Combined high-pressure liquid chromatography and radioimmunoassay method for the quantitation of delta 9-tetrahydrocannabinol and some of its metabolites in human plasma.

A high-pressure liquid chromatography-radioimmunoassay (HPLC-RIA) method for the measurement of cannabinoid levels in plasma is described. The method is capable of quantifying 0.1 ng of a cannabinoid in 1 ml of plasma. The experimental procedure consists of an initial separation of cannabinoids in a plasma extract by HPLC followed by collection of the HPLC eluate and RIA. A chromatogram consisting of the cross-reacting cannabinoids in plasma may then be constructed. The plasma concentrations of cannabinoids with retention volumes equivalent to those of delta 9-tetrahydrocannabinol, cannabinol and mono-hydroxylated metabolites have been measured by this technique.