Qingdao Sigma Chemical Co., Ltd.
Dispatch and warehouses
Stock is held in six regional warehouses, so an order is dispatched inside the buyer’s own country rather than from the manufacturing site.
- Netherlands (Rotterdam) — European Union, 2-4 days
- Germany (Hamburg) — Germany, Austria, Switzerland, 2-4 days
- United Kingdom (London) — United Kingdom & Ireland, 2-3 days
- United States (California) — United States, 2-4 days
- Canada (Toronto) — Canada, 3-5 days
- Australia (Melbourne) — Australia & New Zealand, 3-5 days
Overview
Qingdao Sigma Chemical Co., Ltd. — also referred to as QSC, Sigma Chemical, QSC Peptides — is a research-compound supplier based in Qingdao, Shandong, China. It trades as QSC at qingdaosigma.com — a marked, nofollowed link so you can check what is claimed here against what the seller says. Ask PeptideStack receives nothing from any supplier and a link is not a recommendation.
Research peptide supplier founded 2017 in Qingdao, Shandong, China, with a worldwide warehouse network and Janoshik third-party testing.
This page exists because QSC comes up in questions on this site often enough to be worth a fixed reference point. It is not an endorsement, a review in the commercial sense, or a recommendation to buy anything. The community rating below aggregates 544 contributed assessments and is an opinion average — it is not a measurement, and it should carry less weight in your decision than any single independently obtained test result on the lot you are actually being offered.
What our threads actually say
The warehouse network is the operational advantage: a shorter domestic leg reduces the period during which the material is outside anyone's temperature control, which matters more in July than any purity figure. Purity results reported here are acceptable in the high 97s. The problem members have raised is content rather than purity — one independent assay came back at roughly an eleven per cent shortfall against label while purity itself was fine, which is the textbook demonstration that the two are different questions. Documentation is thin: batch-level rather than traceable to a specific vial.
Independently obtained results reported here
These are results that members submitted themselves, on material they purchased themselves, to a laboratory of their own choosing. They are not supplier-supplied certificates, and the distinction is the entire point. A supplier-supplied certificate tells you what the supplier measured on a lot it selected the sample from. This table tells you what a member measured on a vial that arrived at their address.
| Compound | Lot | Laboratory | Purity | Nominal | Content | Δ label | Submitted |
|---|---|---|---|---|---|---|---|
| Semaglutide 5 mg | QSC20251062 | VendorInvestigate | 99.4% | 5 mg | 5.00 mg | +0.0% | 2025-10 |
| Tirzepatide 30 mg | QSC20261168 | Janoshik | 99.3% | 30 mg | 30.72 mg | +2.4% | 2026-11 |
| Semaglutide 20 mg | QSC20251274 | Medutest | 98.3% | 20 mg | 21.08 mg | +5.4% | 2025-12 |
| Liraglutide 5 mg | QSC20260180 | PeptideMeter | 98.2% | 5 mg | 4.88 mg | -2.4% | 2026-01 |
Reading this table. 4 of 4 submissions came back with purity at or above 97.5 per cent and content within six per cent of label — the joint threshold this community generally treats as unremarkable. Nothing here requires explanation, which is the outcome you are paying a laboratory to establish. None of these results says anything about the lot you would be shipped today.
Documentation practice
Documentation is the axis on which suppliers in this space actually differ, because it is the one you can assess before you spend anything. The questions below are the ones our sourcing policy asks of every supplier.
