What is a certificate of analysis (COA)?

A COA is a one-page report of a batch's test results.

A labelled example

An illustrative example, not a real batch.

What each part means

• Batch or lot number: links the report to one specific production run.
• Sequence and formula: what the molecule is meant to be.
• Expected vs observed mass: the mass spectrometry check. If they match, the identity is confirmed. Try the calculator to work out the expected mass yourself.
• Purity (HPLC): how much of the sample is the target peptide. See HPLC purity.
• Appearance: a quick visual check, usually a white powder.
• Test date and lab: when and where the testing was done.

Good habits when reading a COA

Check that the batch number on the COA matches the batch number on the vial, that the observed mass matches the expected mass, and that the test date is recent and relevant to that batch.