Structural determination of nerve agent markers using gas chromatography mass spectrometry after derivatization with 3‐pyridyldiazomethane

Abstract

Nerve agents are a class of organophosphorous chemicals that are prohibited under the Chemical Weapons Convention. Their degradation products, phosphonic acids, are analyzed as markers of nerve agent contamination and use. Because the phosphonic acids are non-volatile and very polar, their identification by GC-MS requires a derivatization step prior to analysis. Standard derivatization methods for gas-chromatography electron-impact mass-spectrometry analysis give very similar spectra for many alkyl phosphonic acid isomers, which complicates the identification process. We present a new reagent, 3-pyridyldiazomethane, for preparing picolinyl ester derivatives of alkyl methylphosphonic acids facilitating the determination of their structure by enhancing predictable fragmentation of the O-alkyl chain. This fragmentation is directed by the nitrogen nucleus of the pyridyl moiety that abstracts hydrogen from the O-alkyl chain, inducing radical cleavage of the carbon-carbon bonds and thereby causing extensive fragmentation that can be used for detailed structure elucidation of the O-alkyl moiety. The separability of related isomers was tested by comparing the spectra of the picolinyl esters formed from twelve hexyl methylphosphonic acid isomers. Spectral library matches and principal component analysis showed that the picolinyl esters were more effectively separated than the corresponding trimethylsilyl derivatives used in the standard operating procedures. The suggested method will improve the unambiguous structural determination process for phosphonic acids.

Analysis of Organophosphorus-Based Nerve Agent Degradation Products by Gas Chromatography-Mass Spectrometry (GC-MS): Current Derivatization Reactions in the Analytical Chemist’s Toolbox

“…In 2013, Nyholm et al, at FOI disclosed another remarkable report this time involving the use of 3-pyridyldiazomethane to yield picolinyl ester derivatives of a panel of phosphonic acids [ 101 ]. Some of the phosphonic acids used in the evaluation of the protocol were direct hydrolysis products of G- and V-series nerve agents and included EMPA (VX), IMPA (GB), BMPA (CVX), IBMPA (VR), PMPA (GD) among others.…”

The application of derivatization techniques in chromatographic analysis of food security

“…程中对水异常敏感, 衍生化产物稳定性差, Nyholm 等 [9] 合成的新型的衍生试剂 3-吡啶重氮甲烷可解决 这类问题. Nakano 等 [10] 合成了一种柱前衍生化试剂 柱前衍生化法具有衍生化效率高, 可选择衍生 化试剂较多, 可与多种样品前处理手段联用, 应用范 围较广等优点, 并且可以采用超声 [31] 、 微波 [32] 等场辅 助手段提高衍生反应效率、 缩短反应时间.…”