Automated analysis of drugs in urine

A totally automated procedure has been developed for the preparation and analysis of 34 basic and neutral drugs in urine samples using an integrated HP 7686 PrepStation-HP 6890 gas chromatographic system. The automated preparation of the sample consisted of a liquid-liquid extraction of 250 microliters urine at alkaline pH with 100 microliters of methyl tert.-butyl ether. After phase separation the organic solvent was automatically placed in the injector of the gas chromatograph and analysed. High recoveries of extraction were obtained. The limits of detection of most of the drugs were less than 0.5 microgram/ml. The method, which allows the preparation and analysis of the samples to be completely synchronised, showed good accuracy and precision.