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Stable Isotope Dilution Analysis (stable + isotope_dilution_analysis)
Selected AbstractsStable isotope dilution analysis of the Fusarium mycotoxins deoxynivalenol and 3-acetyldeoxynivalenolMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 3 2006Michael Bretz Abstract Trichothecenes are secondary metabolites produced by several fungi of the Fusarium genus during their growth period. They inhibit protein biosynthesis in eukaryotic cells resulting in numerous toxic effects such as diarrhea, vomiting, and gastro-intestinal inflammation. Considering its occurrence in food and feedstuff, deoxynivalenol (DON) is one of the most important trichothecenes. We report the synthesis of stable isotope labeled 15- d1 -deoxynivalenol (15- d1 -DON) from its natural precursor 3-acetyldeoxynivalenol (3-AcDON) as starting material. Furthermore, a method for the analysis of DON and 3-AcDON using HPLC-MS/MS with stable isotope labeled 15- d1 -DON and 3- d3 -AcDON as internal standards has been developed. In total, 18 cereal product samples were analyzed with contamination levels ranging from 10,301 ,g/kg for DON and 5,14 ,g/kg for 3-AcDON. This is the first report of an isotope dilution MS method for the analysis of type B-trichothecenes. [source] Stable isotope dilution analysis of N-acetylaspartic acid in urine by liquid chromatography electrospray ionization tandem mass spectrometryBIOMEDICAL CHROMATOGRAPHY, Issue 9 2007Osama Y. Al-Dirbashi Abstract N -acetylaspartic acid (NAA) is a specific urinary marker for Canavan disease, an autosomal recessive leukodystrophy. We developed a ,dilute and shoot' stable isotope dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for determination of NAA in urine. Deuterated internal standard d3 -NAA was added to untreated urine and the mixture was injected into the LC-MS/MS system operated in the negative ion mode. Chromatography was carried out on a C8 minibore column using 50% acetonitrile solution containing 0.05% formic acid at a flow rate of 0.25 mL/min. The retention time was 1.6 min and the turnaround time was 2.2 min. NAA and d3 -NAA were analyzed in multiple reaction monitoring mode. Calibrators and quality control samples were prepared in pooled control urine. The assay was linear up to 2000 µmol/L with limit of quantification at 1 µmol/L (S/N = 12). Interassay and intraassay coefficients of variation were less than 7% and recovery at three different concentrations was 98.9,102.5%. The LC-MS/MS method for NAA as described involves no extraction and no derivatization, showed no interference and gave excellent recovery with low variability and short analytical time. The method was successfully applied for the retrospective analysis of urine from 21 Canavan disease cases. Copyright © 2007 John Wiley & Sons, Ltd. [source] Analysis of aldehydes via headspace SPME with on-fiber derivatization to their O -(2,3,4,5,6-pentafluorobenzyl)oxime derivatives and comprehensive 2D-GC-MSJOURNAL OF SEPARATION SCIENCE, JSS, Issue 19 2008Hans-Georg Schmarr Abstract A method for the analysis of the homologous series of alkanals, (E)-2-alkenals, and (E,E)-2,4-alkadienals is described utilizing a headspace solid-phase microextraction (HS-SPME) step and on-fiber derivatization with O -(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) hydrochloride. Oxime derivatives formed on the fiber are desorbed in the gas chromatographic injector and analyzed by comprehensive 2-D GC coupled to quadrupole MS (GC×GC-qMS). Selecting specific fragment ions within the electron impact mass spectra of the oxime derivatives provides a suitable method for the target analysis of these aldehyde classes, which furthermore benefits from the increased separation efficiency by GC×GC. The analysis of higher molecular weight aldehydes is described in wine and grape seed oil as examples. Quantification of the aldehydes utilizes a stable isotope dilution analysis (SIDA) assay with octan-d16 -al as isotopomeric internal standard. Besides the selectivity and sensitivity of aldehyde analysis using PFBHA derivatives, critical aspects on background level contamination and repeatability of the sample preparation method are discussed. Optimization of GC×GC-qMS parameters allowed a considerable saving of the cryogenic medium, involving additional (unmodulated) conditioning runs, rendering the method more amenable to routine analysis. [source] Identification and analysis of 2-chloro-6-methylphenol, 2,6-dichlorophenol and indole: causes of taints and off-flavours in winesAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2010D.L. CAPONE Abstract Background and Aims:, The aim of this study was to determine the cause of taints and off-flavours in a number of commercial wines and to develop methods for quantitative analysis of the compounds responsible. Methods and Results:, Three compounds, 2-chloro-6-methylphenol (i.e. 6-chloro- ortho -cresol), 2,6-dichlorophenol and indole, were identified by gas chromatography (GC)/mass spectrometry (MS)/olfactometry as causes of taints or off-flavours in the wines. New methods for quantitative analysis of these three compounds, as well as some other chloro- and bromophenols were developed. The methods employed GC/MS and stable isotope dilution analysis, and confirmed the presence of 2-chloro-6-methylphenol, 2,6-dichlorophenol and indole in some wines at concentrations well above their odour and taste detection thresholds. Conclusions:, 2-Chloro-6-methylphenol, 2,6-dichlorophenol and indole were confirmed as causes of taints and off-flavours in commercial wines. Significance of the Study:, The development of new analytical methods will make it possible to determine whether chlorophenol (and perhaps also bromophenol) taint in wine is more widespread than previously recognised. Similarly, the simple, rapid and accurate method for quantifying indole in wine will allow large numbers of wine and ferment samples to be studied to determine those factors that can result in unacceptably high concentrations in commercial wines. [source] | ||||||||||