Determination of the novel antipsychotic drug olanzapine in human plasma using HPLC with amperometric detection

A new sensitive high performance liquid chromatograpic method has been developed for the analysis of the novel antipsychotic drug, olanzapine, in human plasma. Chromatography was performed on a reversed-phase column (C8, 150 x 4.6 mm i.d., 5 ?m) with acetonitrile-phosphate buffer (pH = 2.5) as the mobile phase. The detection voltage was +900 mV and the cell and column temperature were 50°C. The flow rate was 1 mL min-1. The method provides a linear response over an olanzapine concentration range of 2-100 ng mL-1. Isolation of olanzapine from plasma was accomplished by a solid-phase extraction procedure, using C8 cartridges, which gave high extraction yields and needed a small amount of human plasma (only 0.25 mL). The results obtained analysing plasma samples from patients in therapy with olanzapine were satisfactory in terms of precision and sensitivity, and were compared to those obtained by means of a method based on HPLC with UV detection.