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  • Humans  (53)
  • Analytical Chemistry and Spectroscopy  (51)
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  • 11
    Electronic Resource
    Electronic Resource
    Effects of Injected Volume and Applied Voltage on Column Efficiency in Capillary Electrochromatography with Open Tubular Columns of 10 μm i. d. (2000)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 373-378 
    Details
    ISSN: 0935-6304
    Keywords: Open tubular columns ; capillary electrochromatography ; column efficiency ; injected volume ; applied voltage ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of some instrumental parameters on column efficiency in open tubular capillary electrochromatography (OTCEC) has been evaluated. First, it was investigated whether band broadening due to the sample injection process is within a tolerable range when an open tubular column (OTC) of about 10 μm i. d. is used. As a result of the small injection profile factor (K2 = 1.3), injected volumes must be sufficiently small (less than 10 pL) to avoid a significant efficiency loss (〉5%) when hydrodynamic injection by siphoning is employed. Secondly, the kinetic performance of OTCs in a CEC system was estimated from the variation of the reduced plate height (h) with the reduced linear velocity (ν) which was controlled by the voltage applied. Reasonable agreement was obtained between the theoretical h versus ν curve and the experimental values for a group of polycyclic aromatic hydrocarbons used as test compounds. Values of 0.25 for minimum h at an optimum ν of 16 are estimated, which permit separations with around 400,000 plates per meter to be obtained in less than 5 min. Finally, the possibility of estimating the diffusion coefficients of the solutes in the mobile phase from the plot of the height of a theoretical plate versus electroosmotic flow velocity is shown.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana, and in Vitro Evaluation of Its Antioxidant Activity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 343-349 
    Details
    ISSN: 0935-6304
    Keywords: Capillary gas chromatography ; gas chromatography-mass spectrometry ; essential oil analysis ; Lepechinia schiedeana ; antioxidant activity ; lipid peroxidation ; Ledol; Ledol HMQC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO2) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C15H26O, was the major constituent (20.04-36.87%) in all extracts. Oxygenated sesquiterpenes (24.36-43.14%), C10H16, monoterpenes (27.70-39.87%), and C15H24, sesquiterpenes (10.04-22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (Cn 〉 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.
    Additional Material: 4 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    HRGC and GC-MS analysis of essential oil from colombian ylang-ylang (Cananga odorata Hook fil. et Thomson, forma genuina) (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 441-444 
    Details
    ISSN: 0935-6304
    Keywords: High resolution capillary gas chromatography ; High resolution gas chromatography-mass spectrometry ; Essential oil analysis ; Ylang-ylang oil composition ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Samples of essential oil from Colombian ylang-ylang trees were analyzed by means of HRGC, HRGC-MS, IR and 1H- and 13C-NMR. 57 components were detected, 51 of which were positively identified. Camphene and anethol were identified in ylang-ylang essential oil for the first time. Among the composition-determining variables studied (extraction time, part of the flower, and flower freshness), the extraction time and the flower condition (fresh versus dry) were found to have the largest incidence in the quality of the essential oil.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160713
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  • 14
    Electronic Resource
    Electronic Resource
    Single-column ion chromatography for the determination of chloride, sulfate, and nitrate in water (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 568-569 
    Details
    ISSN: 0935-6304
    Keywords: HPLC-IC ; Inorganic anions ; Water analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240120822
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  • 15
    Electronic Resource
    Electronic Resource
    Mass spectra of some 2-(o-R1-phenyl)-indole-3-carboxaldehyde derivatives. IIContribution No. 1067 from Institute de Quimica, UNAM. (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 1095-1096 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron impact mass spectra of thirteen new substituted 2-(o-R1-phenyl)-indole-3-carboxaldehydes which have potentially useful pharmacological properties, ate presented.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210261213
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  • 16
    Electronic Resource
    Electronic Resource
    Electron impact mass spectrometry of 3-(2-hydroxyphenylcarbonyl)-4-(o- and p-R-phenyl)-1,2,3,4-tetrahydro-2H-benzo [f]quinolin-2-onesContribution No. 1083 from Institute de Quimica, UNAM, Mexico. (1992)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 27 (1992), S. 121-122 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The major features of the mass spectra of eight substituted quinolones of potential pharmacological interest are reported.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210270210
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  • 17
    Electronic Resource
    Electronic Resource
