How to Read a Peptide Certificate of Analysis
A certificate of analysis is useful only when it can be tied to the material being reviewed. Treat it as a batch record to verify, not as a decorative purity badge.
Research-use boundary: This article concerns non-clinical laboratory documentation. It does not establish suitability for human or veterinary use and does not provide administration or protocol guidance.
1. Match identity before reading the percentage
Start with the material name, labeled quantity, lot or batch identifier, report number, and sample description. Those fields should match the container and the supplier record. A report for a different lot cannot establish the properties of the item in front of you.
2. Separate identity from purity
Identity asks whether the expected analyte was detected. Purity asks what proportion of a measured signal is attributed to the principal component under the stated method. These are different questions. A chromatographic area percentage, by itself, is not a complete identity determination and does not describe sterility, endotoxin, residual solvents, water content, or every possible impurity.
3. Read the analytical method and acceptance criteria
Look for the named method, instrument, reference standard, sample preparation, system-suitability information, result, units, and acceptance criteria. A bare number with no method or limit is difficult to interpret or reproduce. Confirm whether the report describes HPLC/UPLC, mass spectrometry, or another validated procedure, and whether the result shown is qualitative or quantitative.
4. Check dates, laboratory identity, and traceability
Record the sampling or receipt date, test date, report date, laboratory name, and authorized approval. If the report was amended, retain the revision history. Traceability means that the result can be connected through an unbroken record to the sample, method, reference material, and responsible laboratory process.
5. Note what the COA does not show
Do not infer unreported tests. If a property matters to an approved laboratory procedure, request the relevant lot-specific result and method. A marketing statement such as “lab tested” is not a substitute for the actual report.
COA review checklist
- Material name and labeled quantity match
- Lot or batch identifiers match
- Report number and revision are present
- Method and instrument are named
- Result, units, and acceptance criteria are clear
- Test and approval dates are present
- Laboratory and authorization are identifiable
- Limitations and untested properties are not overstated
Primary references
Peptide Simplified editorial team. Last reviewed July 29, 2026.