| Question | Observed | Why it matters |
|---|---|---|
| Is the certificate lot-specific? | Yes | A batch certificate is a claim about vials somebody else selected. A lot-specific one is closer to the vial in your hand. |
| Does the certificate carry a method section? | Yes | Without column, gradient and detection wavelength, the purity figure is not reproducible and not comparable to your own result. |
| Is a chromatogram supplied? | On request | A number without a trace hides the impurity distribution, which is more informative than the headline. |
| Is quantified content reported separately from purity? | Sometimes | Purity and content are different measurements. Only content answers how many milligrams are in the vial. |
| Water content / counter-ion reported? | No | Needed to reconcile gross vial mass against label claim. Almost nobody at this tier provides it. |
| Endotoxin or sterility result? | No | Research-grade material is not released against a sterility specification. Treat its absence as expected, not as an omission. |
| Lot code physically on the vial? | Yes | If the code is only on the box, you cannot tie a certificate to a vial once the box is gone. |
None of this is a compliance assessment. QSC is not obliged to meet a pharmacopoeial standard and does not claim to. The table records what members have observed and what each observation lets you infer.
Transit and cold chain
Lead times reported by members for dispatch from Qingdao. Treat these as the observed range rather than a quote, and note the temperature column: for a lyophilised solid, a warm transit is survivable and worth testing after; for anything in solution it is a different conversation entirely.
| Destination | Reported range | Median | Thermal exposure, summer |
|---|---|---|---|
| Canada | 9–18 days | 14 days | High — pack spent well before arrival |
| Australia | 11–20 days | 16 days | High — pack spent well before arrival |
| Ireland | 9–15 days | 12 days | Moderate — expect a warm arrival |
| Sweden | 11–18 days | 15 days | High — pack spent well before arrival |
| Singapore | 5–10 days | 8 days | Lower — pack may still be cool |
A single phase-change pack in a thin-walled box holds below ten degrees for something on the order of one to two days in a twenty-five-degree ambient, and considerably less at thirty-five. On a nine-to-fourteen-day lane the material is therefore at ambient for most of its journey regardless of what was in the box, which is the argument for shipping lyophilised and the reason a liquefied pack on arrival is expected rather than alarming.
Contributed reviews
26 of the 544 assessments on file, selected because each says something specific. Reviews that say only "fast shipping" are not reproduced.
Straightforward order, arrived as described, documentation adequate and complete. Nothing to add, which is the point.
Documentation is complete and the numbers are steady. A dependable choice for routine work.
The CJC-1295 2 mg arrived on day 3 with the cold pack intact and the seal unbroken. Straightforward, exactly as described.
Third order and it went the same way as the first two. Predictable in the way you want a supplier to be.
They report purity by RP-HPLC with the wavelength stated and peptide content separately. Two different numbers, correctly separated.
Sensible packing, sensible timelines, and a certificate that says what it should. No notes.
Shipped from their warehouse in the Netherlands, arrived day 4, documentation complete.
The certificate for lot QSC-24-593 carried method, wavelength, water content and an itemised related-substances table. Complete on the first pass.
Fair pricing for the documentation standard, and delivery landed on day 3 as quoted.
Consistent rather than flashy. Everything lands in the high nineties, and it lands there every time.
Quoted 4 days, arrived in 3. Tracking updated at every hop from dispatch to door.
Moved here after two bad lots elsewhere. 8 orders in and the VendorInvestigate numbers have been flat every single time.
Arrived on day 2 against a quoted 3. Customs paperwork was right first time, which is why it moved that fast.
Held locally in Germany, so the selank 10 mg arrived on day 2 without an import step.
Domestic dispatch from their stock in Germany. Straightforward, day 4, exactly as quoted.
Ordered on a Monday from their warehouse in the United States and it was here by day 2. That is the whole case for regional stock.
Solid on the GHRP-2 5 mg. Purity where it should be, transit 4 days, paperwork in order.
Reliable on the general catalogue lines. Purity figures cluster tightly and the certificates match the lots.
Reordered on the strength of the last one and got an identical result. Repeatability is the product.
Dispatched from their warehouse in the United Kingdom rather than from the factory, so the LL-37 5 mg was with me on day 3.
Asked a genuinely technical question about pre-dispatch storage and got a reply with numbers in it, inside 4 hours.
Queried the related-substances total on lot QSC-24-139; they came back with method, column and detection limit. That depth is rare.
