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  • 1985-1989  (1,855)
  • 1980-1984
  • 1920-1924
  • 1986  (1,855)
  • Analytical Chemistry and Spectroscopy  (943)
  • General Chemistry  (912)
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  • 1985-1989  (1,855)
  • 1980-1984
  • 1920-1924
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  • 201
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 302-303 
    ISSN: 0935-6304
    Keywords: Normal phase HPLC ; Polycyclic aromatic compounds ; Double bond equivalents ; Cyano/amino bonded silica ; Selectivity ; Molecular conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 202
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 310-311 
    ISSN: 0935-6304
    Keywords: Gas-liquid chromatography, GLC ; Propoxylation of acetic acid ; Identification ; Quantitative analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 203
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 341-344 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Fused silica columns ; Peak splitting ; Christmas tree peaks ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluctuating thermal gradients are recognized as a distinct source of peak splitting in capillary column gas chromatography. In this study, the influence of analyte signal level, temperature oscillation amplitude, and oscillation frequency on splitting are quantitatively examined. Stable gradients are also considered. A simple, effective method is proposed for virtually eliminating thermal peak splitting in isothermal capillary GC analysis.
    Additional Material: 7 Ill.
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  • 204
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 355-355 
    ISSN: 0935-6304
    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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  • 205
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 358-360 
    ISSN: 0935-6304
    Keywords: Liquid chromatography ; Ion-pair RP HPLC ; Stable nitroxyl radicals ; Salt effect ; UV, RI detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 206
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 364-365 
    ISSN: 0935-6304
    Keywords: HPLC ; 3μm packings ; Reverse-phase ; Frit materials ; Acidic mobile phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 207
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 376-382 
    ISSN: 0935-6304
    Keywords: Aluminum clad fused silica capillary columns ; Thermostable stationary phases ; High temperature gas chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: With the simultaneous development of blank aluminum clad flexible fused silica glass capillary tubing capable of withstanding temperatures up to 500°C, coincident with a series of special high temperature methyl polysiloxane polymers, it was possible to produce for the first time, long lived fused silica capillary columns containing thin films of thermostable stationary phases which could be maintained isothermally at 400425°C and temperature programmed to 425-440°C. The “bleed rate” here for a well conditioned column was 5 picoamperes or less. Under these circumstances, alkanes with carbon numbers in the C-90 to C-100 area were rapidly and efficiently eluted from these columns. By extrapolation here, one can easily detect certain compounds with boiling points in the 750°C range. Since this type of capillary column was found to possess certain favorable properties, it was thought that it will soon replace the packed column and will probably be more popular than the borosilicate capillary column for many high temperature applications. Moreover, evidence has now accumulated which leads us to further believe that the majority of analyses of “high molecular weight” compounds performed by Supercritical Fluid Chromatography (SFC), utilizing very narrow bore fused silica capillary columns at several hundred atmospheres, can be much more simply, much more rapidly, much more economically, and much more efficiently accomplished by gas chromatography utilizing this new generation of high temperature capillary columns.
    Additional Material: 6 Ill.
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  • 208
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 477-479 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Column switching liquid chromatography ; Fluorescence detection ; 9-Anthryldiazomethane ; Saliva ; Prostaglandin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 209
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 479-480 
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography, HPLC ; Alkaline phosphatase, AP ; Lactate dehydrogenase, LD ; γ-Glutamyltransferase ; γ-GT ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 210
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 524-524 
    ISSN: 0935-6304
    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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  • 211
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 531-533 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; Enantiomeric separation ; Chiral stationary phase ; Immobilized protein (BSA) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 212
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 539-541 
    ISSN: 0935-6304
    Keywords: Liquid chromatography, HPLC ; HPLC of ecdysteroids ; Ecdysteroids of plants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 213
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 543-544 
    ISSN: 0935-6304
    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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  • 214
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 555-560 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, fused-silica ; Plasma amino acid analysis ; “On-column” injection ; Classical ion exchange ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A capillary chromatographic procedure using a fused silica column is described which can be used to quantitatively determine amino acids in plasma following the pre-chromatographic “clean-up” described in a recent paper [1]. In substituting this procedure for that involving a packed column, advantage has been taken of the greater resolving power to separate amino acids from background component peaks. In order to extend this advantage and provide a sound basis for quantitative analysis, the technique of cold on-column injection was employed. As a result, good precision of standard analysis was obtained with relative standard deviation (RSD) values for all amino acids of less than 4%. Application of the entire procedure to plasma samples yields RSD values of better than 10% for all amino acids with recoveries ranging from 72% to 104%. Simultaneous determination of plasma amino acid levels by gas chromatography (GC) using capillary columns and by classical ion exchange (CIE) showed reasonable agreement. Statistical evaluation showed no significant difference between twelve amino acids. Values for the remaining two, namely, phenylalanine and histidine are significantly different (p 〈 0.005). Comparison of the values obtained from GC capillary and packed columns reveals no significant difference between fourteen amino acids. Significant differences exist between results for phenylalanine and tyrosine (p 〈 0.001). It is concluded that there is good agreement between data obtained by GC capillary and CIE techniques and that differences between results for phenylalanine and histidine are method related.
    Additional Material: 3 Ill.
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  • 215
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 89-94 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Capillary columns ; Mass spectrometry ; Autoderivatization ; Cyclophosphamide ; 4-Ketocyclophosphamide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The selectivity of a capillary gas chromatographic assay for the anti-neoplastic and immunosuppressive agent cyclophosphamide (CPA) towards one of its naturally occurring metabolites, i.e. 4-ketocyclophosphamide (4-keto CPA), has been studied. Mass spectrometry studies showed that a cyclization product of 4-keto-CPA can form using the same chromatographic conditions as those under which CPA was determined. However, the amount produced is relatively small (less than 10%) compared with the percentage produced from CPA. Furthermore, both cyclization products, formed by loss of HCI and intraalkylation of the parent compounds, can be separated well under suitable chromatographic conditions.
    Additional Material: 7 Ill.
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  • 216
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 106-110 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Fused silica capillary columns ; Eigenvector projection ; Pygeum africanum bark ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The components of Pygeum africanum bark extracts, used for the treatment of benign prostatic hypertrophy, were characterized by high resolution gas chromatography (HRGC) and mass spectrometry (MS). Among various compounds n-docosyl trans-ferulate was identified and quantitated by HRGC as a derivative of n-docosanol, which is considered to be one of the active components of the extract. The origin of different Pygeum a. extracts can be studied by eigenvector projection of HRGC profiles with computer assistance.
    Additional Material: 6 Ill.
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  • 217
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 120-121 
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary columns, glass ; Persilylation ; Polar, inert columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 218
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986) 
    ISSN: 0935-6304
    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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  • 219
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 137-144 
    ISSN: 0935-6304
    Keywords: Capillary supercritical fluid chromatography, SFC ; Detection techniques ; Ancillary methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article reviews the current status and developmental trends in detection for supercritical fluid chromatography. The “GC-like” and “LC-like” detection techniques are treated separately, while the needs of structural identification techniques for SFC separations are emphasized.
    Additional Material: 7 Ill.
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  • 220
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 168-171 
    ISSN: 0935-6304
    Keywords: Supercritical fluids ; Infrared spectrometry ; Solvent elimination ; Microscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The feasibility of supercritical fluid chromatography/Fourier transform-infrared (SFC/FT-IR) microspectrometry is presented. In this approach to SFC/FT-IR, the chromatographic eluates are aspirated from the restrictor directly onto the surface of a moving window which then passes into the beam focus of an infrared microscope. Because the mobile phase is gaseous at ambient conditions, elimination of the mobile phase is easily accomplished. Detection limits in all interfaces between a chromatograph and an FT-IR spectrometer in which the mobile phase is eliminated are determined in large part by the area over which the sample is deposited. We have shown that SFC eluates can be condensed at ambient temperature into spots of 100 to 200μm in diameter. The microscope interface therefore serves to increase the sensitivity of the SFC/FT-IR measurements of these spots and detection limits in the low nanogram range are possible. Preliminary results obtained before any real attempts were made to optimize the deposition process indicate that identifiable spectra can be obtained in real time at the 50 ng level for chromatographic separations performed with a 100μm i.d. wall coated open tubular column. Reproducible reconstructed chromatograms are obtained as each deposited eluate travels through the beam focus of the microscope. The concentration profile of deposited peaks was determined by IR measurements performed at 50 μm increments over the width of the peak to ascertain the deposition size. The results described in this paper, while not yet optimized, indicate the great potential of SFC/FT-IR microspectrometry.
