Quantitative high-performance liquid chromatography of diazepam and N-desmethyldiazepam in blood.

High-performance liquid chromatography on porous silica has been employed to determine diazepam and N-desmethyldiazepam in human blood. For forensic purposes, 1.0 ml of blood is sufficient for a quantitative determination of the benzodiazepines in concentrations above 100 ng/ml. In cases where lower levels, 25-100 ng/ml, are of interest, 2.0 ml of blood together with a somewhat more elaborate extraction procedure are necessary.