How to read a certificate of analysis

A certificate on its own proves nothing. It only means something once you have checked that it belongs to the vial in front of you — which is what this page is for.

The lot number is the document

Every synthesis run is a distinct lot. The reagents, the run and the yield differ each time, so purity is measured per lot, not per compound. A certificate for one batch says nothing about the next — it is a different material with its own result.

The lot number printed on the vial label is what ties a specific certificate to a specific vial. If the two numbers do not match, the certificate describes different material, however similar it looks otherwise.

What HPLC measures

Reversed-phase HPLC separates a sample by how strongly each component binds to the column, then reports the result as a chromatogram: a series of peaks, each one a distinct compound eluting at its own retention time.

Purity is the area of the target peak as a proportion of the total area under every peak — the figure printed on our certificates, to two decimal places, never rounded up. HPLC is precise about proportion. On its own it is not proof of identity: a contaminant that happens to elute at the same retention time as the target compound would not be flagged as separate. That is what mass spectrometry is for.

What mass spectrometry adds

Mass spectrometry measures the mass-to-charge ratio of the ionised sample and compares it against the compound's theoretical molecular weight. Where HPLC answers how much of the sample is the target compound, MS answers whether that compound is actually the right one.

A certificate carrying both an HPLC purity figure and an MS result is confirming two separate things: proportion, and identity. Ours are published together for that reason.

Three ways a real certificate misleads

None of the following require a forged document. All three happen with a certificate that is entirely genuine.

1. Wrong lot, right compound. The document is authentic, but it was issued for a different batch than the one in your hand. Nothing on it is false — it simply is not a certificate for your vial. The lot number is what tells you.
2. Salt form, not peptide content. A purity figure can describe the compound including a counter-ion — an acetate or TFA salt — rather than the peptide itself, which reads several points higher than a freebase figure would. Check what the percentage is measured against, not only the number.
3. In-house testing, presented as verification. A certificate produced by the seller's own laboratory is not independent, whatever the letterhead says. An independent certificate names a testing laboratory that is not the seller.

How we publish ours

Every batch is sent to an independent laboratory for HPLC and MS testing before its certificate exists. The result is published against the lot number as soon as it returns — the certificate itself, not a summary of it.

A lot still at the laboratory is marked AWAITING LAB rather than left off the site, and is listed as pending in the COA library alongside the lots already released.