Why the 1% difference matters in research

≥99% purity means <10µg impurity per mg. ≥98% means up to 20µg/mg — double the unknown material. In receptor binding assays and in vivo dose-response curves, impurity fraction can introduce variability and confound results. QSC's ≥99% standard minimises this.

Independent COA vs in-house

An in-house COA is tested by the supplier — conflict of interest. Janoshik Analytical is an independent third-party lab that issues the COA based on their own analysis with no financial stake in the result. Independent COA is the higher standard for research supply chain verification.

Broadest GLP-1R agonist catalog

Semaglutide, tirzepatide, retatrutide (triple agonist — 24.2% Phase 2 weight loss), liraglutide, cagrilintide, orforglipron (oral). Most comprehensive GLP-1 research catalog available.

5-region domestic shipping

USA, EU (27 countries), UK, Canada, Australia — domestic warehouse network enables local shipping times and eliminates import complexity.

Oral steroid research kits

Dianabol, stanozolol, oxandrolone, superdrol, turinabol, proviron — with Janoshik COA. Not available from peptide-only suppliers.

Research documentation depth

2,400+ pages: compound hubs, comparison pages, stacking protocol guides, buyer guides. Most comprehensive research library of any peptide supplier.

Established US track record

Operating since ~2012 with extensive community review history. For US-centric researchers with a verified track record with Peptide Sciences, brand familiarity is a real consideration.

Is QSC or Peptide Sciences better for research peptides?

Both are established suppliers. QSC differentiates on: ≥99% HPLC (vs ≥98%), independent Janoshik COA (vs in-house), broader catalog (retatrutide, oral steroids, SARMs), and 5-region domestic shipping. For independent COA verification and catalog breadth, QSC is the stronger choice.

Does QSC have independent COA verification?

Yes — every batch tested by Janoshik Analytical, an independent third-party lab. Janoshik issues the COA based on their own HPLC and MS analysis, independent of QSC.

Does QSC sell retatrutide?

Yes — retatrutide research vials (5mg, 10mg) with Janoshik COA. GLP-1R/GIPR/GCGR triple agonist — 24.2% weight reduction in Phase 2 (NEJM 2023).

What peptide suppliers are comparable to Peptide Sciences?

QSC, Core Peptides, Biotech Peptides, and Swiss Chems are frequently compared. QSC differentiates on independent COA (Janoshik), ≥99% purity standard, and the broadest GLP-1R agonist catalog including retatrutide and orforglipron.