How We Test Every Batch Before It Ships
The three checks every SKU passes in-house before release, what's actually printed on a COA, and how independent third-party verification works if you want it.
"Tested for purity" is a claim almost every research-peptide supplier makes somewhere on their site. It rarely comes with specifics — which test, what threshold, run by whom, on every batch or just the ones someone happens to ask about. This post is about what that claim actually means at QSC Peptidology: the three tests every batch goes through before it's allowed to ship, what a Certificate of Analysis (COA) actually contains, and the mechanism we use for independent verification when a customer wants it.
The three in-house checks
Every production batch — not a sample of batches, every one — passes three sequential checks in-house before it's released to the catalog. A batch failing any one of them is rejected outright; we don't blend a failing batch with a passing one to bring an average back into spec, and we don't ship partial batches.
Reverse-phase HPLC (high-performance liquid chromatography) at 220 nm measures purity — the main peak has to clear 99.0% before a batch passes. This is the same analytical method used across the pharmaceutical industry to separate a compound from its synthesis byproducts and degradation products, and it's the number most customers mean when they ask "what's the purity."
LC-MS (liquid chromatography–mass spectrometry) confirms identity — that the molecule in the vial actually has the molecular weight of the peptide on the label, within a tight tolerance of the theoretical value. Purity alone doesn't tell you that; a batch could be 99% pure and still be the wrong molecule if something went wrong upstream in synthesis. LC-MS is the check that catches that.
An endotoxin (LAL) test screens for bacterial endotoxin contamination, reported in EU/mg (endotoxin units per milligram). This matters most for anything that will be reconstituted and used in cell or animal research, where endotoxin contamination can confound results independent of the peptide itself.
All three run before a batch is released — not after, not on request. It's the baseline every SKU on the site has already cleared by the time you can add it to a cart.
What's actually on a COA
Every order ships with that specific batch's Certificate of Analysis: the batch ID (which also appears on the vial label and the product page you ordered from), the HPLC purity percentage and chromatogram, the LC-MS mass comparison (theoretical value vs. what was actually observed, with the delta reported), and the endotoxin result. It's tied to one batch, not a generic template — if a batch turns over, the COA for the new batch reflects that new batch's actual results, not a copy-pasted old one.
Independent third-party verification
In-house testing is the release gate on every batch, automatically. Independent third-party testing is a separate, customer-initiated option on top of that — it isn't run by default on every SKU, and we won't tell you a specific batch already has a third-party result unless it genuinely does.
If you want it: send a sample of your batch to an independent lab (Janoshik.com is the one we point customers to) and share the report with us. If it passes, we reimburse the cost of the test. If it fails, we refund the full order — including the test cost — and pull that batch from sale. That last part matters as much as the reimbursement: a failed independent test doesn't just get made right for the one customer who tested it, it takes the batch off the site.