VendorInvestigate result on a Suzhou liraglutide lot lands 4.2 points above the supplier’s stated figure

Two laboratories analysing vials from the same liraglutide lot have returned figures 4.2 percentage points apart. VendorInvestigate reported 98.9%; Medutest reported a lower number on a shallower gradient with a tighter integration threshold. Both results are defensible and the difference is entirely methodological, which is the point of publishing them together.

Reported figures across the set were: highest 98.9%, lowest 95.8%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 10 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

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.

Marek Doležal, analytical chemist and former QC laboratory manager, 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."

QST’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.