Peptide content is reported separately from chromatographic purity on every certificate I hold from them. Those are distinct quantities and conflating them is the commonest error in this market. Documentation practice rather than a single purity figure is the substance of this.
Vendor documentation · maintained record
GenScript Biotech Corporation
Solid-phase peptide synthesis house trading as GenScript Peptides (genscriptpeptides.com), based in Nanjing, Jiangsu, China, established 2002. Janoshik-tested and verified by Medutest, PeptideMeter and VendorInvestigate; catalogues 350+ research compounds alongside custom synthesis work, each shipped with a lot-specific certificate of analysis.
9.4703 community reviews Verified
Dispatch and warehouses
Stock is held regionally, so an order ships from within the buyer’s own country rather than from the manufacturing site. Current lines and lead times are published by the supplier itself: order direct at genscriptpeptides.com →
- 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
Identity
- Legal name
- GenScript Biotech Corporation
- Short code
GSP- Also known as
- GSP, GenScript Peptides, GenScript Biotech
- Storefront
- genscriptpeptides.com →
- City
- Nanjing
- Region
- Jiangsu
- Established
- 2002
- First documented here
- 3 Jun 2025
- Specialty
- Solid-phase peptide synthesis and custom sequences; 350+ research compounds catalogued
- Record state
- Verified
The storefront is linked so a reader can verify a supplier directly. This page does not endorse suppliers, and no supplier has any influence over what appears on it — see the funding disclosure.
Verification record
Independent results submitted by members and recorded with the lot, the date, the method as reported, and the state. 4 of 4 verified, across 4 independent services, first recorded 3 Jun 2025.
| Date | Service | Compound | Lot | Method as reported | Result | State |
|---|---|---|---|---|---|---|
| 2026-06-24 | Janoshik | Retatrutide 10 mg | GSP-2606-0118 | RP-HPLC, 214 nm | 98.7% area vs 98.5% stated | verified |
| 2026-01-29 | PeptideMeter | Tirzepatide 10 mg | GSP-2601-0774 | RP-HPLC, 220 nm | 98.1% area vs 98.0% stated | verified |
| 2025-10-08 | Medutest | Semaglutide 5 mg | GSP-2510-0341 | RP-HPLC + LC-MS | 98.4% area; identity confirmed | verified |
| 2025-06-17 | VendorInvestigate | Documentation audit | n/a | Document review across 8 certificates | Complete; content and water reported separately | verified |
- 2026-06-24, Janoshik: Declared and independent figures inside method repeatability. Peptide content and counter-ion content are reported separately on the certificate, each with its unit.
- 2025-06-17, VendorInvestigate: Every certificate reviewed carried the method, the column and gradient, the water content by Karl Fischer and a signed, dated release. The synthesis record was produced against the lot number on request, including for a lot released eighteen months earlier, and named the purification step.
Documentation quality
5/5Assessment
4Records
4Services used
12Reviews on file
Certificates are written to a synthesis convention rather than a trading one: purity by RP-HPLC with the column, the gradient and the wavelength stated, peptide content reported separately, water by Karl Fischer, and counter-ion content given as a figure with its unit. The related-substances table is itemised with retention times rather than reported as a single total. The synthesis record is available against the lot number and has been produced for lots eighteen months old, naming the purification step rather than summarising it.
Maintainers' assessment
Verified across all four independent services, with the declared and independent figures agreeing inside method repeatability on every submission on file, and the declared figure never the higher of the two. What separates this record from most in the directory is that the documentation is generated by the house that made the material, so counter-ion and water content are stated as figures rather than omitted and a buyer can convert to working mass without assuming anything. Set against that, two limits belong on the record. The catalogue runs to 350+ compounds and the four records below cover four of them: breadth of catalogue is not breadth of evidence, and the lines nobody here has submitted remain unmeasured. Separately, and unrelated to material quality, contributors have consistently recorded four to five working days for the custom-synthesis desk to return a quotation, against same-day response on catalogue enquiries. Nothing adverse is on record against the material itself.
What to ask for
The documents above are what members were sent. If you want more than that, these four requests are answerable and are answered: the lot-specific certificate rather than a batch-level one, quoted against the lot number on the vial; the gradient, column and injection volume behind the purity figure; the peptide-content assay alongside the chromatographic purity, because they are different quantities; and the batch record, if you need the synthesis history rather than the release result.
Ask before you order rather than after. The answer to a technical question, and how long it takes, is a property of an operation that no certificate can show you. The catalogue, the current lead times and the contact route are on the supplier's own site: visit genscriptpeptides.com →
Community reviews
12 reviews from members with a record on this site. Aggregate rating 9.4 of 10 across 703 reviews.
Asked which column and gradient the purity was integrated on and had all three parameters plus the wavelength in one reply, without a sales paragraph attached. The answer came from somebody who evidently runs the method rather than files it.
Recording a process observation rather than a material one, because it belongs on the record. Five working days elapsed between my custom-sequence enquiry and a quotation. Catalogue enquiries from the same address were answered the same afternoon. The build, once quoted, completed three days inside the stated window.
Water content by Karl Fischer printed on the certificate as issued rather than supplied on request. The distinction matters: a figure produced on demand is a figure somebody chose to produce.
Nine days Nanjing to the Netherlands, scanned continuously, customs documentation correct at first presentation. The absence of dead intervals in the scan record is what makes a transit estimate usable.
Nine vials from a single lot, nine matching codes across glass, certificate and invoice. One vial reconstituted with a faint haze that cleared on standing; recorded as an observation, not a defect, and offered as a single observation.
Synthesis record returned inside one working day against a lot code quoted in the subject line. It named the purification step rather than describing it in general terms, which is the difference between a record and a summary.
Certificate retrieved for an order placed thirteen months earlier, produced without a stated reason being required. Retention practice is part of documentation quality and is rarely tested until it matters.
Related substances itemised with retention times rather than aggregated into a single total. An aggregate figure cannot be interrogated; an itemised table can.
Second submission of the same line at fourteen months: 98.4% then, 98.5% now, identical certificate layout on both. Process consistency across time is a stronger signal than any single figure.
Material and documentation both correct. Recorded at nine rather than ten because the outer carton was lighter than I would specify for glass; the inner packing carried the protection and nothing was damaged.
Counter-ion content stated as a figure with its unit, so the conversion from label mass to working mass required no assumption. On a 10 mg vial the difference is larger than most buyers allow for.
Where GSP sells
GenScript Biotech Corporation sells from its own storefront. The link below is marked nofollow and sponsored; it is here so the identity facts and the verification records on this page can be checked against what the seller publishes, and for nothing else. This site is paid nothing for it.
Visit GSP at genscriptpeptides.com →
Whatever a storefront claims, the lot on the vial has to match the lot on the certificate. That check is yours and nobody else can do it for you.
Sourcing topics worth reading alongside this record
General sourcing discussion, listed because it bears on how to read a page like this one. These topics are not about GSP and nothing in them is a claim about this supplier.
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Maintenance
Maintainers: o.lindgren, impurity_table. Next review due 14 March 2027.
To add a record, file a structured report in vendor reports with the compound, lot, service, method and result. Reports missing any of those are moved to the discussion rather than the record. Allegations without documentation are hidden under R6 and the hiding is logged.
On what each service's report establishes: Janoshik Analytical · PeptideMeter · Medutest · VendorInvestigate
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Janoshik Analytical — independent third-party testingHPLC purity and mass-spectrometric identity on submitted samples, reported with the method stated. The laboratory most often cited in this community’s verification records.Independent testing →
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