    Reaction-induced mass discrimination in XQQ instruments. Absolute cross-sections for N2+· + SF6 → N2 + SFx+ (x=1-5) (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 41-46 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Dynamically-correct branching ratios can be measured in a XQQ tandem mass spectrometer (MS/MS) under single-collision conditions when the key MS/MS parameters are properly selected to correct for reaction-induced mass discrimination within the RF-only quadrupole mass filter (Q2). The energy dependence of the cross-section, σ(E), for the reaction N2+· + SF6 → N2+SFx+ (x = 1-5) was measured in the NBS triple quadrupole (QQQ) tandem mass spectrometer. For P≃0.02-0.13 mTorr and E ≃ 5-60 eV (Lab) [the range of collision energies used for collisionally activated dissociation (CAD)], identical σ(E) were measured from both the rate of reactant ion decay and the rate of product ion formation. Therefore, these σ values are substantially free from kinetic interferences (i.e., no back reactions, no impurity reactions, no scattering losses, minimal fringing fields, no mass discrimination, well-defined gas target, etc.). Moreover, there is probably no significant systematic error in our measurements of the absolute σ values for N 2+· + SF6 → N2+SFx+ (x = 1-5) because the σ values we measured with this same technique for Ne +·+ Ne → Ne+Ne+·, Ar+· + Ar → Ar+Ar+·, and Ar+·+N2 → Ar+N2+· agreed well with literature values obtained with several well-established techniques.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290020207
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  • 18
    Electronic Resource
    Electronic Resource
    Standard reference spectra for tandem mass spectrometry quality assurance, performance evaluation and proficiency testing: Tandem mass spectrometers which use RF-only multipole collision cells (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 245-248 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The collisionally activated dissociation (CAD) of the acetone cation (m/z 58) can be used for quality assurance, performance evaluation, and proficiency testing of CAD measurements in tandem mass specstrometry (MS/MS) instruments which use RF-only multipole collision cells. The absolute branching ratios (product distributions) of the CAD fragment ions, when measured as a function of the center-of-mass collision energy Ecm, can provide an objective basis for quality assurance whenever MS/MS methods are used (viz, to validate how well the target thickness, ion-containment efficiency, and collision energy are being controlled in various instruments).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050508
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  • 19
    Electronic Resource
    Electronic Resource
    Instrument-independent database for collisionally activated dissociation in RF-only quadrupoles. The case of C2H3O+ and C3H7+ (1989)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 3 (1989), S. 377-380 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Dynamically correct (i.e., instrument-independent) branching ratios can be measured under single-collision conditions in tandem mass spectrometers incorporating RF-only quadrupole collision cells. The absolute branching ratios were measured as a function of the center-of-mass interaction energy ECM for the collisionally activated dissociation (CAD) of CH3CO+ (m/z43) from several source compounds (ethanol, oxirane), and CH3CO-X (where X = H, CH3, CH3CH2, CH3CO, CH3COCH2, and C6H5)). The energy dependences of the branching ratios for C2H3O+ from CH3CO-X source compounds are quite distinct from those observed for C2H3O+ from ethanol or ethylene oxide, or for the C3H+7 ions (also m/z 43) from n-pentane. Hence, one can use the CAD of m/z 43 to distinguish CH3CO-X compounds from other source compounds, including sources of C3H7+ ions. Therefore, the characteristic branching ratios of ionic substructures may provide for tandem mass spectrometry a „fingerprinting“ capability analogous to the use of group frequencies in infrared spectroscopy.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290031102
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  • 20
    Electronic Resource
    Electronic Resource
    Adsorption of tryptophan metabolites from physiological fluids on XAD-2 and determination by single ion monitoringPresented in part at the 10th International Symposium on Advances in Chromatography, Munich, Germany 3-6 November 1975.Abbreviations: T = tryptamine; IAA = indole-3-acetic acid; 5-HT = 5-hydroxytryptamine; 5-HIAA = 5-hydroxyindole-3-acetic acid; 5-HTP = 5-hydroxytryptophan; TP = L-tryptophan; EA = ethyl acetate; ACN = acetonitrile; PFPA = pentafluoropropionic anhydride. (1976)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1976), S. 91-96 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Endogenous tryptamine, 5-hydroxytryptamine, indoleacetic acid, 5-hydroxyindoleacetic and tryptophan have been recovered from urine and cerebro-spinal fluid by adsorption on XAD-2 resin (0.3 g). After adsorption of the sample on the resin, desorption with methanol provides a single fraction that contains all of these metabolites. The mass spectra of their pentafluoropropionyl derivatives show prominent ions at m/e 276 and 438 which are characteristic of indoles and 5-hydroxyindoles, respectively, a feature that allows the concurrent determination of all the components of each group by functional group analysis. A method has been developed to carry out single ion monitoring with the peak matching system of an Hitachi RMU-6H mass spectrometer. Identifications are based on the respective Kovats Indices and single ion monitoring of two characteristic ions per compound: tryptophan (m/e 276 and 347); tryptamine (m/e 276 and 289); indoleacetic acid (m/e 276 and 335); 5-hydroxytryptamine (m/e 438 and 451); 5-hydroxyindoleacetic acid (m/e 438 and 497). The method described illustrates the feasibility of assaying biogenic indoleamines and acidic metabolites, as well as their precursor amino acid on a single fraction in contrast to other standard fractionation methods. This is possible even if the mass spectrometer is not equipped with an alternating voltage accelerator provided that it has a peak matcher, although the lack of an alternating voltage accelerator requires two separate injections of the same sample, for quantification and identification; one for the indole profile and another for the 5-hydroxyindole profile. Both profiles can be verified by individual monitoring of the other confirmatory ions. With this method the use of a multiple ion detector would allow a simultaneous determination of all of these metabolites in one gas chromatograph mass spectrometer run.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200030210
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