Determination of transformation products of unsymmetrical dimethylhydrazine in water using vacuum-assisted headspace solid-phase microextractionDetermination of transformation products of unsymmetrical dimethylhydrazine in water using vacuum-assisted headspace solid-phase microextraction Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2019-09-092018enA new, sensitive and simple method based on vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) followed by gas chromatography-mass-spectrometry (GC–MS), is proposed for the quantification of rocket fuel unsymmetrical dimethylhydrazine (UDMH) transformation products in water samples. The target transformation products were: pyrazine, 1-methyl-1H-pyrazole, N-nitrosodimethylamine, N,N-dimethylformamide, 1-methyl-1Н-1,2,4-triazole, 1-methyl-imidazole and 1H-pyrazole. For these analytes and within shorter sampling times, Vac-HSSPME yielded detection limits (0.5–100 ng L−1) 3–10 times lower than those reported for regular HSSPME. Vac-HSSPME sampling for 30 min at 50 °C yielded the best combination of analyte responses and their standard deviations (<15%). 1-Formyl-2,2-dimethylhydrazine and formamide were discarded because of the poor precision and accuracy when using Vac-HSSPME. The recoveries for the rest of the analytes ranged between 80 and 119%. The modified Mininert valve and Thermogreen septum could be used for automated extraction as it ensured stable analyte signals even after long waiting times (>24 h). Finally, multiple Vac-HSSME proved to be an efficient tool for controlling the matrix effect and quantifying UDMH transformation products.http://creativecommons.org/licenses/by/4.0/Journal of Chromatography A1555June 201830-36 Orazbayeva Dina Kenessov Bulat Psyllaki Eleftheria Ψυλλακη Ελευθερια Nassyrova Dayana Bektassov Marat Elsevier Dimethylhydrazine Headspace solid-phase microextraction Multiple headspace solid-phase microextraction Transformation products Vacuum-assisted headspace solid-phase microextraction Water analysis