HIGH-PRESSURE LIQUID-CHROMATOGRAPHIC ANALYSIS OF DIAZEPAM, OXAZEPAM AND N-DESMETHYLDIAZEPAM IN HUMAN-BLOOD

We describe a rapid method for precisely measuring concentrations of diazepam, oxazepam and N-desmethyldiazepam in blood by high-pressure liquid chromatography. The drugs, together with an internal standard, prazepam, are exitracted from 2 ml of blood and analyzed isocratically on a reversed-phase column with a mobile phase consisting of acetonitrile-0.01 M sodium acetate buffer (35:65 v/v). The eluted drugs are detected by their absorption at 240 nm. The sensitivity of this method is 30 μg/1 for oxazepam and N-desmethyldiazepam, 40 μg/1 for diazapam, for 2-ml blood samples. Relative recovery of added drugs to blood varies from 91 to 110%. The day-to-day precision (coefficient of variation) established by 10 replicate analyses was 2.8 to 9.6%. © 1978.