How to Read a Peptide COA
A Certificate of Analysis (COA) is the batch-specific lab document that proves what is actually in the vial - its identity and its purity. You cannot judge a research peptide by looking at the powder, so the COA is the single most important trust document. This guide explains every section, what the numbers mean, and how to spot a weak or fake COA.
In short: a genuine peptide COA is tied to a specific batch or lot number and shows real test data, not just a claim. It should include an HPLC purity figure with a chromatogram (research standard is ≥97-98%), a mass-spectrometry (MS) identityresult confirming the molecular weight, the net peptide content, plus the test date and the testing lab. If any of those are missing, treat the number with caution.
What is on a real COA
1. Identity - Mass Spectrometry (MS)
Confirms the vial actually contains the peptide it claims to, by measuring the molecule's mass. The observed mass should match the theoretical mass of the peptide (within a small tolerance).
No MS on the COA means the identity is unverified - you may have a pure sample of the wrong thing.
2. Purity - HPLC
High-Performance Liquid Chromatography measures what percentage of the sample is the target peptide versus impurities. Shown as a percentage and a chromatogram - look for one dominant peak. Many small peaks mean more impurities.
Research standard is ≥97-98%. Below ~95% is questionable for reproducible work.
3. Net Peptide Content
The actual mass of peptide versus total powder. The rest is water and counter-ions (salts) left over from synthesis. A sample can be 99% pure by HPLC but only ~80% peptide by mass - both numbers matter.
4. Water & Counter-ion Content
Residual moisture (often by Karl Fischer titration) and the counter-ion (commonly acetate or TFA) from the synthesis process. Reported as percentages; useful context for the net peptide figure above.
What the numbers mean
| Field | What good looks like | Why it matters |
|---|---|---|
| HPLC purity | ≥97-98%, with a chromatogram | How much of the sample is the target peptide |
| MS identity | Observed mass matches theoretical mass | Confirms it is the right molecule |
| Net peptide content | Stated as a %, the higher the better | Actual peptide mass vs total powder |
| Batch / lot number | Present and matches the vial label | Ties the data to your specific vial |
| Date + lab | Test date and testing lab named | Traceability and accountability |
How to spot a weak or fake COA
- No batch or lot number, or one that does not match the vial label.
- A purity claim with no method named and no HPLC chromatogram - just "99%" written on a page.
- The same COA reused for every order, rather than one tied to your specific batch.
- No mass-spectrometry identity - a purity figure tells you how pure, but not pure of what.
- No test date, no lab name, no analyst or signature.
- An image-only PDF with no readable data or traceability.
- A rounded "100%" purity - real HPLC almost never reads exactly 100%.
Quick checklist before you trust a COA
See real per-batch COAs
Most vendors claim to have COAs; far fewer publish them. Every compound we list is backed by a per-batch Certificate of Analysis with HPLC purity and mass-spec identity, published for anyone to check - use this guide to read them yourself.
View our lab reportsRelated research resources
Research Use Only: This guide is informational and describes how laboratory documentation is structured. It is not medical, legal, or investment advice. Baltic BioLabs content and products are for laboratory research purposes only and are not intended for human consumption.