Quantitative Analysis of Tetrahydrocannabinol For Forensic Applications In Seized Drugs

Cannabis and its’ associated psychoactive cannabinoid THC have become more popular within the public community. And with popularity comes the political, social, medical, and fiscal concerns associated with cannabis demands not only governmental scrutiny, but also rigorous research and scientific examination. The forensic community needs to be prepared and competent in every aspect. In order to demonstrate an exhaustive research and scientific analysis, a quantitative method was developed using an Agilent GCMS quadrupole as this is the main workhorse in many forensic drug laboratories. The internal standard tribenzylamine was initially chosen along with the drug standard THC. The calibration curve was linear with correlation a coefficient of 0.98 – 0.99, however the internal standard and drug standard began interacting with each other and degrading after approximately 2 weeks. A new internal standard, tetradecane, was chosen for its non-polar properties. Results with tetradecane proved to be very unreproducible. Quality control samples regularly did not pass their ± 20% accuracy requirement. Relative standard deviation of the internal standard ranged from 6.10-25.77%. The limit of detection for both Agilent GCMS instruments was 0.1% THC on a total dry weight basis while the limit of quantitation was 0.4%. Relative standard deviation of the seized THC samples ranged 0-3.13%. Next a quantitative method was developed using a Waters LC-UV-MS single quadrupole. A 5 point calibration curve was used each day. Calibration curves were run on 3 different days. Standard calibration curves were linear with a correlation coefficient of 0.99 or above each day. The limit of detection was 0.0002% THC on a total dry weight basis while the limit of quantitation was 0.00085%. The GCMS detectors were not sensitive enough to quantitate the wide dynamic range of THC needed. Clearly the LCMS with a UV detector is more than sensitive enough to be able to quantify the range of THC concentrations that are routinely seen in the forensic laboratory