How to vet a Chinese peptide manufacturer: a 12-point testing checklist for new brands

How to vet a peptide manufacturer in China: the short version

Judge a manufacturer on paper first, then on your own test results. Ask for documents that show how it tests each lot. Send its samples to an outside lab before you order. Test the first production batch before you pay the balance. Then keep testing every lot. This checklist covers each step.

Why test results decide

In-house quality control varies from one manufacturer to the next, and testing is how a brand finds out where its supplier stands. Origin alone tells you little. Several of the sellers at the top of Finnrick’s per-peptide leaderboards are direct sellers based in China (Finnrick data). Of the products it tests, Finnrick wrote in February 2026 that “roughly one in three fail basic expectations” (Finnrick).

Many listings on Janoshik’s public results page come from manufacturers in China that publish their reports as marketing; Janoshik states it does not endorse the companies listed (Janoshik). A public report is a good sign that a factory tests at all. It shows the one sample the factory chose to send.

Your customers will also look past the factory’s paperwork. Peptigrity, a rating site, does not accept a vendor’s in-house testing (Peptigrity). What counts for your brand is an outside report on your own lot.

The 12-point checklist

#	Check	A good answer looks like
1	Lot-specific in-house COA	Lot number, test date, method per result, chromatogram, mass spectrum
2	Identity method	A mass match by LC-MS, not a retention time alone
3	Basis of the mg figure	Net peptide or total powder stated; counter-ion named
4	Release specification	Purity, impurity and endotoxin limits written down
5	Retained samples	Sealed vials kept from each lot, for a stated period
6	Outside reports	Verifiable at the issuing lab, for the same lot
7	Your own sample test	Identity, purity and content, with the label claim withheld
8	Production batch test	Random vials tested before the balance is paid
9	Batch ID on the vial	Printed on every vial, not only on the box or website
10	Terms for a failed batch	Remake or refund on a failed outside result, in writing
11	Change notice	Warning before any change of route, line or raw material
12	Every lot tested	A per-lot log of results

Documents to ask for (checks 1 to 6)

1. A COA for the exact lot. The WHO model certificate lists the fields a complete COA carries: batch number, manufacture and expiry dates, the specification, and for each test the method, acceptance criteria, result and conformity statement (WHO TRS 1010). A COA with no lot number, or a lot that does not match your sample, describes some other material.

2. How identity was shown. ICH Q6A says identification by a single chromatographic retention time is not specific (ICH Q6A). Ask for the mass spectrum with the expected and measured mass. See identity by LC-MS.

3. What the mg means. Peptide powder also holds counter-ion and water. The EMA peptide guideline expresses assay on a counter-ion-free, anhydrous basis and says the counter-ion must be defined and controlled with an upper limit (EMA). Ask whether “10 mg” means powder or peptide, and whether the salt is TFA or acetate. A counter-ion test answers the second question.

4. The release specification. Ask for the limits the factory releases against. For reference, under the EMA guideline peptide-related impurities are reported above 0.1%, identified above 0.5% and qualified above 1.0% (EMA).

5. Retained samples. Ask the factory to keep sealed vials from each lot. WHO guidance for quality control labs asks for retained samples large enough for at least two re-analyses (WHO TRS 957).

6. Outside reports you can check. Open each one on the issuing lab’s own site with its report code. Confirm the lot and the product match.

Tests to run yourself (checks 7 and 8)

7. Test the samples. Send the factory’s pre-production samples to a lab for identity, purity and content per vial. Withhold the label claim. Compare the result with the factory COA on the same basis; our guide to the factory COA vs a lab test shows how.

8. Test the first production batch before the balance. A sample may come from a different run than your order. Random vials from the finished lot tell you what you are buying. The method is in pre-shipment testing.

Terms that protect you (checks 9 to 12)

9. Batch ID on every vial. Finnrick’s labelling score gives 2 for a batch ID printed on the vial, 1 for one on an insert and 0 for one on a website only (Finnrick).

10. Written terms for a failed batch. Agree what happens when an outside result misses the specification. Resellers use lab data to reject batches and claim on supplier guarantees (r/Biohacking).

11. Notice of changes. A new synthesis route, filling line or raw-material source can change the product. Ask to be told first, and re-test after any change.

12. Test every lot. One good batch qualifies one batch.

Lines in a factory COA that need a second look

• Purity printed to three decimals, with no chromatogram.
• Identity given as a peptide name only, with no mass data.
• The label claim printed as if it were a measured quantity.
• One report reused across several products, or a lot number shared with another seller. PeptideBenchmark lists both among its COA anomaly signals and says the signals are not allegations (PeptideBenchmark).
• Endotoxin shown as “pass”, with no number or unit.
• “Sterility” that turns out to be a PCR screen or a microbial count.

None of these proves the material is wrong. Each one is a reason to test before you rely on the document. More in how to verify a Chinese manufacturer’s COA.

What HK Analytical does for brands vetting a manufacturer

Our lab is in Hong Kong. Samples from mainland China reach it by cross-border courier; declare them accurately, follow your courier’s rules, and we send the sample form on request. One order covers any mix of identity (LC-MS), purity (HPLC), content per vial, counter-ion (TFA, acetate), water content (Karl Fischer), endotoxin (LAL), Sterility (USP <71>, 14 days) and vial-to-vial consistency. Results within days of receipt. Sterility (USP <71>, 14 days) is the one test that takes 14 days, because the method incubates for 14 days. Every number comes with its raw data. Each report carries our photo of the vial as received and is a signed record you can check on /verify. See the example report and batch testing.