A semi-automated extraction and spotting system for drug analysis by TLC. I. Procedure for analysis of the major metabolite of delta 9-tetrahydrocannabinol in urine.

A procedure is described for the detection and quantitative analysis of the major metabolite of tetrahydrocannabinol in urine. Following alkaline hydrolysis of the conjugate, the metabolite is extracted, eluted, and spotted on a high performance silica gel thin layer chromatographic plate using a semi-automatic apparatus. The method has an average recovery of 95.9% and an average precision of 6.3%. A study of 32 drugs and metabolites showed no interferences. The method has a visual detection limit at 100% reliability of 2 ng/ml using 2 mL of spiked urine. It was 100% accurate at detecting authentic samples which were positive by the Enzyme Multiplied Immunoassay Technique. There was a good correlation between urine samples analyzed by gas chromatography/mass spectroscopy and the TLC procedure. The method is suitable for the simultaneous analysis of 60 samples.