How to Read a Peptide Certificate of Analysis (COA)

What a COA is for

A certificate of analysis (COA) is the document that links a specific production batch to the analytical results obtained for that batch. It is not a general product description: it describes one lot, identified by a batch or lot number printed on the vial label and on the certificate.

For a laboratory, the COA is the starting point for traceability. It allows the material used in an experiment to be documented and, if results need to be reviewed later, traced back to the exact batch.

The header: product, batch and dates

The header normally states the compound name, the batch or lot number, the date of manufacture or analysis and, where applicable, a retest or expiry date. Check that the batch number on the certificate matches the label on the vial you received.

Identity

Identity testing answers the question 'is this the intended molecule?'. For peptides it is commonly performed by mass spectrometry, which compares the measured molecular mass with the theoretical mass of the sequence. The COA should state the method and the observed result.

Purity

Purity is usually measured by high-performance liquid chromatography (HPLC) and reported as a percentage of the main peak relative to all detected peaks. It describes how much of the detected material is the target peptide, not how much peptide is in the vial by weight — that is a separate measure (net peptide content), which is not always reported.

What can vary between batches

The set of tests listed can differ by product and by batch. Additional analyses such as water content, counter-ion content or endotoxin testing may or may not be included. Read what is actually listed rather than assuming a standard package.

Pepteria COAs list exactly which analyses were performed on the batch in question. If a document you need is not available for a batch, contact us and we will tell you plainly whether it exists.