Adsorption, and the dose that stayed on the glass
At low concentrations a measurable fraction of peptide can adsorb to glass and plastic surfaces, and the loss is largest exactly where it is least expected.
TheCompound Journal
Reporting on incretins, compounding & the peptide supply chain
Testing Dispatch
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
An independent purity determination on liraglutide material sold by MKM has returned 96.2%, a figure 3.0 percentage points above the number printed on the accompanying certificate, which the supplier had reported against a shorter gradient and a tighter threshold. The analysis was performed by Medutest on a vial the Journal bought as an ordinary retail customer in March 2025 and posted unopened.
The Journal purchased 14 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.
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.
"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."MKM’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.
At low concentrations a measurable fraction of peptide can adsorb to glass and plastic surfaces, and the loss is largest exactly where it is least expected.
Reported from the analysis, not from a warning notice.
Reported from the analysis, not from a warning notice.
The limit for a parenteral product is calculable from the dose and the body weight in two lines. Almost nobody in this trade performs the calculation.
The result is unremarkable. What the report states alongside it is not.
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.