Determination of delta 9-tetrahydrocannabinol from human saliva by tandem immunoaffinity chromatography--high-performance liquid chromatography.

Smoking or ingestion of cannabis causes cognitive, perceptual and behavioural changes, which are responsive for impaired performance in driving motor vehicles. In this paper a novel liquid chromatographic assay for the selective quantification of delta 9-tetrahydrocannabinol, the major indicator of a present cannabis intoxication in saliva, is described. The method involves a column-switching procedure and requires an extremely simple pre-treatment of the sample. Deproteinized saliva was directly injected into the chromatographic system. The clean-up and enrichment procedure was performed in an immunoaffinity column, followed by the transfer of the antigens to an octysilica analytical column. The immunoaffinity sorbent was obtained by covalent immobilization of specific antibodies on epoxy-activated silica. The mobile phase consisted of methanol-aqueous 0.15 mol/1 NaCl solution (elution programmed) and the analyte was detected by measuring the UV absorption at 220 nm. Using an injection volume of 4.5 ml (dilution 3:2, v/v) the limit of quantification was 20 ng/ml, at a signal-to-noise ratio of 5. Recoveries were estimated to be in the range of 70%. Both intra- and inter- day coefficients of variation were below 5%.