Quick answer: Match the lot number on the certificate to the lot on your vial, then look at who tested it, which methods were used, the purity figure, an identity test and the lot.
Start with the lot number
A certificate belongs to a specific batch. If the lot number on the document does not match the lot on your vial, the document says nothing about what you received.
Who did the testing
A certificate can come from the vendor, a manufacturer or an independent lab. An independent lab with a named address, a report number and a signature is easier to verify than an unsigned in-house page. You can contact a lab to confirm a report it issued.
Typical sections
- Purity: often reported as a percentage from HPLC. Look for the method and the chromatogram, not only the number.
- Identity: often mass spectrometry, which checks that the measured mass matches the expected one.
- Appearance, date and batch details.
What a COA does not prove
A COA does not show that a product is safe, legal for a given purpose or suitable for any use. It also covers only what was tested, on the sample that was tested. Treat it as one piece of evidence.
Red flags
- No lot number, or a lot number that does not match.
- No lab name, no date, or a document that looks edited.
- A purity figure with no stated method.
- The same certificate shown for several different products.
FAQ
Do vendors publish COAs?
Many list certificates on their product pages or in a COA library. Check the lot on the certificate against your vial.
Is a high purity number enough?
No. Check the lot, the method, the identity test and who ran it.