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  • 1
    Electronic Resource
    Electronic Resource
    Calculation of the polychlorinated terphenyl congener distribution and gas chromatographic retention behavior of selected single standards on four stationary liquid phases (1998)
    Springer
    Fresenius' journal of analytical chemistry 362 (1998), S. 404-408 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The distribution of the 8557 theoretically possible structures of polychlorinated terphenyls (PCT) over the different degrees of chlorination and basic terphenyl backbones has been calculated and is presented in detail. As congeners missing chlorine atoms in an ortho position are suspected to be as noxious to organisms as dioxins, the number of these congeners is specified as well. The gas chromatographic retention behavior of 14 PCT single standards is studied on four stationary liquid phases for capillary columns (HP-Ultra 1, HP-5MS, RSL-300 and Polycarbonate) relative to 2,2′,3,4,4′,5,5′-heptachlorobiphenyl and shows no consequent separation of PCT in terms of the degree of chlorination. Individual congeners have been assessed for their suitability as internal standards in PCT analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051094
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  • 2
    Electronic Resource
    Electronic Resource
    Chiral Capillary Electrochromatography on a Vancomycin Stationary Phase (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 575-576 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography (CEC) ; chiral separations ; Vancomycin stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Experiments with Organic Modifiers in Reversed-Flow MEKC (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 605-607 
    Details
    ISSN: 0935-6304
    Keywords: Reversed-flow MEKC ; separation according to polarity ; organic modifiers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Reversed-flow MEKC, i.e. MEKC at low pHs to suppress the electroosmotic flow, was evaluated for the separation of some homologous series. At low pHs compared to MEKC, the elution order reverses and normal phase type migration is obtained. Moreover, the elution window is nearly infinite. Efficiencies are very high and reproducibilities in absolute migration times are acceptable (%RSD 〈 5). The influence of a series of alcohol modifiers was investigated.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Capillary GC Determination of Amines in Aqueous Samples Using Sorptive Preconcentration on Polydimethylsiloxane and Polyacrylate Phases (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 645-648 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography (GC) ; nitrogen-phosphorus detection (NPD) ; sorptive extraction/thermal desorption (SE/TD) ; amines ; in-situ derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of sorptive extraction/thermal desorption (SE/TD) for the enrichment of amines from aqueous samples was investigated. The amines were derivatized in situ in the water sample by pentafluorobenzoyl chloride and subsequently enriched onto the SE cartridge. Two SE/TD cartridges were used, a commercially available polydimethylsiloxane (PDMS) packed cartridge and a similar cartridge prepared with newly synthesized poly(butyl acrylate) (PBA). Blank profiles of PBA were not as good as those obtained from the PDMS phase. A complex chromatogram was obtained using mass spectrometric detection. Fortunately, the use of a nitrogen-phosphorus detector (NPD) resulted in clean blanks. The PBA phase showed superior performance for the enrichment of the polar amine derivatives from water samples compared to the PDMS material. Using a CGC-NPD set-up and only 1 mL samples, detection limits are in the sub-ppb range.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of Enantioselective Interactions in Direct Separation of Enantiomers by Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 197-199 
    Details
    ISSN: 0935-6304
    Keywords: Chiral recognition of 2-pentanol enantiomers ; enantioselective interactions ; capillary gas chromatography ; permethylated-β-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Sorption Tubes Packed with Polydimethylsiloxane: A New and Promising Technique for the Preconcentration of Volatiles and Semi-Volatiles from Air and Gaseous Samples (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 332-340 
    Details
    ISSN: 0935-6304
    Keywords: gas chromatography ; sorptive preconcentration ; air sampling ; VOCs ; nitro-PAH's ; PAHs ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper is concerned with the determination of volatile and semi-volatile organic components in air and gaseous (headspace) samples, focusing primarily on polar analytes. Samples were analyzed by preconcentration on different (ad)sorbents followed by thermal desorption and analysis by capillary gas chromatography. The performance of a cartridge filled with 100% polydimethylsiloxane (PDMS) particles was compared to that of adsorbents like Tenax TA and Carbotrap 300. Though the PDMS phase is non-polar it showed adequate retention for both polar and non-polar components. The blank runs of the PDMS trap were significantly better than those of most adsorbents and did not deteriorate, as was the case with all the conventional adsorbents investigated. With respect to trapping efficiencies, the PDMS phase performed better for most of the analytes under investigation compared to the adsorbents. For a range of analytes including triethylamine, butanone, diacetyl, nicotine, and acetic acid the PDMS phase performed exceptionally well whereas all adsorbents showed unsatisfactory performance. The packed PDMS traps were employed for the determination of organic acids, PAH's and nitro-PAH's in air and for the analysis of the headspace of cacao and hop.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Enantiomeric Separations in Capillary Electrophoresis Using 18-Crown-6-tetracarboxylic Acid (18C6H4) as Buffer Additive (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 323-331 
