Simultaneous determination of barbiturates in human biological fluids by direct immersion solid-phase microextraction and gas chromatography-mass spectrometry

Simultaneous determination of seven barbiturates in human whole blood and urine by combining direct immersion solid-phase microextraction (DI-SPME) with gas chromatography-mass spectrometry (GC-MS) is presented. The main parameters affecting the DI-SPME process, such as SPME fibers, salt additives, pHs, extraction temperatures and immersion times were optimized for simultaneous determination of the drugs. The extraction efficiencies were 0.0180-0.988 and 0.0156-2.76% for whole blood and urine, respectively. The regression equations of the drugs showed excellent linearity for both samples; the correlation coefficients (r(2)) were 0.994-0.999. The detection limits for whole blood were 0.05-1 microg x ml(-1), and those for urine 0.01-0.6 microg x ml(-1). Actual quantitation could be made for pentobarbital in whole blood and urine obtained from volunteers, who had been orally administered a therapeutic dose of the drug. The DI-SPME/GC-MS procedure for barbiturates established in this study is simple and sensitive enough to be adopted in the fields of clinical and forensic toxicology.