Urine samples used in this study made part of those submitted to our toxicological laboratory for drug screening and were confirmed positive for one of the following substances: amphetamine, MDMA, tetrahydrocannabinol, heroin, cocaine, diazepam, or alprazolam (Table 2 ). The last two were selected as the most commonly abused benzodiazepines. Drug-free urine samples were prepared from pooled urine collected from three healthy donors. They were used as control in urine sample integrity tests.
For analysis we used the Waters Alliance® liquid chromatograph with a Waters Micromass® ZQ™ mass spectrometer (Waters Corporation, Milford, MA, USA). All analytical methods have been validated for everyday use at laboratory accreditation. Diazepam and alprazolam were determined without previous hydrolysis and their concentrations are low, but the strip test was positive due higher concentrations of their metabolites (23 (link)).
For analysis we used the Waters Alliance® liquid chromatograph with a Waters Micromass® ZQ™ mass spectrometer (Waters Corporation, Milford, MA, USA). All analytical methods have been validated for everyday use at laboratory accreditation. Diazepam and alprazolam were determined without previous hydrolysis and their concentrations are low, but the strip test was positive due higher concentrations of their metabolites (23 (link)).