    Details
    ISSN: 0935-6304
    Keywords: Capillary zone electrophoresis ; chiral separations ; chiral crown ethers ; 18-crown-6-tetracarboxylic acid ; synthesis ; applications ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An overview is presented of the applicability of the crown ether 18-crown-6-tetracarboxylic acid (18C6H4) as buffer additive in capillary electrophoresis (CE) for the separation of enantiomers. The chiral selector 18C6H4 is particularly useful for the separation of racemates having a primary amino function. Unfortunately, the crown ether is no longer commercially available. The synthesis and spectroscopic characterization are therefore described in detail. Moreover, a method is presented for the regeneration of the crown ether after CE application. Some new enantiomeric separations of amino acids i.e. NORLEU, ARG, GLU, m-TYR, and o-TYR are listed and the influence of the pH and temperature of the separation buffer is discussed. An intermediate in the synthetic pathway, namely 18-crown-6-tetracarboxamide, did not exhibit any enantioselectivity in CE.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Analysis of the Triglycerides and the Free and Derivatized Fatty Acids in Fish Oil by Capillary Electrochromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 545-548 
    Details
    ISSN: 0935-6304
    Keywords: Capillary electrochromatography (CEC) ; fish oil ; triglycerides ; free fatty acids (FFAs) ; fatty acid methyl esters (FAMEs) ; fatty acid phenacyl esters (FAPEs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Capillary ElectroChromatography (CEC) on a fused silica capillary column (40 cm L × 100 μm i.d.) packed with 3 μm octadecylsilica (ODS) was evaluated for the analysis of the triglycerides and their fatty acids in fish oils, and more especially in the oil of Moroccan Sardinia pilchardus. The very high complexity of the lipids in fish oil is well illustrated by CEC with a nonaqueous mobile phase consisting of acetonitrile/isopropanol/n-hexane in the ratio 57/38/5 to which 50 mM ammonium acetate has been added. In order to unravel the complexity, the oil was hydrolyzed and the free fatty acids (FFAs), the methyl esters (FAMEs), and the phenacyl esters (FAPEs) were analyzed by CEC on the same column used for the analysis of the triglycerides. Isocratic elution was achieved with the mobile phase acetonitrile/50 mM MES pH 6 in ratio 9/1. The migration characteristics of FFAs, FAMEs, and FAPEs are compared. The analysis of FAPE derivatives has the advantage that quantification applying UV detection is possible and moreover that the number of double bonds in the fatty acid chains can be elucidated by measuring the UV abundance ratio 240/210 nm.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Capillary electrophoresis and capillary electrophoresis - electrospray - mass spectroscopy for the analysis of heterocyclic amines (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2213-2219 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Electrospray mass spectroscopy ; Heterocyclic amines ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Fourteen heterocyclic amines (HAs) were analyzed by capillary electrophoresis (CE) on a polyvinyl alcohol (PVA)-coated capillary column. The optimized electrolyte is composed of 20 mM ammonium acetate, pH 3.0, and 20% methanol. Similar conditions were applied in electrospray - mass spectrometry (CE-ES-MS). The CE-ES-MS optimization procedure includes the position of the capillary in the stainless steel interface, the flow of the sheath liquid and its composition.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191228
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  • 10
    Electronic Resource
    Electronic Resource
    Separation of chiral compounds by capillary electrophoresis (1998)
    Weinheim : Wiley-Blackwell
    Electrophoresis 19 (1998), S. 2798-2833 
    Details
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; Chiral separations ; Chiral selectors ; Applications ; Review ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: This review presents the different chiral selectors used in capillary electrophoresis (CE) for the separation of enantiomers. The use of charged cyclodextrins, crown ethers, polysaccharides, proteins, natural and synthetic micelles, macrocyclic antibiotics and ergot alkaloids is discussed in detail. Neutral native and derivatized cyclodextrins are not treated because several review articles have already been published on this topic. Recent developments like the application of two chiral selectors in the same background electrolyte are highlighted.
    Additional Material: 29 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150191607
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