How to Read a Peptide Certificate of Analysis

A certificate of analysis (COA) is the primary document tying a peptide vial back to the analytical work that verifies it. Knowing how to read one is the difference between accepting a supplier's word and verifying their work.

Identity fields

The top of a COA identifies the material: compound name, lot or batch number, test date, and storage conditions. The lot number is what ties this certificate to a specific physical inventory — when you receive a vial, the lot on the vial label must match the lot on the COA.

Purity (HPLC)

High-performance liquid chromatography separates the peptide of interest from impurities. The purity percentage reflects the area under the main peak relative to total integrated area. For most research applications a ≥98% floor is the convention; we publish a 99% floor on all batches before release.

Identity (Mass spectrometry)

Mass spec confirms that the molecule you bought is the molecule the vial says it is. The COA lists observed monoisotopic mass alongside theoretical mass — a delta under 0.05% is the accepted norm for confident identity confirmation.

Appearance and storage

Most peptides ship as a white-to-off-white lyophilized powder. Significant color, oily residue, or visible particulates on the COA appearance line warrant follow-up with the supplier before use.