Gas chromatography combined with negative-ion chemical ionization mass spectrometry (GC/NICI-MS) improves the sensitivity and specificity for quantitation of clonazepam and its metabolite 7-aminoclonazepam in whole blood, significantly exceeding these parameters achieved by traditional electron impact ionization mass spectrometric detection. Common liquid-liquid extraction and derivatization parameters such as nature of the extraction solvent, sample pH, extraction time, derivatization time and temperature were optimized. Analytes were extracted using n-butyl acetate, then derivatized with N-methyl-N-(tert-buty-ldimethylsilyl) -trifluoroacetamide (MTBSTFA) followed by GC/NICI-MS analysis. The limits of detection of clonazepam and 7-aminoclonazepam in blood sample were 1.0 and 1.4 ng mL^–1, respectively, and the calibration curves were linear in the concentration range 5–200 ng mL^–1 with r2 > 0.995. The relative standard deviations during investigation of samples used for quality control were lower than 7.0% (at n = 20).
Obtained results showed that the developed GC/NICI-MS method is relatively simple, accurate, sensitive and selective. Finally, it was demonstrated that this method is applicable for the determination of trace concentrations of clonazepam and 7-aminoclonazepam in whole blood samples.

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