PeptideMeter result on a Guangzhou liraglutide lot lands 3.3 points above the supplier’s stated figure

An independent purity determination on liraglutide material sold by MKM has returned 96.5%, a figure 3.3 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 October 2024 and posted unopened.

Content by elemental nitrogen determination returned 97% of the labelled nominal mass, which on a 2 mg vial corresponds to roughly 8.03 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 11 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.

"Ask for the suitability summary before you argue about the percentage," said Dr Emiko Tanabe, mass spectrometrist. "If the tailing factor and the replicate precision are outside limits, you are arguing about arithmetic performed on an unfit separation."

MKM’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.