Certificate-of-analysis

A purity percentage without its method is not interpretable. What "99% purity by HPLC" is (area normalization per USP <621>), the ten method parameters that must be stated beside it for the number to mean anything, why area percent is not mass percent (ICH Q2(R2) response factors; the peptide bond vs tryptophan at 214 nm), and the impurity classes — counterion, water, residual solvents, inorganics, co-eluting species — that a chromatographic purity figure never sees.

The full Certificate of Analysis data for Retatrutide lot 06242026, issued by BTLabs: 99.8% HPLC peptide-assay purity, 22.2 mg content against a 20 mg label claim, FTIR identity confirmation, and a 1:2.9 peptide-to-excipients ratio — transcribed in full, with the scanned certificate available to download.