Medutest result on a Xi'an tirzepatide lot lands 2.1 points above the supplier’s stated figure

An independent purity determination on tirzepatide material sold by SWB has returned 98.3%, a figure 2.1 percentage points above the number printed on the accompanying certificate, which the supplier had reported against a shorter gradient and a tighter threshold. The analysis was performed by Medutest on a vial the Journal bought as an ordinary retail customer in November 2024 and posted unopened.

Content by elemental nitrogen determination returned 93% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 11.55 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 93% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 11.55 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.

Discrepancies of one to two percentage points between a supplier’s figure and an independent determination are common and usually explicable: a faster gradient resolves fewer impurities, a higher integration threshold discards more small peaks, and a wider solvent-front exclusion window removes early-eluting fragments from the calculation altogether. None of that is misconduct. All of it is invisible unless the method is disclosed.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Marek Doležal, analytical chemist and former QC laboratory manager. "Purity is what you can afford. Content is what you need."

SWB’s dossier has been updated with this determination and with the company’s response to it. The dossier’s ordering box records the lead times, the minimum quantities and what a buyer should ask for at the point of order.