SOLVENT-MODIFIED SOLID-PHASE MICROEXTRACTION FOR THE DETERMINATION OFDIAZEPAM IN HUMAN PLASMA SAMPLES BY CAPILLARY GAS-CHROMATOGRAPHY

This paper describes microextraction and gas chromatographic analysis of diazepam from human plasma, The method was based on immobilisation of 1.5 mu l of 1-octanol on a polyacrylate-coated fiber designed for s olid-phase microextraction. The solvent-modified fibre was used to ext ract diazepam from the samples. The plasma sample was pre-treated to r elease diazepam from the protein binding. The fibre was inserted into the modified plasma sample, adjusted to pH 5.5, an internal standard w as added and the mixture was carefully stirred for 4 min. The fibre wi th the immobilised solvent and the enriched analytes was injected into the capillary gas chromatograph. The solvent and the extracted analyt es were evaporated at 300 degrees C in the split-splitless injection p ort of the gas chromatograph, separated on a methylsilicon capillary c olumn and detected with a nitrogen-phosphorus detector. The method was shown to be reproducible with a detection limit of 0.10 nmol/ml in hu man plasma.