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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 149-153 
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conditions for normal phase high performance liquid chromatrography-chemical ionization mass spectrometry of underivatized glycosphingolipids with the use of a moving belt transport interface were investigated. Chromatography was performed on a 2 mm ID × 3 cm column packed with 5 μm spherical silica. A gradient of increasing methanol and water in methylene chloride was used to resolve mono-, di-, tri-, and tetraglycosylceramides and sulfatides in less than 15 min. A polyimide belt was used to transport the sample residues to the mass spectrometer where ammonia chemical ionization mass spectrometry was used to obtain spectra. One to 5 μg of each component was sufficient to obtain full spectral scans. Mono- and dihexosylceramide spectra showed [M + H]+ ions of good abundance, while the higher glycosphingolipids have molecular weights that exceed the range of the mass spectrometer utilized. All glycosphingolipids gave ions characteristic of their ceramide, fatty acid, long chain base and carbohydrate components. Sequence information which reflected the relative position of hexose and N-acetylhexosamine residues was also obtained.
    Additional Material: 8 Ill.
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  • 2
    ISSN: 1040-7685
    Keywords: gas chromatography ; stationary phases ; cyanobiphenyl phasesshape selectivity ; polychlorinated biphenyls ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selectivity for polychlorinated biphenyl (PCB) congeners was examined for a series of cyanobiphenyl stationary phases, and the results were compared to a nonpolar 5% phenyl methylpolysiloxane phase and a shape-selective smectic liquid crystalline phase. For all of the columns studied, the degree of ortho substitution of the congener was found to be a significant factor controlling chromatographic retention of PCBs. The retention pattern on six different cyanobiphenyl phases followed the same general pattern as on the liquid crystalline column, though the trends were more exaggerated on the liquid crystalline phase. While the general retention pattern was similar for all of the cyanobiphenyl phases studied, subtle differences were observed, resulting in significant selectivity differences. For isomeric planar PCB congeners, elution order could be correlated to length-to-breadth ratios. Among the cyanobiphenyl phases, the p,p- and the o,p,p-cyanobiphenyl phases had the greatest enhancement of retention for planar congeners. A shapeselective test mixture reflected the similarity of retention on the cyanobiphenyl phases to both the 5% phenyl methylpolysiloxane phase and the smectic liquid crystalline phase. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 8 (1981), S. 316-321 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper describes the development of two easily constructed, inexpensive interfaces for combined liquid chromatography mass spectrometry. The first interface directly introduces a small percentage of liquid chromatographic eluent into the ion source of the mass spectrometer, whilst the second employs vacuum nebulization to vaporize sample and solvent. Both interfaces have been designed as removable probes. The construction and operation of the interfaces are discussed in detail and a comparison of their performance is made. Examples of the application of liquid chromatography mass spectrometry to the determination of low levels of specific components in complex matrices are given.
    Additional Material: 8 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: A sensitive and selective assay has been developed for the identification and quantitation of 3-amino-1-phenylbutane (3-APB), a metabolite of labetalol, in biological fluids using electron impact gas chromatography/mass-selective detection. Samples were extracted with n-hexane, derivatized with heptafluorobutyric anhydride and chromato-graphed on a cross-linked fused-silica capillary column. A positive EI spectrum was obtained using a mass-selective detector. Identification of the metabolite was accomplished using an authentic standard; quantitation was performed in the selected ion monitoring mode using ions m/z 345 (M+) and 132. The assay was linear over the calibration range of 0.5-1000 ng of the analyte and the intra-sample coefficients of variation were less than 12% in all cases. The absolute recovery of 3-APB following extracton from urine and bile was found to be 102.9 ± 4.9% and 98.3 ± 1.45% (mean ± SEM) respectively. The minimum quantitation limit of the assay was 0.5 ng ml-1 (≈ 2 pg injected). Application of the assay in a pharmacokinetic-pharmacodynamic study of labetalol in sheep is demonstrated. The metabolite was detected in urine and bile samples obtained from adult non-pregnant sheep following labetalol administration. The cumulative amount of 3-APB excreted in urine over 24 h was found to be 71.55 μg in one animal following a 100 mg dose of labetalol. Evidence for biliary excretion, glucuronidation and sulfation of 3-APB was also found.
    Additional Material: 7 Ill.
