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  • 2010-2014
  • 2000-2004
  • 1985-1989  (1,448)
  • 1980-1984
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  • 101
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 345-351 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A previously unreported metabolite of the mammalian phytanic acid breakdown pathway, 2-oxophytanic acid, was isolated and analysed by mass spectrometry. The metabolic origin of the 2-oxoacid is the oxidation by a rat kidney peroxisomal H2O2-generating oxidase of L-2-hydroxyphytanic acid, a well-established intermediate in phytanic acid α-oxidation.
    Additional Material: 6 Ill.
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  • 102
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 635-635 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 103
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 659-667 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of reproducing electron capture negative ion mass spectra has been addressed by studying parameters that affect negative ion abundance on a Hewlett Packard 5985B mass spectrometer. Parameters affecting negative ion formation in the ion source, such as ion source temperature, pressure, sample concentration and electron energy, were studied in conjunction with the effect of lenses used to extract and transmit ions to the quadruples. From these experiments, it was found that, in addition to ion source temperature, the ion focus potential has the most dramatic effect on the abundance of molecular ions relative to fragment ions like Cl-. With proper control, it was found that the relative abundance of ions from decafluorotriphenylphosphine could be reproduced over a period of one year.
    Additional Material: 6 Ill.
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  • 104
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 677-679 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 105
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extraction-derivatization method suitable for the analysis of subnanogram amounts of biogenic amines in aqueous solution has been developed. The most satisfactory procedure for the analysis of these compounds was reaction with 3,5-ditrifluorobenzoylchloride (DTFMBCl) in phosphate buffer at pH 7.2 followed by extraction of the resultant amide esters into ethyl acetate. This was followed by hydrolysis of the phenolic ester functionalities by shaking the organic layer with 10 M ammonium hydroxide. The phenolic and alcoholic hydroxyl groups were then reacted with bistrimethylsilylacetamide and the trimethylsilyl-DTFMB amides were then analysed by gas chromatography/mass spectrometry in the negative ion chemical ionization mode with methane as reagent gas. The limits of detection for these derivatives was 〈1 pg and the method was readily applicable to the extraction and analysis of 0.5 ng of a given biogenic amine.
    Additional Material: 7 Ill.
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  • 106
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tributyltin (TBT) is a biocide which has been shown to enter the aquatic environment by release from antifouling paints. TBT is acutely toxic to some marine organisms at concentrations near 1 μg I-1 and physiological changes may occur at low nanogram per liter concentrations. Gas chromatography/mass spectrometry (GC/MS) (methane chemical ionization) has been used for identification (full scanning) and quantification (selected ion monitoring) of TBT, dibutyltin (DBT) and monobutyltin (MBT). The butyltins were extracted from environmental water samples with hexane/0.2% tropolone and derivatized with hexyl magnesium bromide to form hexylbutyltins. Selected ion monitoring was at m/z 319 (TBT) and m/z 347 (DBT, MBT and tripentyltin, the internal standard). Calibration curves prepared in natural water were linear and detection limits were 〈2 ng I-1, GC/MS and GC with flame photometric detection were compared as quantification methods for environmental samples and were shown to give similar results at the low nanogram per liter levels.
    Additional Material: 3 Ill.
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  • 107
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three flavonoid glycosides isolated from plants were identified using fast atom bombardment mass spectrometry and gas chromatography/mass spectrometry. In the latter studies, electron impact and ammonia chemical ionization were used.
    Additional Material: 3 Ill.
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  • 108
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 609-613 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of six representative underivatized steroids and three parent hydrocarbons were obtained using laser desorption/Fourier transform (LD/FT) mass spectrometry. The carbonyl steroids, with the exception of aldosterone, yielded abundant [M + H]+ ions. For cholesterol, a major fragment ion was that corresponding to dehydration. The hydrocarbons produced [M + H]+, M+ and [M - H]+ ions, in addition to expected alkyl cleavage ions including those resulting from methyl loss. The LD/FT mass spectra of all were qualitatively similar to electron ionization spectra, but showed somewhat less fragmentation.
    Additional Material: 7 Ill.
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  • 109
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 17 cysteine, N-acetyl cysteine, glutathione, and N-trifluoroacetyl glutathione conjugates have been prepared, and their thermospray (TSP) spectra have been recorded in the positive and negative ion modes. The compounds undergo extensive fragmentation, which primarily occurs at the carbon-sulfur bonds. For most of the compounds, positive ion TSP is more sensitive than negative ion thermospray. Probably due to the thermal lability of these adducts, the quality of the spectra obtained are dependent on source conditions, requiring fine control of the vaporization/desolvation process.
    Additional Material: 4 Ill.
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  • 110
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 685-685 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 111
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 239-242 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 112
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 249-252 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Determination of the low concentrations (〈10-100 pg ml-1) of melatonin in blood plasma by gas chromatography/mass spectrometry has previously required the use of negative ionization (electron capture) mass spectrometry, a technique particularly delicate to set up. We show that a general-purpose medium-resolution instrument gives adequate sensitivity in electron impact mode, when used with a capillary gas chromatographic column-switching device. A straightforward extraction procedure gives good specificity, and the limit of useful measurement is better than 10 pg per 1 ml sample.
    Additional Material: 3 Ill.
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  • 113
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Residues of octylphenol polyethoxylates (OPEO) are frequently found in wastewater effluents. OPEO are commonly used surfactants. The polyethoxy chain of OPEO may be shortened or carboxylated during biological wastewater treatment and the aromatic ring chlorinated or brominated during wastewater disinfection with chlorine. Mass spectral data obtained using electron ionization (EI) and chemical ionization (CI) are presented which positively characterize these residues. For CI, methane was used as the reactant gas and protonated molecular ions were observed. The most prominent ions formed under EI resulted from benzylic cleavage while the prominent ions formed under CI resulted from alkyl ion displacement and olefin displacement. EI and CI mass spectra are summarized and fragmentation mechanisms are proposed. Response factors are presented for quantitative analysis by single ion monitoring.
    Additional Material: 5 Ill.
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  • 114
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rapid and sensitive identification and quantification of important pyrrolizidine alkaloid metabolites using tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/MS) is described. Identifications of N-oxide and hydrolytic metabolites of the pyrrolizidine alkaloids senecionine and monocrotaline in extracts of mouse hepatic microsomal incubations were accomplished by comparing collisionally activated decomposition/mass-analyzed ion kinetic energy spectra of specific ions from microsomal extracts with spectra obtained from synthetic standards of suspected metabolites. Trace amounts of the toxic metabolite dihydropyrrolizine (DHP) were observed by GC/MS of trimethylsilyl (TMS) derivatives, but the amounts present in hepatic microsomal extracts were below the MS/MS limit of detection. Quantitative determinations of senecionine N-oxide were performed by fast atom bombardment MS/MS. Suppression of N-oxide ionization by other substances in the extracts was judged to be minimal. The TMS derivatives of the metabolites senecic acid, monocrotalic acid and DHP were quantified using capillary GC/MS. Results from the study demonstrate that the relative contributions of the three major pathways of pyrrolizidine alkaloid metabolism (N-oxidation, hydrolysis and oxidation to pyrrolic compounds) can be assessed using a single analytical instrument and minimal sample preparation.
