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

PeptideMeter has published a purity determination of 96.2% on a 15 mg vial of orforglipron supplied by GL Biochem, against a figure of 93.5% on the certificate that accompanied the vial. The sample was submitted by the Journal in May 2024 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

Content by elemental nitrogen determination returned 99% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 14.19 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 99% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 14.19 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.

Lorcan Feeney, analytical services director at an independent laboratory, wanted the wavelength printed. "A method reading at 280 nanometres cannot see a fragment that has lost its aromatic residue. That is not a failure of the laboratory, it is a fact about the question they were asked."

GL Biochem’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.