ONLINE AUTOMATED SAMPLE PREPARATION - CAPILLARY GAS-CHROMATOGRAPHY FOR THE ANALYSIS OF PLASMA SAMPLES

An automated sample preparation module, (the automated sample preparat ion with extraction columns, ASPEC), was interfaced with a capillary g as chromatograph (GC) by means of an on-column interface. The system w as optimised for the determination of the antidepressant trazodone in plasma. The clean-up of untreated plasma was carried out with disposab le C18 cartridges, using several washing steps. The analyte was desorb ed with methanol, the extract was diluted on-line with buffer and prec oncentrated on a PLRP-S trapping column. The trapping column was dried by purging with nitrogen gas. Desorption (phase switching) of the tra pping column was carried out with ethyl acetate which was introduced i nto a retention gap using partially concurrent solvent evaporation con ditions. Trazodone was determined by GC with flame ionisation detectio n (FID). With a 1 ml sample, this resulted in a detection limit for tr azodone in plasma of 3 ng/ml. The system showed good linearity and rep eatability in the range 00.1-1 mu g/ml, thus covering the range of pha rmacokinetic/dynamic-to-therapeutic concentrations of trazodone in pla sma. Preliminary results for benzodiazepines are promising. They indic ate that the use of a selective detector such as the nitrogen/phosphor us detector, is to be recommended.