Confirmation of urinary benzodiazepines by gas chromatography/mass spectrometry

Abstract

A new method is described for the quantitative analysis of urinary benzodiazepines by gas chromatography/mass spectrometry. Development work was aimed at satisfying federal requirements for methods used in forensic urine drug testing which have become the standard in the laboratory industry. Trimethylsilyl (TMS), tert-butyl-dimethylsilyl (TBDMS) and benzophenone derivatives were tested in the development of the new assay. TBDMS derivatives were found to be the most suitable for the analysis of six common benzodiazepine metabolites. Precision for all metabolites tested, as measured by the within run coefficient of variation, was less than 7% at 100 ng/ml (n = 15). Assay sensitivity varied with the specific analyte in the range of 5 to 10 ng/ml. Validation of the procedure included the reanalysis of benzodiazepine positive urine specimens obtained from a forensic drug testing laboratory and comparison of the results from the independent assays. These specimens were tested first by radioimmunoassay using a 100 ng/ml cutoff and then confirmed by GC/MS. Sensitivity was sufficient to confirm the presence of benzodiazepine metabolites in all specimens tested.