Get a certificate of analysis (COA) before your lab works with any peptide batch. A COA from a third-party lab tells you what is actually in the vial — not just what the seller claims. Here is exactly what to look for and what the numbers mean.
What a Peptide COA Actually Shows
A COA is a lab report. An independent lab receives your peptide, runs tests on it, and writes down the results. "Third-party" means the lab has no financial interest in the product passing — it is not the manufacturer’s own in-house lab.
A complete peptide COA will list at minimum:
- Purity percentage — how much of the powder is the target compound versus everything else
- Identity confirmation — proof the compound is what it claims to be
- Batch or lot number — ties this report to a specific production run
- Test date — tells you when the analysis was done
- Lab name and accreditation — who ran the tests and whether they are qualified
If any of those five items are missing, the document is incomplete. A purity number with no lab name attached to it is just a number someone typed.
HPLC Peptide Testing
HPLC stands for high-performance liquid chromatography. The lab pushes the dissolved peptide through a column at high pressure. Different compounds travel through at different speeds. The machine plots a graph — each peak is a different compound. The area under the target peptide peak, divided by the total area of all peaks, gives you the purity percentage.
That percentage is the number you care about most. For research-grade peptides, ≥98% purity by HPLC is a widely used benchmark. Results below 95% mean a meaningful fraction of the sample is something unknown. Results below 90% represent a more significant concern for analytical work.
The COA should show the actual chromatogram graph, not just the final number. If you only see "purity: 98.5%" with no supporting data, you cannot verify how that number was calculated. A real lab report includes the peak areas so the math is checkable.
HPLC confirms purity but does not always confirm identity on its own. That is why a complete COA pairs HPLC with a second test.
The Full Test Suite
Purity alone is not enough. A compound can be highly pure and still be the wrong compound. The tests that belong on a complete peptide COA are:
| Test | What it checks |
|---|---|
| HPLC | Purity — how much is the target compound vs. other material |
| Mass spectrometry (MS) | Identity — confirms the molecular weight matches the stated compound |
| Moisture content | How much water is in the powder, which affects the actual mass of active material |
| Residual solvents | Leftover chemicals from manufacturing |
Mass spectrometry is the identity test. Every peptide has a specific molecular weight. The mass spec either matches or it does not. If the COA only shows HPLC and skips mass spec, identity cannot be confirmed.
Moisture content matters because peptide powders absorb water from the air. A vial labelled 5 mg might contain less active material than stated if moisture content is high and has not been corrected for. Look for a moisture figure on the COA.
Third-Party Tested Peptides in the USA
Third-party tested means the testing lab is separate from the company that made or sold the peptide. In the USA, reputable labs used for peptide testing include accredited analytical facilities that hold ISO/IEC 17025 certification — a standard that means the lab’s measurement methods have been independently audited.
When reviewing a COA, check whether the lab name is searchable. A real lab has a website, a physical address, and contact information. You should be able to contact them and ask whether a specific report is genuine. Some labs now provide QR codes or report numbers you can verify directly on their site.
One practical check: compare the test date to the batch date. If the COA was issued for an earlier production run, the report does not cover what you have. Each batch needs its own COA. Reusing an old report for a new batch tells you nothing about current quality.
The Short Version
A peptide COA is only useful if it comes from a genuinely independent lab, shows HPLC purity of 98% or above, includes a mass spec identity confirmation, and is dated to the same batch you are receiving. Check that the lab is real and that the report number is verifiable. If the document checks all those boxes, you have meaningful evidence about what is in the vial. If it skips any of them, you are working with incomplete information.
NXT Labs products are sold strictly as research chemicals for in vitro research, laboratory testing and analytical purposes only, and are not intended for use in any human or animal application.
NXT Labs supplies research peptides for laboratory use. Browse the full range or view current Certificates of Analysis.
