Quality · 7 min read
How to Read a Peptide Certificate of Analysis
A field-by-field guide to a research peptide COA: lot number, HPLC purity, LC-MS identity, net peptide content, endotoxin, and what a trustworthy certificate looks like.
A certificate of analysis (COA) is the only document that connects a specific vial to specific test results. For a laboratory, it is the difference between a reagent you can cite and one you cannot. This guide walks through each section of a peptide COA and the questions worth asking before a lot goes into an experiment.
1. Lot number and traceability
Every COA should name a lot (batch) number that matches the label on the vial. A certificate that shows no lot number, or a lot number that does not match the vial, tells you nothing about the material in your hands. North Wall prints a QR code on every label that opens the certificate for that exact lot.
2. The testing laboratory
Look for the name of the laboratory that ran the analysis and its accreditation. ISO/IEC 17025 is the international standard for the competence of testing and calibration laboratories. A certificate issued by the seller alone, with no named third-party lab, is a claim rather than evidence.
3. Purity by HPLC
High-performance liquid chromatography (HPLC) separates the target peptide from synthesis by-products such as truncated or deletion sequences. Purity is reported as the target peak's share of total peak area, usually at a UV wavelength near 214 or 220 nm. A chromatogram should be attached so the reader can see the main peak and any impurities, not just a single percentage.
4. Identity by mass spectrometry
HPLC shows how pure a sample is, but not what it is. Liquid chromatography-mass spectrometry (LC-MS) confirms identity by comparing the observed molecular mass with the theoretical mass of the sequence. The two tests answer different questions, and a complete COA reports both.
5. Net peptide content
A lyophilized vial contains the peptide plus counter-ions (often acetate or trifluoroacetate) and residual water. Net peptide content is the share of the powder that is actually peptide, measured by quantitative methods such as amino acid analysis or quantitative HPLC. Two vials with the same purity can hold different amounts of peptide.
6. Safety and contaminant screens
Endotoxin (typically by the LAL method), sterility or microbial screening, and heavy metals (by ICP-MS) are reported as pass or fail against a stated specification. The specification limit should be printed next to each result.
7. Dates and signatures
A COA should show the date of analysis and the name or signature of the reviewing analyst. A certificate older than the lot it describes, or with no date at all, should be questioned.
A short checklist
- Lot number matches the vial
- Named, accredited third-party laboratory
- HPLC purity with the chromatogram attached
- LC-MS identity against theoretical mass
- Net peptide content
- Endotoxin, microbial, and heavy-metal results with limits
- Date of analysis and reviewer
Every North Wall lot is tested against an eight-assay panel and the certificate is posted before the lot ships. See the full testing panel or search the COA library.
Educational content for laboratory professionals. North Wall products are for in-vitro research only and are not for human or veterinary use.