Sensitive UPLC-MS-MS assay for 21 benzodiazepine drugs and metabolites, zolpidem and zopiclone in serum or plasma.

This paper reports an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS-MS) method to quantitate 21 benzodiazepines, zolpidem and zopiclone in serum and plasma. After liquid-liquid extraction, an Acquity UPLC with a TQ Detector and BEH C18 column was used (Waters, Milford, MA). The injection-to-injection run time was 7.5 min. Forty-eight authentic serum and plasma patient specimens were analyzed and results compared to those obtained using a previously published method. Average r(2) values for linearity (1 to 1,000 ng/mL over five days) were all above 0.995, except α-hydroxytriazolam (0.993). Intra-day and inter-day relative standard deviation values were within ± 15% and the percent deviation from the expected concentrations were within ± 11%. Recovery ranged from 62 to 89%. Matrix effects ranged from -28% to +6%. The limits of detection were 1 ng/mL, except for lorazepam, nordiazepam, oxazepam and temazepam (5 ng/mL). Ion ratios were ± 15% for all analytes. For authentic patient specimens (n = 48, 76 positive results), there was excellent correlation between the UPLC-MS-MS results and the previous method. The best least-squares fit had an equation of y = 1.0708x + 1.6521, r(2) = 0.9822. This UPLC-MS-MS method is suitable for the quantification of benzodiazepines and hypnotics in serum and plasma, and offers fast, reliable and sensitive results.