AUTOMATED PREPARATION AND ANALYSIS OF BARBITURATES IN HUMAN URINE USING THE COMBINED SYSTEM OF PREPSTATION AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A system for an automatic sample preparation procedure followed by on- line injection of the sample extract into a gas chromatography-mass sp ectrometry (GC-MS) system was developed for the simultaneous analysis of seven barbiturates in human urine. Sample clean-up was performed by a solid-phase extraction (SPE) on a C-18 disposable cartridge. A SPE cartridge was preconditioned with methanol and 0.1 M phosphate buffer. After loading a 1.5 mi volume of a urine sample into the SPE cartridg e, the cartridge was washed with 2.5 mi of methanol-water (1:9, v/v). Barbiturates were eluted with 1.0 mi of chloroform-isopropanol (3:1, v /v) from the cartridge. The eluate (1 mu l) was injected into a GC-MS system. The calibration curves, using an internal standard method, dem onstrated a good linearity throughout the concentration range from 0.0 2 to 10 mu g/ml for all barbiturates extracted. The proposed method wa s applied to several clinical cases. The total analysis time for 20 sa mples was approximately 14 h. (C) 1998 Elsevier Science B.V.