Rapid analysis of metabolites and drugs of abuse from urine samples by desorption electrospray ionization-mass spectrometry
ABSTRACT Urine samples obtained from drug abusers were screened for drugs of abuse and their metabolites using DESI-MS and the results obtained were compared to results obtained from GC-MS experiments. The detected analyte classes included amphetamines, opiates, cannabinoids and benzodiazepines. The compounds detected were codeine, morphine, oxymorphone, 11-nor-9-carboxy-Delta(9)-tetrahydrocannabinol, Delta(9)-tetrahydrocannabinol, alprazolam, temazepam, oxazepam, N-desmethyldiazepam (nordiazepam) and hydroxytemazepam. Identities of all the analytes were confirmed by tandem mass spectrometry, matching MS/MS spectra with authentic standard compounds. The concentrations of the analytes in the samples were obtained from semi-quantitative GC-MS studies and were in the range of 270-22,000 ng mL(-1). The analytes could be detected by DESI even after a hundred-fold dilution indicating that the sensitivity of DESI was more than adequate for this study. Selectivity in the DESI-MS measurements for different kinds of analytes could be increased further by optimizing the spray solvent composition: the use of an entirely aqueous solvent enhanced the signal of polar analytes, such as the benzodiazepines, whereas the use of a spray solvent with a high organic content increased the signal of less polar analytes, such as codeine and morphine.
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ABSTRACT: In recent years, ambient desorption ionization techniques for mass spectrometry were introduced. Among them, the most established techniques are Direct Analysis in Real Time (DART) and Desorption Electrospray Ionization (DESI). Therefore, the current review focuses on the bioanalytical applications of ambient desorption ionization techniques by the example of DART and DESI mass spectrometry. The potential and also limitations of both ambient mass spectrometry (MS) techniques in such areas, as identification and quantitation of small molecules, coupling DART-MS and DESI-MS with planar chromatography, protein/peptide analysis, as well as molecular imaging applications, are discussed. KeywordsAmbient mass spectrometry–Direct analysis in real time–DART–Desorption electrospray ionization–DESI–Bioanalytical methods–Identification–QuantitationBioanalytical Reviews 04/2011; 3(1):1-9. DOI:10.1007/s12566-010-0019-5
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ABSTRACT: The behaviour of a 7.5 kW high efficiency cage induction motor fed by distorted supply has been investigated in this paper. Experimental data were collected by developing a testing facility consisting of a three phase harmonic generator, a double chamber calorimeter and a PC based data acquisition system. Motor additional losses due to the presence of harmonics were estimated using the calorimetric method. It has been shown that a distorted voltage containing low order harmonics causes more losses in the motor as compared with the high order harmonics. Accordingly, weighted THD (WTHD) has been defined to specify the limits for additional losses in a motor supplied by distorted voltages. The variation of test motor parameters with harmonic order as well as the variation of additional losses with WTHD has led to establishment of derating factor (DF) for the test induction motor. Applicability of the DF on several induction motors with different power ratings has been examined. It has been demonstrated that with a service factor of 1.15, most induction motors are capable to handle distorted voltages as defined by standardsElectrical and Computer Engineering, 2000 Canadian Conference on; 02/2000
Conference Paper: Information: a key to supply chain performance[Show abstract] [Hide abstract]
ABSTRACT: This paper makes several critical points related to the intrinsic nature of the relationship between information and performance in supply chains. It highlights the co-dependence of information and supply-chain management decisions, stresses the impact of this co-dependence on supply-chain performance, and, raises research issues that are fundamental to a better understanding of both.Automation Congress, 2002 Proceedings of the 5th Biannual World; 02/2002