Every lot we ship comes with a Certificate of Analysis. It is the document that turns a vial of white powder into a known quantity, and it is worth more than a glance before the lot goes into a protocol.
Identity
Mass spectrometry confirms that the observed molecular weight matches the one predicted from the sequence. A result inside the expected tolerance tells you the right molecule was made. It does not, on its own, tell you how much else is in the vial.
Purity
Purity is measured by high-performance liquid chromatography and reported as a percentage of total peak area. Our catalogue lots are specified at 98% or better.
The number matters less than the trace behind it. A chromatogram shows where the remaining few percent sit: one close-eluting shoulder is a different situation from a scatter of small late peaks. Ask for the trace if it is not attached.
A purity figure without a chromatogram is a claim. The chromatogram is the evidence.
Appearance and water content
Lyophilised peptide is normally a white to off-white cake or powder. Colour, stickiness or a collapsed cake can indicate moisture ingress, which matters because residual water drives hydrolysis during storage.
Lot number and date
A certificate describes one lot, not a product line. Check the lot on the certificate against the lot on the vial. If you are comparing results across months, note that two lots of the same compound are two different samples and should be recorded as such.
What a CoA does not do
It does not qualify a compound for your assay. Solubility in your buffer, behaviour at your concentrations and stability under your conditions are all things you establish yourself. The certificate tells you what you received; the rest is method development.
If anything on a certificate does not match the vial you have, stop and tell us before using the material.
