Room-Temperature Urine Storage Affected Cannabinoids Unequally
In fortified urine, parent cannabinoids and the measured metabolites showed markedly different losses during room-temperature storage. One stability statement could not accurately describe every analyte in the panel.
The reported contrast was substantial
After twenty-four hours near 25°C, the investigators reported losses greater than 80% for total CBD, CBN and THC. The corresponding losses for total 11-hydroxy-THC and THC-COOH were approximately 5% and 12%. These were laboratory stability experiments in fortified urine, not measurements of ongoing metabolism in a participant.
Cooling changed the observation
At 4°C, the report described approximately 10–30% loss of total CBD, THC and CBN after three days, without obvious losses of the two metabolites. No significant decrease was observed at temperatures at or below −20°C during the same study period. Those intervals do not establish indefinite frozen stability.
A later result needs analyte-specific context
Identify the specimen, measured chemical form, temperature and elapsed time before using the findings. Fortified urine may differ from authentic specimens, and this study does not provide a universal percentage for correcting another laboratory’s result. Postcollection loss must also remain separate from physiological elimination, new cannabis use and impairment. The absence of one unstable parent compound does not establish absence of all exposure-related metabolites.
Related analysis: the urine assay’s two analytical ranges.
Research cited
Wei, Wang and Blount (2015). Analysis of Cannabinoids and Their Metabolites in Human Urine. DOI: 10.1021/acs.analchem.5b02603.
