Simultaneous determination of 1,1-dimethylhydrazine and products of its oxidative transformations by liquid chromatography–tandem mass spectrometry

Abstract

A liquid chromatography–tandem mass spectrometry method is proposed for the simultaneous determination of 1,1-dimethylhydrazine, methylhydrazine, N,N-dimethylformamide, 1-methyl-1H-1,2,4-triazole, dimethylguanidine, N-nitrosodimethylamine and 1,1,4,4-tetramethyltetrazene, important rocket fuel pollutants of soils. Chromatographic separation was conducted according to previously published results in an isocratic mode on an analytical column with a Nucleosil-100–5SA sulfo-cation-exchanger. The mobile phase composition was optimised in order to achieve effective separation of all analytes and provide high sensitivity of mass spectrometric detection – an ammonium acetate buffer solution (50 mM, pH 5.4) containing methanol (25%) was used. Detection was performed in the positive electrospray ionisation mode with multiple reaction monitoring (MRM). The parameters of ion source, ion optics, the inlet potentials of the quadrupoles and the collision energy for the detection of the found product ions were optimised. Calibration dependences for all compounds are linear in wide concentration ranges, covering 3–4 orders of magnitude. The detection limits vary from 40 pg mL−1 for dimethylguanidine to 18 ng mL−1 for methylhydrazine. No significant matrix effects were observed in the analysis of acid peaty soil extracts. The method was validated and successfully used to analyse a real soil sample collected at the place of impact of the first stage of a carrier rocket.