    Additional Material: 8 Ill.
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  • 115
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 303-303 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 116
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 117
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 323-328 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radiolabeled cisapride was administered orally to male Wistar rats. The drug was metabolized extensively, resulting in the formation of a large number of urinary and faecal metabolites. In bile-cannulated rats a major metabolite was excreted with the bile whose structure could not be elucidated with the aid of the registered electron impact and desorption chemical ionization spectra. Therefore the biliary metabolite was subjected to extensive analytical procedures combining fast atom bombardment mass spectrometry, thermospray liquid chromatography/mass spectrometry, nuclear magnetic resonance and ultraviolet analysis. The results of this study allowed the identification of the biliary metabolite as the O-sulphate of metabolically formed 3′-hydroxycisapride.
    Additional Material: 5 Ill.
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  • 118
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 333-343 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient algorithm is described for sequencing peptides from sequence ions appearing in fast atom bombardment (FAB) and FAB tandem mass spectra. The following features are incorporated in the algorithm. The members of the set of sequence ions are represented by all possible combinations of N- and C-terminal fragment ions. From the known N- and C-terminating groups and molecular weight (MW) of the peptide, the sequence ions are mathematically re-expressed as N-terminal residue ions and arranged in ascending order. The peptide sequence is computed, in a stepwise iterative procedure, from the mass differences between the mathematically re-expressed N-terminal residue ions and the predicted peptide subsequences for the neighboring ions of lower mass. These mass differences correspond to combinations of known amino acid residues which have previously been computed and tabulated, based upon the FAB fragmentation rules for peptides. The algorithm was successfully applied to sequence the following peptides from their respective FAB or FAB tandem mass spectrum: decapeptyl (MW 1310), angiotensin II (MW 1045), and two ‘unknown’ peptides (MW 1227 and 1485, respectively). Two criteria used to predict the correct peptide sequence from among many possibilities are the minimum number of amino acid residues and the maximum fragmentation probability per amino acid residue.
    Additional Material: 5 Ill.
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  • 119
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 403-410 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: n-Propyl-delta-8-tetrahydrocannabinol (n-propyl-delta-8-THC and n-propyl-delta-9-THC were synthesized by condensation of (1S)-cis-verbenol with 5-n-propyl-1,3-dihydroxybenzene and administered to male Charles River CD-1 mice. Hepatic merabolites were isolated by solvent extraction and chromatography on Sephadex LH-20 and identified by gas chromatography/mass spectrometry. Seven metabolites were identified from each cannabinoid. Metabolism was similar to that previously observed from the pentyl homologues, with the major biotransformation pathway being the production of 11-hydroxy-propyl-THCs and their oxidation to carboxylic acid metabolites. Other metabolites were mainly hydroxylated derivatives of these compounds and the corresponding 11-alcohol. Less hydroxylation at C(8) was found with n-propyl-delta-9-THC than with the pentyl homologue, and the monohydroxy metabolite, 8-alpha-hydroxy-n-propyl-delta-9-THC, was not observed, even though it was a prominent metabolite from delta-9-THC itself. Hydroxylation occurred in the side-chain at C(2′).
    Additional Material: 4 Ill.
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  • 120
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact mass spectra of poly(trimethylsiloxy) derivatives of polyenic long-chain carboxylic acids containing a conjugated diene unit clearly locate all double bonds. Abundant, diagnostic fragment ions arise from cleavage of the bonds at the positions of the original double bonds, combined with loss of a molecule of trimethylsilanol for every two vicinal trimethylsiloxy groups, with the exception of similar ions formed by rupture of an original conjugated double bond and containing the other conjugated double bond, which are weak or absent. The method was applied to several alkadienoic, alkatrienoic and alkatetraenoic acids containing a conjugated diene unit.
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  • 121
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Long-chain unsaturated fatty acids (UFA) can easily be converted on a microgram scale to the corresponding 2-alkenyl-4,4-dimethyloxazolines by condensation with 2-amino-2-methylpropanol (AMP). These modified molecules with a ‘hidden’ carboxyl group have been proved to be a class of useful derivatives for gas chromatography/mass spectrometry (GC/MS) of UFA mixtures. While possessing very good GC characteristics, the title compounds show regular, well-recognizable diagnostic ion peaks of the double bond position in the chain. Detailed description of the method as well as electron impact (E1) mass spectra of derivatives resulting from mono-, di and polyenoic (maximally containing six double bonds) acids are presented.
    Additional Material: 5 Ill.
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  • 122
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    Biological Mass Spectrometry 15 (1988), S. 63-66 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stable isotope assay for the quantification of debrisoquine (1) and its major urinary metabolite 4-hydroxydebrisoquine (2) is described. The method consists of extractive derivatization of 1 and 2 by use of 1,3-diketones, chiral derivatization of the 4-hydroxy group of 2, and gas chromatography/negative ion chemical ionization mass spectrometry in the presence of deuterated analogues of 1 and 2. In comparison with synthetic R-(-)-2 and S-(+)-2 it is shown that in vivo benzylic 4-hydroxylation of 1 is highly stereoselective, leading predominantly to S-(+)-4-hydroxydebrisoquine (enantiomeric excess ≥90%).
    Additional Material: 1 Ill.
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  • 123
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    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 75-77 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [MH]+ ions of peptides are degraded in one step to acyl ions, indicating the presence of different [MH]+ species. In contrast to protons, cations are added mainly at the carboxylate function of a peptide zwitterion. These species are degraded by loss of the C-terminal amino acid in the form of CO and an imine.
    Additional Material: 3 Ill.
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  • 124
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for qualitative and quantitative analysis of trace amounts of quaternary organoarsenicals such as arsenocholine and acetylarsenocholine has been developed. The method is based on pyrolysis, gas chromatography/mass spectrometry and use of deuterium-labelled internal standards. Arsenocholine and acetylarsenocholine have been estimated in fish from arsenic-polluted brackish water and compared with the same species of fish from unpolluted water. The investigation also includes some fish and crustacea from marine water. The presence of arsenocholine and acetylarsenocholine in different aquatic organisms indicate the existence of a general metabolic pathway for these compounds in aquatic ecosystems.
    Additional Material: 5 Ill.
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  • 125
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    Biological Mass Spectrometry 15 (1988), S. 183-184 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 126
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Steviol (ent-13-hydroxykaur-16-en-19-oic acid), the aglycone of various plant-derived glycoside sweeteners consumed by human populations, is known to be mutagenic toward Salmonella typhimurium strain TM677 when metabolically activated using a 9000 × g supernatant fraction derived from the liver of Aroclor 1254-pretreated rats. Mass spectral analysis of this diterpenoid and some analogs revealed characteristic patterns reflecting differential stereochemistry at the C/D rings and variations in the nature of the substituents present. Such information has been used to help identify several in vitro metabolites of steviol in conditions known to produce a mutagenic response, when analyzed by human populations, is known to be mutagenic toward Salmonella typhimurium strain TM677 when metabolically be allylic oxidation and epoxidation. 15-Oxosteviol, a product of oxidation of the major steviol metabolite, 15α-hydroxysteviol, was found to be a direct-acting mutagen.
