Electrospray ionization mass spectral studies of N,N-dialkylaminoethane-2-sulphonic acids

Oxidative reactions of VX type compounds and N,N‐dialkylaminoethane‐2‐thiols that are precursors for VX compounds produce N,N‐dialkylaminoethane‐2‐sulphonic acids, N(R1)(R2)‐CH2‐CH2SO3H (where R1 and R2 = methyl, ethyl, n‐propyl and isopropyl, 1–10), as the degradation products, and these degradation products are considered as markers for the detection of chemicals listed in the schedules of Chemical Weapons Convention (CWC) chemicals. Off‐site detection of such degradation products in aqueous samples is an important task in the verification of CWC‐related chemicals. Here we report a simple method involving the direct analysis of aqueous samples using positive and/or negative ion electrospray ionization (ESI) for the screening, detection and identification of N,N‐dialkylaminoethane‐2‐sulphonic acids, avoiding sample preparation and chromatographic steps. The positive ion ESI mass spectra of all the compounds result in abundant [M+Na]+ ions, and the negative ion spectra show abundant [M−H]− ions to confirm their molecular weight. The collision‐induced dissociation spectra of [M+Na]+ and [M−H]− give characteristic product ions by which it is easy to detect and identify all the studied N,N‐dialkylaminoethane‐2‐sulphonic acids including those of isomeric compounds. The method is successfully applied to detect the spiked chemical, N,N‐diisopropylaminoethane‐2‐sulphonic acid, present in a water sample received in a proficiency test. Copyright © 2007 John Wiley & Sons, Ltd.