PeptideMeter result on a Xi'an dulaglutide lot lands 2.6 points above the supplier’s stated figure

An independent purity determination on dulaglutide material sold by SGN has returned 97.7%, a figure 2.6 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 PeptideMeter on a vial the Journal bought as an ordinary retail customer in March 2025 and posted unopened.

Content by elemental nitrogen determination returned 95% of the labelled nominal mass, which on a 2 mg vial corresponds to roughly 13.97 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.

The Journal purchased 16 vials from the same lot at retail and had four of them analysed separately, in order to distinguish vial-to-vial variation from method variation. Vial-to-vial agreement was within 0.4 percentage points. Method-to-method disagreement was an order of magnitude larger.

Four independent services — PeptideMeter, Janoshik, and the two others operating in this market — carry the analytical burden for a trade that has no release-testing obligation of its own. Each is paid by whoever submits the sample, which is usually the vendor. The Journal’s position is that a submitter-pays model is workable but that its incentive structure has to be stated whenever a result is quoted as verification.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Dr Emiko Tanabe, mass spectrometrist. "Purity is what you can afford. Content is what you need."

SGN’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.