Independent analysis puts a SSA semaglutide lot at 98.0%, against 94.0% on the certificate

A peptide content determination commissioned by the Journal on a 15 mg semaglutide vial from SSA has returned 93% of the labelled mass, the balance being the counter-ion and residual water that every lyophilised salt carries. Chromatographic purity on the same vial was above 98.0%. The two numbers measure different things, and this is one of the few certificates in the trade to print both.

Content by elemental nitrogen determination returned 93% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 10.91 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.

The Journal purchased 20 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 16 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.

"Ask for the suitability summary before you argue about the percentage," said Dr Sirichai Boonmee, peptide chemist, Chulalongkorn University. "If the tailing factor and the replicate precision are outside limits, you are arguing about arithmetic performed on an unfit separation."

SSA’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.