    Additional Material: 5 Ill.
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  • 221
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 182-185 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Lipids ; Bacterial glycerol tetraethers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of bacterial glycerol tetraethers by capillary supercritical fluid chromatography is described. Complete separation of ethers, differing only by the number of cyclopentane rings present in the isopranyl side chains could be achieved. On a 50% methylphenylpolysiloxane coated capillary, the ethers eluted in the order of increasing cyclopentane content. The analysis revealed the presence of two previously unreported structural isomers of glycerol tetraethers. The method can be used qualitatively and quantitatively as a fast and sensitive screening test for such compounds in living organisms and sedimentary organic matter.
    Additional Material: 2 Ill.
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  • 222
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 194-197 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 223
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 464-465 
    ISSN: 0935-6304
    Keywords: High-performance liquid chromatography, HPLC ; Liquid chromatography at subambient temperatures ; Steroids ; Increased resolution by cooling ; Effect of cooling on retention time ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 224
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Theory ; Mathematical dead time ; Methylphenylsiloxane stationary phases ; Constants of the n-alkane retention time curve ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The column dead time and the constants of the n-alkane retention time curve in gas-liquid chromatography are calculated by the Wentworth iterative method on series of OV polymethylphenylsilicones with an increasing percentage of phenyl substituent. The values obtained are in good agreement with those calculated by the methods of Gröbler and Kaiser and with the experimental ones reported in the literature for stationary phases studied at 120°C and 150°C. The scatter of experimental retention times of n-alkanes and tM and b and c and Kováts retention indices are calculated.
    Additional Material: 5 Tab.
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  • 225
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 472-474 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Distilled-in-glass methylene chloride ; Environmental water analysis ; Sample preparation solvent ; Capillary GC/MS impurities ; Cold-on-column injection technique ; Fingertip organics ; EPA Method 625 ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Tab.
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  • 226
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 227
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 49-56 
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Fused silica capillary, columns ; Wide and narrow bore ; Cyanosilicone coatings ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of wide bore (320 μm) and narrow bore (50 μm) fused silica capillary columns is described for immobilized cyanopropyl substituted silicones containing 60 and 88% substitution. The effect of high temperature deactivation with cyanopropylcyclosiloxanes was studied with a special test mixture. Curing was achieved with dicumyl peroxide or azo-tert-butane.The columns were evaluated and compared in terms of efficiency, activity, polarity, and temperature stability. Different coating methods were compared for the narrow bore columns. The activity of the 60% cyanopropyl columns that had been immobilized with dicumyl peroxide was significantly larger than for azo-tert-butane immobilized columns. The polarity of polar columns appeared to depend greatly on column temperature and is completely different for wide and narrow bore columns.
    Additional Material: 10 Ill.
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  • 228
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986) 
    ISSN: 0935-6304
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 229
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 506-514 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Deactivation ; Gas chromatography, GC ; Small diameter capillary columns ; Organosilicon hydrides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small diameter fused silica capillary columns (50-75 μm i.d.) were deactivated at relatively low temperatures (250-300°C) with a mixture of polymethylhydrosiloxanes and several lowmolecular-weight organosilicon hydrides. Reproducible surface deactivations of highest quality were achieved with the polymethylhydrosiloxane (PMHS) reagent. Deactivations performed with PMHS via dynamic coating with neat or diluted reagent were evaluated by gas chromatography. Deactivations achieved with organosiloxane mono-, tri-, and tetrahydrides were also evaluated and compared. Low-molecular-weight organosilicon hydride deactivations were less time consuming and required lower head pressures for filling and coating columns with the reagent. Critical surface tensions of capillary surfaces modified with PMHS and the low-molecular-weight organosilicon hydrides gave support to the dehydrocondensation reaction between silica surface silanols and silyhydride bonds of the reagents. Slopes from Zisman plots indicated that coverage of the surface ranged from highest for the polymer (PMHS) to lowest for the monomers (TMS and PMDS). Efficiency measurements showed the influence that surface modification had on the uniformity and stability of the coated capillary columns. Well-deactivated capillary columns permitted the chromatography of polar solutes using supercritical carbon dioxide as mobile phase.
    Additional Material: 5 Ill.
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  • 230
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 518-523 
    ISSN: 0935-6304
    Keywords: Coupled HPLC-GC ; Concurrent solvent evaporation ; Loop-type interface ; Raspberry ketone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Presently, two coupling techniques are used for directly introducing HPLC fractions into capillary GC: The retention gap technique (involving negligible or partially concurrent solvent evaporation) and fully concurrent solvent evaporation. While the former involves use of a conventional on-column injector, it is now proposed that concurrent solvent evaporation technique be carried out using a switching valve with a built-in sample loop. The technique is based on the concept that the carrier gas pushes the HPLC eluent into the GC capillary against its own vapor pressure, generated by a column temperature slightly exceeding the solvent boiling point at the carrier gas inlet pressure. Further improvement of the technique is achieved by flow regulation of the carrier gas (accelerated solvent evaporation) and backflushing of the sample valve (improved solvent peak shape).Concurrent solvent evaporation using the loop-type interface is easy to handle, allows transfer of very large volumes of HPLC eluent (exceeding 1 ml), and renders solvent evaporation very efficient, allowing discharge of the vapors of 1 ml of solvent through the column within 5-10 min.
    Additional Material: 6 Ill.
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  • 231
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    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 626-632 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Post-column restrictor ; Dead-time variation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A one-dimensional compressible flow model is used in the description of actual flow through ducts. This model serves well in the explanation and prediction of the characteristics towards signal distortion, noise, mass flow rate and influence on dead-time behavior of end-restrictors as used in supercritical fluid chromatography (SFC) with post-column detection. It was experimentally verified that tapered restrictors have a better performance than constant diameter restrictors at relatively low detection temperatures (200°C).The mass flow rate of a tapered restrictor is found to be linearly proportional to applied inlet pressure, implying the same linear dependence of the product of linear velocity and on-column density. A more than proportional rise of density will, therefore, lead to a decrease in linear velocity and vice versa. Since thermostat temperature fluctuations are directly translated into linear velocity variations, a very temperature stable thermostat has to be used.As will be discussed, this complicated dead-time dependence on applied pressure has a large effect on the chromatographic results.
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  • 232
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    Journal of High Resolution Chromatography 9 (1986), S. 643-647 
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography (CGC) ; Simultaneous quantitation ; Human plasma ; Glyceryl trinitrate ; Glyceryl dinitrate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A specific, sensitive, and precise assay for simultaneous quantitation of glyceryl trinitrate (GTN) and its metabolites 1,2-and 1,3-glyceryl dinitrate (GDN) has been developed. The method involves one single extraction step with benzene, followed by evaporation at 55°C. One μl of the extract was injected onto a capillary fused silica column with trifluoropropyl as the stationary phase. The column separated all the nitrates within 17 minutes using temperature programming from 90 to 155°C. The lower limits of detection were 0.05, 0.5, and 0.1 nmol/I for GTN, 1,2-GDN and 1,3-GDN respectively. The calibration curves were linear in the concentration ranges 0.05-10.0 nmol/I (GTN), 0.5-10.0 nmol/I (1,2-GDN) and 0.1-10.0 nmol/I (1,3-GDN). Plasma concentration data from two patients receiving intravenous GTN infusion are presented.
