排序方式: 共有70条查询结果,搜索用时 15 毫秒
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A. Vonaparti E. Lyris Y. S. Angelis I. Panderi M. Koupparis A. Tsantili‐Kakoulidou R. J. B. Peters M.W.F. Nielen C. Georgakopoulos 《Rapid communications in mass spectrometry : RCM》2010,24(11):1595-1609
Unification of the screening protocols for a wide range of doping agents has become an important issue for doping control laboratories. This study presents the development and validation of a generic liquid chromatography/time‐of‐flight mass spectrometry (LC/TOFMS) screening method of 241 small molecule analytes from various categories of prohibited substances (stimulants, narcotics, diuretics, β2‐agonists, β‐blockers, hormone antagonists and modulators, glucocorticosteroids and anabolic agents). It is based on a single‐step liquid‐liquid extraction of hydrolyzed urine and the use of a rapid‐resolution liquid chromatography/high‐resolution time‐of‐flight mass spectrometric system acquiring continuous full scan data. Electrospray ionization in the positive mode was used. Validation parameters consisted of identification capability, limit of detection, specificity, ion suppression, extraction recovery, repeatability and mass accuracy. Detection criteria were established on the basis of retention time reproducibility and mass accuracy. The suitability of the methodology for doping control was demonstrated with positive urine samples. The preventive role of the method was proved by the case where full scan acquisition with accurate mass measurement allowed the retrospective reprocessing of acquired data from past doping control samples for the detection of a designer drug, the stimulant 4‐methyl‐2‐hexanamine, which resulted in re‐reporting a number of stored samples as positives for this particular substance, when, initially, they had been reported as negatives. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Ilse Becue Christof Van Poucke Jeroen C. W. Rijk Toine F. H. Bovee Michel Nielen Carlos Van Peteghem 《Analytical and bioanalytical chemistry》2010,396(2):799-808
DHEA (3β-hydroxy-androst-5-en-17-one) is a natural steroid prohormone. Despite a lack of information on the effect, DHEA and
other prohormones are frequently used as a food supplement by body-builders. DHEA is suspected for growth promoting abuse
in cattle as well. Considering the latter, urine samples from a previous exposure study in which calves were exposed to 1 g
DHEA per day for 7 days, were used. The calves were divided in three groups: one orally treated, one intramuscularly injected,
and a control group. The effect of this treatment on the urinary profile of several precursors and metabolites of DHEA was
investigated. Urine samples were collected several days before and during the 7 days of administration and were submitted
to a clean-up procedure consisting of a separation of the different conjugates (free, glucuronidated, and sulfated forms)
of each compound on a SAX column (Varian). An LC-MS/MS method was developed for the detection and quantification of several
metabolites of the pathway of DHEA including 17α- and 17β-testosterone, 4-androstenedione, 5-androstenediol, pregnenolone,
and hydroxypregnenolone. Elevated levels of DHEA, 5-androstenediol, and 17α-testosterone were observed in the free and sulfated
fraction of the urine of the treated calves, thus indicating that the administered DHEA is metabolized mainly by the ∆5-pathway with 5-androstenediol as the intermediate. Sulfoconjugates of DHEA and its metabolites were found to constitute the
largest proportion of the urinary metabolites. The free form was also present, but in a lesser extent than the sulfated form,
while glucuronides were negligible. 相似文献
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M W Nielen A J Valk R W Frei U A Brinkman P Mussche R De Nijs B Ooms W Smink 《Journal of chromatography. A》1987,393(1):69-83
The design of an automated cartridge exchange module for on-line sample handling in liquid chromatography is described. When combined with a low-cost purge pump, a solvent selection valve and an auto-sampler, a fully automated sample handling system is obtained. Samples are sorbed on a disposable cartridge packed with 40 micron octyl-bonded silica, purged for clean-up and eluted on-line to the analytical column. Unattended operation of the system is demonstrated for various examples, i.e., the determination of anti-epileptic drugs in serum, an anti-cancer drug in plasma, barbiturates in urine, phenylurea herbicides in river water and caffeine in a soft drink. 相似文献
