How to Read a Certificate of Analysis (COA) for Research Peptides

A Certificate of Analysis (COA) is the primary document describing the identity, purity, and quality of a research compound. For laboratory work, the COA is how a researcher verifies that a material matches its specification before it is used in any experimental protocol. This overview explains the sections you will typically find on a peptide COA and what each one tells you.

Identity and structure

The identity section confirms that the material is the intended molecule. For peptides this usually includes the sequence, molecular formula, and molecular weight, often verified by mass spectrometry (MS). The measured mass should correspond to the theoretical mass for the stated sequence within the method's tolerance.

Purity (HPLC)

Purity is most commonly reported by high-performance liquid chromatography (HPLC), expressed as a percentage representing the proportion of the main peak relative to total detected material. Research-grade peptides are frequently specified at high purity thresholds; the COA should state the method, column conditions, and the resulting chromatogram or value.

Mass spectrometry data

MS data accompanies HPLC to confirm identity. The reported observed mass, alongside the calculated mass, allows verification that the dominant HPLC peak corresponds to the target molecule rather than an impurity of similar retention time.

Physical description and content

This section describes appearance (for example, a white lyophilized powder), net peptide content, and the counter-ion or salt form where relevant. Net peptide content can differ from gross weight because lyophilized material may include water and counter-ions.

Lot, storage, and handling

A COA is lot-specific. It should reference a lot or batch number that matches the vial, along with recommended storage conditions for the research material. Matching the lot number on the document to the lot on the container is a basic verification step.

What to verify before use

• The lot number on the COA matches the vial.
• The stated identity (sequence, formula, mass) matches the product specification.
• The purity method and value are reported, not just a headline percentage.
• MS observed mass corresponds to the calculated mass.

COAs document analytical characteristics of a research material; they describe identity and purity, not suitability for any human or therapeutic application. All materials referenced here are intended for laboratory and research use only.