[Analysis of 7-aminonitrazepam in urine by trimethylsilyl derivatization-gas chromatography/mass spectrometry].

A highly sensitive method has been developed for the analysis of 7-aminonitrazepam (7-ANIZ), the major metabolite of nitrazepam, in urine by trimethylsilyl derivatization-gas chromatography/mass spectrometry. Urine samples were extracted with ethyl ether-ethyl acetate (99:1, volume ratio). The extracts were derivatized with N,O-bis (trimethylsilyl) trifluoroacetamide, and the total ion current chromatograms of derivatives were acquired. 7-ANIZ was identified by the relative abundance of major characteristic ions in the mass spectrum of its derivative and the retention time of the mass chromatogram peaks of these characteristic ions. Based on the mass chromatogram of the base peak ion, quantification was performed using 7-aminoclonazepam (7-ACLZ) as the internal standard. The extraction efficiency of 7-ANIZ was 82.8%. The linear range was 10 microg/L - 500 microg/L. The limit of detection was 1.2 microg/L and the limit of quantification was 3.5 microg/L. The recoveries were 94.7% - 103.5%, and the RSDs were 3.9% - 5.4%. 7-ANIZ in the urine sample excreted by the subject over 96 h period after oral administration of 10 mg nitrazepam was measured. It is demonstrated that the method can be applied to the forensic identification.