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Koster S Duursma MC Boon JJ Nielen MW de Koster CG Heeren RM 《Journal of mass spectrometry : JMS》2000,35(6):739-748
The molecular structure of a series of homo- and copolyesters was studied using sustained off-resonance irradiation collisionally activation dissociation on a Fourier transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used as an ionization technique. The most important fragmentation pathways of the homopolyesters poly(dipropoxylated bisphenol-A/adipic acid) and poly(dipropoxylated bisphenol-A/isophthalic acid) were studied. Six different dissociation mechanisms were observed which are very similar to the mechanisms found to occur during pyrolysis of these compounds. Four of these mechanisms are a result of cleavages of the ester bond and the others are due to cleavages of the ether bond or bisphenol-A unit. Some of the fragments expected are not present in the spectrum, indicating that each fragment has a specific sodium affinity. Sequence-specific fragments of two of the three copolyester sequences that theoretically can exist were experimentally observed. Fragments that originate from the third sequence are not unique and can also be formed from other sequences. Therefore, it was not possible to determine the presence of the third sequence. Copyright 2000 John Wiley & Sons, Ltd. 相似文献
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Nielen MW Elliott CT Boyd SA Courtheyn D Essers ML Hooijerink HH van Bennekom EO Fuchs RE 《Rapid communications in mass spectrometry : RCM》2003,17(14):1633-1641
A new approach to the search for residues of unknown growth promoting agents such as anabolic steroids and beta-agonists in feed is presented. Following primary extraction and clean-up, samples are separated using gradient liquid chromatography (LC). The effluent is split towards two identical 96-well fraction collectors and an optional electrospray quadrupole time-of-flight mass spectrometry (QTOFMS) system for accurate mass measurement. One 96-well plate is used for a bioassay (enzyme-immuno assay, receptor assay) and will detect the bioactivity and position of the relevant peak in the chromatogram. The positive well in the second 96-well plate is used for identification by LC/QTOFMS/MS. The value of this LC/bioassay/QTOFMS/MS methodology is highlighted by the finding and structure elucidation of a new beta-agonist in a feed extract. 相似文献
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Ruud J. B. Peters Marcel C. van Engelen Manja E. Touber Costas Georgakopoulus Michel W. F. Nielen 《Rapid communications in mass spectrometry : RCM》2009,23(15):2329-2337
Glucocorticosteroids are a restricted class of substances and appear on the ‘in‐competition’ prohibited list of the World Anti‐Doping Agency (WADA). Analysis of glucocorticosteroids is complicated since they show significant phase 1 and 2 metabolism in the human body and are excreted into urine in concentrations in the µg/L range. Full scan, high‐resolution time‐of‐flight mass spectrometry analysis generates information on all ionisable components in urine, including known and unknown metabolites of steroids and even designer modifications of anabolic steroids. However, evaluation of the data obtained can be difficult and time‐consuming because of the need to differentiate between endogenous components and compounds of interest. MetaboLynx?, a spectral and chromatographic search program, was modified for the determination of in silico predicted metabolites of glucocorticosteroids and designer modifications of anabolic steroids in human urine. Spiked urine samples were successfully screened for known components in a targeted approach and for unknown species in a non‐targeted approach using data filtering to limit potential false‐positives. A simplified combined approach of targeted and untargeted screening was used for the detection of metabolites and designer modifications of existing compounds. This approach proved successful and showed its strength in the detection of tetrahydrogestrinone (THG), a designer modification of gestrinone. THG was positively detected in a spiked urine sample and correctly identified as a twofold hydrogenation of gestrinone. The developed screening method can easily be adapted to specific needs and it is envisaged that a similar approach would be amendable to the discovery of metabolites or designer modifications of other compounds of interest. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献