Pre-shipment testing in China: how peptide brands test a batch before it ships

Pre-shipment inspection vs pre-shipment testing

The WTO agreement on pre-shipment inspection (PSI) covers checks of the quality, quantity, price and customs classification of goods before export (WTO). For most products bought from factories in China, that means an inspector visits, counts cartons, checks labels and packaging, and samples units for visible defects. Sampling of this kind often follows the acceptance-sampling tables indexed by acceptance quality limit (AQL), as set out in ISO 2859-1 (ISO).

A peptide vial defeats a visual check. A vial of white powder looks the same whether it holds the right peptide, the wrong one, half the dose or nothing. For peptides, pre-shipment testing means sending sealed vials from the finished batch to a lab before you pay the balance and before the goods leave.

	General pre-shipment inspection	Lab pre-shipment test
What it checks	Quantity, packaging, labels, seals, visible defects	Identity, purity, content in mg, endotoxin, sterility, vial-to-vial spread
How it samples	Many units, by AQL table	A few sealed vials, picked at random
Where it happens	At the factory or warehouse	At the lab
What you get	An inspection report	A certificate of analysis with raw data

The two work well together. A third party inspection firm, or your own agent, can pick and seal the vials that go to the lab.

Why test before you pay the balance or before the batch ships

Before the balance is paid, a failed result is a reason to remake the batch. After the goods ship, the same result becomes a dispute about a shipment you no longer control.

Failures are common enough to plan for. Finnrick, which tests retail peptides bought from many sellers, wrote in February 2026 that “roughly one in three fail basic expectations” (Finnrick). Under its default standard (purity at least 99.5%, fill within ±35% of the label), its published counts include 2,988 passes and 824 fails for retatrutide, 391 passes and 395 fails for BPC-157, and 83 passes and 210 fails for CJC-1295 (Finnrick methodology; Finnrick data).

Origin does not decide the result. Several of the sellers at the top of Finnrick’s per-peptide leaderboards are direct sellers based in China (Finnrick data). In-house quality control varies from one manufacturer to the next, and testing is how a brand finds out where its own supplier stands. Resellers also use outside lab data to reject batches and to claim on supplier guarantees (r/Biohacking).

What to ask the manufacturer for before you sample

Ask for these before the batch is finished, and make the balance payment depend on an outside result that meets the agreed specification.

• A batch record summary: lot number, synthesis and fill dates, quantity filled, vial count, and the purification and freeze-drying steps.
• The in-house COA for this lot. The WHO model certificate lists what a complete one carries: batch number, manufacture and expiry dates, the specification, and for each test the method reference, acceptance criteria, result and conformity statement (WHO TRS 1010). Ask for the chromatogram and the mass spectrum behind it.
• The basis of the mg figure: total powder weight or net peptide, and which counter-ion (TFA or acetate).
• Retained samples: sealed vials of the same lot kept at the factory for a re-test. WHO guidance for quality control labs asks for retained samples large enough for at least two re-analyses (WHO TRS 957).
• Photos of finished vials with the lot number printed on them.

Our checklist for vetting a manufacturer covers the questions to ask before the first order.

How to sample a peptide batch

Who picks. You, your agent or an inspector. If the factory chooses the vials, it can choose good ones.

Which vials. Pick at random from different cartons, or from the start, middle and end of the fill run. Fill weight can drift during a run, and a spread of vials shows it.

Blind samples. Blind works in two directions. The factory should not know in advance which vials you will take. The lab should not see the label claim until the result is final; order with the label withheld. For GLP-1 products, a blind identification test reports which peptide is present without being told what to expect.

Seal and record. Put tamper-evident tape on each vial or bag, photograph each vial with its lot number, number them 1 to n, and note who picked them and when.

How many. Identity, purity and content can share one vial. Vial-to-vial consistency needs one vial per result, three at least. Endotoxin usually needs its own vial. Sterility needs its own unopened vials. Ask the lab for its numbers before the batch is picked.

Which tests to order at each stage

Stage	When	Tests	What it tells you
Sample approval	Before the first order	Identity (LC-MS), purity (HPLC), content per vial	The factory can make the right peptide at the right strength
Pre-shipment	Batch filled, balance not yet paid	Identity, purity and content on several random vials; vial-to-vial consistency; endotoxin; Sterility (USP <71>, 14 days) where it applies	This lot meets the agreed specification
Bulk powder lots	Before filling or resale	Add counter-ion, water content and residual solvents	What else is in the powder, and why the mg differs from the weight
Arrival check	Goods received	Identity and content on one or two vials	The shipped stock is the lot that was tested

Sterility incubates for at least 14 days, so send those vials first. The chemistry results usually arrive well before it.

Compare the factory COA with the outside result

Put the two reports side by side and check each line:

Factory COA line	What to check	Why it matters
Purity, e.g. 99.5%	Wavelength, chromatogram, how peaks were integrated	Purity is a share of UV peak area; integration choices move it
Content, e.g. 10 mg	Total powder or net peptide; which counter-ion	Bachem’s worked example: 5 mg of powder at 85% net peptide content and 98.7% purity holds 4.195 mg of the target peptide (Bachem)
Identity “conforms”	Mass match or retention time	ICH Q6A: a single retention time alone is not specific (ICH Q6A)
Lot and dates	Same lot as the vials; test date after the fill date	A COA covers its own lot only
Endotoxin “pass”	A number, in EU per mg or EU per vial	A bare pass cannot be compared

The EMA peptide guideline expresses assay on a counter-ion-free, anhydrous basis (EMA). A factory that reports total powder weight will show more mg than a lab that reports net peptide, with neither one wrong.

Agree a tolerance before the test. Labs also differ: one published comparison of a single retatrutide batch at five labs found mass results 26% apart (Peptide Critic). Public reference points help: Peptigrity treats 95% to 110% of the label as “in line” (Peptigrity). Our guide to the factory COA vs a lab test goes line by line.

Sending samples and keeping each new batch tested

Samples from a factory in mainland China travel to the lab by courier. Declare them accurately, follow your courier’s rules and the rules of your market, and pack the lab’s sample form with them. Our guide to sending samples from China to Hong Kong covers packing.

Every lot is a new batch, even from the same factory and the same specification. Test each lot before the balance, check one or two vials on arrival, and keep a log of results per lot to spot drift. Re-test from scratch after any change: a new synthesis route, a new filling line or a new source of raw peptide. For the brand side, see what to test before your first batch ships.

What HK Analytical does for pre-shipment testing

Our lab is in Hong Kong. Samples from mainland China reach it by cross-border courier, and we send the sample form on request. One order covers any mix of identity (LC-MS), purity (HPLC), content per vial, blind GLP-1 identification, endotoxin (LAL), Sterility (USP <71>, 14 days), residual solvents, counter-ion (TFA, acetate), water content (Karl Fischer) 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.

Each report carries its raw data and our photo of the vial as received, and it is a signed record you can check on /verify. See the example report, batch testing for brands or ask for a quote.