How to read a peptide COA: purity, identity and copper content

What a COA is

A certificate of analysis (COA) is a report for one specific batch. It lists the tests performed, the method used for each, the result and the date. A COA that is not tied to a batch number tells you little.

Purity by HPLC

HPLC purity is usually reported as an area percentage: the share of the detected peak area that belongs to the target peptide. It measures UV-absorbing, peptide-related impurities. It does not account for water, salts or counter-ions, so a purity figure is not the same as the peptide content of the powder.

Ask for the chromatogram as well as the number, and for the method conditions: column, gradient and detection wavelength.

Identity by mass spectrometry

Mass spectrometry checks that the measured molecular weight matches the expected one. For a copper complex, the isotope pattern of copper (63Cu and 65Cu) is a useful additional check that copper is actually present in the detected species.

Peptide content, water and counter-ions

Lyophilized peptide powder contains water and counter-ions such as acetate. Net peptide content tells you how much of the weighed powder is actual peptide. If you need to prepare solutions by weight, this matters.

Copper content

For copper peptides, the amount of copper and its ratio to the peptide are part of the specification. Ask which elemental method was used to measure it.

Red flags

• No batch number, or a batch number that does not match the label.
• No method, no date, or no named laboratory.
• One generic COA used for every batch.
• A screenshot or image instead of a report.
• The product name on the COA differs from the product name on the label.

Check a batch on this site

Enter a batch number on the COA lookup page to see the batch record held by us. If a batch is not listed yet, contact us and ask for its documentation.