Only five of 13 commercial e-liquids tested by Mazzetti and colleagues were within 10% of their labeled CBD concentration. The same paper showed that CBD could decline during controlled storage. Those observations address different questions: how the product tested when sampled and how an initially measured concentration can change over time.
After 30 days at 37 °C, average CBD losses reached about 20% under the reported conditions. Light exposure produced average losses up to about 15% after 30 days. The study tested CBD in the liquid. A liquid concentration cannot supply the dose emitted by a vaping device or inhaled by its user.
For a forensic comparison, record the lot, seal history, sampling date, container, and any known heat or light exposure. A low result from a recovered bottle may reflect its original composition, subsequent changes, or both. The study’s percentages describe its test conditions and cannot reconstruct a particular bottle’s original concentration.
Mazzetti et al., Scientific Reports (2020), with a 2021 author correction · Author correction