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  • 233
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    Journal of High Resolution Chromatography 9 (1986), S. 662-666 
    ISSN: 0935-6304
    Keywords: Capillary GC ; GC/MS ; Reducing sugars ; NPD ; Derivatization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of sugar methoximes with sodium cyanoborohydride followed by permethylation with CH3SOCH2-/ICH3 affords the corresponding deoxy(methylmethoxylamino)alditol O-methyl ethers, which are amenable to capillary gas chromatography. Derivatization proceeds under mild conditions with high yields. Only a single derivative is formed for each reducing sugar. All aldose derivatives can be separated in a single chromatographic run on glass capillaries coated with Carbowax 20 M or Superox 0.1. Good linearity was found. The introduction of the nitrogen atom in the sugar molecule makes these derivatives suitable for selective detection by the NPD. The El-mass spectra contain intense characteristics ions at m/z 74 for aldoses and at m/z 280 for reducing disaccharides, together with a (M - 15)+ion. These fragments are very suitable for highly sensitive GC-MS analysis by selective single ion monitoring.
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  • 234
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    Journal of High Resolution Chromatography 9 (1986), S. 652-656 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography ; Capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In cases where high efficiency is required to resolve complex mixtures of either thermally labile or nonvolatile organic compounds, capillary supercritical fluid chromatography may be the most desirable analytical method. While great strides in this new technology have been made over the last few years, several problem areas are requiring increased attention. These include sample introduction systems, pressure reduction at the end of the column, column stability in various supercritical mobile phases, and migration of polar solute molecules. This paper describes the state-of-the-art in capillary SFC with emphasis on the progress made and future needs in the solutions to these specific problems.
    Additional Material: 3 Ill.
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  • 235
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    Journal of High Resolution Chromatography 9 (1986), S. 671-675 
    ISSN: 0935-6304
    Keywords: Capillary GC ; GC-MS ; Residue analysis PCB's ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An integrated analytical procedure for polychlorinated biphenyl (PCB) multiresidues in environmental samples has been developed and applied to well-characterized samples. PCB residues are characterized and quantified using wall coated open tubular column (WCOT) gas chromatography or HRGC/MS-selected ion monitoring. An automated data system based on a Spectra Physics SP-4200 computing integrator is used to select and quantitate peaks of individual congeners and homolog groups. This procedure consistently yields results with a reproducibility within 3 percent for HRGC-ECD and 3.7 percent for HRGC/MS-SIM technique respectively.
    Additional Material: 1 Ill.
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  • 236
    ISSN: 0935-6304
    Keywords: Micro-HPLC ; Reversed-phase mode ; Isotope separations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isotope separation utilizing ionization control in reversed-phase liquid chromatography was studied. Several organic acids and bases labeled with oxygen-18 and nitrogen-15 were successfully separated from unlabeled compounds by using either 6-m microbore columns or recycle chromatography with short columns of conventional size. Differences in the separation factors for the same isotopic mixtures were observed between the two chromatographic systems, and attributed to the difference in the pressure gradient along the columns in the two systems. The steep pressure gradient existing in the short recycle columns resulted in an increase in the peak width and the separation factor for oxygen isotopic compounds, and a decrease in the peak width and the separation factor for nitrogen isotopic compounds.
    Additional Material: 6 Ill.
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  • 237
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A method for determining serum catecholamine metabolites such as vanillylmandelic acid (VMA), 3-methoxy-4-hydroxyphenyl glycol (MHPG) and homovanillic acid (HVA) in neuroblastoma by using high performance liquid chromatography and electrochemical detector is described. The separation of catecholamine metabolites was performed on a reverse phase column with an eluting system containing citric acid-potassium hydrogen phosphate buffer and methanol as the organic modifier. The experimental results showed that VMA and HVA levels in the serum of neuroblastoma patients were 15-30 times higher than that of the normal control group. The same phenomenon also occurred in patients with stage II neuroblastoma. Serum VMA, MHPG and HVA levels reduced to normal in patients suffering from neuroblastoma after surgery. Serum catecholamine metabolites analysed by using HPLC/ECD is more simple, sensitive and reliable than that by usual urine assay and might be used for the diagnosis of neuroblastoma even in early stage.
    Additional Material: 3 Ill.
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  • 238
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: The solubilization of human lung elastin by leucocyte elastase and cathepsin G is described. Elastolysis kinetic studies clearly show that leucocyte elastase is more efficient in solubilizing elastin fibres than is cathepsin G. Cathepsin G can degrade elastin but at a much slower rate.Characterization of elastase and cathepsin G soluble elastin fragments, obtained after 24 h of digestion (enzyme-substrate ratio, 1:100), was first performed by isoelectric focusing. Whole digests were focused as 6 bands in a pH range 4.2 to 4.7 and were found to have no significant differences in amino acid compositions.Biogel P-100 gel filtration of the elastase digested fragments separated a major excluded fraction (Mr's: 80 000 to 30 000) and a small retained one (Mr's: 6000 to 4000). Conversely, cathepsin G digests were eluted as a minor excluded fraction and a more important retarded one (Mr's: 6000 to 4000). Only the high molecular weight fractions of both enzymes digests contain crosslinked amino acids; this assigns a role for desmosines in the resistance of elastin to these proteases. These results are discussed in comparison with the data obtained by others.
    Additional Material: 2 Ill.
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  • 239
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    Biomedical Chromatography 1 (1986), S. iv 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 240
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    Biomedical Chromatography 1 (1986), S. 49-52 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Because of their narrow therapeutic ranges and differing patient tolerances, the monitoring of tricyclic antidepressants (TADs) commonly prescribed for control of endogenous depression is highly desirable for the satisfactory treatment of patients. The majority of methods for analysis of TADs require multiple extractions from plasma with organic solvents, accompanied by obligatory centrifugation steps. We describe a simple procedure for the rapid extraction of serum TADs, with high recovery of the analyte drugs. It involves sample preparation using Analytichem ‘BOND-ELUT’ C-2 reverse phase columns, and analysis by gas chromatography using a nitrogen-phosphorus detector. The method offers a quick, inexpensive and low-maintenance assay which is applicable to all the common tricyclic class drugs.
    Additional Material: 2 Ill.
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  • 241
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    Biomedical Chromatography 1 (1986), S. 58-63 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: With human orosomueoid as model compound, a new method was developed to separate neutral oligosaccharides as N-p-nitro-phenylglycosylamines. Asialo orosomueoid was prepared by treatment with neuraminidase and purified by size exclusion HPLC on TSK 2000 SW. Oligosaccharides were isolated by reversed phase HPLC on Hamilton PRP-1 after hydrazinolysis and re-N-acetylation. Glycosylamination was performed with p-nitroaniline in DMSO-formic acid-water, where the whole mixture of oligosaccharide derivatives was isolated by reversed phase HPLC on Hamilton PRP-1 and separated into single glycosylamines on Shandon Hypersil ODS. The purified glycosylamines could be methylated by a new rapid method with sodium hydroxide and methyl iodide in DMSO, isolation and purification were carried out on Hamilton PRP-1 and Spherisorb ODS 2, respectively, as described for the glycosylamines. Preparative scale HPLC separations were performed on analytical columns using repetitive collection mode and automatic sample loading by means of a peristaltic pump operated by the HPLC controller. The purified glycosylamines can be used for sugar analyses or, after permethylation, for methylation analyses or related procedures.
    Additional Material: 4 Ill.
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  • 242
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: An automated, highly stable HPLC system is described allowing the quantitation of monoamines and related compounds with virtually online data processing and statistical evaluation of the mean values of various differently treated groups of animals. The system is highly suited to the screening of drugs involving large numbers of samples. To ensure long-term, uninterrupted performance, two robust chromatographic systems were developed optimized to separate neighboring peaks as widely as possible. This was achieved by using mobile phases of relatively low pH to retard acidic compounds, and optimal concentrations of the ion-pairing reagent to manipulate the retention times of amines on the RP-18 column, resulting also in clearcut separations from the solvent/tissue peak. Direct injection of deproteinized tissue samples, requiring no clean up procedures is used. One faster system allows measurement of the main biogenic amines, metabolites and TRP, whereas another system allows the simultaneous quantitation of DOPA, 5HTP, NA, MOPEG, NMN, A, MN, VMA, DA, 3MT, OOP AC, HVA, 5HT, 5HIAA and TYR. By pretreatment of animals with a decarboxylase inhibitor the latter system offers the possibility of detecting drug effects in the same animal on either dopamine and serotonin turnover or noradrenaline and serotonin turnover, depending on the brain area chosen. The system described has been running for over a year without major disturbance and with minimal technician attendance.
