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  • Analytical Chemistry and Spectroscopy  (657)
  • 1985-1989  (657)
  • 1
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method for the quantitative determination of chlorpromazine and five of its major metabolites in a single sample of biological fluid in the ng/ml range has been developed utilizing gas chromatography/mass spectrometry with selected ion recording. The assay is highly specific and quantification is accomplished by an inverse stable isotope dilution technique, using deuterium-labeled variants of the compounds as internal standards. In this way the concentrations of chlorpromazine and five of its major metabolites (the sulfoxide, the N-oxide, the monodemethylated, the didemethylated, and the 7-hydroxylated compounds) can be determined in biological fluids. Levels in humans have been measured both in plasma and in red blood cells and are compared to those found in related in vitro studies.
    Additional Material: 2 Ill.
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  • 2
    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.
    Additional Material: 6 Ill.
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  • 3
    ISSN: 1040-7685
    Keywords: supercrirical fluid chromatography ; mass spectrometry ; capillary column ; inositol ; phosphate ; phytic acid ; silyl derivatives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary supercritical fluid chromatography with flame ionization detection appears promising for the separation and detection of silylated inositol phosphates. Inositol triphosphate and phytic acid, following ion exchange to their fully protonated forms, were silylated in one step with the addition of 9 and 12 trimethylsilyl groups, respectively. The resulting derivatives are well behaved in open-tubular chromatography columns with methyl-silicone stationary phase when CO2 is used as the mobile phase. Both flow-splitting and directinjection methods were evaluated. The identities of the derivatives were confirmed by supercritical fluid chromatography-mass spectrometry using chemical ionization with both ammonia and isobutane, and using electron ionization - CO2 charge exchange.
    Additional Material: 9 Ill.
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  • 4
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selected ion monitoring of vitamin D metabolites has previously been described but there has been only one detailed description of the measurement by gas chromatography/mass spectrometry (GC/MS) of a number of metabolites in a single plasma sample. We describe here a GC/MS method, using stable isotope labelled internal standards, which allows the estimation of vitamins D2 and D3, and their 25-hydroxy, 24,25-dihydroxy and 25,26-dihydroxy metabolites in a single 2 ml sample of plasma, although more is needed for the measurement of 1,25-dihydroxyvitamin D3. Plasma was extracted on Bond Elut C18 cartridges and initial fractionation carried out on Sep-Pak SIL. Straight-phase high-performance liquid chromatography was required for separation of polyhydroxylated metabolites prior to GC/MS using an LKB 2091 mass spectrometer with conventional packed columns. n-Butylboronate esters were formed across vicinal hydroxyls, followed by formation of trimethylsilyl ethers using trimethylsilylimidazole. The [M - 90 - 15]+ ion for each compound was monitored. Deuterated internal standards were not available for all metabolites and it was necessary to use (2H6)D3 and (2H6)25OHD3 as standards for the measurement of D2 and D3, and 25OHD3 and 25OHD2, respectively, and (2H6)24,25(OH)2D3 as a standards for 24,25(OH)2D3 and 25,26(OH)2D2. Although the [M - 90 - 15]+ ion of 24,25(OH)2D and 25,26(OH)2D has the same mass: charge ratio, derivatives of these compounds are completely separated in the GC system used. The intra-assay precision for all these assays is usually less than 5%.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 16 (1987), S. 161-165 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Oil was chosen as a new sampl type for total reflection XRF. A thin-film sample procedure is described which requires minimal sample preparation. This involves first bringing the oil into solution with a volatile solvent, then pipetting microliter amounts on to the reflector substrate followed by evaporation of the solvent. The linear dynamic range was found to extend to at least 5000 ppm. Detection limit measurements show that minute sample quantities are necessary for optimal detection limits of nanogram amounts. A maximum sample loading is required for the best detection limits in ppm. Using an Mo or Cu X-ray tube, limits were found to be a few ppm or sub-nanogram amounts. The spectrometer was calibrated by an internal standardization method and the results of determinations on sample solutions were typically within 10% relative accuracy.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 1040-1045 
    ISSN: 0749-1581
    Keywords: α-retinal ; α-ethyl retinoate ; α-retinol ; α-retinoic acid ; 3,4-dehydroretinal ; 3,4-dehydroretinol ; ethyl 3,4-dehydroretinoate ; 3,4-dehydroretinoic acid ; 2D heteronuclear-correlated spectroscopy ; APT ; empirical chemical shift calculations ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR assignments have been made for a series of 36 α- and 3,4-dehydroretinoids with different substituents (alcohol, ester, aldehyde and acid) and for their separated E and Z geometrical isomers. The assignments were made by using 2D heteronuclear-correlated NMR experiments. From the chemical shift data of 24 systematically related retinoids, empirical chemical shift changes due to four polar end groups (alcohol, aldehyde, carboxylic acids and esters), three chain configurations (all-E, 9Z and 13Z), and two ring substitutions (2,6,6-trimethyl-cyclohex-2-enyl and 2,6,6-trimethylcyclohexa-1,3-dienyl) were determined. All trends were found to be independent of each other, except for the dependence of the chemical shift change of the 13Z-isomers on the polar end groups. The chemical shift changes were used to predict the chemical shifts of other retinoids based on two different ring structures (2,6,6-trimethylcyclohexenyl and 4-methoxy-2,3,6-trimethylphenyl).
