-457 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Reversed phase ; 2-benzoylbenzoic acids ; Anionic and cationic counter ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The 2-benzoylbenzoic acid series was investigated by reversed-phase, high-performance, thin-layer and column chromatography using various alkylammonium salts and di(2-ethylhexyl)orthophosphoric acid as polar associating reagents. The effects of the individual substituents on retention were quantified by Δlog k′ and ΔRM values. The compounds investigated differing in molecular structure (hydrophilic and hydrophobic substituents) commonly occurring groups in drugs and biologically active substances provide information on molecular interaction in these ion-pair systems. The combined effects on retention of organic modifier and ion-pair reagent concentration were investigated.
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    High performance liquid chromatography of disaccharides on a porous graphitic carbon column applying post-column derivatization with benzamidine (1996)
    Springer
    Chromatographia 43 (1996), S. 254-260 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Anomer separations ; Post-column derivatization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive post-column fluoresence method based on the reaction of reducing sugars with a fluorigenic reagent (benzamidine) under alkaline conditions and elevated temperature is described. Optimum reaction conditions suitable for the detection of fluorescent reaction products have been investigated. A porous graphitized carbon column (shandon Hypercarb) was employed as the chromatographic solid phase and elution was isocratic by an aqueous acetonitrile mixture. A special problem in sugar analysis is the tendendy of anomer formation giving doublet peaks. This tendency varies largely among the different sugars, and systematic studies on conditions that eliminate this problem were performed. Efficient and selective separations of a series of disaccharides were obtained using high temperatures and a low concentration of acetonitrile in the mobile phase. The detection limits (S/N=3) with an injection volume of 20 μL ranged from 10–60 picomoles. Linear calibration graphs were obtained in the 2–20 μM concentration range (r 2〉0.99). A relative standard deviation between 1–3% (n=6) demonstrated good precision of the developed system.
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    Simultaneous determination of tetrahydro-β-carbolines and β-carbolines (1996)
    Springer
    Chromatographia 43 (1996), S. 419-425 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluorimetric detection ; Tetrahydro-β-carbolines ; β-Carbolines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reversed-phase ion-pair HPLC with fluorimetric detectors connected in series was studied for the simultaneous determination of two tetrahydro-β-carbolines and two β-carbolines. After additon of internal standards the samples were reacted with fluorescamine, and then subjected to serial extractions to remove their precursor (tryptamine) from the analytical system. This treatment not only suppressed the artefactual formation of tetrahydro-β-carbolines and β-carbolines during analysis, but also effectively purified them. Under optimum conditions, using trifluoroacetic acid as counter ion, all analytes were separated within 14 min and without major interfering peaks. The quantitative ranges were 0.25–80.0 ng mL−1 for both tetrahydro-β-carbolines and 0.1–30.0 ng mL−1 for both β-carbolines. Replicate spiking experiments showed that recovery from most of the samples tested was over 90% and the relative standard deviation ranged from 0.7 to 10.4% within and between assays. The proposed method was applicable to various materials such as soy sauce, vinegar, ketchup, tabasco, beer, wine, sake, whisky, brandy, cows' milk, coffee, cocoa, cheese, cigarette smoke and urine.
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    URL: http://dx.doi.org/10.1007/BF02271022
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    Retention on Diol column—A case study (1996)
    Springer
    Chromatographia 43 (1996), S. 436-438 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol columns ; Optimisation ; Ephedrine ; Synopen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of simultaneous variation of buffer pH, molarity and organic modifier concentration when Diol stationary phase is used was experimentally studied. An equation has been derived for the retention time in the interpolation region of ephedrine and synopen—principal active components in an antihistamine formulation.
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    URL: http://dx.doi.org/10.1007/BF02271026
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    Open tubular liquid chromatography using a sol-gel derived stationary phase (1996)
    Springer
    Chromatographia 43 (1996), S. 477-483 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Open tubular columns ; Sol-gel coatings ; Laser-induced fluorescence detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An organically modified silica glass material containing octyl groups (C8) was fabricated by the sol-gel process and coated onto the inner walls of fused silica capillaries. The coating was used as the stationary phase for reversed-phase open tubular liquid chromatography (OTLC). The sol-gel process facilitated the fabrication of a porous silica glass layer with the stationary phase in one single step. The high surface area of the coating, characteristic of materials fabricated by the sol-gel process, resulted in capillary columns with a stronger retention than those prepared by a conventional procedure. The molar ratio of the precursors was used as a tunable parameter to adjust the retention and selectivity of the stationary phase. The column performance was evaluated using anthracene derivatives as model analytes which were monitored by laser-induced fluorescence (LIF) detection. Separation efficiencies of 200,000 theoretical plates/meter were typical for the model compounds. Solute selectivity of the sol-gel derived stationary phase was found to be similar to the selectivity of HPLC monomeric-type phases.
