Analysis of THC in Whole Blood

Automation Compatibility: Hamilton, Integra

Cannabis is the most widely abused illicit drug in the US. Results from the 2013 National Survey on Drug Use and Health show that between 2007 and 2012 the rate of marijuana use rose from 5.8% to 7.3%. As use of marijuana increases, it becomes more prevalent in clinical and forensic case work, particularly in impaired driving cases. In 2007 the National Highway Traffic Safety Administration (NHTSA) reported that 8.6% of nighttime drivers tested positive for cannabinoids—a rate almost four times higher than those with blood alcohol levels equal to or above 0.8 g/L. Recent marijuana use is associated with a 2–6 fold increased crash risk, depending on dose, than when unimpaired.

The LC-MS/MS method developed in this study minimizes required sample volume and provides sensitive quantitation of THC, 11-OH-THC and THC-COOH in whole blood. Notably, our method simplifies sample preparation for analysis of THC and its metabolites in whole blood using an automated dispersive pipette extraction without subsequent dilution or solvent evaporation. The extraction process is rapid, minimizes matrix effects (~ 30% or less), and maximizes analyte recoveries (>93%). LODs and LOQs were below 0.75 ng/ mL and 2 ng/mL, respectively. These outcomes clearly provide the necessary sensitivity to meet laboratory cut-offs with minimal imprecision (<8%). All calibrations were linear (R2 >0.99) over two orders of magnitude (0.5–50 ng/mL).

This work was further expanded upon by the National Institute of Drug Abuse (NIDA) to include additional cannabinoid metabolites and application to urine.