    Additional Material: 8 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 157-161 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A gas chromatographic/mass spectrometric assay for quantifying two catechol estrogens, 2-hydroxyestradiol and 4-hydroxyestradiol, in microsomal preparations is described. The assay employs deuterium-labeled analogs of the catechol estrogens as internal standards and permits quantification of catechol estrogens, in microsomal incubations, at low (1-2) μM concentrations. The compounds are analyzed as their trimethylsilyl derivatives following separation by capillary gas chromatography.
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An increasing amount of evidence is accumulating to support the proposal that steroidogenesis can occur by a sesterterpene pathway as well as the cholesterol pathway. Key intermediates on the sesterterpene pathway are 23,24-dinor-5-cholen-3β-ol (guneribol) and some of its metabolites, e.g. 23,24-dinor-4-cholen-3-one (guneribone). It has been reported that these intermediates are biosynthesized and converted to steroid hormones by a range of endocrine tissues in vitro. Monitoring the pentafluorobenzyloxime derivatives by negative ion chemical ionization mass spectrometry in the electron capture mode provided evidence for the presence of guneribone in extracts of bovine testicular and human adrenal tumour tissue. Complementary evidence was obtained from gas chromatographic/tandem mass spectrometric data generated on a triple-quadrupole instrument by monitoring daughter ions (in the multiple ion detection, MID mode) of the molecular anion of derivatized guneribone in both standards and tissue extracts. The present findings that sesterterpene pathway intermediates are present as endogenous compounds in tissue extracts, together with the previously reported radiochemical data, give further support to the sesterterpene pathway hypothesis.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 713-718 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Advanced glycation products have been investigated by parent ion spectroscopy, employing B2/E = constant linked scans of furoyl ions obtained from hydrolysed glycated albumin and polylysine mixtures, without any extraction procedures. Using such an instrumental approach, together with exact mass measurements and collision spectroscopy, the identification of 2-(2-furoyl)-4-hydroxyl-1H-imidazole and 2-(2-furoyl)-4-carboxy-1H-imidazole among the advanced glycation products has been achieved.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 213-220 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray HPLC/MS analysis of the metabolites of arachidonic acid proved to be sensitive and specific. The compounds included were hydroxy-fatty acids (5-HETE, 12-HETE, and 15-HETE) and prostaglandins PGD2, PGE2, PGF2α, PGA2, PGA1, TXB2, and 6-Keto-PGF1α. Thermospray HPLC/MS analysis allows for simultaneous monitoring of each compound without the need for additional sample preparation or derivatization. The thermospray spectra for the metabolites exhibited [M + NH4]+ ions and fragment ions because of sequential loss of equivalents of H2O. HPLC/MS showed detection limits in the 0.5 to 5 ng range when using multiple ion detection for most of the metabolites. Post-column derivatization of these metabolites using trimethylanilinium hydroxide (TMAH) to form the methyl esters is also presented. This derivatization resulted in a gain in ion current by a factor of 3-6 for most compounds while adding potential specificity to the analysis. The thermospray spectra of the derivatives were nearly identical to the spectra of the free acid except the peaks were incremented by 14 daltons due to the methyl ester formation. The derivatization of the carboxylic acid group proved to be complete under thermospray conditions producing the maximum ion current and causing no compromise in operation of the interface.
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