How do I read a peptide COA?

1. The header: who, what, when

• Laboratory name and address, and a unique report number.
• Sample or item identification and the lot or batch number.
• Dates: when the sample was received or tested, and when the report was issued.
• The person authorizing the report. ISO/IEC 17025 expects these items on an accredited lab's report.

2. Identity: is it the named peptide?

EMA's guideline says identity can rest on molecular mass and sequence confirmation by mass spectrometry, retention time, LC-MS or peptide mapping. If the COA lists no identity result, nothing on it shows the sample is the compound named. For drug components, 21 CFR 211.84 treats at least one specific identity test as the minimum for relying on a supplier's report.

3. Purity: how much of the sample is other material?

EMA describes purity control as limits on total and individual impurities. Look for the method named, the result, and the limit it was held to. Check whether a chromatogram or spectrum is attached or available. 21 CFR 211.194 expects lab records to hold those graphs and spectra, though whether a given COA attaches them varies.

4. Content: how much peptide is there?

EMA lists liquid chromatography, amino acid analysis, nitrogen analysis and qNMR as ways to assay peptide content, with limits expressed on a counter-ion-free, anhydrous basis. Water and counter-ion (such as acetate or residual TFA) are separate items in EMA's specification and characterisation sections.

Our inference from that basis: a freeze-dried powder includes water and counter-ion, so its peptide content is below its total weight, and a purity percentage cannot be turned into milligrams per vial. If a COA reports no content result, it does not report one.

5. Other results

• Residual solvents: ICH Q3C groups them into classes to avoid, to limit by permitted daily exposure, and low-toxicity solvents.
• Elemental impurities: ICH Q3D sets permitted daily exposures for 24 elements.
• Endotoxin: FDA's Q&A describes gel-clot, photometric and kinetic methods. It is a different test from sterility.

6. Limits and conclusions

WHO's model pairs each result with the acceptance criteria applied. A result with no limit cannot be judged as pass or fail. We do not give a purity percentage or an endotoxin level that counts as acceptable, because acceptable values depend on the product and use.