Determination of sedative–hypnotics in human hair by micropulverized extraction and liquid chromatography/quadrupole-Orbitrap mass spectrometry†
A method was developed for quantification of 13 major sedative–hypnotics in human hair by liquid chromatography/high-resolution accurate mass spectrometry. A hair sample (5 mg) was micropulverized with 3.0 mol L−1 aqueous ammonium phosphate (pH 8.4). Liquid–liquid extraction was carried out twice with acetonitrile; the organic layer was concentrated and then reconstituted with 50 μL of 0.1% formic acid in 10% acetonitrile, and then filtered. The filtrate (10 μL) was analyzed with a Q Exactive™ hybrid mass spectrometer coupled with a liquid chromatograph. Using multiplexed selected ion monitoring mode, the quadrupole mass filter of the Q Exactive™ successfully eliminated large interferences, which enabled detection of the small peaks of the analytes. The lower limits of quantification (LLOQ) were 1.0 pg mg−1 for brotizolam, diazepam, N-desmethyldiazepam, estazolam, flunitrazepam, nitrazepam, triazolam, ramelteon and zolpidem, and 4.0 pg mg−1 for alprazolam, N-desmethylfludiazepam, etizolam and zopiclone. The accuracy and precision of the repeated analyses for all the analytes met FDA guidelines at three concentrations (LLOQ, 100 pg mg−1 and 2.0 ng mg−1). The developed method was applied to hair samples from four patients with sleep disorders. Daily uses of brotizolam (8.8 pg mg−1), ethyl loflazepate (443 pg mg−1 as desmethylfludiazepam), flunitrazepam (46.0 pg mg−1) and zolpidem (10.2 ng mg−1) were detected for Donor A. Occasional uses of etizolam (below the LLOQ) and zolpidem (60.0 pg mg−1) were detected for Donor B. The occasional use of etizolam (4.9 pg mg−1) was detected for Donor C. The concentration of zopiclone in the gray hair of Donor D was >10 ng mg−1 in black hair and 187 pg mg−1 in white hair.