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  • 1
    Electronic Resource
    Electronic Resource
    Characterisation of organoboron ligands by electrospray mass spectrometry using anhydrous solvent application (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 29 (1994), S. 806-807 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210291212
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  • 2
    Electronic Resource
    Electronic Resource
    Electron caputure detection in high-speed narrow-bore capillary gas chromatography: Fast and sensitive analysis of PCBs and pesticides (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 397-402 
    Details
    ISSN: 0935-6304
    Keywords: High-speed GC ; Electron capture detector (ECD) ; Detection limits ; PCBs ; Pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this work the combination of high-speed narrow-bore capillary GC with electron capture detection is evaluated. The make-up gas flow rate is a key parameter in the successful coupling of narrowbore columns and ECD detection. The make-up flow has to be as high as possible to eliminate peak tailing caused by the large detection cell volume. The sensitivities at these elevated make-up flow rates (400 to 1000 ml/min), measured for some pesticides like HCB and dieldrin, were very good. Detection limits for these compounds of 0.1 pg were obtained, resulting in minimum detectable concentrations of approximately 0.2 ppb. The performance of the system is illustrated by several high-speed analyses of environmentally relevant samples of PCBs and pesticides.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240180702
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  • 3
    Electronic Resource
    Electronic Resource
    The Use of Non-Splitting Injection Techniques for Trace Analysis in Narrow-Bore Capillary Gas Chromatography (1998)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 21 (1998), S. 491-497 
    Details
    ISSN: 0935-6304
    Keywords: Fast GC ; narrow-bore columns ; trace analysis ; splitless injection ; on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The use of hot splitless, cold splitless, and on-column injections for trace analysis in narrow-bore capillary GC is evaluated. Despite the low flow rates for the columns used, the required splitless times for splitless injections can be surprisingly short if liners with a small inside diameter are used. On-column injection can be applied by using an appropriate normal-bore precolumn coupled to the narrow-bore analytical column using a specially designed low dead volume column connector. The effects of the experimental conditions such as sample volume, injection temperature, and initial oven temperature on peak focusing and the discrimination and degradation behavior of the analytes are discussed. The possibilities to obtain sensitive and fast separations are illustrated by various applications.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure drop effects on selectivity and resolution in packed column supercritical fluid chromatography (1996)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 19 (1996), S. 449-456 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography (SFC) ; Packed columns ; Pressure drop ; Selectivity ; Resolution ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of pressure drop on retention, selectivity, plate height and resolution was investigated systematically in packed supercritical fluid chromatography (SFC) using pure carbon dioxide as the mobile phase. Numerical methods developed previously which enabled the prediction of pressure gradients, diffusivities, capacity factors, plate heights and resolutions along the length of the column were used for the model calculations. The effects of inlet pressure and supercritical fluid flow rate on selectivity and resolution are studied. In packed column SFC with pure carbon dioxide as the mobile phase, the pressure drop can have a significant effect on resolution. The flow rate is shown to have a larger effect than generally realized. The calculated data are shown to be in good agreement with the experimental results. Finally, the variation of the chromatographic parameters along a 5.5 meter long model SFC column is illustrated. The possibilities and limitations of using long packed columns in SFC are discussed. It is demonstrated that long columns with large plate numbers do not necessarily yield better separations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240190806
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  • 5
    Electronic Resource
    Electronic Resource
    Compressibility effects in packed and open tubular gas and supercritical fluid chromatography (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 458-466 
    Details
    ISSN: 0935-6304
    Keywords: SFC Pressure drop ; Efficiency ; Compressibility effects ; Analysis time ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of the pressure drop on the efficiency and speed of analysis in packed and open tubular supercritical fluid chromatography (SFC) is described: methods previously developed to describe the effects of mobile phase compressibility on the performance of open tubular columns in SFC have been extended to packed columns.The Horvath and Lin equation has been used to elucidate the influence of variations in velocity, diffusivity, and capacity factor along the column on the overall efficiency of packed column SFC. In packed columns, in contrast with the situation in open tubular columns, because the increase in velocity is no longer compensated by an increase in diffusion coefficients, the increase in both linear velocity and capacity factor which result from a significant pressure drop cause the plate height to increase along the column.The effect of fluid decompression along the length of the column on the speed of analysis in SFC has been studied and numerical expressions derived which enable calculation of compressibility correction factors for the plate height. Both the f1 and f2 correction factors remain very close to unity for acceptable pressure drops, which means that the pressure drop has virtually no effect on the number of plates generated per unit time for an unretained component. For retained species, the decompression of the mobile phase across the column causes the capacity factor to increase and hence leads to increased analysis times.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150711