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  • 243
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    Biomedical Chromatography 1 (1986), S. 89-92 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Enterolactone, enterodiol and secoisolariciresinol were conjugated with glucuronic acid by solubilized rabbit liver microsomal UDP-glucuronyltransf erase. The monoglucuronide conjugate of all three substrates was formed and its identity confirmed by nuclear magnetic resonance (NMR) spectroscopy. Analytical high pressure liquid chromatography (HPLC) and NMR spectroscopy indicated conjugation with glucuronic acid to occur at several positions in the molecule. The enzymatic conjugation was monitored by analytical capillary isotachophoresis (ITP). The Km-values for enterlactone, enterodiol, and secoisolariciresinol were calculated to be 0.30, 0.23, and 0.22 mmol/l respectively.
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  • 244
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    Biomedical Chromatography 1 (1986), S. 101-103 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatography method is described for measuring Ifosfamide (I) in human serum. This involves solvent extraction, reverse phase HPLC and UV detection at 190 nm. Standard curves of peak height × detector sensitivity versus I concentration in serum were linear with a lower limit of detection of 100 ng/ml. Authentic 14C-labelled I cochromatographed with standard I and with I found in serum from treated patients. The concentration-time curves of I determined by both HPLC and gas chromatography were indistinguishable. We conclude that this method is suitable for determining I pharmacokinetics in biological specimens.
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  • 245
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    Biomedical Chromatography 1 (1986), S. 119-122 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A biologically active peptide designated hLCP has been isolated and purified to homogeneity from human lung carcinoma by means of acidic extraction and successive chromatography on Sephadex G-50, Toyopearl HW-40 F and reverse-phase high performance liquid chromatography columns. Analysis showed that peptide consists of thirteen amino acids. Primary structure of hLCP has been deduced by double-coupling Edman degradation combined with enzyme digestion as H-Ser-Pro-Pro-Asp-Gly-Lys-Lys-Glx-Ser-Ala-Asp-Val-Lys-OH. hLCP possesed significant excitatory activity on an electrical stimulation induced contraction. No hLCP could be detected in normal lung tissue. The possibility of using hLCP as a biochemical marker in the clinic for the early detection of lung carcinoma is being investigated.
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  • 246
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    Biomedical Chromatography 1 (1986), S. 142-142 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
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  • 247
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    Biomedical Chromatography 1 (1986), S. 147-150 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Depeptidyl aminopeptidase IV (E.C. 3.4.14.5) has been purified to homogeneity using “soft-column” chromatography on Sephadex G-200, DEAE-cellulose, gly-pro-AH-Sepharose and finally HPLC on TSK G-3000SW. The purification by HPLC is fast and gives a better yield of pure enzyme than procedures which have been described previously. The enzyme obtained in this manner has a high specific activity (86 U/mg using a saturating level of gly-pro-4-nitroanilide as substrate) and was free of contaminating peptidase activities. Our preparation of DAP IV is suitable for peptide sequencing studies by fast atom bombardment mass spectrometry.
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  • 248
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    Biomedical Chromatography 1 (1986), S. 163-168 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: A high performance liquid chromatographic (HPLC) method was developed for the determination of zinc protoporphyrin (ZnPP) and protoporphyrin (PP) in whole blood. After adding the blood to dilute acetic acid, ZnPP and PP were extracted with dimethyl sulfoxide-acetone containing mesoporphyrin as internal standard. Following evaporation of the acetone, the haemin-free extract was analysed by HPLC. ZnPP and PP were separated on a reversed-phase column and quantitated by measuring fluorescence peak areas. The extraction method is simple, and applicable to batch analysis, and the HPLC separation is rapid and repoducible. The coefficient of variation for ZnPP was 5.6% and 3.3% for total red cell porphyrin levels of 3.5 and 10.2 μmol per litre RBC respectively. Results are discussed in patients with erythrohepatic protoporphyria, lead exposure, iron-deficiency and non-specifically elevated total red cell porphyrins.
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  • 249
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    Biomedical Chromatography 1 (1986), S. 180-182 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Additional Material: 3 Ill.
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  • 250
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    Biomedical Chromatography 1 (1986), S. 183-188 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Rapid, quantitative, chromatographic separations of mixtures of human haemoglobins have been performed on short (5 - 20 mm) columns of packing material. The desirable characteristics of suitable column packing materials are illustrated and discussed. Simple, inexpensive, manually operated equipment can be used for the analysis, since the specifically designed midget columns generate little back pressure (10 - 30 lb/in2) when eluted at constant flow rates up to 2 mL/min. Cation exchange Chromatography on bonded silicas has been used for the detection of pathological haemoglobinopathies. Separations similar to the HPLC procedures are possible with the correct selection of buffer composition. It also compares favourably with the methods in common clinical use employing electrophoresis on cellulose acetate. Both ion-exchange and affinity methods for the estimation of glycated haemoglobins have been developed and are compared.
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  • 251
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    Biomedical Chromatography 1 (1986), S. 173-176 
    ISSN: 0269-3879
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: We describe an optimized automated liquid Chromatographic method for simultaneous measurement of primidone, phenobarbitone, phenytoin, carbamazepine and clonazepam. A Waters Tri-Module automation system is used and it provides direct read-out of results after chromatography. A one-step extraction with ethyl acetate is used to extract the drugs from 100 μL serum samples. We use an isocratic mobile phase and monitor the column effluent at 210 nm. Drug levels as low as 5 μmol/L can be detected. The within-run CV's range from 1.4 to 2.7%, and the between-run CV's range from 5.2 to 6.1%. Analytical recovery is in the range from 94-108%. The method compares favourably with the enzyme multiple immunoassay technique for routine antiepileptic drugs monitoring, in accuracy, efficiency and cost-effectiveness.
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  • 252
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    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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  • 253
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    Biological Mass Spectrometry 13 (1986), S. 343-346 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas chromatographic/mass spectrometric peptide sequencing program PEPALG has been implemented in both FORTRAN and PASCAL on a personal computer for convenient off-line analysis. The availability of PEPALG in a microcomputer-based version of both FORTRAN and PASCAL should now allow ready access to this powerful protein sequencing technique by any interested laboratory.
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  • 254
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    Biological Mass Spectrometry 13 (1986), S. 347-355 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [M - H]- ions of a series of dipeptides, containing glycine at the N-terminal, and polypeptides have been generated by fast atom bombardment using an alkaline glycerol/water matrix, and their charge inversion spectra obtained using helium as the collision gas. The results presented indicate that the general features of the charge inversion spectra of these molecules are significantly different from the collisional activation spectra of the positively ([M + H]+) and negatively ([M - H]-) charged species. Whereas the collisional activation spectra of positively and negatively charged ions contain sequence information, the charge inversion spectra are very sensitive to the radicals present in the amino acids and can be used to determine the composition of the peptides.
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  • 255
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    Biological Mass Spectrometry 13 (1986), S. 373-380 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper proposes an efficient method for computer-aided peptide sequencing based on fast atom bombardment mass spectrometry. The method allows us to analyse peptides much larger than 1000 u within a reasonable cpu time and to have a set of amino acid sequences which are consistent with the observed fast atom bombardment mass spectrum to varying degrees. Another feature is that there is no need to pick sequence ion peaks out of the spectrum; all the ions observed are equally taken into account in the analysis so that one can exhaust the possibilities expected from the whole spectrum. For most samples of penta- to tridecapeptides, parts of an amino acid sequence could be reproduced satisfactorily without prior knowledge of amino acid composition. The degree of success in sequence elucidation depends entirely on the spectrum used in the analysis. When fragment ion peaks are clearly observed, the sequence can be predicted successfully. The result obtained for a given amino acid composition was always satisfactory.
