A walkthrough of every field on a certificate of analysis: batch number, sequence, molecular formula, purity method, appearance, water content and release date.
Match the batch code first
A certificate that does not carry the batch code printed on your vial does not describe your material. Stop and contact us before beginning work.
What a certificate of analysis is
A COA is the analytical record for one specific batch. It is not a marketing document and it is not transferable between lots. If the certificate you hold does not carry the batch code printed on your vial, it does not describe your material.
Field by field
- Product name and sequence — the compound identity in one-letter or three-letter amino acid code.
- Batch or lot number — must match the vial label exactly.
- Molecular formula and theoretical molecular weight — the calculated values for that sequence.
- Observed molecular weight — measured by mass spectrometry for this batch; should match the theoretical value within tolerance.
- Purity and method — the HPLC peak-area percentage, ideally with the gradient, column and detection wavelength.
- Appearance — normally ‘white lyophilised powder’.
- Water content — residual moisture, where determined.
- Quantity per vial — the nominal peptide content.
- Manufacture and release dates — when the batch was made and cleared for supply.
- Testing laboratory — whether analysis was in-house, third-party, or both.
Reading the attached chromatogram
Most certificates append the HPLC trace and the mass spectrum. Look for a single dominant, symmetrical peak with a clean baseline, and a deconvoluted mass that lands on the theoretical figure. A shoulder on the main peak, a rising baseline, or an unexplained secondary peak of any size is worth a question before the batch enters a study.
Red flags
- No batch number, or a batch number that does not match the vial.
- A purity figure with no stated method.
- No mass spectrometry data, only HPLC.
- A certificate dated long before the batch, or with no dates at all.
- Identical chromatograms reused across different compounds.
Supplied for laboratory research use only. Not for human or veterinary use.