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  • 6
    Electronic Resource
    Electronic Resource
    Bimodal internal energy distribution as a consequence of Cul-de-sac isomerization reactionsDedicated to Professor Dr H.-Fr. Grützmacher on the occasion of his 60th birthday. (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 369-376 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A simple model is developed to examine the internal energy distribution for metastable ions and the probability of reaction in the field-free regions of sector mass spectrometers in systems where the reactant ions in the ion source react by dissociation in competition with reversible isomerization to non-dissociating species. The internal energy distribution for the reacting ions is strongly dependent on whether dissociation is preceded by isomerization and back-isomerization, and it is shown that a range of reasonable combinations of rate constants for the forward and reverse isomerization result in a bimodal distribution of the internal energy for the ions that dissociate in the field-free regions. The isomerization effectively provides a kinetic reservoir of higher energy reactant ions. The reaction probability of the metastable ions varies strongly with internal energy, and the back-isomerized ions may in some instances be responsible for most of the reactions observed. A bimodal energy distribution will give rise to composite metastable peaks even though neither non-statistical behavior nor multiple reaction channels are involved.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270405
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  • 7
    Electronic Resource
    Electronic Resource
    Assay of the concentration and stable isotope enrichment of short-chain fatty acids by gas chromatography/mass spectrometry (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 747-754 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isotope dilution gas chromatographic mass spectrometric assays were developed for the concentration of shortchain fatty acids and of lactate in plasma. The assays involve spiking the samples with 2H- and/or 13-C-labeled internal standards and direct derivatization with 2,4-difluoroaniline, using 1,3-dicyclohexylcarbodiimide as a coupling agent. The assay can be used to determine the isotopic enrichment or mass isotopomer distribution of the fatty acids and of lactate. Blanks by ubiquitous formate, acetate and lactate are minimized by the one-step derivatization procedure without deproteinization, using reagents dissolved in hydrocarbons. The assays were applied to experiments conducted in live dogs, pigs and monkeys, and in perfused rat livers. These techniques, in conjunction with appropriate stable isotope models, can be used to study carbohydrate fermentation in humans, ruminants and non-ruminant mammals.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300514
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  • 8
    Electronic Resource
    Electronic Resource
    A regiospecific cycloaddition: Successive reactions of ·CH2CH2OH+2 with CH2OContribution from the 2nd European FTMS Workshop, Antwerp, Belgium, September 1993. (1994)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 8 (1994), S. 53-55 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Four dominant reactions can be observed when the β-distonic ion ·CH2CH2OH+2 reacts in the cell of a Fourier-transform ion cyclotron resonance spectrometer with a number of neutral molecules: protonation of the neutral molecule, ethylene radical-cation transfer, hydride abstraction from the neutral molecule, and charge exchange. Among the ethylene transfer reactions, which can lead to a variety of other distonic ions, we have throroughly studied the reaction with formaldehyde. The reaction of a first molecule of CH2O yields ·CH2CH2OCH+2. The addition of a second one leads to 1,3-dioxane which stabilizes by H· loss. This latter reaction is regiospecific.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290080110
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  • 9
    Electronic Resource
    Electronic Resource
    Unimolecular reaction of the (H3CO)3C+ cation (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1185-1188 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: From metastable ion studies, Fourier transform ion cyclotron resonance experiments and semi-empirical calculations, the unimolecular reaction of the (H3CO)3C+ cation 1 is discussed. The first step of the reaction is an irreversible, 1,3-CH3+ transfer giving the H3COC(O)O(CH3)2+ ion, 2. This ion either cleaves or isomerizes into the ion-neutral complex [H3COCO+, CH3OCH3], 3. Since the H3COCO+ cation is a very good CH3+ donor, a CH+3 transfgr then occurs within the complex, 3, to yield the predominant fragment (CH3)3O+.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091220
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  • 10
    Electronic Resource
    Electronic Resource
    Biosynthesis and characterization of 3-hydroxyalkan-2-ones and 2,3-alkanediols: Potential products of aldehyde metabolism (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 21 (1992), S. 242-248 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A mass spectrometric study of an enzymatic synthesis of 3-hydroxyalkan-2-ones (acyloins) is presented. Incubation of pyruvate or (13C3)pyruvate and various alkanals in the presence of pig heart pyruvate dehydrogenase or yeast pyruvate decarboxylase resulted in the formation of acyloins with chains two carbons longer than the alkanals. Product formation was rapid for all saturated aldehydes with chain lengths from 2 to 12 carbons. Incubation with 2,3-unsaturated aldehydes did not produce condensation products. Reduction of acyloins with sodium borohydride produced the corresponding 2,3-alkanediols. Analysis by gas chromatography/mass spectrometry was used to characterize the 3-hydroxyalkan-2-ones as the oxime-trimethylsilyl derivatives and the 2,3-alkanediols as the bistrimethylsilyl derivatives.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200210504
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