The benzodiazepines are most frequently encountered drugs in emergency toxicology screening, drugs of abuse testing and forensic medicine examinations. The identification of nitrazepam and clonazepam, the most frequently used benzodiazepines is described by simple, rapid and sensitive thin­layer chromatographic method. The structures of these benzodiazepines contain nitro group which is reduced by acidified stannous chloride to give amino group. This couples with diazotized sulphanilic acid to give a yellow brown coloured compound. The detection limit was found to be 3µg and 5µ per spot for nitrazepam and clonazepam respectively. The reaction was not given by other benzodiazepines commonly encountered in toxicological screening.

Keywords: Benzodiazepines; Thin­Layer Chromatography; Spray Reagent; Stannous Chloride; Sulphanilic Acid.