How to Read a Certificate of Analysis
A field-by-field walkthrough of a COA: identity, purity, the methods behind the numbers, and the batch it belongs to.
Scan the QR on your vial to watch a two-minute walkthrough of that lot's certificate.
What a COA is
A Certificate of Analysis (COA) is a lab document describing what a specific batch of material was tested to be. It ties a set of measurements to a particular lot, on a particular date, from a particular laboratory.
A COA is only as meaningful as its traceability. The strongest ones name the testing lab, the methods used, and the exact batch — so the paper in your hand can be matched to the vial on your bench.
Identity
Identity answers 'is this the sequence it claims to be?' Mass spectrometry is commonly used to confirm the molecular weight matches the expected structure. Look for a stated expected mass and an observed mass that agree.
If a certificate lists a purity number but never confirms identity, it is telling you how clean the sample is without confirming what the sample is.
Purity
Purity is usually reported from high-performance liquid chromatography (HPLC) as a percentage — the share of the sample attributable to the target versus everything else. A chromatogram (the trace with peaks) should accompany the number so you can see it, not just read it.
A single large peak with small neighbors is the visual you are looking for. Percentages without a chromatogram are assertions, not evidence.
Batch, date, and signature
A trustworthy COA is specific: a batch or lot number, the test date, and an identifiable laboratory. Those three let you confirm the certificate belongs to the vial in front of you rather than to some other lot.
When a lot number on a vial does not appear on any certificate — or a certificate has no lot number at all — treat the document as decorative until it can be reconciled.