A certificate of analysis (COA) is the lab report that says what's actually in a sample. Almost nobody explains how to read one, so here's every line, taken apart.
1. Batch number. Every certificate belongs to one specific batch. If the number on the report doesn't match the batch it's attached to, the report tells you nothing about what's in front of you.
2. Identity. The name of the compound tested, usually with its molecular weight or sequence. This is where you confirm the report is actually about the thing it claims to be about.
3. Method: HPLC. High performance liquid chromatography separates a sample into its component parts and measures how much of the total is the target compound versus something else. That ratio is the purity figure.
4. Method: mass spectrometry. This weighs the molecules in the sample. If the measured mass matches the expected mass for the target compound, identity is confirmed. Purity tells you how much; mass spec tells you what.
5. The result. The purity percentage, shown with its chromatogram. A number without a chart behind it is a claim. A number with a chart is evidence you can actually inspect: peak shape, baseline noise, and other peaks all carry information a bare percentage hides.
6. Dates. Manufacture date, test date, and expiration. A test run against a different, earlier batch than the one in hand doesn't verify anything about the batch you actually have.
7. The lab. Who ran the test, and whether they're independent of the seller. A real testing lab has a name, a physical address, and typically an accreditation that can be looked up independently.
8. Verification. Many labs allow direct verification of a certificate using a reference or accession code. No way to verify a certificate independently of the seller is itself a red flag.
Five red flags on any certificate: no batch number, or one that doesn't match; a purity figure with no chromatogram; no named, traceable laboratory; suspiciously round numbers (real HPLC results are rarely exactly 99.00%); and the same certificate reused across batches from different years.