Mass spectral studies of N-oxides of chemical weapons convention-related aminoethanols by gas chromatography/mass spectrometry after silylation

Abstract

N-Alkylaminoethanols, N,N′-dialkylaminoethanols, and triethanolamine are the hydrolyzed products or precursors of V-agents/nitrogen mustards. These compounds are prone to undergo oxidation in environmental matrices. Detection of the oxidized products provides a clue for the presence of parent amine compounds and it is an important task in the verification process of chemical weapons convention. Gas chromatography/mass spectrometry is the technique of choice for the detection of most of the chemical warfare agents; however, it is ideal to develop gas chromatography/mass spectrometry techniques for all the possible degradation products of chemical warfare agents as well. In general, the N-oxides of amines are expected to be thermally unstable; hence, the gas chromatography/mass spectrometry analysis of the N-oxides of triethanolamine, N-alkyldiethanolamines and N,N′-dialkylaminoethanols is not explored. In this study, the N-oxides of chemical weapons convention-related aminoethanols (13 compounds) were successfully silylated and then analyzed by gas chromatography/mass spectrometry under electron ionization and chemical ionization techniques. The electron ionization mass spectra showed abundant molecular ions and structure indicative fragment ions including [M-(O+CH₂CH₂OH)]⁺. The alkyl groups attached to nitrogen resulted in structure-specific fragment ions that enable differentiation of isomeric compounds. The methane/chemical ionization spectra showed considerably abundant [M+H]⁺ (>10%) and the expected adduct ions. The retention indices of all the compounds were calculated using Van den Dool's formula. The gas chromatography/mass spectrometry data together with retention index values could be used for unambiguous identification of the N-oxides of aminoethanols during off-site analysis or proficiency tests.