Sensitive determination of delta 9-tetrahydrocannabinol in human tissues by GC-MS

A reliable, simple, and sensitive method was devised to determine the levels of delta 9-tetrahydrocannabinol (THC) in human solid tissues. THC was effectively extracted with acetonitrile, and interfering compounds were removed by washing with a solution of sodium hydroxide and hydrochloric acid. THC was then derivatized by methylation and subjected to gas chromatography-mass spectrometry. Deuterated methyl THC (THC-CD3) was used as an internal standard. The calibration curves were linear in the concentration range from 1 to 100 ng/g, and the lower limit of detection was 1 ng/g in all samples examined. The accuracy and precision of the method were evaluated in every tissue sample at two different concentrations, 5 and 50 ng per sample. The coefficient of variation ranged from 3.4 to 11.6%. We used this method to identify THC in tissues from an autopsied individual, and the distribution of this drug in the tissues was evaluated based on medico-legal criteria.