Highly sensitive quantification of unconjugated 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol in a cannabis user's hair...

We previously developed a simple and highly sensitive analytical method for 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol (THC-COOH) in spiked hair using micropulverized extraction (MPE) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). Using this method, we were able to quantify THC-COOH at 0.2pg/mg, which is the cut-off level recommended by the Society of Hair Testing. However, it was impossible to prove the validity of the method and the presence of THC-COOH conjugated with glucuronide in hair because we did not have authentic hair containing THC-COOH at the cut-off levels at that time. In this study, the previously developed method was verified using recently obtained hair from a cannabis user. The concentrations of THC-COOH quantified using the method were 0.36±0.01pg/mg without hydrolyzation for glucuronide and 0.49±0.05pg/mg with hydrolyzation after MPE, whereas the concentration quantified using the conventional alkaline dissolution and gas chromatography/tandem mass spectrometry with negative ion chemical ionization was 0.50±0.02pg/mg. The results proved that THC-COOH could be extracted completely from authentic hair containing THC-COOH at the recommended cut-off level using MPE. In addition, MPE with and without hydrolyzation, unlike alkaline dissolution of hair, enabled the measurement of the percentage of the conjugate form in total THC-COOH. The percentage of conjugated THC-COOH in hair measured using the MPE was approximately 26%, which was greatly different from previously reported data (>75%). The discrimination between conjugated and unconjugated compounds in hair is important to understand the mechanism of drug uptakes into hair. More data obtained with our simple and highly sensitive method from the hair of cannabis users would help to understand the relationship of concentrations between THC-COOH and its conjugate in hair.