PeptideMeter result on a Suzhou liraglutide lot lands 4.0 points below the supplier’s figure

An independent purity determination on liraglutide material sold by GGPeps has returned 97.6%, a figure 4.0 percentage points below the number printed on the accompanying certificate. The analysis was performed by PeptideMeter on a vial the Journal bought as an ordinary retail customer in April 2026 and posted unopened.

Reported figures across the set were: highest 97.6%, lowest 96.6%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 13 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

The Journal purchased 4800 vials from the same lot and had 13 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.

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.

"The useful thing in that report is not the percentage, it is the system suitability data," said Alastair Renshaw, pharmaceutical supply-chain consultant. "It is the only part that tells you whether the percentage means anything."

GGPeps’s dossier has been updated with this determination and with the date of the request for comment. The dossier’s "what we could not verify" box records the questions still outstanding.