Five lines that would change what a certificate is worth
A reader holding a certificate can work out what it does not cover in about ninety seconds, and that is a useful ninety seconds.
Testing Dispatch
Independent analysis puts a Homopeptide cagrilintide lot at 98.1%, against 94.7% on the certificate
The supplier has not disputed the finding. It has not explained the gap either.
Two laboratories analysing vials from the same cagrilintide lot have returned figures 3.2 percentage points apart. PeptideMeter reported 98.1%; VendorInvestigate 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.
The Journal purchased 3300 vials from the same lot and had 21 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.
Reported figures across the set were: highest 98.1%, lowest 94.7%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 21 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.
"The useful thing in that report is not the percentage, it is the system suitability data," said Lorcan Feeney, analytical services director at an independent laboratory. "It is the only part that tells you whether the percentage means anything."
Homopeptide’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.
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