Amid on-going relaxation of state legislation around recreational marijuana use in the U.S., recent findings suggest America’s relationship with cannabis is evolving. According to a Yahoo News/Maris survey conducted in 2017, approximately 35 million Americans smoke cannabis on a regular basis.
Growing use of hair as a sample for cannabis testing
The main psychoactive ingredient in cannabis is tetrahydrocannabinol (THC). Two key metabolites of THC commonly used to establish deliberate marijuana consumption are 11-hydroxytetrahydrocannabinol (THC-OH) and 11-nor-D9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH).
While bodily fluids such as urine and saliva are widely used for drug testing, practical challenges around collection and the relatively fast rate at which most recreational drugs are excreted from the body limits their usefulness. Urine samples, for example, are intrusive to collect and suffer from an increased risk of tampering.
An alternative and increasingly used specimen sample for drug testing is hair, due to the non-invasive nature of collection and the ability to probe an individual’s history of drug use over a more prolonged period of time. Growing use of hair samples in routine drug testing has led global regulatory bodies, including the Substance Abuse and Mental Health Services Administration (SAMHSA), to establish guidelines around minimum cut-off concentrations for THCCOOH determination in hair of 1 pg/mg for screening and 0.05 pg/mg for confirmation testing.
Highly sensitive determination of THCCOOH in hair samples by GC-MS/MS
To perform accurate quantitation of THCCOOH in hair at these low levels, drug testing workflows require highly sensitive analytical techniques. While GC-MS/MS is well-established as an analytical tool for robust and reliable determination of THCCOOH in hair, the latest instrument advances are pushing the limits of detection even further.
Well, we put the Thermo Scientific TSQ triple quadrupole GC-MS/MS system, in its Extractrabrite ion source configuration through its paces to determine the limit of detection for THCCOOH analysis in hair.
We prepared internal standards by spiking THCCOOH and THCCOOH-d3 into drug-free human hair. Each calibration standard was analysed five times. The calibration curve generated by the instrument showed good linearity over a range of 0.05 to 1 pg/mg, with an r-squared value of 0.996.
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To determine measurement reproducibility at the recommended cut off of 0.05 pg/mg, five injections of the spiked 0.05 pg/mg standard were analyzed. These results highlighted the exceptional consistency of results. Using Thermo Scientific TraceFinder software, a limit of detection of 0.022 pg/mg was automatically calculated according to the Student’s t-test method, at 99 percent confidence.
These results highlight the suitability of the method for sensitive determination at the recommended cut-off level of 0.05 pg/mg. If indeed more sensitivity is required, with the TSQ 9000, there is also the option to use the Advanced Electron Ionization (AEI) source as an alternative approach.
Reproducibility of five injections of 0.05 pg/mg spiked THCCOOH standard and limit of detection (LOD).
GC-MS/MS offers high-throughput analysis and enhanced productivity
It’s not just the analytical sensitivity that makes GC-MS/MS well suited for THCCOOH quantitation in hair. The speed of analysis and high-throughput capability allows rapid screening of large numbers of samples. Furthermore, the new TSQ 9000 GC-MS/MS system, through NeverVent™ technology allows quick and easy switching between chemical ionization (CI) and electron ionization (EI) modes. The instrument’s vacuum probe interlock allows changing between the two ionization modes in just two minutes, without breaking the vacuum. Additionally, a unique V-lock source plug allows GC columns to be exchanged without venting the mass spectrometer, and without the need for any additional column connections or complicated fluidics.
Learn more about highly sensitive THCCOOH quantitation in hair by downloading the application note “Sensitive determination of THCCOOH in hair to regulatory requirements using Triple Quadrupole GC-MS/MS.”
For Forensic Use Only.