Quantification of VX Vapor in Ambient Air by Liquid Chromatography Isotope Dilution Tandem Mass Spectrometric Analysis of Glass Bead Filled Sampling Tubes

Abstract

An analysis method has been developed for determining low parts-per-quadrillion by volume (ppqv) concentrations of nerve agent VX vapor actively sampled from ambient air. The method utilizes glass bead filled depot area air monitoring system (DAAMS) sampling tubes with isopropyl alcohol extraction and isotope dilution using liquid chromatography coupled with a triple-quadrupole mass spectrometer (LC/MS/MS) with positive ion electrospray ionization for quantitation. The dynamic range was from one-tenth of the worker population limit (WPL) to the short-term exposure limit (STEL) for a 24 L air sample taken over a 1 h period. The precision and accuracy of the method were evaluated using liquid-spiked tubes, and the collection characteristics of the DAAMS tubes were assessed by collecting trace level vapor generated in a 1000 L continuous flow chamber. The method described here has significant improvements over currently employed thermal desorption techniques that utilize a silver fluoride pad during sampling to convert VX to a higher volatility G-analogue for gas chromatographic analysis. The benefits of this method are the ability to directly analyze VX with improved selectivity and sensitivity, the injection of a fraction of the extract, quantitation using an isotopically labeled internal standard, and a short instrument cycle time.

Qualitative and Quantitative Analysis of Tumor Cell Metabolism via Stable Isotope Labeling Assisted Microfluidic Chip Electrospray Ionization Mass Spectrometry

“…Recently, the stable isotope labeling technique has been extensively used to study metabolism and pharmacokinetics of drugs in vitro. − Because of the similarity of their structure and chemical properties, previous reports have already demonstrated that there was no metabolic discrimination between analytes and their isotopic analogues. Consequently, despite complex biological matrixes, the metabolites can be easily recognized and identified by a coeluted pair of isotopomers using a dual-isotopic labeling strategy. , Moreover, the isotopic dilution technique can compensate variations caused by matrix effects and ion suppression from other coeluting analytes in liquid chromatography–mass spectrometry analysis (LC–MS). ,− Thus, stable isotope labeling analysis could be an alternative strategy for qualitative and quantitative analysis of cell-based drug metabolism by using a microfluidic chip combined with mass spectrometry.…”

On‐substrate derivatization for detection of highly volatile G‐series chemical warfare agents via paper spray mass spectrometry

“…Typically, these tubes contain sorbent substrates such as activated carbons, silica gels, resins, and organic polymers. Innovative materials for sorbent capture from air and water have included carbon nanotubes, hydrophilic–lipophilic balance (HLB), and glass . However, most of these systems require large volumes of sampled media, long sampling times, meticulous storage and extraction procedures, and chromatography in tandem with a chemical detector.…”