    Additional Material: 10 Ill.
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  • 127
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive ion fast atom bombardment mass spectra of maltooligosaccharides reductively aminated with 2-aminopyridine (Gn-AP) contain abundant [M + H]+ ions. Determination of G2-AP and G3-AP produced from G5-AP by the action of α-amylases, based on the abundance of their [M + H]+ ions relative to that of cellobiose reductively aminated with 2-amino-6-methylpyridine as the internal standard, allowed rapid and reproducible assay of these enzymes. It was advantageous for clinical investigation that the proportion of pancreatic and salivary α-amylase activities could be determined.
    Additional Material: 4 Ill.
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  • 128
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 129
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of biologically active steroids was analyzed by both, ‘filament on’ thermospray using 100% methanol as the mobile phase with ammonium acetate as buffer, and direct chemical ionization with NH3 gas. The mass spectra obtained were very similar. Addition of pyridine instead of ammonium acetate showed selectivity in adding to the steroid molecule.
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  • 130
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A multi-stage screening and identification scheme for the diagnosis of inborn errors in amino acid, fatty acid, carbohydrate and intermediary metabolism is described. The method is based on a computerized analysis of data obtained with dual-column gas chromatography/FID (GC/FID) and gas chromatography/mass spectrometry (GC/MS) profiling of urinary organic acids. It involves: (1) isolation of the compounds by solvent or solid-phase extraction; (2) conversion into trimethylsilyl (TMS) or TMS-oxime derivatives; (3) GC/FID analysis on SE-52 and OV-1701 capillary columns; (4) tentative identification by comparing the methylene unit (MU) values on both columns with a user-built library of reference compounds; (5) quantitative evaluation of the excretion profile; and (6) analysis by GC/MS of samples with an abnormal profile using an automated peak identification programme.
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  • 131
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    Biological Mass Spectrometry 15 (1988), S. 357-357 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 132
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    Biological Mass Spectrometry 15 (1988), S. 359-363 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact (EI) mass spectra (75 eV) of the new carboxylic acid ionophore griseochelin and some of its derivatives are discussed. The mass spectral fragmentation was studied using exact mass measurements and deuterium labelling. Furthermore, the negative ion mass spectra (2-4 eV) of these compounds are compared with their EI mass spectra.
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  • 133
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    Biological Mass Spectrometry 15 (1988), S. 399-402 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fast atom bombardment/collisional activation/linked-scan at constant B/E (tandern mass spectrometric) method is described which can distinguish between α- and β-aspartyl and α- and μ-glutamyl underivatized peptides. The method is based upon differences in loss of CO from aspartyl or glutamyl B-fragment ions (IB) in these isomers which are rationalized from the stability of the resultant A-fragment ions (IA). It was observed that the ratio of IB:IA which was used in this determination was dependent upon the collision cell pressure. The higher the collision cell pressure, the larger the difference between the IB: IA ratios for these linkages.
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  • 134
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 135
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A tandem mass spectrometric method is described which allows the assignment of stereochemistry to fragment ions comprising intact sugar subunits of larger glycosides without chemical degradation and product isolation by chromatography. The approach relies on the mass selection of the ‘sugar ion’ of interest followed by analysis of stereoselective fragmentation induced by low-energy collisional activation. The daughter ion spectra provide configurational fingerprints of the selected sugar ions which can be matched for identity with reference spectra obtained from suitable precursors of known stereochemistry. Glucose, mannose and galactose furnished the required set of the most important reference ions. By using peracetyl (and perdeuterioacetyl) derivatives, galactose was readily identified as the glycosidic sugar constituent of the (known) antibiotic papulacandin B and a further (unknown) congener.
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  • 136
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    Biological Mass Spectrometry 15 (1988), S. 473-478 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the calculation of stable isotope enrichments from the mass spectra of organic compounds obtained by gas chromatography/mass spectrometry. Correction factors for the natural abundance of stable isotopes account for the probabilities of observing more than one stable isotope atom in a molecule and these are particularly significant when analysing trimethylsilyl derivatives containing 29Si, 30Si and 13C. It was demonstrated that 15N-labelled molecules, as well as 13C-labelled molecules, elute earlier than their unlabelled analogues in a gas chromatographic peak, and thus enrichment values should be calculated from sample scans taken at regular intervals throughout the peak.
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  • 137
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    Biological Mass Spectrometry 15 (1988), S. 495-499 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron ionization mass spectra of 2-amino-4-(5-nitro-2-furyl)thiazole metabolites obtained from microsomal incubations and chemical syntheses were studied. The identities of the metabolites were established by chemical ionization, high resolution, and metastable measurements. The compounds studied showed multiple modes of cleavage, skeletal rearrangements and hydrogen back-transfer.
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  • 138
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary column gas chromatography combined with ion-trap detector mass spectrometry was used in the identification of 85 constituents of the polycyclic aromatic hydrocarbon fraction of diesel fuel. The main constituents are an extensive range of alkylnaphthalenes; alkylated tetrahydronaphthalenes, benzothiophens, dibenzothiophens biphenyls, fluorenes and phenanthrenes were also identified. Chromatographic retention indices for these compounds were determined to calibrate retention data for routine analysis with flame-ionization detection, and to identify positions of alkyl substitution.
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  • 139
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass and ion abundance calibration of gas chromatograph/mass spectrometer responses is essential for the production of good data. In 1975, ion abundance criteria based on the mass spectrum of decafluorotriphenylphosphine (DFTPP) were proposed to standardize quadrupole mass spectra against magnetic sector spectra. This paper reports an investigation of DFTPP ion chemistry with the determination of the effects of some gas chromatograph/mass spectrometer operating parameters on the mass spectrum of DFTPP. New ion abundance criteria are proposed and discussed in relation to the findings of this investigation.
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  • 140
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    Biological Mass Spectrometry 15 (1988), S. 447-451 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method was developed and validated for measuring the CO2 concentration in the breath by mass spectrometric analysis. Argon, an inert gas that is present in air in a constant concentration of 0.923%, was used as an internal standard. By determining the ratio of CO2 (mass 44) to Ar (mass 40) in a breath sample, it was possible to read the CO2 concentration from a standard curve, relating CO2 concentration to CO2: Ar ratio. By combining mass spectrometric determination of CO2 concentration in breath with spirometric measurement of expired volumes, the CO2 production was determined in 67 subjects at rest. The mean value was 8.86 mmol kg-1 h-1, but there was considerable interindividual variation. This new method was applied to glucose oxidation studies in 10 normal subjects, 10 post-gastrectomy patients and 7 obese type II diabetic subjects. Measurement of the 13CO2 exhalation with quantitative determination of CO2 production allowed more accurate determination of the CO2 excretion rate in relation to blood levels of glucose, insulin and free fatty acids than assuming the constant CO2 production of 300 mmol unit body surface-1 h-1 or 9 mmol kg-1 h-1. It also resulted in a better discrimination between normal subjects and diabetics.
