How to Read a Peptide Certificate of Analysis (COA)
A peptide COA is a lab report on one batch. Check that it names the batch, the lab, the methods and the results, and that you can verify it with the lab that issued it.
What a COA is
A certificate of analysis is a laboratory report on a sample from one batch. It is evidence about that batch, not about a brand or a product line. A useful COA lets you trace the report to the vial in your hand.
The lines to look for
| Line on the report | What it tells you |
|---|---|
| Product name and batch or lot number | Which material was tested |
| Laboratory name and test date | Who tested it, and when |
| Identity (mass spectrometry) | Whether it is the right molecule |
| Purity (HPLC) | How much of the detected material is the target peptide |
| Methods | How each result was measured |
| Sample or report ID | How to look the report up with the lab |
Reading the HPLC purity result
HPLC separates the sample into its parts. Purity is the main peak's share of the total peak area, given as a percentage. If a chromatogram is attached, look for:
- One dominant peak.
- A flat, steady baseline.
- Any smaller peaks small and well separated from the main one.
Peptides are usually read at a wavelength of about 214 to 220 nm. A good report names the wavelength and method.
Reading the mass spec identity result
Mass spectrometry measures the mass of the molecules in the sample. If the observed mass matches the expected mass for that peptide within the instrument's tolerance, the sample is consistent with the right compound.
The strongest reports show the expected mass, the observed mass and the difference. A line that just says 'conforms' is a conclusion with less to check. Larger peptides often show several charge states, so you may see a raw spectrum and a calculated single mass. Both are normal.
Purity and identity answer different questions. See HPLC vs mass spectrometry.
What a COA does not tell you
- Exact amount in the vial. HPLC purity is a ratio, not milligrams. See purity vs content.
- Untested contaminants. Endotoxin or heavy metals need their own panels. If a panel is not listed, it was not run.
- Batches it does not name. A report covers its own batch only.
A five-point check
- Does the product name and strength match what you ordered?
- Does the batch on the report match the batch on your vial or order?
- Is the lab named, and is it independent of the seller?
- Are both identity (mass spec) and purity (HPLC) reported?
- Can you look the report up on the lab's own site and see the same results?
The last point matters most. A PDF can be edited or reused. A report you can pull up on the lab's own website, by its report ID, is much harder to fake.
Warning signs
- One certificate used for several products or many batches.
- No lab name, or only a logo with no contact details.
- Results that cannot be found with the issuing lab.
- Certificates available only after you pay.
Common questions
Is a 99% purity figure enough on its own?
No. Purity says how clean the sample is, not what it is. Look for an identity result from mass spectrometry alongside it.
Why does the batch number matter so much?
Because a certificate only speaks for the batch that was sampled. A report for a different batch tells you nothing certain about the vial you received.
How old can a certificate be?
There is no single rule, but the report should match the batch you are buying. A recent batch with an old, unrelated certificate is a reason to ask questions.
How we handle it
Every MPGA Labs batch is tested by HPLC and mass spectrometry to 99% purity or better. The certificate comes from Purity Spectrum Analytics, an independent lab, and you can verify it on that lab's own site. See how it works on our testing page, then browse the catalog.