Reading a Certificate of Analysis: batch traceability for research peptides

A certificate of analysis is a short document, rarely more than a single page, that accompanies every batch of research peptide you order from a serious supplier. It answers four questions a careful researcher should always ask before opening the vial.

Identity

The COA confirms the compound is what it claims to be. Expect a mass spectrum reference, either ESI or MALDI, with the observed monoisotopic mass alongside the theoretical value. The two should agree to within one or two daltons. A mismatch here is worth a phone call before anything else.

Purity

The HPLC trace is the main piece of evidence. Look at the target peak (it should dominate the chromatogram), at the integration percentage, and at the method: column, mobile phase, gradient, flow rate. A 99% purity figure means different things at 210 nm vs 280 nm detection — the wavelength matters.

Net-peptide content

This number tells you how much of the powder in the vial is actually target peptide, as opposed to salts, counter-ions and water. For lyophilized research material, net-peptide content is typically 60–90% of the gross weight. Your concentration calculations for reconstitution should use net, not gross — or your nominal 1 mg/ml stock will actually be closer to 0.7 mg/ml.

Traceability

The lot number and manufacture date tie the COA to the vial in your hand. If you run the same experiment with two different batches and the results diverge, the lot numbers are the first thing to reconcile. Our lab-account archive keeps every COA we have ever issued under your profile — searchable by compound, date or order number.

If your COA is missing from the shipment, or the batch number on the vial does not match the certificate in your account, contact us immediately. Reconciliation takes minutes; publishing a result on the wrong batch does not.