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 below the number printed on the accompanying certificate. 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 3600 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.
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 Havel Novotný, independent laboratory quality manager. "It is the only part that tells you whether the percentage means anything."
MKM’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.
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 omits is not.
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.