What Is a COA?
A Certificate of Analysis (COA) is a document issued by a laboratory (ideally independent and third-party) that certifies the identity, purity, and quantity of a compound. For research peptides, a COA should confirm: the peptide is what the seller claims it is, the purity percentage, the absence of contaminants (endotoxins, heavy metals, residual solvents), and the quantity per vial.
What to Look For
Key elements of a trustworthy COA: (1) Issued by a third-party lab (not the manufacturer's own lab). (2) Purity >98% by HPLC (High-Performance Liquid Chromatography). (3) Correct molecular weight confirmed by mass spectrometry. (4) Endotoxin testing (Limulus Amebocyte Lysate or recombinant Factor C) — critical for injectable peptides. (5) The COA should be dated and reference a specific lot number that matches the product you received.
Red Flags
Red flags on or around a COA: No third-party testing. COA is a generic document with no lot number. Purity listed below 95%. No endotoxin testing for injectables. COA is undated or from years ago. The lab name is vague or not independently verifiable. Sellers who refuse to share COAs or make them difficult to find.