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  • 141
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 142
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    Biological Mass Spectrometry 15 (1988), S. 501-508 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analysis of doxylamine N-oxide and pyrilamine N-oxide as synthetic standards and biologically derived metabolites by thermospray mass spectrometry (TSP/MS) provided [M + H]+ ions for each metabolite. TSP/tandem mass spectrometry (TSP/MS/MS) of the [M + H]+ ions provided fragment ions characteristic of these metabolites. In addition, TSP mass spectrometry and TSP/MS/MS analysis of ring-hydroxylated N-desmethyldoxylamine, N-desmethylpyrilamine and O-dealkylated pyrilamine is also reported. A fragmentation pathway for analysis by MS/MS of pyrilamine and its metabolites is also proposed. The results demonstrate the utility of TSP/MS for biologically derived metabolites of pyrilamine and doxylamine.
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  • 143
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: γ-Hydroxybutyric acid (GHB) and trans-γ-hydroxycrotonic acid (HCA) together with their respective internal standards were derivatized to give the pentafluorobenzyl esters of the N-tert-butyldimethylsilyl derivatives. These compounds give, under electron capture conditions, very simple negative ion mass spectra. A very sensitive and specific assay for GHB and HCA in brain tissue (detection limit of about 5 pg per injection) using gas chromatography/negative ion mass spectrometry is described. The average levels measured in the whole brain were 1.10 ± 0.18 nmol GHB/g wet weight and 0.18 ± 0.02 nmol HCA/g wet weight.
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  • 144
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    Biological Mass Spectrometry 15 (1988), S. 525-528 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The negative ion mass spectra of some dihydropyridine analogues of nifedipine are studied; they show a fragmentation which is highly dependent on the position of the nitro group on the phenyl ring: 3′-nitro derivatives give essentially the molecular anion, whereas 2′-nitro derivatives lose successively H2O, RO and O. In addition, (2,1,3-benzoxadiazol-4-yl) derivatives show essentially a [M—ROH]- peak. Possible pathways for these fragmentations are given.
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  • 145
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Paim I, a protein α-amylase inhibitor, is a single-chain polypeptide which consists of 73 amino acids, including 4 half-cystine residues. The positions of disulphide bonds in Paim I have been determined with the combination of enzymatic digestion and fast atom bombardment (FAB) mass spectrometry. Denatured Paim I was digested to peptides with Staphylococcus aureus V8 protease. These peptides were subjected to FAB mass spectrometry, with or without isolation by high-performance liquid chromatography. The positions of disulphide bonds in Paim I were determined from the relative molecular masses of the peptides containing a disulphide bond and by the enzyme specificity of S. aureus V8 protease. It is deduced that Paim I has two disulphide bridges at Cys(8)-Cys(24) and Cys(42)-Cys(70).
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  • 146
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    Biological Mass Spectrometry 15 (1988), S. 577-581 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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  • 147
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermospray high-performance liquid chromatography/mass spectrometry method for the separation and quantification of cortisol in human serum has been developed. The technique does not require derivatization, allows for both qualitative and quantitative determinations, provides increased specificity not available from conventional high-performance liquid chromatography, and has a detection limit of 5 pmol on-column. This isotope dilution mass spectrometry method, using d3-cortisol as an internal standard, allows precise determinations even at low isotopic ratios (2%-5 mole%). Evidence that this technique can be applied to the quantification of serum cortisol and to the determination of daily cortisol production in humans is presented.
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  • 148
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    Biological Mass Spectrometry 15 (1988), S. 615-621 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The collisionally activated decomposition of [M + H]+ ions, generated by fast atom bombardment (FAB) of glutathione conjugates, has been studied by tandem mass spectrometry (MS/MS) using hybrid sector/quadrupole instruments. Abundant fragments of diagnostic utility were present in the daughter ion spectra. Common fragmentation modes were observed but their relative importance was strongly dependent on the nature of the conjugated species. As an example of a general approach to the characterization of glutathione conjugates in biological samples, the acetaminophen-glutathione conjugate was identified in rat bile, following coadministration of (2H0)- and (2H3)acetaminophen, using the experimental sequence: (i) conventional FAB mass spectrometric analysis, (ii) MS/MS using constant neutral loss (129 u) scanning to identify parent ions corresponding to glutathione conjugates, (iii) MS/MS to yield daughter ion spectra of parents so identified and corresponding to (2H0)- and (2H3)-labeled conjugates.
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  • 149
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    Biological Mass Spectrometry 15 (1988), S. 411-411 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 150
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of extracts from the South American plant Justicia pectoralis Jacq. permitted the identification, among other compounds, of coumarin, dihydrocoumarin, umbelliferone and 3-(2-hydroxyphenyl)propionic acid by gas chromatography/mass spectrometry (GC/MS); the acids and phenolic compounds were derivatized with diazomethane. GC/MS of simple coumarins, phenylpropionic acids and their hydroxylated isomers was performed after derivatization through methylation and trimethylsilylation; these results may be useful for the identification and quantification of these compounds in other biological materials.
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  • 151
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    Biological Mass Spectrometry 15 (1988), S. 419-427 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fast atom bombardment mass spectra of 24 α-amino acids have been studied. These include the mass spectra as well as the metastable ion MI and collisional activation CA spectra of [M + H]+ and [M - H]- ions. The extent of the common neutral losses as NH3, H2O and CO2H2 in the positive ion spectra is governed by the nature of the side chain. The relationship between the fragmentation behaviour of the negative ions and the presence of particular functional groups is less obvious. Mixtures of amino acids in glycerol show pronounced surface effects.
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  • 152
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    Biological Mass Spectrometry 15 (1988), S. 461-463 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 153
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorinated and oxygenated cyclohexene derivatives detected in methylene chloride extracts of chlorinated drinking water were demonstrated to be artifacts produced during sample preparation. Commercial methylene chloride contains cyclohexene as a preservative, and this reacted during the extraction/concentration process to produce microgram amounts of chlorocyclohexene, 2-chlorocyclohexanol, trans-1,2-dichlorocyclohexane, cyclohexenone and cyclohexenol. Quantitative analysis indicated that over 90% of the initial cyclohexene was consumed during the process. Dechlorination of drinking water with sodium arsenite significantly reduced but did not eliminate cyclohexene artifact formation.
