High-throughput toxicological analysis of Δ9-THC and 11-nor-9-carboxy-Δ9-THC by LC/MS/MS

A new high-throughput liquid chromatography / tandem mass spectrometry (LC-MS/MS) method for the quantification of Δ-tetrahydrocannabinol (THC) in suspect plant material and of its principal metabolite, 11-nor-9carboxy-Δ-tetrahydrocannabinol (THC-COOH), in human urine was developed and validated. The separation was performed on a Zorbax SB-C18 column under isocratic conditions using a mixture of 2 mM ammonium formate in water and methanol (17:83, v/v) for THC or acetonitrile (45:55, v/v) for THC-COOH at 40oC with a flow rate of 1 mL/min. The detection was performed in MRM mode using an ion trap MS equipped with an APCI ion source using positive mode ionization for THC and negative mode ionization for THC-COOH. The plant samples (0.2 g) were extracted in methanol and diluted before the analysis. The urine samples were heated for 30 min at 80°C with 85% phosphoric acid and centrifugated before the analysis. The method showed a good linearity (r > 0.994), precision and accuracy (< 8.5%) over the concentration ranges of 2 -128 ng/mL for THC and 0.5 32 ng/mL for THC-COOH, respectively. The method is not expensive, requires a minimum time for sample preparation and has a run-time of 3.5 min for instrument analysis (retention times for THC and THC-COOH were 2.6 and 2.55 min, respectively). The developed and validated LC-MS/MS method is very simple and more rapid than other similar methods. It was successfully applied for the rapid quantification of THC in plant samples and of THC-COOH in human urine in forensic toxicology analyses.