A certificate of analysis is a piece of paper, or more often a PDF, that says: this batch of compound, when tested by this method, came out at this purity and this identity. Every credible seller in this category publishes one for every lot. The problem is that almost any document can be made to look like a COA, and most buyers do not know what they are looking at when they download one.
This guide walks through what a real COA contains, what the numbers actually mean, and what to look for when you read one — from us or from anyone else in the category. It is not a defense of our reports. We hope you will compare ours to several others and reach your own conclusions about which sellers are credible.
What a COA actually is
A COA documents the result of analytical testing on a defined batch of material. For peptides, the two tests every credible COA must contain are identity (does the molecule have the structure it claims to have?) and purity (what fraction of the material is the molecule, vs. impurities?). Identity is usually established by mass spectrometry; purity is usually established by reverse-phase HPLC.
Below is a real COA from one of our recent BPC-157 lots, with the six things you should be checking labeled in blue. Read it like an inspector, not like a customer.
The six things every COA must contain
If any of these are missing, the document is not a COA in the meaningful sense — it is a marketing leaflet shaped like a COA.
- Compound name and sequence. Not a category, not a blend — the molecule, by its name, with its amino acids listed in order.
- Mass spec identity. Expected and observed mass, with the deviation. ESI-MS is the standard; MALDI is fine for some compounds.
- HPLC purity at a stated wavelength. 220 nm is the convention for peptides. Purity is the integrated area of the main peak.
- Retention time. The position of the main peak on the chromatogram. Lets you compare the same compound across lots and across sellers.
- Lot number and synthesis date. Must match the lot printed on the vial. Without this, the document is for some batch, somewhere, possibly years ago.
- Testing lab named. The COA documents an analysis performed somewhere. If the lab is not named, the document does not document an analysis.
Every lot we sell has its COA posted on our public lab reports page. No login, no email gate, no PDF behind a contact form. If you want to check a lot before you order, scroll the page and check the lot.
Three red flags that should make you walk away
The other side of a good COA is a bad one. These are the three patterns we see most often in COAs published by sellers we do not trust.
| pattern | what's actually going on |
|---|---|
| No mass spec — only HPLC. | HPLC alone proves a single peak. It does not prove that peak is the molecule you ordered. The vial could be 99 % pure something else. |
| Tested in-house. | A seller testing its own product on its own equipment has every incentive to round up. If you cannot independently verify the lab, you cannot independently verify anything. |
| One COA, used for every lot. | If the lot number on the COA never changes, the seller is showing you a single old analysis and stapling it to every new vial. Demand the COA for your lot. |
What a COA does not show
A COA covers identity and purity. It does not cover sterility, endotoxin load, or heavy metals unless those tests are explicitly listed. For most research applications, this is fine. For applications where sterility matters, ask the seller for the additional reports — and treat the absence of them as data.
A COA also does not prove the compound was synthesized recently. Peptide stability varies. A clean COA from two years ago is less informative than a clean COA from two months ago, even if the test numbers are identical. Look at the synthesis date alongside the test result.
Why we wrote this
The honest answer is that the category is full of sellers who use the language of analytical chemistry without doing analytical chemistry. We compete with them on price and we cannot compete with them on price all the way down, because part of our cost is paying a third-party lab on every batch.
If you read this and then look at a COA on a competitor's site and decide it looks better than ours, that is a fine outcome for us. We would rather lose a sale to a credible seller than win one against a buyer who could not tell the difference.