Verification · FAQ
Peptide COA questions, answered
The questions buyers ask about peptide Certificates of Analysis — answered directly, without the marketing. Each answer links into the full guides when you want the detail.
Contents
Before you order
Most peptide COA questions come down to three: is this document real, does it cover my batch, and what do the numbers actually mean? The answers above take each in turn. If you read nothing else, read the first three.
For the full walkthrough — every section of the document, line by line — see how to read a peptide COA (and spot a fake). For the foundations, start with what a peptide COA is.
Going deeper
Some answers deserve their own guides:
- Endotoxin testing for peptides — LAL vs rFC, EU limits, and when the result is required.
- Common peptide impurities — what the smaller peaks on the chromatogram actually are.
- Why third-party testing matters — the independence argument in full.
- Is your peptide actually third-party tested? — the buyer-side diagnostic.
And when you want a vial tested rather than a document checked, the cost guides for BPC-157, TB-500, semaglutide, and retatrutide itemize what a complete verification costs.
Frequently asked questions
What is a peptide COA?
A peptide COA (Certificate of Analysis) is a laboratory report for one specific batch of one peptide. It records what a lab measured: the identity of the molecule, its HPLC purity, and how much actual peptide is in the vial. It applies only to the lot number printed on it.
What should I check first on a peptide COA?
The lot number. If the lot on the COA does not match the lot on your vial, nothing else on the document is evidence about what you are buying. After that: the issuing lab's name, the LC-MS identity result, the HPLC purity with its method, and the quantitative content in mg.
Does 99% purity mean the peptide is good?
Not by itself. HPLC purity is the percentage of UV peak area belonging to the main peak under one method. It says nothing about identity (is it the right molecule?), content (how many mg are actually in the vial?), or endotoxin. A 99% pure vial of the wrong molecule is still the wrong molecule.
What is the difference between a vendor COA and a third-party COA?
Who issued it. A vendor COA comes from the manufacturer or seller, who profits from the result. A third-party COA comes from an independent lab with no stake in the sale. The instruments and methods can be identical; only the independent result is free of the conflict of interest.
Can one COA cover every batch a vendor sells?
No. A COA is a result for one production run, identified by its lot number. A vendor showing the same COA across months of sales, or across multiple products, is showing you a document — not evidence about your batch.
How can I tell if a peptide COA is fake?
Common signs: the same document reused across products, implausibly perfect numbers on every batch, a lab you cannot find or contact independently, a molecular weight that does not match the sequence, and no way to verify the report with the issuing lab. The strongest defence is a verification route hosted by the lab — a URL, QR code, or report number that shows the record the lab actually holds.
Why does the molecular weight on the COA matter?
Because it is the cheapest identity check available to a buyer. The theoretical mass of a peptide is calculated from its sequence. If the observed mass on the COA does not match within a small deviation, either the document is wrong or the vial does not contain the claimed molecule.
What is quantitative content, and why isn't purity enough?
Content (assay) is how many milligrams of actual peptide are in the vial. Lyophilized peptides carry water and counter-ion, so a vial labelled 5 mg often contains 3.8–4.5 mg of active peptide. Purity measures the chromatogram; content measures the vial. You need both.
Does a peptide COA need an endotoxin result?
For research-grade material, no. For anything intended to enter a living system, yes — a numeric value in EU with the method (LAL or rFC) named. Sterile filtering does not remove endotoxin, so 'sterile' on a label is not a substitute for an endotoxin result.
Should a COA show the HPLC chromatogram, or just the number?
The chromatogram. A purity percentage without the underlying trace cannot be checked: you cannot see the impurity profile, the baseline, or whether the integration was honest. A lab that will not share the chromatogram is asking you to trust a number you cannot reproduce.
What does a QR code or verification link on a COA prove?
Only what it points to. A QR code that opens the seller's own website proves nothing — the seller controls that page. A verification route hosted by the testing lab, showing the record for that exact lot, is meaningful because the party with no stake in the sale is the one vouching for it.
How much does it cost to get a peptide COA from an independent lab?
It depends on the peptide and the tests included — identity, purity, quantitative content, and endotoxin are priced separately. Our cost guides for BPC-157, TB-500, semaglutide, and retatrutide break down what a complete verification costs, item by item.