What a certificate of analysis actually shows

A certificate of analysis, usually abbreviated to CoA, is a record of analytical results for a defined batch of material. At minimum a meaningful certificate identifies the material, identifies the batch, names each test performed, states the method used, gives the acceptance criterion, gives the result, and identifies who performed the work and when.

What it shows

• That named tests were carried out on material bearing that batch identifier.
• What those tests returned, expressed against a stated acceptance criterion.
• Which analytical methods were used, which determines what the results can mean.
• When the testing took place, which matters for anything that changes over time.

What it does not show

• That the material in front of you is the material that was tested. A certificate travels as a document; the link to the physical container depends entirely on the traceability system around it.
• That anything untested is absent. A purity figure derived from chromatography describes what the detector saw under those conditions, not everything present in the vial.
• That the material is sterile, endotoxin-free or microbiologically acceptable, unless those specific tests appear on the certificate.
• That the material is suitable, safe or lawful for any particular purpose. A certificate is an analytical record, not an authorisation.
• That the results are independent, unless the certificate identifies a third-party laboratory and that laboratory can be checked.

How to read one

1. Check the batch identifier against the physical container, not against the product name.
2. Check the date. Results describe the material as it was then, not necessarily as it is now.
3. Read the method column before the results column. A result without a method is uninterpretable.
4. Read the acceptance criteria. A result that passes a loose criterion may be weaker than a result that fails a strict one.
5. Note which tests are absent. Absence is information.
6. Check who signed it, and whether that party is independent of whoever supplied the material.

Independence and accreditation

A certificate produced by the supplier of the material is not independent. That does not make it worthless, but it does mean the document and the material come from the same source, and a reader has no external check on either. Independent testing means testing commissioned from a laboratory with no commercial interest in the result.

Accreditation is a further and separate question. A laboratory may hold accreditation for some methods and not others, so the relevant check is not whether a laboratory is accredited but whether its accreditation covers the specific test being relied upon. In the UK, accreditation scopes are published by the national accreditation body and can be inspected directly.