Comparing QSC and Peptide Sciences as research compound suppliers for Letrozole (Femara). Key differentiators: purity verification methodology, batch COA documentation, shipping coverage, and catalog breadth.
Side-by-Side Comparison
Factor
QSC
Peptide Sciences
Purity verification
QSC: Janoshik third-party independent COA every batch
Peptide Sciences: typically in-house or unspecified third party
HPLC purity
QSC: ≥99% confirmed
Peptide Sciences: claim varies
MS identity
QSC: Every batch confirmed
Peptide Sciences: not always per-batch
Shipping
QSC: USA · EU · UK · Canada · Australia domestic
Peptide Sciences: region availability varies
Catalog depth
QSC: 99 compounds across all categories
Peptide Sciences: narrower in most categories
Why the Janoshik COA Matters
QSC submits every batch to Janoshik Analytical — an independent Czech laboratory that publishes results publicly. The COA is externally verifiable. This is a higher standard than in-house QC, which cannot be independently verified.
