A certificate of analysis is the formal report a testing laboratory issues for a sample. A complete COA identifies the lab and its accreditation, the client, the sample and batch ID, sampling and receipt dates, the methods used, each result with units, the LOD or LOQ, pass/fail against any limits, and a signature from an authorised analyst.
In practice
Read a COA from the top: is it the right product and batch, from a lab accredited for that method, dated recently? Then check the basis (dry weight or as received), the moisture figure, and whether "total THC" was calculated with the 0.877 factor. A flower COA reading 20.4% total THC at 11% moisture as received is a coherent document. One reading 38% with no moisture data and no method reference deserves suspicion.
A COA describes only the sample the lab received. It does not prove that every jar from the batch matches, and it says nothing about samples the lab never saw.
Don't confuse with
- Label: the number printed on retail packaging, which may be rounded or taken from a different test.
- Spec sheet: a seller's description, not an independent measurement.
Myth check
A COA is only as good as the sample and the lab. House position: inflated labels and lab shopping are well documented (Jikomes & Zoorob 2018; Schwabe et al. 2023). See buyer beware.
Homogenisation is grinding and mixing a sample so every portion the lab tests represents the whole; together with representative sampling it often matters more than the instrument.The LOD (limit of detection) is the lowest amount of a compound a method can reliably tell apart from zero, but not necessarily measure accurately.The weight of cannabis after drying (and usually trimming), the basis growers use for yield; it is typically about 20-25% of trimmed wet weight.Dry-weight basis reports a result per gram of sample with its water removed, while as-received basis reports it per gram as delivered, water included; dry-weight figures are always higher.THC (Δ9-tetrahydrocannabinol) is the neutral, decarboxylated cannabinoid mainly responsible for cannabis's reported intoxicating effects; the living plant makes it almost entirely as THCA.Total THC is a calculated figure, Δ9-THC plus 0.877 × THCA, estimating the maximum THC a sample could yield after full decarboxylation.Label inflation is the gap between the potency printed on cannabis packaging and what independent testing finds, a documented, mostly upward bias in retail THC claims.Lab shopping is the practice of choosing testing labs because they report higher potency or more passing results, rather than because they are most accurate.Potency testing is laboratory measurement of a sample's cannabinoid content, normally by HPLC, reported as % w/w or mg/g for each cannabinoid plus calculated totals.The LOQ (limit of quantitation) is the lowest concentration a method can measure with acceptable accuracy and precision; below it a result is reported as <LOQ.A batch (or lot) is a defined quantity of product from the same plants, harvest and processing run that is sampled and tested as one unit and carries one ID.ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories; accreditation to it shows a lab's specific methods have been independently assessed.
