Medutest result on a Hangzhou liraglutide lot lands 4.1 points above the supplier’s stated figure
A reminder that a purity figure is the output of a method, and that methods differ.
Testing Dispatch
Independent analysis puts a QST dulaglutide lot at 95.3%, against 91.7% on the certificate
The result is unremarkable. What the report states alongside it is not.
VendorInvestigate has released a batch of 19 analytical reports on research-grade dulaglutide lots, including material from QST and CPC. Reported purities range across roughly 2.7 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.
The Journal purchased 9 vials from the same lot at retail and had four 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.
Content by elemental nitrogen determination returned 93% of the labelled nominal mass, which on a 10 mg vial corresponds to roughly 8.62 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.
Four independent services — VendorInvestigate, Medutest, and the two others operating in this market — carry the analytical burden for a trade that has no release-testing obligation of its own. Each is paid by whoever submits the sample, which is usually the vendor. The Journal’s position is that a submitter-pays model is workable but that its incentive structure has to be stated whenever a result is quoted as verification.
"Ask for the suitability summary before you argue about the percentage," said Dr Beatriz Sarmiento, clinical pharmacologist, Universidad de Navarra. "If the tailing factor and the replicate precision are outside limits, you are arguing about arithmetic performed on an unfit separation."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.
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