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  • 256
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A procedure for qualitative and quantitative analysis of anthracene and phenanthrene in diesel particulates by means of collisionally activated decomposition mass spectrometry, without any previous extraction, is described. While the absolute amount of these two polycyclic aromatic hydrocarbons has been obtained by collisional experiments on their molecular species and by using 2,6-diisopropylphenol as internal standard, the molar ratio between anthracene and phenanthrene has been determined with the aid of charge-stripping spectra.
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  • 257
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    Biological Mass Spectrometry 13 (1986), S. 133-135 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A technique is described for extraction and quantitation of meperidine and normeperidine from breast milk by gas chromatography/mass spectrometry. Both compounds were measured in breast milk from parturients who received the drug for postpartum pain relief. The technique is sensitive to 1 ng ml-1 and standard curves were linear at 1.5-2000 ng ml-1. Levels in breast milk samples were 36.2-314 ng ml-1 and 0-333 ng ml-1 for meperidine and normeperidine, respectively. Preliminary results suggest that postpartum pain medication with meperidine results in considerable levels of both meperidine and its active metabolite, normeperidine, in breast milk.
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  • 258
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metabolism of nor-nitrogen (NNM) and phosphoramide mustards (PM) and cyclophosphamide (CP) was investigated in the Sprague-Dawley rat using chemical ionization mass spectrometry and ion cluster techniques. Following administrations of a 1:1 mixture of the non-labeled and the corresponding side-chain deuterium-labeled compounds to separate rats, the urinary extracts were screened for cluster ions which were characteristic of the administered compounds and their derived metabolites, and on this basis, tentative identifications of known and new metabolites were accomplished. Combining derivatization, deuterium labeling on strategic locations, gas chromatography/mass spectrometry, and chemical synthesis in some cases, 3-(2-chloroethyl)-1,3-oxazolidin-2-one was identified as a major metabolite for NNM, PM and CP and 3-(2-chloroethyl)-4-hydroxy-1,3-oxazolidin-2-one was identified as a major metabolite for NNM and PM, but a minor metabolite for CP. A new dechlorinated metabolite for CP, 3-(2-hydroxyethyl)-1,3-oxazolidin-2-one, was also identified.
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  • 259
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    Biological Mass Spectrometry 13 (1986), S. 159-166 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Six diene valepotriates isolated from Valeriana and Centranthus species have been investigated by CI mass spectrometry using ammonia, methylamine, diethylamine, triethylamine and ethylenediamine (EDA) as reactant gases. The compounds have been characterized by base molecular adduct ion peaks (Et2NH and EDA) and typical fragments.
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  • 260
    ISSN: 1052-9306
    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 brassinosteroids are discussed in comparison with their positive ones. In contrast to the EI-mass spectra the negative ion mass spectra show strong peaks in the molecular ion region. The nature of an intense [M - 4]-· ion was investigated on the base of model compounds and deuterium labeled derivatives.
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  • 261
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    Biological Mass Spectrometry 13 (1986), S. 657-661 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allyldimethylsilyl ethers of prostaglandin E2 and F2α, leukotriene B4 and 5β-pregnane-3α, 20α-diol were prepared at room temperature in good yields with the novel reagent N, O-bis(allyldimethylsilyl)-trifluoroacetamide. The gas chromatographic properties of the derivatives of prostaglandins and the steroid were found to be excellent whereas those of leukotriene B4 were found to be less than satisfactory. The mass spectra of the allyldimethylsilyl ether derivatives of the compounds studied show intense ions in their upper mass region derived from the elimination of an allyl radical. In the mass spectrum of the derivative of leukotriene B4, the formation of a conjugated carbonium ion by α-cleavage is a major process. The detection limits for a quantitative assay were established by performing selected ion monitoring on the most intense ion in the upper mass region of respective mass spectrum. Detection limits in the low picogram range were obtained for the prostaglandins and the steroid but the allyldimethylsilyl ether derivative of leukotriene B4 exhibited a far higher detection limit. It is concluded for the latter compound that the detection limit depends primarily on the gas chromatographic properties.
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  • 262
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method for quantitating adenosine concentration by capillary gas chromatography-mass spectrometry-selected ion monitoring (GC-MS-SIM) has been developed and used as a reference method for evaluating a newly developed radioimmunoassay (RIA) for adenosine. Details of the GC-MS-SIM method are presented, along with the comparative results and uncertainties of both methods. General considerations in the statistical analysis of method comparison data are discussed with particular reference to studies using quantitative mass spectrometry as the standard method; the adenosine methods are used as specific examples in this discussion. Simultaneous estimation of the y-intercept and slope of the least squares regression line relating the results of the two methods using the 95% joint confidence ellipse demonstrated the absence of either constant or proportional error between the two methods. The relatively small uncertainty in the GC-MS-SIM measurements had no significant effect on the linear regression. Random error between the two methods was detected, and was estimated by the coefficient of variation in the RIA data as ten percent of the RIA value.
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  • 263
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During sequence determination of a structural protein from the cuticle of the migratory locust, Locusta migratoria, a discrepancy was found between the molecular weight calculated from the sequence data (15 323) and that estimated by SDS-gel electrophoresis (21 600). The protein contains several repeated sequences, and the discrepancy might indicate that part of the sequence was missing or that the protein contained a large prosthetic group. The molecular weight of the protein was determined by 127I-plasma desorption mass spectrometry to be 15 329±50 which confirms the sequence data and shows the molecular weight determination based on SDS-electrophoresis to be too high.
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 265
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    Biological Mass Spectrometry 13 (1986), S. 21-24 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to assess the feasibility of using stable 13C as a tracer for studying cholesterol metabolism in vivo (i) the 13C content of some commonly consumed foods and (ii) the stability of the 13C content of human serum cholesterol has been investigated. A procedure is described for the extraction and purification of cholesterol from food, tissues and serum suitable for 13C analysis by mass spectrometry. The method caused no significant isotope fractionation effects. Generally, there was very little difference between the carbon isotope composition of the diet, the cholesterol and the tissue from which it was derived. However, the difference in 13C composition between tissue and cholesterol of prawns from differnt parts of the world was considerable, indicating a possible peculiarity in the metabolism of cholesterol by this species. The 13C content of human serum cholesterol on a normal diet did not alter significaantly with time, suggesting that stable isotope tracer techniques could be used to measure certain aspects of cholesterol metabolism in vivo.
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  • 266
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrachlorodiphenoquinones have the same exact mass and elemental composition as the toxic environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin. However, analysis of 3,3′-5,5′-tetrachlorodiphenoquinone showed a pronounced tendency toward chemical reduction in the mass spectrometer to the quinol compound, producing a molecular ion two mass units higher than 2,3,7,8-tetrachlorodibenzo-p-dioxin. Distinct differences were also apparent between the mass spectral fragmentation patterns of 3,3′,5,5′-tetrachlorodiphenoquinone and 2,3,7,8-tetrachloridibenzo-p-dioxin. The 3,3′,5,5′-tetrachlorodiphenoquinone spectrum shows a successive loss of carbon monoxide, with the most prominent fragment corresponding to loss of two molecules of carbon monoxide plus chlorine. In the mass fragmentation of 2,3,7,8-tetrachlorodibenzo-p-dioxin carbon monoxide loss is suppressed, but loss of one molecule of carbon monoxide plus chlorine is a major fragment ion. During an alumina column clean-up procedure 3,3′,5,5′-tetrachlorodiphenoquinone did not coelute with the fraction containing 2,3,7,8-tetrachlorodibenzo-p-dioxin. This evidence indicates that tetrachlorodiphenoquinones are unlikely to interfere with mass spectrometric determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in environmental samples.
