How to read a peptide COA: identity, purity and batch
Updated: October 8, 2026
A COA (certificate of analysis) is a laboratory report with the results of the tests run on a specific batch. On its own it guarantees nothing: it is worth as much as the method, the laboratory and the traceability of the batch.
What it should contain
- Identification: product, batch number, test date, laboratory and report number.
- Identity: mass spectrometry (MS) confirming that the measured mass matches the theoretical mass of the peptide.
- Purity: high-performance liquid chromatography (HPLC) with UV detection, usually at 214–220 nm.
- Optionally, net peptide content, water and counter-ion (TFA or acetate).
Purity is not identity or content
A 99% HPLC purity means the main peak takes up 99% of the chromatogram area. It does not prove that peak is the right molecule (the mass confirms that) nor how many milligrams of peptide are in the vial (that requires measuring net content).
How to check it is genuine
- The batch number on the report matches the vial label.
- The laboratory lets you verify the report with its number or a code on its website.
- The full chromatogram is shown, with time axis and integrated peaks, not just a number.
- Date, client and method are consistent. A report issued to a distributor describes the sample that client sent.
How we do it at PureGen
On the Quality page we publish the reports from external laboratories supplied by the manufacturer, with laboratory, date, report number and purity. They cover manufacturer batches and not necessarily the exact batch you will receive, and we say so on every product page.