What is a COA (Certificate of Analysis), and how do I read one?

Question

pepmg · Accepted Answer

A Certificate of Analysis is a lab's report on a specific batch of material. For research peptides it usually reports two things: identity (is this molecule actually the peptide on the label, confirmed by mass spectrometry) and purity (what fraction of the sample is the intended peptide, measured by HPLC and reported as a percentage; research-grade is typically at or above 98 percent). Some COAs add mass or quantity and tests for specific contaminants.

Reading one is a short checklist: does the peptide name and sequence match what you are buying; is there a mass-spec result; is HPLC purity stated as a real number rather than just “passed”; is there a batch or lot number and a date; and is a testing lab named, ideally one whose results you can look up independently. A COA covers the batch that was tested, not necessarily your individual vial, and it never proves safety or fitness for human use.