Novel automated extraction method for quantitative analysis of urinary 11-nor-Δ<sup>9</sup>-tetrahydrocannabinol-9-carboxylic acid (THC-COOH)

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Journal Article
Journal of Analytical Toxicology, 2008, 32 (4), pp. 292 - 297
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An automated extraction method for extracting the major urinary metabolite of cannabis, 11-nor-Δ9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH) was developed on the four-probe Gilson ASPEC XL4™ solid-phase extraction (SPE) system. The method works on liquid-liquid extraction principles but does not require the use of SPE cartridges. The limits of detection and quantitation and the upper limit of linearity (ULOL) of the developed method were found to be 1, 2, and 1500 ng/mL, respectively. There was no detectable carry over after 10,000 ng/mL analyte. For a batch of 76 samples, the process uses less than 100 mL methanol, 450 mL extracting solvent hexane/ethyl acetate (5:1, v/v) and 1 L rinsing solvent, 30% methanol in water. The automated extraction process takes 5 h to complete. Precision and accuracy of the method are comparable to both manual liquid-liquid extraction and automated SPE methods. The method has proven to be a simple, speedy, and economical alternative to the currently popular automated SPE method for the quantitative analysis of urinary THC-COOH.
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