How to Read a Peptide Certificate of Analysis (COA)
A certificate of analysis ties an analytical result to the powder in a specific batch. The essential checks take about ten minutes to learn: confirm the batch identity, then read the purity and contaminant results in context.
The identity block
Every legitimate COA starts by identifying exactly what was tested: peptide name, batch/lot number, test date, and the laboratory that performed the analysis. The batch number is the critical item: it must match the batch printed on your vial. A COA without a batch number, or one reused across many batches, functions as decoration rather than batch-level evidence.
HPLC purity — the headline number
High-performance liquid chromatography separates the contents of the vial into peaks; the purity figure is the target peptide's share of the total peak area. A "99.4% purity" result means 99.4% of detected material was the intended peptide, with the remainder typically being truncated sequences and synthesis by-products.
What to check on the chromatogram: a single dominant peak, a stated retention time, and the analysis wavelength (usually 214 or 220nm). Be skeptical of round numbers when no chromatogram is attached. Actual results are typically reported as values such as 99.42%, rather than "99%+".
Mass spectrometry — identity, not just purity
HPLC alone shows how clean the material is, not what it is. Mass spec confirms that the molecular weight matches the target sequence; for example, BPC-157 has a molecular weight of ~1419 Da. A COA carrying both HPLC and MS is the standard for identity plus purity. The observed mass should sit within roughly one dalton of theoretical.
Endotoxin (LAL) testing
Endotoxins are bacterial cell-wall fragments that can confound biological assays even at trace levels. A peptide can be 99.9% pure and still carry meaningful endotoxin. The limulus amebocyte lysate (LAL) assay reports results in endotoxin units (EU) per mg or mL against a stated threshold. "PASSED" with a stated limit is acceptable; a numeric result is better.
Heavy metals and sterility
ICP-MS screening covers lead, mercury, arsenic and cadmium introduced through raw materials or equipment. Sterility testing confirms the lyophilized product carries no viable microbes. Both matter most for long-duration studies where contaminants accumulate.
Red flags, in order of severity
- No batch number, or COA batch doesn't match the vial.
- No named, independent laboratory; "in-house testing" is not verification.
- Purity claimed with no chromatogram or method details.
- HPLC only, with no mass-spec identity confirmation.
- One aging COA covering a product sold continuously for years.
Batch-testing policy
Independent laboratories test every batch we list before sale for HPLC purity, endotoxin, heavy metals and sterility. We publish the certificates on our certifications page and match each one to the batch ID on the vial. If a batch fails any assay, it is destroyed and never discounted. For research use only — not for human or veterinary use.