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    Urine clean-up method for determination of six arsenic species by LC-AAS involving microwave assisted oxidation and hydride generation (1996)
    Springer
    Chromatographia 43 (1996), S. 507-512 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Urine clean-up ; Arsenic speciation ; Microwave assisted oxidation ; Atomic absorption spectrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An effective clean-up method based on the precipitation of most high molecular mass inorganic salts and organic compounds in ethanol at −15°C has been developed for the determination of arsenite, arsenate, monomethylarsonate (MMA), dimethylarsinate (DMA), arsenobetaine (AsB) and arsenocholine (AsC) in urine. Analyte recovery was close to 100%. The six species were separated on an anionic HPLC column and determined by microwave-assisted oxidation-hydride generation-atomic absorption spectrometry. The detection limits and relative standard deviation of the whole procedure were within the 8–15 μg L−1 and 2.5–5.3% ranges, respectively, which allows application to the analysis of urine of people exposed to arsenic.
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    Reversed-phase high-performance liquid chromatographic separation of mono- and divinyl chlorophyll forms using pyridine-containing mobile phases and a polymeric octadecylsilica column (1997)
    Springer
    Chromatographia 44 (1997), S. 43-49 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Mono-and divinyl chlorophylls ; Polymeric ODS phases ; Pyridine containing mobile phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The separation of chlorophyll forms was studied employing a wide bore polymeric octadecylsilica column and pyridine containing mobile phases, giving consideration to considering the influence of mobile phase composition and column temperature on the resolution of monovinyl forms from their divinyl analogues. A method involving gradient elution and operating at 15°C is proposed for the separation of several polar and non-polar mono- and divinyl chlorophylls from etiolated tissues of higher plants and from marine phytoplankton. The advantages of pyridine as a mobile phase additive in the reversed-phase liquid chromatography of chlorophylls are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466514
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  • 91
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    HPLC analysis of fat-soluble vitamins on standard and narrow bore columns with UV, electrochemical and particle beam MS detection (1997)
    Springer
    Chromatographia 44 (1997), S. 605-612 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; UV and electrochemical detection ; Particle beam-mass spectrometry ; Fat-souble vitamin ; Standard-bore and narrow-bore columns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The application of different detection techniques; UV, electrochemical (ED) and particle beam-mass spectrometry (PB-MS) for the high-performance liquid chromatography analysis of fat-soluble vitamins were studied. Separation of all compounds examined was performed using both C8 standard-bore and narrow-bore columns for UV and MS detection, whereas in the case of HPLC-ED, a C8 standard-bore column only was used. Detector responses were studied in terms of linear range, detection limit and precision. The HPLC methods with UV, PB-MS and electrochemical detection were applied to the assay of vitamins A and E in an infantformula, powdered-milk sample. Recovery studies showed good results both for vitamins A and E, within-run precision being 2–4% for LC-UV and LC-ED techniques. In addition, excellent aggrement between the results obtained with the detection systems explored was found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466663
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  • 92
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    Determination of sorbic acid in wines with a hydrogen sulfonated divinyl benzene-styrene copolymer HPLC column (1997)
    Springer
    Chromatographia 44 (1997), S. 645-648 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Wine ; Sorbic acid ; Styrene-DVB sorbents ; Detection limit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A method is proposed for the determination of sorbic acid in wines using a hydrogen sulfonated divinyl benzene-styrene copolymer (DVB-H) HPLC column and isocratic elution with 0.01N H2SO4:CH3CN (75:25). UV detection at 258 nm permits analysis by direct injection of white and red wines without significant interference between the peaks of sorbic acid and other sample components. The limit of detectability of the method is 0.01 mg L−1 with an average recovery of 99.6% and an average % RSD of 0.87. Analyses of 30 wine samples by the proposed method and the official EEC spectrophotometric method show that there is a good correlation between the results of the two methods, although the HPLC analyses are clearly more precise and accurate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466668
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  • 93
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    An exprimental design approach to selecting the optimum liquid chromatographic conditions for the determination of vitamins B1, B2-phosphate, B3, B6 and C in effervescent tablets containing saccharin and sunset yellow FCF (1997)
    Springer
