How to Read a Certificate of Analysis
A certificate of analysis (COA) is the document that tells you what is actually in the vial. Plenty of suppliers publish something they call a COA; far fewer publish one that would survive scrutiny. Here's how to read one properly and what separates a real test report from a marketing graphic.
The four things a real COA must have
- A lot or batch number that matches the number printed on your vial.
- The name of the testing laboratory and the date the analysis was performed.
- The analytical methods used — at minimum HPLC for purity and mass spectrometry for identity.
- The raw data: an actual chromatogram and mass spectrum, not just a summary number.
HPLC purity — what the number means
High-performance liquid chromatography separates a sample into its components and measures the area under each peak. A purity figure of 99.1% means the main peak accounts for 99.1% of the total detected peak area.
Read the chromatogram, not just the headline number. You want one dominant, symmetrical peak. A cluster of smaller peaks around the main one suggests related impurities — typically truncated or deleted sequences from synthesis.
Mass spectrometry — proving identity
HPLC tells you the sample is pure. It does not tell you it's the right compound. Mass spectrometry measures molecular weight, which should match the theoretical mass of the sequence within a small tolerance.
A COA with purity data but no identity data is incomplete: it confirms you received something pure, not that you received the peptide you ordered.
Lot numbers and traceability
The lot number is the link between the paperwork and the physical vial. If the COA's lot doesn't match your label, the document describes different material and tells you nothing about what you have.
Reputable suppliers can produce the COA for your specific lot on request, not just a generic example from an unrelated batch.
Red flags
- No lot number, or a lot number that doesn't match your vial.
- A purity percentage with no chromatogram behind it.
- No testing lab named, or an in-house-only report with no third-party verification.
- Reported purity of exactly 100% — real chromatography does not produce that.
- An undated report, or one dated years before the batch was produced.
- Image-only PDFs that look assembled in a design tool rather than exported from instrument software.
What Nexeva Labs publishes
Every lot we sell is tested by an independent laboratory using HPLC and mass spectrometry, and the report for your specific lot is available on request. Batch testing details live on our Batch Testing page, and you can request a lot-specific COA through our contact form with the number printed on your vial.
Frequently asked
Is 99% purity meaningfully better than 98%?
For most research applications the difference is small, but the trend matters: a supplier consistently reporting 98–99% with full chromatograms is more credible than one claiming 99.9% with no supporting data.
Should the COA be from a third-party lab?
Yes. In-house testing can be legitimate, but independent third-party analysis removes the conflict of interest and is the standard you should expect.
How do I get the COA for my specific lot?
Send us the lot number printed on your vial through the contact form and we'll email the matching report.
Does a COA mean the product is approved for human use?
No. A COA is a statement of chemical purity and identity only. All materials sold here are for laboratory research use only and are not approved for human or veterinary use.
All products and information referenced here are for laboratory research use only. Not for human or veterinary consumption, diagnostic, or therapeutic use.