How to read a peptide COA: every field, line by line

A certificate of analysis looks technical, but it answers three questions: what was analysed, what was found, and does this paper belong to the batch in front of you. Here is every field, in reading order.

The header: who analysed, and when

The top of the page names the laboratory, the report date and a report number. The laboratory name is checkable — a real lab exists outside this document, with an address and, ideally, an accreditation you can look up (see our guide on verifying the lab itself). A report with no lab name, or a lab that only exists on certificates, fails at line one.

The batch line: the field that decides everything

Somewhere near the top sits a batch or LOT reference. This single string ties the paper to physical material. If the reference on the certificate and the reference on the vial label are not the same string, character for character, the document describes something you do not have — however good its numbers look. This is the ten-second check, and it is the one most often skipped.

The analyses: purity, identity, and what each can say

A purity line (usually HPLC) reports how cleanly the material separated. An identity line (usually mass spectrometry) reports whether the molecule is the one named. These are different instruments answering different questions — a certificate can carry a beautiful purity number for the wrong substance. If only one analysis appears, it is almost always purity, and the identity question is simply unanswered. Our guide on what a purity percentage hides goes deeper.

The signature block

A responsible analyst or reviewer, named, with a date. Unsigned certificates and image-only stamps are weaker evidence, not none — but every missing element shifts the document from record toward decoration.

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