Simultaneous determination of zolpidem and zopiclone in human plasma by gas chromatography-nitrogen-phosphorus detection.

A simple, specific and selective method for the simultaneous determination of zolpidem and zopiclone in human plasma is described. After a liquid-liquid extraction, the extract is injected into a capillary gas chromatograph with an OV-1 fused-silica column coupled to a nitrogen-phosphorus detector. The detection limits are 1 and 2 ng/ml for zolpidem and zopiclone, respectively. The method described is reproducible and linear over a range of concentrations, rendering it suitable for use for pharmacokinetic studies or toxicological evaluations. Absolute identification of the chromatographed compounds is accomplished by gas chromatography--mass spectrometry in both electron-impact and positive-ion chemical ionisation modes.