Liquid-phase microextraction as a sample preparation technique prior to capillary gas chromatographic-determination of benzodiazepines in biological matrices

Liquid-phase microextraction (LPME) and gas chromatography were applied to determine diazepam and the main metabolite N-desmethyldiazepam in human uri ne and plasma. The analytes were extracted from 3.0-3.5 mi sample volumes d irectly into 25 mul of extraction solvent. The microextraction device consi sted of a porous hollow fiber of polypropylene attached to two guiding need les inserted through a septum and a 4 mi vial. The hollow fiber filled with extraction solvent was immersed in sample solution. The extraction device was continuously vibrated at 600 rpm for 50 min. An aliquot (1 mul) of the extraction solvent with preconcentrated analytes was injected directly into the capillary gas chromatograph. Thirty samples were extracted simultaneou sly on the vibrator, providing a high sample capacity. The limits of detect ion were from 0.020 to 0.115 nmol/ml for diazepam and N-desmethyldiazepam i n plasma and urine using a nitrogen-phosphorus detector (NPD). (C) 2000 Els evier Science B.V. All rights reserved.