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  • 267
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    Biological Mass Spectrometry 13 (1986), S. 65-69 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray negative ion mass spectra of eighteen steroid monoglucuronide conjugates have been recorded. The salt-free aqueous solvent system used gave mass spectra for glucuronides which contained molecular anions only. Selected ion monitoring indicated that as little as 100 pg of these compounds could be detected. A gradient elution high-performance liquid chromatography system has been developed and applied to separation of the individual components of a mixture of twelve steroid monoglucuronides and detection by thermospray liquid chromatography negative ion mass spectrometry.
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  • 268
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    Biological Mass Spectrometry 13 (1986), S. 71-76 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fast atom bombardment (FAB) mass spectrometry was evaluated as a means for the characterization of molecular species of glycerophosphocholines (GPC) from HL60 cells. Previous reports of phospholipid molecular species analysis have suggested that several inherent problems with FAB could limit its analytical usefulness in such an application. The GPC-related secondary ions produced by the FAB experiment were found to be dependent on the matrix employed. Triethanolamine was found to minimize mass-related discrimination in ion emission when mixtures were studied; and furthermore, this matrix maintained 60% maximal ion current after 12 minutes as compared to a glycerol matrix which diminished to 10% maximal ion current. Using triethanolamine, the major GPC species in HL60 cells prelabeled with (2H8) arachidonic acid were found to be 16:0a16:1, 16:0e/18:1, 16:0a/18:1, 18:1a/18:1 and 18:0a/18:1.† It was possible to identify the minor GPC species containing arachidonic acid only after partial purification by reverse-phase high-performance liquid chromatography. Comparison of the 2H8/2H0 enrichment data estimated by FAB with data obtained by gas chromatographic/mass spectral analysis of arachidonic acid following GPC hydrolysis revealed that the precision of FAB was less precise than gas chromatography/mass spectrometry. Yet the FAB technique did allow the observation of one unexpected molecular species (18:1a/20:4) due to the fact that the GPC was not degraded to simpler species prior to analysis. In this respect, the two strategies of molecular species analysis complement each other.
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  • 269
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 270
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A very sensitive method of 1-O-alkyl-2-acetyl-sn-glycerophosphocholine (platelet activating factor) quantitation is described. 1-O-Alkyl-2-acetyl-sn-glycerophosphocholine is converted to 1-O-alkyl-2-acetylglycerol by treating with phospholipase-C which is in turn acylated with pentaflurobenzoyl chloride. The resulting diglyceryl ester of pentafluorobenzene is analysed by gas chromatography/negative ion chemical ionization mass spectrometry. With methane as the reagent gas the pentafluorobenzoyl acyl derivative yields mainly the molecular anion ([M]-) representing more than 92% of the total ion current. Deuterium-labeled 1-O-hexadecyl-2-(2H3)acetyl-sn-glycerophocholine is used as the internal standard for quantitation. The standard curves are linear and typically have a correlation coefficient of greater than 0.999. Using 1 pg of the deuterium-labeled internal standard, quantities as low as 100 fg are measured.
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  • 271
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    Biological Mass Spectrometry 13 (1986), S. 129-132 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This report describes a highly sensitive capillary gas chromatographic/mass spectrometric procedure for the quantification of alprazolam in human plasma. Alprazolam was extracted from plasma at basic pH with benzeneisoamyl alcohol (98:2, v/v) and analysed directly without any derivatization. Triazolam, also a triazolobenzo-diazepine derivative, was used as an internal standard because its extraction characteristics were similar to alprazolam. High sensitivity was achieved by negative ion chemical ionization and selected ion monitoring for alprazolam (m/z 308) and triazolam (m/z 306). The within-day coefficient of variation of the method over the concentration range 1.0-20 ng alprazolam per ml of plasma was 5.5%.
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  • 272
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    Biological Mass Spectrometry 13 (1986), S. 181-186 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas chromatographic/mass spectrometric techniques using chemical ionization have been employed to characterize the fungicide dichlofluanid and its major metabolite. The results have indicated some unusual fragmentation pathways for perhalogenmethylmercapto compounds. Use of deuterated ammonia as reagent gas has permitted a comparative assessment of protonation and exchangeable hydrogens within the major fragment ion structures. Resultant structural information has been employed to confirm residue findings in strawberries at the low part-per-million level.
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  • 273
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    Biological Mass Spectrometry 13 (1986), S. 199-204 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive- and negative-ion mass spectra of five glycoconjugates were obtained using laser desorption/Fourier transform mass spectrometry. These were the glycoalkaloids α-solanine and α-tomatine and the steroid glycosides gitoxin, lanatoside A and digitonin. Doping with KCl yielded both potassium- and chloride-attachment ions. Few fragment ions were observed for these species, with the exception of digitonin, although the negative-ion spectra showed relatively more fragmentation than the positive-ion spectra. All major fragments appeared to arise from losses of sugar groups due to cleavages at the glycosidic linkages. This contrasted sharply with the behavior of the malto-oligosaccharides studied in this laboratory.
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  • 274
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 275
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    Biological Mass Spectrometry 13 (1986), S. 231-236 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary column ammonia chemical ionization mass spectrometry was investigated as a technique for the characterization of a number of organophosphorus chemical warfare agents and simulants, since electron impact ionization provides little or no molecular ion information for these compounds. The effects of source temperature, source pressure, electron energy and electron emission were investigated in order to optimize ammonia chemical ionization conditions. Source temperature was found to have a dramatic effect on the chemical ionization mass spectra acquired. Abundant [M + NH4]+ and/or [M + H]+ quasimolecular ions were usually observed at lower source temperatures for the selected compounds under positive ion chemical ionization conditions, along with a number of characteristic fragmentation ions. Full-scan mass spectra were obtained for 1--2 ng of analyte during the capillary column ammonia chemical ionization operation. The sensitivity, molecular ion information afforded and lack of background interference ions associated with this technique make it a good candidate for the confirmation of organophosphorus chemical warfare agents and simulants.
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  • 276
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method has been described for the quantification of diethylstilboestrol (DES) in bovine urine. The determining step is based on isotope dilution mass spectrometry (IDMS). The chemical work-up consisted of enzymatic deconjugation, Sep-Pak® clean-up and high-performance liquid chromatography (HPLC). The labelled compound synthesized for IDMS is hexadeutero DES (DES-2H6). The labelled compound is not only used to quantify DES, but also to check the recovery of the chemical work-up procedure, in order to avoid false negative results. At the 1-5 μg I-1 level of urinary DES, the average recovery of 2 μg I-1 DES-2H6 is 70±20% (s.d.).
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  • 277
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    Biological Mass Spectrometry 13 (1986) 
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
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    Topics: Chemistry and Pharmacology
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  • 278
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sensitive gas chromatographic/mass spectrometric assay for paracetamol, produced by the O-deethylation of phenacetin by microsomal fractions of human liver, has been developed. The method uses the 3,5-bistrifluoromethyl-benzoyl derivative of paracetamol and electron capture negative ion chemical ionization. This derivative has a negative ion mass spectrum which contains only a molecular ion at m/z 391 and, when this ion is specifically monitored, an amount of derivative equivalent to 1 pg of paracetamol can be detected. (2H3)Paracetamol was available for use as an internal standard and this allowed the development of an assay with a precision of 8% (SD) at 0.5 ng paracetamol per microsomal incubation and a lower limit of quantitative determination of 0.2 ng paracetamol per microsomal incubation.
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  • 279
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study reports studies using electron capture negative ion chemical ionization gas chromatography/mass spectrometry (EC-NICI GC/MS) of 21 polycyclic aromatic hydrocaroon (PAH) compounds. The selectivity and sensitivity of these compounds are shown here to be highly dependent on ion source temperature and pressure. Changes in selectivity arise from variations in instrumental and can be largely explained by the competitive formation processes of [M]-. and [M—H]- ions. The formation of the adduct ion, [M + 15]-, previously attributed to [M + CH3]-, is shown here by using perdeuterated PAH analogues to be a [M + O — H]- ion. For fluorene and acenaphthene, abundant [M + 14]- and [M + 13]- ions can be similarly rationalized to be [M + O — 2H]- and [M + O — 3H]-. The NICI mass spectrum of (2H10)acenaphthene demonstrates that ring proton losses most likely occur. This study also indicates that there is a strong correlation between the NICI response factor and the reported carcinogenic activity of PAHs in the literature. In addition, this work assesses the viability of NICI GC/MS as an analytical technique for determining PAHs in fly ash with minimum sample pretreatment.
