AUTOMATED PROCEDURE FOR DETERMINATION OF BARBITURATES IN SERUM USING THE COMBINED SYSTEM OF PREPSTATION AND GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A system of an automatic sample preparation procedure followed by on-l ine injection of the sample extract into a gas chromatograph-mass spec trometer (GC-MS) was developed for the simultaneous analysis of seven barbiturates in human serum. A sample clean-up was performed by a soli d-phase extraction (SPE) on a C-18 disposable cartridge. A SPE cartrid ge was preconditioned with methanol and 0.1 M phosphate buffer. After loading 1.5 mi of a diluted serum sample into the SPE cartridge, the c artridge was washed with 2.5 mi of methanol-water (1:9, v/v). Barbitur ates were eluted with 1.0 mi of chloroform-isopropanol (3:1, v/v) from the cartridge. The eluate (1 mu l) was injected into the GC-MS. The c alibration curves, using an internal standard method, demonstrated a g ood linearity throughout the concentration range from 0.1 to 10 mu g m l(-1) for all barbiturates extracted. The proposed method was applied to 27 clinical serum samples from three patients who were administrate d secobarbital. (C) 1998 Elsevier Science B.V. All rights reserved.