Liquid chromatography-tandem mass spectrometry for detection of low concentrations of 21 benzodiazepines, metabolites, and analogs in urine: method with forensic applications.

Background: Commonly used methods for detecting benzodiazepines (BZPs) and BZP-like substances, such as zolpidem and zopiclone, may not detect low concentrations of these drugs. We developed a liquid chromatographic-tandem mass spectrometric method for identifying these drugs and their relevant metabolites.

Methods: We extracted BZPs from urine by solid-phase extraction with a mixed-mode phase (OASIS HLB cartridges).