Saliva Sampling Reveals All
Quantifying THC in oral fluid by turning convention on its head
Identifying drivers under the influence of THC has clear implications for road safety. But it’s not easy, demanding tests of behavioral impairment complemented by chemical analysis of defined biological specimens, including blood, which can be expensive, time consuming, and invasive.
Now, researchers from the Institute of Legal Medicine of the Medical University Innsbruck, Austria, have developed a simple but effective workflow for reliable quantification of THC and its metabolites in oral fluid samples, which can suffer analyte loss.
Sample preparation methods typically remove solid components, such as food particles and debris, from the analytical workflow through centrifugation of the oral fluid. But the Innsbruck team took the opposite approach, extracting the cannabinoids from the solid pellet produced by centrifugation ahead of liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis.
“We demonstrated that processing of the pellet represents a valuable alternative for cannabinoid quantification in oral fluid,” says lead author Herbert Oberacher.
The team have already demonstrated the applicability of the method to forensic testing. With help from local police, the researchers analyzed 195 samples collected either from opioid addicts or persons suspected of driving under the influence of drugs. When they compared their oral fluid analysis results to those from blood analysis (the gold standard for forensic testing of cannabis use), the team found they could identify those individuals with the presence of THC in their blood with an accuracy of 97.9 percent.
“Despite considerable success of swabs for oral fluid drug testing, problems related to analyte loss due to unspecific binding are still encountered – particularly in the context of cannabinoid testing,” says Oberacher. “Our report might help further the understanding the underlying principles involved in oral sample preparation, which could help improve extraction processes and recoveries.”
But there is a slight saliva snag. The team collected samples using the Greiner Bio-One Saliva Collection System (GBO SCS), which rinses the oral cavity with an extraction solution containing a citrate buffer stimulating salivary flow. Unfortunately, the GBO SCS has since been discontinued…
- V Reinstadler et al., PubMed (2023). DOI: 10.1002/bmc.5651.
Associate Editor, The Analytical Scientist