Application of direct urine LC-MS-MS analysis for screening of novel substances in drug abusers

A newly developed liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was used to study 3000 human urine samples from 3 different populations for 23 analytes covering phenylethylamines, benzylpiperazine, and non-benzodiazepine hypnotics. Direct injection of urine and LC-MS-MS with rapid chromatography and atmospheric pressure chemical ionization was used in the screening step. The cutoff levels were chosen to be at the limit of detection for most analytes to identify as many positive samples as possible. Typically one ion transition was monitored from the pseudo-molecular ions in the multiple reaction monitoring mode. Of the 797 positive screening findings, 518 (65%) were confirmed by a second LC-MS-MS analysis including solid-phase extraction. Confirmed analytical findings included 22 cases positive for N-benzylpiperazine, 88 for 3,4-methylenedioxy-N-methylamphetamine and metabolites, 4 for 1-phenyl-2-butylamine, 24 for zolpidem and metabolites, 118 for zopiclone and metabolites, and 1 for zaleplon. In conclusion, LC-MS-MS was found to be a robust alternative for drugs of abuse screening, offering high sensitivity compared with immunochemical screening methodology.