Total THC combines delta-9 THC with the potential THC contribution from tetrahydrocannabinolic acid (THCA) in cannabis plant material. It is not a blood THC result and cannot independently establish impairment.
THCA is an acidic precursor. Heating can remove carbon dioxide and convert it to neutral delta-9 THC. Laboratories may measure the two compounds separately and calculate total THC, or use a validated conversion-based method. The laboratory report should state the definition and method used.
A matrix effect occurs when non-target substances in an extract change the analytical response. In 2025, Mulloor, Wilson, and Sander found that cannabis plant extracts gave different responses from clean calibration solutions in gas chromatography–mass spectrometry. They proposed interactions on heated inlet surfaces as part of the mechanism.
These substances can reduce unwanted interactions at reactive inlet sites. In the cited study, protectants improved agreement between GC–MS and liquid chromatography measurements. The findings concern method performance, not whether a particular person was impaired.
No. It refers to THC-related content, not the sum of all cannabinoids.
No. Product composition, absorbed exposure, and behavioral effects require separate evidence.
Mulloor J, Wilson WB, Sander LC. Forensic Chemistry. 2025;44:100668. DOI: 10.1016/j.forc.2025.100668.