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  • 154
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    Biological Mass Spectrometry 15 (1988), S. 465-465 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 155
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    Biological Mass Spectrometry 15 (1988), S. 485-493 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact (EI) mass spectra of the permethyl, peracetyl and per(trifluoroacetyl) derivatives of hydroxylated benzo[a]pyrene (B[a]P) metabolites were determined and the fragmentation chemistry producing the spectra elucidated. The metabolites investigated were: 3-hydroxy-B[a]P; 7,8-dihydro-7,8-dihydroxy-B[a]P; 7,8,9,10-tetrahydro-7,8,9-trihydroxy-B[a]P; and 7,8,9,10-tetrahydro-7,8,9,10-tetrahydroxy-B[a]P. In addition, the positive and negative methane chemical ionization spectra were determined for the derivatives of the BP-tetrol. The EI fragmentation patterns of the methylated metabolites that contained partially saturated rings were complex and, in the case of the di- and trimethoxy compounds, included apparent violations of the even-electron rule. The permethylated triol and tetrol cleaved through a retro-Diels-Alder reaction. The EI spectra of the peracetates were dominated by losses of acetic acid and ketene. The per(trifluoroacetyl) species fragmented by losing elements of trifluoroacetic acid, trifluoracetate radical and trifluoroacetyl. The spectra obtained from the permethylated tetrol permitted accurate prediction of the corresponding permethylated derivatives of tetrol metabolites of chrysene and benz[a]anthracene. The ability to predict spectra may be useful in trace analysis of hydrocarbon metabolites in biological samples.
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  • 156
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    Biological Mass Spectrometry 15 (1988), S. 509-516 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved direct chemical ionization (DCI) mass spectrometric technique, using a polyimide-coated fused silica fiber as an extended probe tip, was used to obtain molecular ions and diagnostic fragment ions of underivatized arachidonic acid, 5-hydroperoxyeicosatetraenoic acid, 15-hydroperoxyeicosatetraenoic acid, leukotriene B4 (LTB4) and, for the first time, of leukotriene A4 (LTA4)-free acid. In this technique, sample compounds are coated onto the fused silica fiber and vaporized in the plume of the reagent gas plasma of a chemical ionization source without external heating of the probe. Both ammonia and isobutane DCI spectra were obtained for each compound. A volatile alkaline eluent system was developed that allowed reversed-phase high-performance liquid chromatography of LTA4 to be followed rapidly by DCI mass spectrometry. With these techniques, the conversion of LTA4 to LTB4 during incubation with human liver microsomes was confirmed. Selected ion monitoring (SIM) of preselected ion fragments in the spectrum increases the selectivity of this technqiue and improves quantification in the range 100 ng to 10 pg.
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  • 157
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Self-chemical ionization Fourier transform ion cyclotron resonance (FT-ICR) mass spectra are reported for bases, nucleosides, and alkylated and exocyclic adducts of bases and nucleosides. The technique always produces a protonated molecular ion and in the majority of cases this is a single, intense peak. Analysis of a base mixture and a nucleoside mixture demonstrates the technique as an excellent method to identify the constituent compounds qualitatively. The high resolution capabilities and tandem mass spectrometric techniques (msn) in FT-ICR are discussed with respect to developing the technique as a future method to identify and characterize nucleic acid constituents, specifically adducts.
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  • 158
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    Biological Mass Spectrometry 15 (1988), S. 357-357 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 159
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    Biological Mass Spectrometry 15 (1988) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 160
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    Biological Mass Spectrometry 15 (1988), S. 369-374 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C enrichment of the carboxyl carbon of leucine was measured by isotope ratio mass spectrometry after conversion to CO2 by reaction with ninhydrin in a Vacutainer and cryogenic purification using the Finnigan MAT Breath Gas Analysis System designed for processing 13C breath test samples. The sources of error which arise with submicromole samples are examined and corrections provided for suboptimal mass spectrometer signals and contamination of the evolved CO2 with CO2 from the reaction medium. The main limitations to the accuracy and precision of the method are not instrumental but arise from the contamination with residual CO2 in the reaction medium, and this sets a lower limit of around 0.25 μmol leucine on the practical sample size. This is an improvement of about five-fold on the previous manual method of CO2 isolation.
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  • 161
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fragmentation pathways of methyl abscisate and its 2E isomer in methane positive ion chemical ionization (PICI) and methane negative ion chemical ionization (NICI) mass spectrometry have been elucidated using isotopically labelled analogues. It is shown that in PICI the most abundant ions are formed by the loss of water, methanol, both methanol and water and of methyl formate. The PICI mass spectrum of methyl 2E abscisate differs significantly in that the loss of water is much less important. In NICI, the most abundant ions from methyl abscisate are due to the molecular anion, [M - H2O]- and [M - CH3OH]-. It is shown, however, that the methyl ester methyl is not lost in this last fragmentation. Two other significant ions contain the side chain and the ring of methyl abscisate, respectively. In contrast, the NICI mass spectrum of methyl 2E abscisate differs principally in showing an abundant loss of a hydrogen atom.
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  • 162
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    Biological Mass Spectrometry 15 (1988), S. 389-398 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl-delta-8-tetrahydrocannabinol (methyl-delta-8-THC), methyl-delta-9-THC and abn-methyl-delta-8-THC were synthesized by condensation of orcinol and (1S)-cis-verbenol and were administered to male Charles River CD-1 mice. Extracted hepatic metabolites were isolated by chromatography on Sephadex LH-20 and examined by gas chromatography/mass spectrometry as trimethylsilyl (TMS), (2H9)TMS and methyl ester/TMS derivatives. In addition, metabolic fractions were reduced with lithium aluminium deuteride to convert carboxylic acids to alcehols for structural correlation. Metabolites from methyl-delta-8-THC were similar with respect to the positions substituted to those produced by higher homologues; the major metabolite was methyl-delta-8-THC-11-oic acid. abn-Methyl-delta-8-THC was metabolized in a different manner. The location of the aromatic methyl group at the position adjacent to ring fusion appeared to inhibit metabolism at C(11) to a considerable extent and also to reduce the amount of the resulting alcohol from being oxidized to a carboxylic acid. This caused other metabolic pathways to become dominant, with the result that a compound containing a hydroxy group at the gem-methyl position was the major metabolite. Hydroxylation at this position has not been confirmed with any other cannabinoid, although it is thought to result in trace concentrations of hydroxy metabolites from some compounds. Metabolism of methyl-delta-9-THC was also similar to that of the higher homologues, with the exception that less metabolism occurred at C(8) and a higher percentage of the total metabolic fraction was accounted for by the 11-oic acid metabolite. Minor metabolites were mainly dihydroxy compounds and hydroxylated derivatives of delta-9-THC-11-oic acid.
