Defining cannabinoid stability in authentic oral fluid (OF) is critically important for result interpretation. There are few published OF stability data, and of those available, all employed fortified synthetic OF solutions or elution buffers; none included authentic OF following controlled cannabis smoking.
An expectorated OF pool and a pool of OF collected with Quantisal™ devices were prepared for each of 10 participants. Δ9-Tetrahydrocannabinol (THC), 11-nor-9-carboxy-THC (THCCOOH), cannabidiol (CBD), and cannabinol (CBN) stability in each of 10 authentic expectorated and Quantisal-collected OF pools were determined after storage at 4 °C for 1 and 4 weeks and at −20 °C for 4 and 24 weeks. Results within ±20% of baseline concentrations analyzed within 24 h of collection were considered stable.
All Quantisal OF cannabinoid concentrations were stable for 1 week at 4 °C. After 4 weeks at 4 °C, as well as 4 and 24 weeks at −20 °C, THC was stable in 90%, 80%, and 80% and THCCOOH in 89%, 40%, and 50% of Quantisal samples, respectively. Cannabinoids in expectorated OF were less stable than in Quantisal samples when refrigerated or frozen. After 4 weeks at 4 and −20 °C, CBD and CBN were stable in 33%–100% of Quantisal and expectorated samples; by 24 weeks at −20 °C, CBD and CBN were stable in ≤44%.
Cannabinoid OF stability varied by analyte, collection method, and storage duration and temperature, and across participants. OF collection with a device containing an elution/stabilization buffer, sample storage at 4 °C, and analysis within 4 weeks is preferred to maximize result accuracy.
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