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  • 1
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02315138
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  • 2
    Electronic Resource
    Electronic Resource
    Reversed-phase liquid chromatography coupled on-line with capillary gas chromatography use of an anion-exchange membrane to remove an ion-pair reagent from the eluent (1995)
    Springer
    Chromatographia 40 (1995), S. 267-271 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Column liquid chromatography ; On-line coupling ; Ion-exchange membrane ; Ion-pair reagent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In order to enable the coupling of reversed-phase liquid chromatography (RPLC) with capillary gas chromatography (GC), the performance of an anion-exchange micromembrane device has been studied to remove the ion-pair reagent methanesulphonic acid from an acetonitrile/water LC eluent. The regenerant in the membrane was tetrabutylammonium hydroxide dissolved in acetonitrile/water, which effects an anion-exchange of methanesulphonate ions for regenerant hydroxide ions. The efficiency of the exchange process was found to be 99.9%. This enabled the direct introduction of the LC eluent, free of ions and with the proper acetonitrile/water ratio, into the GC. The applicability of the on-line LC-micromembrane-GC system has been illustrated for the potential drug eltoprazine, which is quantitatively recovered with a coefficient of variation for standard solutions of 3% at the 150 μg/ml analyte level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290356
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  • 3
    Electronic Resource
    Electronic Resource
    Potential of short-column liquid chromatography with tandem mass spectrometric detection for the rapid study of pesticide degradation (1998)
    Springer
    Chromatographia 48 (1998), S. 475-480 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Short-Column LC ; Environmental water samples ; MS-MS detection ; Pesticide degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The applicability of solid-phase extraction-LC using two short columns (SPE-LC) and/or single-short-column liquid chromatography (SSC) combined on-line with tandem mass spectrometry (MS) was demonstrated for the rapid study of pesticide degradation. A fast analytical procedure was developed to provide preliminary information concerning experimental conditions, approximate rates of degradation and identity of the degradation products. Surface water samples were spiked at relevant concentration levels with well-known microcontaminants and photolysis was used to transform parent compounds into their degradation products. In general, the strategy was as follows: at 30-min intervals 10-mL samples were on-line enriched, separated by short-column LC and recorded in full-scan MS to obtain information on the disappearance of the parent compound and the appearance of breakdown products. To obtain structural information, product-ion spectra of selected compounds appearing in the full-scan MS chromatogram were recorded; this enabled the identification of several degradation products. Total analysis time of enrichment/separation and detection was about 10–15 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02466637
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  • 4
    Electronic Resource
    Electronic Resource
    Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography (1995)
    Springer
    Chromatographia 41 (1995), S. 6-14 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Two-dimensional separation ; D- and L-amino acids ; Enantioseperation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 μl heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02274188
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