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  • 163
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    Biological Mass Spectrometry 15 (1988), S. 459-460 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 164
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    Biological Mass Spectrometry 15 (1988), S. 465-465 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 165
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    Biological Mass Spectrometry 15 (1988), S. 467-472 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Stable isotope ratio mass spectrometry was used for the analysis of 13C and 18O in CO2 of human breath collected in evacuated serological tubes (Vacutainer® and Venoject®) and in gas sample bottles. There was a 1-2‰0 difference between the δ13CPDB values obtained from breath CO2 collected in gas bottles and that collected in two batches of Vacutainer. δ18OPDB differed between Vacutainers and gas bottles by as much as 14%0 and standard deviations within the two batches of Vacutainer were 0.7 and 1.8%0. The poor reproducibility and accuracy for the δ18OPDB values was caused by the presence of a contaminant which originated from the rubber septa of the Vacutainers. The results show that it is not possible to obtain δ18OPDB values with a high degree of accuracy or precision for breath samples collected in Vacutainers. However, with selection of less contaminated or re-evacuated batches, δ13CPDB analysis of breath CO2 in Vacutainers may provide acceptable accuracy and precision. δ13CPDB and δ18OPDB values measured in breath collected in non-sterile Venoject tubes were also significantly different from those obtained with gas bottles. However, the accuracy and precision of these determinations were considerably better than in sterilized Vacutainer tubes. As a result of these comparisons it is concluded that gas bottles are necessary for the full accuracy and precision of stable isotope ratio analysis mass spectrometers to be exploited in breath CO2 analysis. However, automated analysis of breath CO2 collected in non-sterile Venoject tubes will provide an accuracy and precision that is suitable for most biological studies.
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  • 166
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Prednisolone, dexamethasone and betamethasone were labelled with deuterium via a simple synthetic procedure and used as internal standards in the gas chromatographic/mass spectrometric analysis of the corresponding undeuterated compounds. The mass spectrometer was used in the negative chemical ionization mode, which gave fragmentation of the methoxime trimethylsilyl ether derivatives favourable for their quantification. The method was applicable to the quantification of synthetic corticosteroids contained in human aqueous humour in the 0.1-10-ng range.
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 168
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    Biological Mass Spectrometry 15 (1988), S. 553-564 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary column isobutane chemical ionization was found to be an excellent method for the mass spectral characterization of mustard, other sulfur vesicants and related compounds. Interpretation of [M + H]+ and fragmentation ion information afforded by this technique enabled the identification of many previously unreported mustard impurities. The developed methodology was applied to the analysis of an Iran/Iraq soil sample suspected to have been contaminated with mustard. Mustard and 17 other mustard related impurities were identified and characterized in this sample under electron impact and isobutane chemical ionization conditions.
    Additional Material: 6 Ill.
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  • 169
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 170
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of ion-molecule reactions with NH3 for selected reaction monitoring (SRM) in gas chromatographic/tandem mass spectrometric analysis is demonstrated for 2-methoxyethanol and chlorobenzene in methanol and urine. In the former, the reaction [CH3OC2H4]+ + NH3 → [H2NC2H4]+ + CH3OH was followed; in the latter, the reaction [C6H5Cl]+· + NH3 → [C6H5NH3]+ + Cl·. Increased selectivity and an improvement in sensitivity by factors of up to five were observed when compared to conventional SRM analyses that used collisionally activated decompositions on NH3. SRM analyses with a triple quadrupole tandem mass spectrometer using ion-molecule reactions rather than collisionally activated decompositions have been found to be more sensitive and more selective in two model systems.
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  • 171
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    Biological Mass Spectrometry 15 (1988), S. 89-98 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 35 steroid conjugates (sulfates and glucuronides) and bile salts were investigated by using fast atom bombardment and tandem mass spectrometry. Collisional activation of the [M - H]- anions of sulfate conjugates and bile salts predominantly yields fragment ions arising by reactions occurring remote from the charge site. These reactions are sometimes sensitive to differences in stereochemistry at positions remote from the charge site and are useful for positional isomer differentiation. On the other hand, collisional activation of the [M - H]- anions of the glucouronide conjugates leads primarily to charge-driven fragementations.
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  • 172
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 173
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    Biological Mass Spectrometry 15 (1988), S. 183-183 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 174
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    Biological Mass Spectrometry 15 (1988) 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 175
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    Journal of High Resolution Chromatography 11 (1988), S. 20-24 
    ISSN: 0935-6304
    Keywords: Capillary column liquid chromatography ; Laser-induced fluorescence ; Serum bile acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the determination of individual free and conjugated bile acids in serum using microcolumn liquid chromatography coupled with a laser-induced fluorescence detector is described. Bile acids are separated into free/glycine-conjugate and taurine-conjugate fractions using a Sep-Pak SIL cartridge. The taurine-conjugated bile acid fraction is subjected to enzymatic hydrolysis. Subsequently, free and conjugated bile acids are labeled using 4-(bromomethyl)-7-methoxycoumarin as a fluorogenic reagent, producing stable derivatives that can be excited by the 325 nm line of a He/Cd laser. Prior to their fluorimetric detection, the individual components of a bile acid serum profile are separated by reversed-phase microcolumn liquid chromatography.
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  • 176
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    Journal of High Resolution Chromatography 11 (1988), S. 25-29 
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography ; Mixed mobile phases ; Practical aspects ; Equilibration times ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of mixed mobile phases in supercritical fluid chromatography must include consideration of a number of factors. Phase equilibria and critical parameters of a mixed fluid are very important in both the solvent delivery system and in the chromatographic column. The effects of pressure and temperature on retention with mixed mobile phases were studied and compared to estimated density values. System equilibration times with regard to pressure, temperature, and composition were studied. A mixed mobile phase was applied to the analysis of a high-molecular-weight metalloporphyrin.
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  • 177
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    Journal of High Resolution Chromatography 11 (1988), S. 29-32 
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography ; Injection techniques ; Reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the precision obtained using commercially available microvalve injectors is reported for three modes of injection: conventional split; timed-split; and direct. Results from this study show that good precision (〈 3% RSD for external standard and 〈 1% RSD for internal standard methods) can be obtained with capillary supercritical fluid chromatography (SFC). However, particular attention must be paid to the type of valve used, the orientation of the column relative to the valve, the mode of interfacing or connecting the column to the valve, and the type of pressure or density programming used for the analysis as all of these factors will affect the reproducibility.
    Additional Material: 1 Ill.
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  • 178
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    Journal of High Resolution Chromatography 11 (1988), S. 38-42 
    ISSN: 0935-6304
    Keywords: SFC ; Fluid extraction ; FID detection ; Packed columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of fluid extraction in combination with fluid chromatography with packed column and flame ionization detection is described. Fluid chromatographic equipment is shown. Applications of this system to drug characterization are demonstrated.
    Additional Material: 8 Ill.
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  • 179
    ISSN: 0935-6304
    Keywords: Large PAH ; Retention prediction ; Reversed-phase ; Microcolumn LC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The retention behavior of condensed large polycyclic aromatic hydrocarbons has been investigated with diphenylsilica stationary phases in reversed-phase microcolumn liquid chromatography. The results were correlated with two parameters which indicate size and shape of the molecules. Since the resulting equation can be used for retention prediction of large polycyclic aromatic hydrocarbons, computer-assisted “standardless” identification is accomplished for “unknown” compounds contained in the standard.
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  • 180
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    Journal of High Resolution Chromatography 11 (1988), S. 42-46 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Packed precolumn ; Sampling reproducibility ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The peculiarities of the flow splitting technique for sample injection into a capillary column have been discussed. A comparative investigation of reproducibility of the analytical results obtained for two gas chromatographic systems using flow splitting [1) sample injector-packed predolumn-splitter-open tubular capillary column and (2) sample injector-splitter-open tubular capillary column] has been carried out. It was experimentally shown that the first system ensures considerably better reproducibility for the results concerning the composition of the analyzed mixtures. Other advantages of the first system are also discussed.
