Serum concentrations of clozapine determined by nitrogen selective gas chromatography

A simple gas-liquid-chromatographic method employing a nitrogen selective detector for the quantitative determination of clozapine in serum is presented. The method involves after the addition of dibenzepine as internal standard the extraction into diethylether followed by analysis of the extract dissolved in methanol. Detector linearity was established over the range of 100-1000 ng/ml serum. Clozapine levels of 9 manic patients analysed by this method are presented and discussed. A linear relationship between daily intake (mg/kg body weight) and serum levels (ng/ml) was established.