Laboratory Identification of the Nerve Gas Hydrolysis Products Alkyl Methylphosphonic Acids and Methylphosphonic Acid, by Gas Chromatography-mass Spectrometry after <i>tert</i>-Butyldimethylsilylation

Abstract

Alkyl methylphosphonic acids (RMPAs) and methylphosphonic acid (MPA), both nerve gas hydrolysis products, can be identified by gas chromatography-mass spectrometry (GC-MS). We adopted tertbutyldimethylsilylation (TBDMS) as a derivatization technique for the identification of these products by GC-MS. We found that it was difficult to detect RMPAs and MPA from evidence specimens such as soils and body fluids, and ascertained several causes for this. The first is the interference from the TBDMS derivatization. It was determined that the TBDMS derivatization of RMPAs and MPA was suppressed in the presence of divalent metal cations such as calcium and magnesium ions, as well as some neutral compounds like carbohydrates. A cleanup procedure using a strong anion-exchanger (SAX)-solid phase extraction (SPE) method was optimized to remove the interfering compounds. The second reason that detection was difficult was because of strong matrix adsorption. We elucidated that the aqueous extraction recoveries for all phosphonates were inversely correlated with the phosphate adsorption coefficient in the soil samples. To diminish the adsorption of phosphonates to soils, a method of alkali extraction was adopted. For human serum samples, we adopted acetonitrile or trichloroacetic acid deproteinization which worked to break the binding between the proteins and the phosphonates. The detection yields of RMPAs and MPA from soils and human serum were dramatically increased using these pretreatment procedures combined with extraction and/or SAX-SPE. The method of SAX-SPE was applied to various types of samples, such as seawater, drinks and human urine, and good detection yields of RMPAs and MPA were provided by GC-MS.

Nerve Agents and Their Detection

“…The target sample is exposed to the extraction material which is dispersed on a substrate. The extraction phase that contains the target analytes can be directly connected to a GC or extracted with proper solvents [36][37][38][39].…”

Extraction and Analysis of V-Type Agents (VX, RVX, CVX, and VM) from Various Food Matrices by Ultra-Performance Liquid Chromatography-Time-Of-Flight Mass Spectrometry

“…10,11 The pesticide literature often includes sample-preparation techniques that are commercially available and affordable, such as solid-phase extraction cartridges [12][13][14][15][16][17][18][19][20] or QuEChERS systems (Quick, Easy, Cheap, Effective, Rugged, and Safe); [21][22][23][24][25][26][27][28][29] however, the CWA literature seems to focus more on new techniques and specialized equipment that may not be as readily accessible to every laboratory. 9,[30][31][32][33][34][35] This document reports the efforts of the Agent Chemistry Team from the Research and Technology Directorate of the U.S. Army Edgewood Chemical Biological Center (ECBC; Aberdeen Proving Ground, MD) in developing new extraction and analytical detection methodologies using liquid chromatography-mass spectrometry (LC-MS). The objective of this task was to provide development and laboratory support for extraction of V-type agents ( Figure 1) from various food samples.…”

An Evaluation of the Spectral Properties of Nerve Agents for Laser Ionization Mass Spectrometry

“…Nerve agents such as sarin, VX, and soman act rapidly in the human body and are easily decomposed to phosphonic acid derivatives, such as isopropyl methylphosphonic acid (IMPA), ethyl methylphosphonic acid (EMPA), and pinacolyl methylphosphonic acid (PMPA). 4 These alkyl methylphosphonic acids (alkyl MPAs) are sufficiently stable to permit their use as markers of nerve agents. Alkyl MPAs are ultimately hydrolyzed to methylphosphonic acid (MPA).…”