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  • 181
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    Journal of High Resolution Chromatography 11 (1988), S. 46-50 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Dynamic headspace ; Multivariate data analysis ; Pattern recognition ; Polymers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatographic profiles have been generated from different batches of a polypropylene/polyethylene copolymer. The profiles generated from polymer pellets have been obtained by dynamic headspace/capillary gas chromatography analysis. Initially 10 to 40 peaks were chosen at random from the quantitative reports and transferred to a data table. After appropriate scaling the table has been analyzed by a multivariate statistic program, SIMCA (Soft Independent Modeling of Class Analogy) a pattern recognition technique. The method has been used to differentiate batches according to sensory qualities of the final packaging product and changes in polymer peilet production.
    Additional Material: 6 Ill.
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  • 182
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    Journal of High Resolution Chromatography 11 (1988), S. 51-56 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Air analysis ; Airborne halocarbons ; Chlorocarbons ; Electron capture detector ; Forest decline ; Halocarbons ; Thermodesorption ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The atmospheric levels of C1- and C2-halocarbons are determined by trapping on an adsorbent, thermodesorption, cryofocussing, gas chromatographic separation on a thick-film capillary, and electron-capture detection. The various aspects relevant to reliability and accuracy are discussed, such as type of adsorbent, range of detector response, and levels of contaminants present in blanks. These in turn have implications for optimum sample size and amount of adsorbent. The adopted method is suitable for routine analysis of airborne halocarbons at variable locations. The air concentrations of C1- and C2-halocarbons on the ground of mountain forests are similar to those in cities, a fact which supports the hypothesis that chlorocarbons are involved in the initiation of a phytotoxicological phenomenon commonly referred to as “forest decline”.
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  • 183
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    Journal of High Resolution Chromatography 11 (1988), S. 56-60 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; On-column injection ; Dual column analysis ; Essential oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A system to analyze a complex mixture simultaneously on two different columns after one single on-column injection is described. The splitting device, the possibilities of component identification by searching in a data base for Kovats indices on two different polarity stationary phases, and a practical example of an essential oil analysis are presented.
    Additional Material: 2 Ill.
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  • 184
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    Journal of High Resolution Chromatography 11 (1988), S. 65-69 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Temperature/pressure programming ; Density/temperature programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The theoretical and practical implications of simultaneous temperature/pressure and synchronized density/temperature programming are considered. Examples are shown for separations of dimethylpolysiloxanes where these techniques provide superior separation over their analogous isothermal programming methods.
    Additional Material: 4 Ill.
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  • 185
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    Journal of High Resolution Chromatography 11 (1988), S. 61-64 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography/Mass spectrometry ; Packed column ; Capillary column ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A frit restrictor interface for capillary column supercritical fluid chromatography/mass spectrometry (SFC/MS) has been constructed and used for the analysis of high boiling point alkanes. Packed column SFC/MS is described using both a moving belt liquid chromatographic/mass spectrometric interface and a thermospray source in the filament-on mode.
    Additional Material: 4 Ill.
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  • 186
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    Journal of High Resolution Chromatography 11 (1988), S. 73-75 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; 100 μm i.d. capillary column ; High speed separations ; Lemon oils ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Narrow bore columns (100 μm) have successfully been applied in the analysis of commercial lemon oils. On these columns, high resolution is obtained in a short analysis time. Different Brazillian lemon oils are characterized qualitatively and quantitatively.
    Additional Material: 2 Tab.
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  • 187
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    Journal of High Resolution Chromatography 11 (1988), S. 69-72 
    ISSN: 0935-6304
    Keywords: Ultra-high resolution GC ; Reduced diameter capillary columns ; Capillary direct GC/MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For clinical and environmental analyses utilizing capillary gas chromatography/mass spectrometry (GC/MS), increased sensitivity and speed of analysis are highly desirable. These performance advantages are realized using a WCOT column of 100 μm i.d. as compared to the more conventional 200 μm i.d. capillary columns. The improved sensitivity of capillary direct GC/MS with the 100 μm i.d. column for the confirmation of drugs of abuse will be demonstrated. For environmental analysis, the superior efficiency and resolution of the 100 μm i.d. column can be employed for the separation of priority pollutants. This approach is more amenable to capillary direct GC/MS providing a more effective interface to the mass spectrometer. As a result improved sensitivity and a considerable decrease in analysis time is achieved over that obtained with the larger diameter environmental specialty phase columns.
    Additional Material: 7 Ill.
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  • 188
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    Journal of High Resolution Chromatography 11 (1988), S. 81-84 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Packed fused silica column ; Direct sample injection ; Extraction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct sample injection technique was developed for supercritical fluid chromatography in a packed capillary column, with carbon dioxide as mobile phase and a flame ionization detector. The method allowed solutions, neat liquids, and even solids to be introduced as samples. Also, extraction with supercritical carbon dioxide was combined with this method to separate polymer additives.
    Additional Material: 6 Ill.
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  • 189
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    Journal of High Resolution Chromatography 11 (1988), S. 75-81 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Element selective detection ; Radio frequency plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A radio frequency plasma detector for element specific detection in gas chromatography is described. The detector is comprised of a radio frequency (300 kHz) discharge between electrodes in helium, and utilizes a low-resolution emission spectrometer to monitor selected spectral emission lines produced when the helium discharge decomposes and excites the atomic constituents in the chromatographic column effluent. The spectrometer is tuned to an atomic emission line in the near-infrared portion of the spectrum, and the emission intensity from the discharge region of a selected line is used to monitor the concentration of the element producing that line. Acceptable detector sensitivity was achieved by the use of a high-throughput optical system. Selectivity was achieved by a combination of correct line selection, plasma and carrier gas purification, and plasma gas doping.
    Additional Material: 7 Ill.
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  • 190
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    Journal of High Resolution Chromatography 11 (1988), S. 85-89 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Two-dimensional system ; Mechanical switching valve ; Heart-cutting ; Grob test ; Aroma fractions ; GC-GC/sniffing ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A commercially available mechanical micro switching valve has been tested for inertness. The test mixtures used were a modified Grob test and a solution consisting of eight typical aroma compounds, both at the 2-ng level. Cryogenic focusing of the sample after chromatography including one passage through the valve revealed that irreversible interaction of some test substances with valve components was rather small. A composite main peak of a chromatogram from a fruit juice aroma exhibiting a “mixed odor” was selectively transferred (heart-cutting) to a second column and resolved into three peaks. GC-GC/sniffing assigned a minor peak to a substance formerly hidden under the composite peak. Separate heating of the valve during temperature programming of the column was found to be unnecessary.
    Additional Material: 5 Ill.
