How to Read a Peptide Certificate of Analysis (COA)
A certificate of analysis is the only evidence that the powder in a vial is what the label claims. Learning to read one takes ten minutes and permanently changes how you evaluate vendors. Here's what each section means and what to check.
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 load-bearing item — it must match the batch printed on your vial. A COA without a batch number, or a vendor reusing one COA across many batches, tells you the document is decoration.
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 with no chromatogram attached — real results look like 99.42%, not "99%+".
Mass spectrometry — identity, not just purity
HPLC alone shows how clean the material is, not what it is. Mass spec confirms the molecular weight matches the target sequence — for example, ~1419 Da for BPC-157. 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.
How we handle it
Every batch we list is tested by independent laboratories before sale — HPLC purity, endotoxin, heavy metals and sterility — and the certificates are published on our certifications page, matched to the batch ID on each vial. If a batch fails any assay, it is destroyed, never discounted. For research use only — not for human or veterinary use.