Determination of zaleplon and zolpidem by liquid chromatography-turbo-ionspray mass spectrometry: application to forensic cases.

Zolpidem and zaleplon are two short-acting hypnotic agents used in Europe and in the USA. An atmospheric pressure ionisation liquid chromatography-mass spectrometry (Sciex API 150 EX) method was developed for the determination of zolpidem and zaleplon in whole blood. After single-step liquid-liquid extraction, the hypnotics were separated by gradient-elution with an ammonium formate buffer/acetonitrile eluent on an Inertsil ODS-3 column. Methaqualone was used as internal standard. The recovery was higher than 70% for both hypnotics and the internal standard. The best fit for the calibration curve was achieved, between 1 and 250 ng/ml, with 1/x quadratic regression. Coefficients of intra- and inter-assay variation calculated at 5, 25 and 100 ng/ml were less than 10%. The method was successfully applied to forensic cases.