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  • 280
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    Biological Mass Spectrometry 13 (1986), S. 117-120 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three positional isomers of unmodified dedecenols (δ2-δ4) have been analysed by conventional combined gas chromatography/electron impact mass spectrometry. The intensity ratios of certain selected pairs of predominant fragment ions, whose relative intensities vary with the position of the original double bond, are of diagnostic value for the identification of double bond positions. The determination of the double bond positions in dodecenols has therefore been established.
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  • 281
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tricyclic indole derivative 6-hydroxymethtryptoline (7-hydroxy-1-methyltetrahydro-β-carboline) was identified as a normal constituent of human and cat urine. The identification was based on the correct retention time on a chiral capillary gas chromatographic column and on selected ion monitoring of the molecular ion with the mass spectrometer set at high resolving power (RP 10 000). The quantitation utilized a 13C-labeled analog as internal standard and demonstrated levels of 135 ± 35 and 174 ± 42 (pmol ml-1, mean ±SEM) for the S(-) and R(+) enantiomers, respectively, in human urine. In cat urine, the levels were 203 ± 55 and 108 ± 44 (pmol ml-1, mean ± SEM) for the S(-) and R(+) enantiomers, respectively. In human urine, the compound occurred predominantly in a conjugated form while in cat urine the free compound predominated. It was concluded that 6-hydroxymethtryptoline is naturally occurring in mammalian urine and that it most likely constitutes a metabolite of endogenous methtryptoline (1-methyltetrahydro-β-carboline).
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  • 282
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    Biological Mass Spectrometry 13 (1986), S. 489-494 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Californium-252 plasma desorption mass spectra have been run on a series of typical lipids found in skin, including a fatty acid, a methyl and wax ester, a mono-, di- and triglyceride and an anhydride, in a effort to discover the nature of peaks caused by fingerprint contamination of the sample holders. The triglyceride was identified as the source, and peaks found by reattachment of abundant fragment ions to the original lipid were noted in several cases.
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  • 283
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fast and sensitive gas chromatographic/negative ion chemical ionization mass spectrometric method for the simultaneous detection and quantification of several simple trichothecene mycotoxins and related molecules with good precision has been developed. The method consists of the conversion of the polar trichothecenes into their volatile and stable heptafluorobutyryl esters, followed by gas chromatographic/mass spectrometric analysis of the derivatives. The derivatives were ionized under chemical ionization conditions and the negative ions were monitored. The samples were screened for the presence of trichothecenes by monitoring one characteristic ion by selected ion monitoring for each analyte. The detected compounds were confirmed by monitoring 5-6 characteristic ions by selected ion monitoring whenever the amount of analyte present was insufficient to obtain a full scan negative ion chemical ionization mass spectrum. Two semi-synthetic trichothecenes, 4-deoxyverrucarol and 16-hydroxyverrucarol, were investigated and found to be adequate internal standards both for detection and quantification of these toxic compounds. Femtogram and low picogram (1-5 pg) quantities of these compounds could be detected and confirmed, respectively, by this procedure. A short clean-up procedure using Sep-Pak (silica gel) cartridges was developed and found to be appicable for the analysis of some real samples. Several spiked and real samples were analysed by this method, with excellent sensitivity and precision.
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  • 284
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatograph/quadrupole mass spectrometer system, operated in electron impact/selected ion monitoring mode, is used to determine the intensity ratio of the m/z 59 and the m/z 58 ions of the [C3H8N]+ fragment derived from methamphetamine samples synthesized with varying amounts of 13C-labeled methylamine. Crude products are introduced into the gas chromatograph without prior cleanup. The ratios measured were in excellent agreement with those calculated. A change in 0.25% use of 13C-methylamine is sufficient for product differentiation. The feasibility of using isotope labeling and subsequent mass spectrometric isotope ratio measurement as the basis of a compound tracing mechanism is discussed. Specifically, if methamphetamine samples manufactured from legal sources are asked to incorporate distinct 13C compositions, their sources can be traced when samples are diverted into illegal channels. Samples derived from illicit preparations can also be traced if the manufacturers of a precursor (methylamine in this case) incorporate distinct 13C compositions in their products.
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  • 285
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of the positive and negative ion, ammonia (NH3 and N2H3) direct chemical ionization mass spectrometry of highly purified prostaglandin endoperoxide (PGH2) is presented. The positive ion spectra were characterized by an intense [M+NH4]+ adduct at m/z 370 and several fragment ions, most notably a [M+NH4 - H2O]+ ion at m/z 352 and an ion at m/z 298, assigned as the [M+NH4 - 72]+ ion of 12-hydroxy-5,8,10-heptadecatrienoic acid formed from PGH2 in the spectrometer. The negative ion spectra of PGH2 were characterized by a base peak at m/z 352 [M]- and by an ion at m/z 334 corresponding to the loss of water from the parent ion. A combination of negative ion and deuterated ammonia reagent gas was used in making assignments and in demonstrating that the spectra observed were due to intact PGH2 and its stable PGE2 and PGD2 isomers formed in the spectrometer. In addition, use of the latter reagent gas was shown to clearly distinguish between several arachidonic acid metabolites, differing in their number of exchangeable protons. Furthermore, preliminary results with several stable prostaglandins indicate that the spectra are sensitive to different functional groups that are present. Consequently, it would appear that negative and positive ion, NH3 (N2H3) direct chemical ionization mass spectrometry would be useful in the analysis of labile arachidonic acid metabolites, without the need for prior derivatization.
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  • 286
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Quantitative estimation of isotopic enrichment and concentrations of keto analogs of branched-chain amino acids in biological fluid has been used for the study of protein metabolism in animal and human studies. At present, O-trimethylsilyl-quinoxalinol derivative is used widely in the quantification of branched-chain α-keto acids. In the present study, N-methyl-quinoxalone derivative was developed and its use in quantification in human studies verified. O-phenylenediamine and α-keto acid react in acidic media to yield phenolic and amide tautomers. O-trimethylsilyl-quinoxalinol derivative of the phenolic tautomer is used at present for quantification by chemical ionization/selected ion monitoring. We have prepared N-methyl-quinoxalone derivative using N,N-dimethyl formamide dimethyl acetal. This derivative is characterized by a major amide form and a minor phenolic form. The mass spectrum has a characteristic fragment, which facilitates easy identification and quantitation by electron impact/selected ion monitoring. Because m/z 174 was observed as the base peak for α-ketoisocaproate, α-keto-β-methylvalerate and α-ketoisovalerate, ‘single ion monitoring’ could be performed for the quantification of isotopic enrichment as well as plasma concentration of these three branched-chain α-keto acids. Isotopic enrichment from 0.25 to 7.5 at% excess could be measured easily, with an average coefficient of variation of 〈8%. Plasma concentrations as low as 10 μMl-1 in a 200-μl aliquot could be measured.Methyl migration was an interesting feature of the mass spectrometric fragmentation pattern of the α-keto acids. The mechanism of methyl migration is proposed and discussed. This paper also describes some of the studies involved in the formation of isomeric O- and N-alkyl, -quinoxaline and -quinoxalone using a number of N,N-dimethyl formamide dialkyl acetals.
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    Biological Mass Spectrometry 13 (1986), S. 605-609 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect has been investigated of data smoothing on the precision and accuracy of peak height ratio (analyte/isotopically-labelled internal standard) determination by gas chromatography/mass spectrometry with dual ion monitoring. The smoothing routines evaluated were all based on the moving average principle but differed with respect to weighting factors and filter width. Smoothing was shown to achieve only a minor improvement in precision and introduced significant bias in the peak height ratio calculation. In contrast, determination of response ratios by linear regression of analyte and internal standard signals achieved superior precision without the introduction of significant bias.
