Independent analysis puts a MKM survodutide lot at 96.5%, against 95.5% on the certificate

PeptideMeter has released a batch of 14 analytical reports on research-grade survodutide lots, including material from MKM and GL Biochem. Reported purities range across roughly 3.7 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

The Journal purchased 17 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.

Content by elemental nitrogen determination returned 92% of the labelled nominal mass, which on a 2 mg vial corresponds to roughly 9.78 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.

Dr Sirichai Boonmee, peptide chemist, Chulalongkorn University, said the gap was predictable from the methods alone. "You can reconstruct almost the whole difference from the integration threshold. What you cannot reconstruct is why anyone thinks a number without a threshold is comparable to a number with one."

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.