Detection of benzodiazepines in hair using ELISA and LC-ESI-MS-MS

This study was designed to validate an enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-tandem mass spectrometry (LC-MS-MS) method for the detection of nine benzodiazepines in hair. Sixteen hair case samples were tested from drug-related deaths where a positive benzodiazepine blood result was obtained. The case samples were decontaminated with 0.1% sodium dodecyl sulfate, distilled water, and dichloromethane. For ELISA analysis, the samples were extracted by incubation in monobasic phosphate buffer for 1 h and then neutralized with dibasic phosphate buffer. They were diluted 1:5 with phosphate buffer saline (PBS) prior to analysis. For LC-MS-MS, the samples were incubated overnight in methanol/25% ammonium hydroxide (20:1). The benzodiazepines were extracted by solid phase. Thirteen samples were confirmed positive by LC-MS-MS. The benzodiazepines detected included diazepam, nordiazepam, temazepam, oxazepam, nitrazepam, and lorazepam. Using a cut-off concentration of 0.1 ng/mg oxazepam, the Immunalysis® Benzodiazepine Microplate ELISA demonstrated a sensitivity and specificity of 100% and 81%, respectively, compared with LC-MS-MS results.