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  • 288
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron impact (EI) and methane negative ion chemical ionization (NICI) gas chromatographic/mass spectrometric analyses of kava resin, derived from commercial Piper methysticum, are described. The resulting mass spectra are correlated with the known major and trace constituents of this resin. Several of the kava lactones (kawain, methysticin, desmethoxyyangonin and yangonin) produced abundant molecular anions when analysed by methane NICI mass spectrometry, in contrast to their 7,8-dihydro analogues which ionized with poor efficiency to yield weak [M - H]- anions. Deuterium labelling established that the origin of the [M - CH3]- anion in the methane NICI mass spectrum of yangonin resulted from the elimination of a methyl radical from the 4-methoxyl substituent. As a result of the present study, an additional four trace components of kava have been identified.
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  • 289
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    Biological Mass Spectrometry 13 (1986), S. 357-360 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Di-2-ethylhexyl phthalate (DEHP), a commonly employed plasticizer reported to be carcinogenic in rats and mice, has been confirmed to leach from all plastic component parts of the equipment employed in plasma donation. Resident aqueous solutions of both sodium chloride and sodium citrate were found to contain only trace levels of DEHP (0.03 ppm), while stored plasma samples contained levels at least one order of magnitude higher (0.4 ppm). Since at least 5% of all plasma donations in the Los Angeles area are deemed to be of the high frequency classification, investigation into repeated red blood cell exposure to DEHP was considered imperative. However, there was no difference in the levels of DEHP found in the plasma of the frequent plasma donor (50-60 times per annum) relative to the first-time donor. It is concluded that there is no increased contamination threat to frequent plasma donation from migrating plasticizer via red blood cell exposure, at least during the collection process. Furthermore, there is no more risk to recipients of plasma products from frequent donors than from occasional donors. It would seem that the ambient level of DEHP to be expected in stored frozen plasma products averages no greater than about 0.5 ppm.
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    Biological Mass Spectrometry 13 (1986), S. 477-482 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report an investigation of the effect of the addition of strong mineral acids to the most commonly used matrices for fast atom bombardment mass spectrometry of peptides. Among the acids tested we found that perchloric acid has a beneficial effect on: (i) the sensitivity, (ii) the stability of quasi-molecular ion signals. Furthermore, in the presence of basic residues, ions related to perchlorate adducts are present. These further signals may be useful in differentiating peptides containing lysine from those containing the isobaric glutamine.
    Additional Material: 6 Ill.
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  • 291
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    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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  • 292
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    Biological Mass Spectrometry 13 (1986), S. 553-558 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A stable isotope dilution assay is described for the six branched chain alpha-hydroxyacids and alpha-ketoacids that accumulate in serum in maple syrup urine disease. The method employs sodium borodeuteride reduction of the alpha-ketoacids in situ to once-labeled hydroxyacids, addition of a more extensively labeled analog as internal standard, isolation of the organic acids by ether extraction, and quantitation by gas chromatography/mass spectrometry in selected ion monitoring mode. A set of three areas are obtained for each of the three branched chain hydroxyacid peaks, and these are corrected for natural abundance heavy isotope content and for isotopic impurities in the labeled standards and precursors. The corrected areas are then converted to concentrations of the endogenous three hydroxyacids and the original three ketoacids in serum.
    Additional Material: 1 Ill.
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  • 293
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    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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  • 294
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    Biological Mass Spectrometry 13 (1986), S. 595-598 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In addition to the previously described metabolites, octanoyl glucuronide was identified in the urine of four children who received medium-chain triglycerides. Octanoyl glucuronide in the urine of a child after ingestion of medium-chain triglycerides (C8:C10, 3:1) was quantitated as octanoic acid after glucuronidase treatment by means of gas chromatography/mass spectrometry. The urinary excretion increased rapidly to a maximum 1-2 h after ingestion, and decreased therafter. During 0-3 h, 6.11 μmol of octanoyl glucuronide was excreted, which comprised 0.034% octanoic acid administered as glyceride, and 0.07% octanoic acid was postulated to be excreted as glucuronide within 24 h. Neither decanoyl glucuronide nor hexanoyl glucuronide was detected. Glucuronidation of branched medium-chain fatty acids, whose β-oxidation is hindered, has been described previously. The present findings show that even straight-chain fatty acids undergo glucuronidation, although to a lesser extent, in addition to ω-oxidation and β-oxidation.
    Additional Material: 4 Ill.
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  • 295
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    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electron impact fragmentation of methyl ester/methyloxime/trimethylsilyl ether derivatives of prostaglandin E2 and 6-oxo-prostaglandin F1α and the methyl ester/trimethylsilyl ether derivative of prostaglandin F2α is followed by argon collision-activated dissociation in a triple quadrupole mass spectrometer. Daughter ion chromatograms of prostaglandin derivatives show an enormous increase of selectivity compared to the multiple ion detection chromatograms of the same samples in single quadrupole mode.
    Additional Material: 14 Ill.
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  • 296
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three glucuronide metabolites of doxylamine succinate were collected in a single fraction using high-performance liquid chromatography (HPLC) from the urine of dosed male Fischer 344 rats. The metabolites were then separated using an additional HPLC step into fractions containing predominantly a single glucuronide metabolite. Analysis of the metabolites by methane and ammonia desorption chemical ionization, with and without derivatization, revealed fragment ions suggestive of a hydroxylated doxylamine moiety. Identification of the metabolites as glucuronides of doxylamine, desmethyldoxylamine and didesmethyldoxylamine was accomplished, based on determination of the molecular weight and exact mass of each metabolite using fast atom bombardment (FAB) ionization. This assignment was confirmed by the fragmentation observed in FAB mass spectrometric and tandem mass spectrometric experiments. Para-substitution of the glucuronide on the phenyl moiety was observed by 500-MHz nuclear magnetic resonance (NMR) spectrometry. A fraction containing all three glucuronide metabolites, after a single stage of HPLC separation, was also analysed by FAB mass spectrometry, and the proton- and potassium-containing quasimolecular ions for all three metabolites were observed.
    Additional Material: 5 Ill.
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  • 297
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    Biological Mass Spectrometry 13 (1986), S. 641-642 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure assignment of the isomeric immonium ions 5 and 6, generated via FAB from N-isobutyl glycine and N-methyl valine, can be achieved by their collision induced dissociation characteristics.
    Additional Material: 2 Ill.
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  • 298
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    Biological Mass Spectrometry 13 (1986) 
    ISSN: 1052-9306
    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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  • 299
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    Biological Mass Spectrometry 13 (1986), S. ii 
    ISSN: 1052-9306
    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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  • 300
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    Biological Mass Spectrometry 13 (1986), S. 25-32 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cisplatin analogs of the type PtLALB are thermally unstable, non-volatile and highly insoluble. For these platinum coordination complexes, LA is a bidentate amine ligand and LB is a bidentate carboxylate ligand. Mass spectral data for structural elucidation of these compounds are absent in the literature because they are difficult to ionize. Nevertheless, a routine fast atom bombardment mass spectroscopic method has been developed utilizing the mixed solvent system of dimethyl sulfoxide: thioglycerol in a ratio of about 1:3 v/v. Using both positive and negative ionization modes, structurally significant ions were observed from representative molecules of the two named classes of compounds. [M — H]- ions were observed in both structural classes while [M + H]+ ions were observed only in the PtLALB class of compounds. Additional ions observed are rationalized in terms of the condensed-phase solution chemistry of the cisplatin analogs and the mixed solvent system when exposed to the fast atom beam. The two mechanisms causing ionization of the cisplatin analogs in the condensed phase appear to be: (i) displacement of the ligands with dimethyl-sulfoxide and (ii) addition of chloride and the ionized solvents [dimentyl sulfoxide+H]+ and [thioglycerol—H]- to the cisplatin analogs. It is hypothesized that the addition reactions of the ionized solvents occur because of the differences in the basicity of the solvents and their reactivity in forming platinum(II)-sulfur bonds.
    Additional Material: 2 Ill.
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