Positive- and negative-ion mass spectrometry of 24 benzodiazepines

Positive-ion electron impact (PIEI), positive-ion chemical ionization (PICI) and negative-ion chemical ionization (NICI) mass spectra of 24 benzodiazepines are presented. In the PIEI mode, peaks due to M, M − H, M − CO and a liberated R3-phenyl ring appeared in many compounds. The peaks at mz M − 47 and mz 56 or 70 were characteristic for nitro- and oxazolo-compounds, respectively. In the PICI mode, most spectra showed the base peaks due to M + H and small peaks due to M + C2H5; small peaks due to M − R1 or M − R1 + 2H also appeared for many compounds. For the nitro-compounds, peaks at mz M − 29 commonly appeared. For the oxazolo-compounds, peaks due to the loss of the R3-phenyl ring appeared. In the NICI mode, either molecular or [M − H]− quasi-molecular anions were the base peaks in 10 compounds. Small anions at mz M + 15 (M − H + O) also appeared in many compounds. Anions due to liberated halogens were observed for most compounds; bromine gave its base peaks. An procedure for benzodiazepines from human urine and plasma, and their separation by gas chromatography (GC) with a wide-bore capillary column are also presented to serve for their actual identification by GC/mass spectrometry (MS). The wide-bore capillary column was useful to prevent the drugs from decomposition.