How to read a Certificate of Analysis
A Certificate of Analysis is the only document standing between a stated purity figure and an unverified claim. It is also routinely filed without being read. This guide covers what to check and, more usefully, what a certificate cannot tell you.
Identity
Identity confirmation answers whether the material is the compound named on the label. It is normally established by mass spectrometry, reported as an observed molecular weight compared against the theoretical value for the sequence.
A close match confirms the molecule. A certificate that reports purity without first establishing identity has skipped the more fundamental question.
Purity
Purity is typically determined by high-performance liquid chromatography (HPLC) and reported as a percentage of total peak area.
The percentage alone is less informative than the chromatogram. A single dominant peak with a flat baseline is a different result from the same percentage accompanied by several minor peaks, even though both may be reported as 98%.
Where a certificate includes the chromatogram, read it. Where it reports only a number, the number is an assertion rather than a demonstration.
Lot traceability
The lot or batch reference is what connects the certificate to the material in hand. Without it, a COA describes some batch of the compound rather than yours.
The check is mechanical: the lot on the certificate must match the lot on the container. If they differ, the certificate is documentation of a different production run and tells you nothing about what you received.
The test date matters for the same reason. A certificate predating the production run it claims to describe is an inconsistency worth raising.
What a COA does not establish
A certificate records the condition of a sample at the moment it was tested by the laboratory that tested it. It says nothing about handling afterwards.
Peptides degrade with heat, light and freeze-thaw cycling. A genuine 99% certificate is fully compatible with degraded material if the cold chain broke in transit or storage.
It also does not establish independence on its own. A certificate issued by the supplier attests to the supplier's own testing. Third-party certificates carry the name and accreditation of the testing facility — which is the detail worth locating before anything else on the page.
For research use only. Not for human consumption, diagnostic, therapeutic or veterinary use. This material is provided for laboratory reference and is not medical advice.