A certificate of analysis (COA) is how a supplier shows what’s in a vial. Most COAs look official, but many say much less than they seem to. Here’s how to read one, section by section, with extra checks for a blend like GLOW.
The header: who tested what, and when
- Product name and lot or batch number. These must match your vial. A COA without a lot number is a marketing document.
- Testing laboratory. An independent third-party lab is better than in-house testing. The lab should be a real, contactable business.
- Test date. A COA from several years ago doesn’t describe this month’s stock.
- Verification code or QR link, if the lab offers one. It lets you confirm the report on the lab’s own site.
HPLC: how pure is it?
High-performance liquid chromatography (HPLC) separates the compounds in a sample and reports the target peak’s area as a percentage of the total. That percentage is the purity figure you see advertised, for example “≥99%”.
- Ask for the chromatogram, not just the number. You should see one dominant peak per component, with small or no side peaks.
- Blends are harder. GLOW contains three peptides, so a good COA reports each peak separately instead of one combined purity figure.
- HPLC purity doesn’t confirm identity. A pure sample of the wrong peptide still scores high.
Mass spectrometry: is it the right molecule?
Mass spectrometry (MS) measures molecular mass, which is how you confirm identity. Compare the observed peaks with the expected values:
| Component | Expected mass (approx.) | Common problem |
|---|---|---|
| GHK-Cu | ≈402 Da (complex); GHK alone ≈340 Da | Free GHK without copper, or the wrong copper ratio |
| BPC-157 | ≈1419.5 Da | Truncated sequences, or unstated salt forms |
| TB-500 | ≈889 Da | Full thymosin beta-4 (≈4,960 Da) sold as “TB-500” |
Other tests worth seeing
- Net peptide content. Lyophilized powder also contains counter-ions and water, so a “10 mg” fill can contain less than 10 mg of actual peptide. Net content testing shows how much is real peptide.
- Endotoxin (LAL) testing and sterility results, where they’re relevant to your research model.
- Heavy metals. This is especially relevant for copper-containing GHK-Cu.
Signs a COA may not be genuine
- The same COA image is used for several products or lots.
- There’s no lab name, or the lab can’t be found or contacted.
- Fonts and formatting are inconsistent, or numbers look edited.
- Purity is exactly 100% or suspiciously round.
- There’s an HPLC result but no mass spec, so identity is never confirmed.
Next, see the full buyer’s checklist or vendor red flags.
Educational content only. Research peptides are not approved for human or veterinary use.