The LC-MS/MS Method (morgan + stanley_method)

Distribution by Scientific Domains

Selected Abstracts

Simultaneous measurement of 13C- and 15N-isotopic enrichments of threonine by mass spectrometry

Jean-Philippe Godin
Under conditions of high isotopic dilution, e.g. in a tracer study, the ability to determine accurately and quantitatively small variations in isotopic enrichments of differently labelled chemical compounds (e.g. 13C and 15N in threonine) in a single run by gas chromatography/mass spectrometry (GC/MS) is desirable but remains a technological challenge. Here, we report a new, rapid and simple GC/MS method for simultaneously measuring the isotopic enrichments of doubly labelled threonine ([U13C] and 15N) with isotopic enrichment lower than 1.5 Molar Percent Excess (MPE). The long-term reproducibility measured was around 0.09 MPE for both tracers (throughout a 6 week period). The intra-day repeatability was lower than 0.05 and 0.06 MPE for [U13C]-Thr and 15N-Thr, respectively. To calculate both isotopic enrichments, two modes of calculations were used: one based on work by Rosenblatt et al. in 1992 and the other one using a matrix approach. Both methods gave similar results (ANOVA, P >0.05) with close precision for each mode of calculation. The GC/MS method was then used to investigate the differential utilization of threonine in different organs according to its route of administration in minipigs after administration of both tracers. In plasma samples, the lowest isotopic enrichment measured between two successive time points was at 0.01 and 0.02 MPE for [U13C]-Thr and 15N-Thr, respectively. Moreover, the accuracy of GC/MS 13C-isotopic enrichment measured was validated by analyzing the same plasma samples by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Statistical analysis showed that both techniques gave the same results (ANOVA, P >0.05). This new GC/MS method offers the possibility to measure 13C- and 15N-isotopic enrichments with higher throughput, and using a lower amount of sample, than using GC/C/IRMS. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Quantitative determination of dipyridamole in human plasma by high-performance liquid chromatography,tandem mass spectrometry and its application to a pharmacokinetic study

Ting Qin
Abstract Dipyridamole is a classic platelet inhibitor which has been a key medicine in clinical therapy of thrombosis and cerebrovascular disease. A rapid, selective and convenient method using high-performance liquid chromatography,tandem mass spectrometry (HPLC-MS/MS) was developed for determination of dipyridamole in human plasma. After protein precipitation of 200 ,L plasma with methanol, dipyridamole and diazepam (internal standard) were chromatographed on an UltimateÔ XB-C18 (50 × 2.1 mm i.d, 3 ,) column with the mobile phase consisting of methanol,ammonium acetate (5 mM; 80 : 20, v/v) at a flow rate of 0.25 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring mode via positive eletrospray ionization source (ESI+). The retention times of dipyridamole and diazepam were 1.4 and 1.2 min, respectively. The method was validated over a concentration range of 0.0180,4.50 ,g/mL (r2 , 0.99) with a lower limit of quantitation (LLOQ) of 0.0180 ,g/mL for dipyridamole. The intra- and inter-day precisions (RSD) of the assay at all three QC levels were 1.6,12.7% with an accuracy (RE) of ,4.3,1.9%, which meets the requirements of the FDA guidance. The HPLC-MS/MS method herein described was proved to be suitable for pharmacokinetic study of sustained-release dipyridamole tablet in volunteers after oral administration. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A Case of Fatal Aconitine Poisoning by Monkshood Ingestion,

Ravi Pullela B.Sc.
Abstract:, Accidental aconitine poisoning is extremely rare in North America. This report describes the confirmation of a case of accidental aconitine poisoning using a liquid chromatography,tandem mass spectrometry (LC-MS/MS) method. The case involved a 25-year-old man who died suddenly following a recreational outing with friends where he consumed a number of wild berries and plants including one that was later identified as Monkshood (Aconitum napellus). Postmortem blood and urine samples were available for analysis. All routine urine and blood toxicology screens were negative. The LC-MS/MS method allowed sensitive quantification of aconitine, the main toxin in A. napellus, and showed 3.6 and 149 ,g/L in blood and urine, respectively. These concentrations were similar to that reported in other aconitine-related deaths. This case illustrates the dangers of consuming unidentified plants, and documents concentrations of aconitine in blood and urine in a fatal case of A. napallus -related poisoning. [source]

Stable isotope dilution analysis of N-acetylaspartic acid in urine by liquid chromatography electrospray ionization tandem mass spectrometry

Osama 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]