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  • 5
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two methods, direct injection-continuous flow fast atom bombardment (DI-CF/FAB) mass spectrometry and micro-high-performance liquid chromatography (μHPLC)-CF/(FAB) mass spectrometry were developed for the clinical analysis of urinary bile acids and their conjugates, specifically for the diagnosis of disorders of bile acid metabolism. The method based upon DI of urine extracts into the CF/FAB flow stream was developed for the rapid screening of large numbers of patient samples. It allows injections to be made at 4 min intervals for high sample throughput. Analyses of standard mixtures of bile salts demonstrate that linear response curves are obtained over more than a hundred-fold concentration range with a minimum detectable amount in the picogram range. Oxo bile salts are identified by reduction with sodium borodeuteride followed by reanalysis for detection of any reduction products. This methodology has been used for the analysis of over 1000 specimens. A reverse-phase μHPLC-CF/FAB mass spectrometric method was also developed for use in the confirmation or further investigation of screening results. With no additional sample preparation this method permits the separation, identification and quantitation of urinary bile salt isomers within a 45 min analysis time.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 644-650 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new approach, bio-affinity characterization mass spectrometry (BACMS), aimed at providing a more rapid, sensitive and potentially more flexible alternative to techniques presently employed for the characterization of noncovalent interactions in mixtures, such as would be encountered in combinatorial chemistry, is presented. BACMS avoids some of the difficulties and potential artifacts associated with affinity chromatography since the noncovalent associations occur in solution; thus, BACMS avoids the requirement of solid support media and the development of non-interfering linker species. This paper describes the conceptual basis for the methodology and its potential use in applications which include the screening of high affinity ligands in support of new drug development. BACMS exploits new Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry technologies which, when coupled to electrospray ionization (ESI), allow the investigation of specific noncovalent complexes formed in solution. BACMS utilizes the well-known attributes of FTICR, such as the high resolution mass analysis and (MS)n (n ≥ 2) capabilities; however, it is even more directly a result of recently developed techniques involving quadrupolar excitation, such as selected-ion accumulation. These tools are demonstrated and the results illustrate the extraordinary sensitivity achievable (solution concentrations of 1 × 10-9 M without the use of separations prior to ESI). Thus, the new capabilities demonstrated here, in conjunction with ESI, will be useful for the investigation of very low relative concentration noncovalent association directly from solution, and promote a faster alternative for combinatorial mixture screening and analysis.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 17 (1988), S. 147-151 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The occurrence of small shifts in the cyclotron frequency during the acquisition of very long transients (in excess of 80 s) has been observed to be a limiting factor for ultrahigh-resolution mass measurements of protein ions performed with electrospray-ionization Fourier-transform ion-cyclotron-resonance mass spectrometry. Resolution measurements were restricted to values less than 106 because of the frequency shifts. Measurements of the frequency shifts, performed by sequentially transforming small segments of the transient, allowed the shift to be characterized and fitted to a 4th-order equation. The sampling rate of the acquired transient was then modulated (at a rate equal to the reciprocal of the rate for the frequency shift) to allow ultrahigh resolution, greater than 2 × 106, and improved mass measurement and precision to be achieved for a small protein.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 7 (1980), S. 168-171 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The measurement of plasma free fatty acid turnover and oxidation by means of the isotopic dilution technique using a radiolabeled free fatty acid has proven useful for the in vivo study of fat metabolism in animals. However, because of the ethical considerations regarding the administration of radioisotopes to humans, there is a lack of adequate information regarding the in vivo regulation of free fatty turnover and oxidation in humans, particularly children. Consequently, we have developed a technique using the stable, nonradioactive [1-13C]palmitic acid molecule as free fatty acid tracer to measure plasma free fatty acid metabolism in vivo. We have analysed the isotopic enrichment of plasma palmitate by selected ion monitoring on a gas chromatograph mass spectrometer and we have used an isotope ratio mass spectrometer to determine the much lower isotopic enrichment of the expired CO2. We have found this technique to be safe to administer, to have a high degree of analytical reproducibility, and to yield values in dogs comparable with those obtained using [1-14C]palmitic acid as the tracer.
    Additional Material: 2 Ill.
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  • 10
    ISSN: 1075-4261
    Keywords: pterins ; FTIR ; vibrational analysis ; solvent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Physics
    Notes: Fourier transform infrared (FTIR) spectra have been obtained from solution samples of the heterocycles uracil, lumazine, and violapterin and reveal interpretable carbonyl stretching frequencies. Spectra of conjugate bases of lumazine and violapterin demonstrate decreases in these carbonyl stretching frequencies upon ionization. Based on isotopic shifts from amide deuterated analogs, semiempirical QCFF/PI calculations were used to assign the vibrational frequencies in the region 1100-1800 cm-1 observed from samples in dimethylsulfoxide (DMSO) and aqueous solutions to specific normal modes. The observed deuterium shifts and the calculations suggest that, in some cases, N - H bending motions are coupled to the C=O stretching motions of the pyrimidine ring. These data suggest that for lumazine anions a change in solvent can significantly change the mixing of the N - H bending and C=O stretching vibrational motions. This implies that vibrational analysis for lumazine species in relatively noninteracting media like nonpolar solvents, mulls or pellets cannot necessarily be transferred to the system when it is dissolved in a polar, hydrogen-bonding solvent such as water. Although other explanations can be offered, our vibrational analysis suggests that the changes in normal mode composition of the predominantly C=O stretching vibrations of lumazine anion on going from dimethylsulfoxide to water solution are consistent with a change in the predominant tautomer of the heterocycle. This change appears to correspond to a shifting of the location of the remaining acidic proton to a different ring nitrogen atom. This interpretation is of interest in view of recent ab initio calculations which suggest that proton shifts may occur during the hydroxylation of lumazine as mediated by the enzyme xanthine oxidase. © 1998 John Wiley & Sons, Inc. Biospectroscopy 4: 235-256, 1998
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