Two gradients, one sample, two purities
A shallow gradient resolves impurities that a steep one runs into the parent peak. Both methods are legitimate; only one of them can see the small stuff.
Testing Dispatch
Independent analysis puts a CPC dulaglutide lot at 95.9%, 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 dulaglutide lot have returned figures 1.9 percentage points apart. Janoshik reported 95.9%; PeptideMeter 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 3100 vials from the same lot and had 11 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.
Batch variance rather than vendor quality is the recurring finding of this programme. Across the 11 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.
"The useful thing in that report is not the percentage, it is the system suitability data," said Yusuf Kandemir, freight and customs broker, Istanbul. "It is the only part that tells you whether the percentage means anything."
CPC’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.
Related coverage
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