GC/MS analysis of five common benzodiazepine metabolites in urine as tert-butyl-dimethylsilyl derivatives

A method for the GC/MS confirmation of oxazepam, nordiazepam, desalkylflurazepam, temazepam, and alpha-hydroxyalprazolam in urine is described. The method incorporates a solid phase extraction technique developed by Varian which was found to extract all five metabolites with recoveries exceeding 73%. The extracted metabolites were derivatized with N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA), resulting in the formation of stable tert-butyldimethylsilyl (TBDMS) derivatives. Quantitation was performed by GC/MS using oxazepam-D5, nordiazepam-D5, and alpha-hydroxyalprazolam-D5 as internal standards. The method was found to be linear over the range of 50-2000 ng/mL. Within-run precision, measured as the coefficient of variation at 100 ng/mL, was less than 3% for all analytes except temazepam which was 6% (N = 20).