Five things a certificate has to state
A certificate of analysis is evidence only when it names its laboratory, batch, method, date and result. Why each field matters, and how to check one.
"Certificate of analysis" is not a protected title. Any document can carry it. What makes one evidence is whether it can be tied to a batch and checked against the laboratory that issued it. Five fields decide that, and a certificate missing any one of them is not published on this site.
1. A named laboratory
The first question is who ran the analysis. A purity figure produced by the party selling the material is an assertion, however many decimal places it has. An independent laboratory, named on the document, is a party that can be asked.
2. A batch identifier
The batch identifier ties the document to the material. Without one, a certificate describes a sample, not the vial in the box. The batch reference on the packing note is what it is matched against.
3. A stated method
A result means what its method makes it mean. Purity by HPLC is a ratio of peak areas at one detection wavelength. Identity by mass spectrometry is a measured mass set against a computed one. A certificate that gives a percentage and no method cannot be compared with any other certificate. What an HPLC purity figure measures covers the first of those in full.
4. A test date
A result describes a sample on the day it was analysed. The date says how old the evidence is. An undated certificate could describe any batch from any year.
5. A legible result
The figure itself, readable, and with it the trace it came from where the laboratory supplies one. A cropped scan, or a number retyped into a table, cannot be checked against anything.
Checking a certificate
Where the issuing laboratory runs a public results portal, look the report up there by its reference instead of relying on the copy a seller shows. A certificate that matches the laboratory's own record has been checked. A certificate that only matches the seller's file has been read.
What happens here to one that falls short
It is not published, and the listing it would belong to shows an empty trace in its place. The assay library holds every certificate on file, and counts them.
Reports commissioned by customers go into the same library, unedited and marked as customer-submitted, including when they disagree with ours. The rule in full is in Quality and methodology. What the figures on a listing mean before any certificate exists is in Four figures that identify a peptide.