Quantitative analysis of 11-nor-9-carboxy-tetrahydrocannbinol (THC-COOH) in urine by LC-MS/MS following a simple filtration.

Quantification methods utilizing liquid chromatography tandem mass spectrometry (LC-MS/MS) are common in clinical and forensic toxicology laboratories and the efficiency and rapidity of such methods continues to evolve. In most cases, urine drug confirmation does not require a drug extraction and can quickly and easily be accomplished with a dilution followed by sample filtration. The report describes the validation of a simple confirmation method for 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH) and compared two types of filter extraction columns for sample clean-up. The method achieved a linear range of 10-3000ng/mL, acceptable bias (-4.7-2.6%) and precision (0.9-6.9%) and autosampler stability up to 72h. Universal filter columns offered less variable recovery over the linear range and fewer matrix interferences compared to THC-COOH specific filter columns. Authentic specimens testing positive for THC-COOH by LC-MS/MS were in good agreement with typically used GC-MS methods.