Résumé
An analytical method was developed for the determination of unsymmetrical dimethylhydrazine ( UDMH ) in soil samples by gas chromatography-mass spectrometry with the pretreatment of alkaline distillation and ultrasonic derivatization. After pretreated by the alkaline distillation, the quantitative analysis of UDMH was conducted in selected ion monitoring ( SIM ) mode by using salicylaldehyde as derivatization reagent and ultrasonic to accelerate the derivative reaction. The characteristic ion of the derivative product named salicylaldehyde dimethylhydrazone was m/z 164 . Impact factors including types of the alkaline distillation and the derivative conditions with ultrasonic were investigated. The conditions of derivatization were optimized. Under the optimal conditions, linear range of the method was 0. 4-30 mg/L. The limit of detection (LOD, S/N=3) was 0. 0078 mg/kg. The method was used to detect total UDMH in real soil samples with known concentration. The recoveries ranged from 76% to 108% with relative standard deviations ( RSD) of 12%-19% at different spiked concentration levels from 10 mg/kg to 100 mg/kg. In comparison with the methods of spectrophotometry and Soxhlet extraction-ultrasonic derivatization, this method had lower detection limit, and could be used to detect total UDMH in soil samples.