    Chromatographia 44 (1997), S. 634-644 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Vitamin B and C in tablets ; Experimental design ; Optimization of separation ; Multiple regression modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The ion-pair liquid-chromatographic separation of the water-soluble vitamins thiamine mononitrate, riboflavin phosphate, nicotinamide, pyridoxine hydrochloride, ascorbic acid, saccharin, and the dye Sunset Yellow FCF (E110) has been examined for the analysis of the compounds in effervescent tablets. A Draper-Lin small composite design was used to study the impact on the compounds' retention times and peak-widths (the response variables) of four different mobile phase variables: percentage of methanol as organic modifier, the concentrations of hexanesulfonate as ion pairing reagent and of triethanolamine as competitive base, and pH. The interactions of these variables were also studied. The proposed design enabled derivation of multiple linear regression equations to model each compound's retention time and peak-width at half-height. The statistical reliability of the regression models was established by comparing predicted and experimental values. By introducing the regression models into a spreadsheet program (Excel 5.0), retention times and peak-widths for each compound were calculated at fixed mobile phase pH. The values of all the other combinations of the three mobile phase variables were changed in increments of two units within their examined boundaries, resulting in 225 different rows. For each combination the compounds' calculated retention times and their corresponding peak-widths were sorted in increasing order and the resolution between successive peaks was calculated. The minimum effective resolution (R s min) between each pair of peaks and the maximum retention time (t R max) in each row were then selected and used to construct contour plots indicating the location of zones of mobile phase parameter combinations whereR s min〉1.5 and the analysis was rugged, and wheret R max values were minimum. Their common regions resulted in optimum chromatographic separations. Examples are shown of chromatographic separations obtained using mobile phase combinations which were the best compromise of the three criteria selected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466667
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  • 94
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    The chromatographic behavior of arsenic compounds on anion exchange columns with binary organic acids as mobile phases (1998)
    Springer
    Chromatographia 47 (1998), S. 257-263 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion exchange chromatography ; Anion-exchange chromatography ; Arsenic compounds ; Flame atomic absorption detector
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Identification and quantification of arsenic compunds was performed with high- performance liquid chromatography (HPLC) and flame atomic absorption spectrometry (FAAS) as element-specific detector. Arsenous acid, methylarsonic acid, dimethylarsinic acid, arsenic acid, arsenobetaine, and arsenocholine were separated on two anion-exchange columns (Synchropak Q 300 and PRP-X 100) with different binary organic acids as mobile phases. The infleunce of chromatographic parameters, such as pH and the concentration of the mobile phase were investigated. An unusual chromatographic behavior of arsenous acid was observed when tartaric acid was used as mobile phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466529
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  • 95
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    The application of high performance liquid chromatography, coupled to nuclear magnetic resonance spectroscopy and mass spectrometry (HPLC-NMR-MS), to the characterisation of ibuprofen metabolites from human urine (1998)
    Springer
    Chromatographia 47 (1998), S. 264-270 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; NMR and MS detection ; Ibuprofen metabolites ; Urine extracts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of HPLC-NMR-MS for the detection and identification of the metabolites of ibuprofen present in a solid phase extract of human urine is described. Gradient reversed-phase HPLC was used to separate the components present in the extract, which were then characterised by a combination of stopped-flow1H NMR and on line electrospray-MS. This approach led to the rapid identification of the known phase 1 human metabolites of ibuprofen, including hydroxy- and carboxy- metabolites, together with their respective glucuronide conjugates. In addition a probable artefact resulting from the dehydration of one of the side chainhydroxylated glucuronides was also identified.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466530
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  • 96
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    Retention study on silica gel in high-temperature liquid chromatography (HTLC) (1998)
    Springer
    Chromatographia 47 (1998), S. 278-284 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; High-temperature columns ; Retention behavior ; Column equilibration ; Bilayer formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention volumes (V N) of different kinds of test compound have been measured on silica gel as a function of column temperature (T) in the range 20 to 210°C.n-Heptane and mixtures ofn-heptane and polar modifiers were used as mobile phases. With nC7 and nC7-1,4-dioxane mixtures, there was a good linear relationship between InV N and 1/T for column temperatures above 100 °C. When more polar modifiers such as butanol, ethanol and acetic acid were used, ‘N’-shaped curves were obtained for the plots of InV N against 1/T. Possible explanations of this retention behavior have been proposed on the basis of related studies and common physical chemistry relationships. Column equilibration time after alteration of water content or column temperature is greatly reduced at elevated temperatures. This will benefit the application of LSC on silica gel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466532
