How to Read a Peptide Certificate of Analysis (COA)
A Certificate of Analysis is the paper trail behind a research material. This guide walks through each field on a typical peptide COA and what it does, and does not, tell you.
What a COA is
A Certificate of Analysis (COA) is a document issued by a testing laboratory that reports the results of analytical tests performed on a specific batch of material. For research peptides, it is the main way a lab can check that the compound in the vial matches what was ordered.
A COA describes one batch. It is only meaningful when the batch or lot number on the certificate matches the batch you received.
Header fields: client, sample and batch
The header usually lists the client (the company that submitted the sample), the sample name, the batch or lot number, the date received, and the date tested. Check that the sample name and batch match your vial label.
A report number or unique identifier lets you reference the certificate when contacting the supplier or the lab.
Identity testing
Identity tests confirm that the material is the expected molecule. Mass spectrometry (MS) compares the measured molecular weight against the theoretical weight of the peptide sequence. A close match supports identity.
Some certificates also report the observed retention time on HPLC compared against a reference standard.
Purity results
Purity is usually reported as a percentage from HPLC, based on the area of the main peak relative to all detected peaks. A purity value describes chromatographic purity, not the net peptide content of the vial.
Look for the chromatogram itself, or at least the peak table, so the reported percentage can be traced to data.
Red flags
Missing batch numbers, no test date, no laboratory identification, results that are identical across unrelated products, or a certificate that cannot be tied to the batch received are all reasons to ask questions before using a material in an experiment.
Niho Labs publishes its certificates on the COAs page so researchers can review them before ordering. All materials are for laboratory research use only and are not for human consumption.