How to Read a Certificate of Analysis (COA)

A Certificate of Analysis (COA) is the document that ties a specific production lot to the analytical results measured on it. For research laboratories it is the primary record used to confirm that the material received matches what was ordered, and it should be filed alongside your experimental records.

1. Header and traceability fields

• Product name and nominal quantity (for example, 10 mg per vial).
• Lot or batch number — this must match the number printed on the vial label.
• Date of analysis, and ideally the name of the testing laboratory.
• Molecular formula and theoretical molecular weight of the compound.

If the lot number on the COA does not match the vial, the document does not describe your material. Check this first.

2. Purity by HPLC

Purity is usually reported as a percentage from reversed-phase HPLC with UV detection (commonly 214–220 nm, where the peptide bond absorbs). The figure is the area of the main peak divided by the total area of all integrated peaks. A value such as 99.87% means the target peak accounts for 99.87% of UV-absorbing material detected under that method.

• Look for the chromatogram itself, not just the number — a single sharp dominant peak is expected.
• Note the column, mobile phase and wavelength if listed; purity values are method-dependent.
• HPLC purity does not measure water, counter-ions (e.g. acetate or TFA) or salts, so it is not the same as net peptide content.

3. Identity by mass spectrometry

Mass spectrometry (typically ESI-MS) confirms that the main component has the expected molecular weight. The COA should show an observed mass alongside the theoretical mass; agreement within the instrument's tolerance supports correct identity. Multiply charged ions ([M+2H]²⁺, [M+3H]³⁺) are normal for peptides and are deconvoluted back to the parent mass.

4. Appearance and physical tests

Lyophilized peptides are normally described as a white to off-white powder or cake. Some COAs also list solubility, water content (Karl Fischer) or peptide content. Discoloration or a collapsed, sticky cake that differs from the stated appearance is worth documenting.

5. Quick verification checklist

• Lot number on COA = lot number on vial.
• HPLC purity meets your protocol's acceptance criterion, with the chromatogram shown.
• Observed mass matches theoretical mass.
• Analysis date is recent and the testing lab is identified.
• Appearance on receipt matches the COA description.

Every Zorva Lab lot is published in our COA Library, so you can complete this checklist before ordering.