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  • 97
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    Use of short columns and high flow rates for rapid gradient reversed-phase chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 291-298 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Capillary electrochromatography ; Rapid analysis ; Short columns ; Rapid gradients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Rapid analyses were performed using reversed-phase liquid chromatography with short (20–100 mm) columns swept by fast yet shallow gradients, and the results compared with those obtained with 150 mm columns and slow gradients. The resolution losses incurred with shorter columns were minimised by employing elevated flow rates, to ensure that comparable mean retention factors were experienced by individual analytes during gradients run on different columns. This conserves gradient steepness. High quality performance was obtained with turn-around times of 5–10 minutes. An overall 5-fold enhancement in the rate of information generation was obtained. The relevance of instrumental parameters and of column and packing dimensions, upon the potential for improved performance is discussed. Some implications for the rapidly developing technique of capillary electrochromatography are briefly indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466534
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  • 98
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    Characterization of the precolumn bio trap 500 C18 for direct injection of plasma samples in a column-switching system (1998)
    Springer
    Chromatographia 47 (1998), S. 299-304 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Plasma samples ; Direct injection ; Restricted-access media ; Column-switching
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new restricted access media (RAM) type of precolumn, Bio Trap 500 C18, for direct injection of plasma samples in column-switching systems was evaluated with respect to the elution of plasma proteins in different mobile phases, the loading capacity of plasma samples, the chromatographic behavior during plasma injections and protein contamination of the packing and sealings. More than 95% of plasma proteins could be excluded from the precolumn within three minutes for all selected mobile phases. Quantitative analyte recoveries could be obtained by injecting plasma samples ranging from 5 to 500 μL with the analyte mass〉150 ng onto a BioTrap 500 C18 column (20×4 mm I.D.). One precolumn tolerated about 15 mL of plasma injection without out noticeable change in retention and pressure. Clogging of the precolumn was encountered (≥45 mL of plasma) due mainly to the adsorption of proteins on the packing. The performance of the analytical column (Kromasil C18) was also examined. The column efficiency decreased by 60% after processing 45 mL plasma in total.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466535
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  • 99
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    Correlation between the chromatographic poperties of silica phenyl packing materials and the retention behaviour of methylated β-cyclodextrins (1998)
    Springer
    Chromatographia 47 (1998), S. 383-390 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Stationary phase characterization ; Silica packing materials ; Cyclodextrins ; Partially methylated β-cyclodextrins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The chromatographic properties of five columns packed with phenyl-bonded phases were characterized by an approach based on Tanaka's method for column to column comparisons in order to develop an LC analysis of partially methylated β-cyclodextrins. The retention behaviour of β-cyclodextrin, heptakis(2,6-di-O-methyl)-β-cyclodextrin and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin was examined in order to evaluate the different interactions between phenyl stationary phase and this family of compound. Chromatograms show that the residual silanol activity of the packing materials plays a beneficial role in the partially methylated β-cyclodextrins separation process. It is concluded that knowledge of the interactions involved allows one to make a reasoned choice of the stationary phase in order to obtain the best possible analysis of three different commercial samples of partially methylated β-cyclodextrins.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466468
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  • 100
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    The preparative chromatographic enantioseparation of a racemic morphanthridine analog on a chiral stationary phase (1998)
    Springer
    Chromatographia 47 (1998), S. 440-442 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Preparative scale separations ; Chiral stationary phase ; Enantiomer separation ; Morphanthridine analog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The preparative chromatographic enantioseparation of a chiral morphoanthridine analog has been performed on an analytical column using amylose-tris(3,5-dimethylphenylcarbamate) as chiral stationary phase. The racemate (100 mg) was resolved to baseline within 15 min. This paper describes the development of the method, estimation of the capacity of the chiral stationary phase and discussed the potential of the chromatography if performed under preparative conditions. From the results and calculations presented it seems likely that the resolution of 70 tons year−1 could easily be achieved on 30 kg of stationary phase with a mobile-phase consumption of only 720 L day−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466476
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