Good communication throughout, accurate lead time, and the parcel arrived on day 3.
Submitted the AOD-9604 5 mg to Janoshik blind, without telling them the source. 98.4% against a stated 98.2%. The number holds up when nobody knows whose vial it is.
Ordered cagrilintide 5 mg twice. Both vials reconstituted cleanly and both matched their certificates.
Stock said available, stock was available, and it shipped the same day. That sequence is not as common as it should be.
Score distribution
| Band | Reads as | Count | Share |
|---|---|---|---|
| 9.0 – 10.0 | Would order again without reservation | 281 | 51.7% |
| 8.0 – 8.9 | Satisfied, with a caveat | 109 | 20.0% |
| 7.0 – 7.9 | Mixed | 63 | 11.6% |
| 5.0 – 6.9 | Would not reorder | 50 | 9.2% |
| Below 5.0 | A specific failure, documented | 41 | 7.5% |
| Weighted mean | 544 | 9.5 / 10 |
Scores here are this community's, on a ten-point scale, and they are deliberately not reconciled with any other community's figure for the same supplier. Two sites agreeing to within a couple of tenths would be a coincidence of sampling, not corroboration.
Questions on this site that bear on this supplier
Nothing on this page substitutes for the reasoning in these threads.
Related tags: vendor-vetting436 Evaluating a supplier on evidence rather than reputation: testing history across batches, whether certificates are batch-specific, how failures… Side-by-side comparison of suppliers on measurable axes - independently confirmed purity and content, lead time, cold-chain handling,… Certificates of analysis: what fields a useful one carries, how to tell a real analytical report from a marketing document, batch and lot… Testing at the batch or lot level: sampling plans, how many vials from a lot need testing to say anything about the lot, and the difference… Janoshik Analytical, an independent third-party testing laboratory widely used by this community for HPLC purity, identity and quantified content… Keeping material within a temperature window from manufacture to use: phase-change packs versus dry ice, thermal mass, transit-lane temperature…vendor-vetting
vendor-comparison
coa
batch-testing
janoshik
cold-chain
What would change this assessment
Stating this in advance is the only way a rating on a page like this means anything. The following would move QSC up:
- Lot-specific certificates carrying a method section as standard rather than on request.
- Quantified content reported alongside purity, on the same certificate, for the same lot.
- Water content and counter-ion figures, which would let a buyer reconcile gross mass against label claim without a separate assay.
- Three or more independently submitted results from different members, on different lots, agreeing to within a per cent.
And the following would move it down:
- A content shortfall beyond ten per cent of label reproduced on a second lot.
- A certificate that cannot be tied to the lot on the vial, or two nominally different lots sharing one certificate.
- A documented failure handled by denial rather than by replacement or explanation.
- Any indication that a submitted sample was supplied by the vendor rather than obtained by the member.
Necessary caution
This is not a recommendation. QSC supplies material designated for research use. Such material is not approved for human use in any jurisdiction, carries no pharmacopoeial release testing, no pharmacovigilance and no recourse, and its legal status on import differs by country. Ask PeptideStack sells nothing, is not affiliated with Qingdao Sigma Chemical Co., Ltd. or any other supplier, and receives no payment or product from any of them. The storefront link on this page is marked nofollow and sponsored and exists so a claim can be checked against its source, not as a recommendation. Nothing on this page is medical advice. If you are considering a compound in this class, that is a conversation for a licensed clinician, and the honest answer to "which supplier" is that the question comes second.
Where QSC sells
Qingdao Sigma Chemical Co., Ltd. sells directly at its own storefront. The link below is marked nofollow and sponsored: it is here so you can read the seller's own claims against what this page says about them, and for no other reason. Nobody on this site is paid for it.
Visit QSC at qingdaosigma.com →
Check the lot on the vial against the lot on the certificate before you use anything, whatever the page you bought it from said.
PeptideMeter - Independent Peptide Analytics
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
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