PeptideMeter result on a Tianjin semaglutide lot lands 1.1 points below the supplier’s figure

An independent purity determination on semaglutide material sold by TFC has returned 96.5%, a figure 1.1 percentage points below the number printed on the accompanying certificate. The analysis was performed by PeptideMeter on a vial the Journal bought as an ordinary retail customer in February 2025 and posted unopened.

Content by elemental nitrogen determination returned 97% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 14.17 mg of peptide rather than the labelled figure. The remainder is accounted for by counter-ion, residual water and residual solvent, none of which is visible chromatographically.

Content by elemental nitrogen determination returned 97% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 14.17 mg of peptide rather than the labelled figure. The remainder is accounted for by counter-ion, residual water and residual solvent, none of which is visible chromatographically.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 17 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Alastair Renshaw, pharmaceutical supply-chain consultant. "Purity is what you can afford. Content is what you need."

TFC’s dossier has been updated with this determination and with the date of the request for comment. The dossier’s "what we could not verify" box records the questions still outstanding.