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  • 191
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    Journal of High Resolution Chromatography 11 (1988), S. 89-93 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary columns ; glass ; Complexation GC ; Chiral complexation GC ; Enantiomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomer separation of 2-halocarboxylic acid esters on two chiral nickel(II) bis-((perfluoroacyl)terpeneketonates) by complexation gas chromatography is described. The quantitative entiomer separation of branched 2-halocarboxylic acid esters is achieved with nickel (II) bis (3-(heptafluorobutanoyl)(1R, 2S)-pinan-4-onate) 1 while unbranched 2-halocarboxylic acid esters are preferably separated on nickel(II) bis(3-(heptafluorobutanoyl)-(1S)-10-methylenecamphorate) 2. The metal chelates 1 and 2 are accessible in both enantiomeric forms allowing the determination of the enantiomeric excess (ee) effective and reliable.
    Additional Material: 5 Ill.
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  • 192
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    Journal of High Resolution Chromatography 11 (1988), S. 99-102 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Liquid chromatography, HPLC ; Coupled HPLC-GC ; Human plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the analysis of broxaterol 1-(3-bromoisoxazol-5-yl)-2-(tert-butylamino)ethanol in human plasma and urine an on-line HPLC-GC apparatus was used applying the “concurrent solvent evaporation” technique described in previous studies. Broxaterol is quantitatively determined by capillary GC with ECD detection, after extraction from plasma and derivatization. The detection limit of 0.03 ng/ml permits pharmacokinetic studies in man after oral and intravenous administration of the drug.
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  • 193
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    Journal of High Resolution Chromatography 11 (1988), S. 94-98 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Retention time and peak area reproducibility ; Converging-diverging restrictors ; Cyclosporin ; ionophores ; fat-soluble vitamins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The feasibility of using supercritical fluid chromatography (SFC) for analysis of polar and/or ionic analytes of interest to the pharmaceutical industry is described. Specifically, the analyses of cyclopsporin (a cyclic undecapeptide), several ionophores, and a group of fat-soluble vitamins are illustrated. The separation of group of fat-soluble vitamins is evaluated on two bonded stationary phases, DB-5 (95% dimethyl-5%-diphenylpolysiloxane) and DB-WAX (Carbowax 20M type, “bonded”). Lastly, a new restrictor technology known as a converging-diverging restrictor is described.
    Additional Material: 6 Ill.
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  • 194
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    Journal of High Resolution Chromatography 11 (1988), S. 103-106 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; Plasma ; Verapamil ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A specific, sensitive, and accurate assay for quantitation of verapamil has been developed. The method involves a single extraction step with n-heptane, followed by evaporation at room temperature under nitrogen. 0.1 μl of the extract was injected into a capillary column coated with crosslinked 5% phenylmethylsilicone. The column separated verapamil, norverapamil, and its internal standard within 15 minutes using temperature programming from 90 to 290°C. The lower limit of detection was 1 ng/ml for verapamil. The calibration curve was linear in the concentration range (5-300 ng/ml). Plasma concentration data from dogs receiving intravenous verapamil infusion are presented.
    Additional Material: 5 Ill.
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  • 195
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    Journal of High Resolution Chromatography 11 (1988), S. 106-110 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Tandem capillaries ; Charcoal trapping ; Soil fumigants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Soil fumigants, like 1,3-dichloropropene and metham-sodium (forming methyl isothiocyanate) diffuse into the atmosphere, thus presenting a hazard to people in the surroundings. A method is described in which a large volume (50 μl) of extractant, used to desorb the compounds from charcoal, is injected into a GC, equipped with two capillary columns. By way of Deans switching, the solvent is separated from the compounds of interest. Modification of a GC sampler makes unattended analyses possible.
    Additional Material: 2 Ill.
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  • 196
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    Journal of High Resolution Chromatography 11 (1988), S. 110-113 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary column ; Cyclodextrin stationary phase ; Isomer separation ; Enantiomer pair separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 197
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    Journal of High Resolution Chromatography 11 (1988), S. 119-121 
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; Microcolumn exclusion chromatography ; Proteins ; Peptides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for the determination of the molecular weight of proteins and peptides has been developed. It is based on microcolumn exclusion chromatography in trifluoroacetic acid on silica gel sorbents of different porosities with a linear molecular-weight calibration dependence in the range of 5 × 102 - 7 × 104 Da. It was shown that in this eluent proteins and peptides adopt the random-coil conformation and do not undergo hydrolysis for 2-3 days at room temperature.
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  • 198
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    Journal of High Resolution Chromatography 11 (1988), S. 113-118 
    ISSN: 0935-6304
    Keywords: Static coating ; Biphenyl polysiloxane ; Capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Static coating of phenyl and biphenyl polysiloxane stationary phases on 50 μm i.d. open tubular capillaries was studied. The influence of coating solvents and coating temperatures on the viscosities and surface tensions of the polymer stationary phases and their coating solutions was determined. A measure of the Rayleigh instability paralled the observed coating efficiencies.
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  • 199
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    Journal of High Resolution Chromatography 11 (1988), S. 124-128 
    ISSN: 0935-6304
    Keywords: Chromatography, gas, capillary ; Fatty acids, volatile ; Biological samples ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method was developed to analyze and quantitate volatile fatty acids such as acetic, propionic, butyric, iso-butyric, valeric, and iso-valeric acid from samples of biological origin. A capillary column system including an automatic on-column injection device as well as a precolumn of larger internal diameter than the analytical column was elaborated for this purpose.In order to obtain well resolved and correctly quantifiable chromatographic peaks it turned out to be essential to work under acidic/aqueous conditions. To achieve a better sample transfer into the chromatographic system an organic solvent had to be used together with the aqueous milieu, thus improving wetting properties of the liquid sample plug introduced into the column. Cold on-column injection was applied in order to avoid discrimination of the various acids due to sample splitting and the automatic technique was chosen in view of the large number of samples from biological extractions which had to be analyzed.
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 121-123 
    ISSN: 0935-6304
    Keywords: HPLC ; Injection valves ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In liquid chromatography with “low-dispersion methods”, there is an increasing need to reproducibly inject nanoliter sample volumes. Low-dispersion methods produce very narrow peaks because of short column length, narrow column bore, small particle packing, low particle surface area, open tubular configuration, or combinations of these parameters.This paper describes a new injector method, the “groove-injector” which involves simple plumbing changes for use of a conventional multi-port valve (8-ports or more) to inject sample volumes approximating a single groove in such a valve (e.g 30 nanoliters with aceptable reproducibility, ca. 8% RSD). In addition, by changing a resistor, volumes between 30, and over 2,000 nanoliters (nearly two orders of magnitude) can be injected with reproducibilities generally below 2% RSD. Different samples can be injected by using an autosampler.Compared to commonly used 4-port valves for nanoliter injections, multi-port valves have a number of advantages. Multiport valves generally are more commonly available and they are a better financial investment because of their versatility for column switching, sample enrichment, or variable volume injections. Previously, submicroliter (nanoliter) injections have not been possible with multi-port valves in as direct and simple a manner as described here.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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