Vol. 3, No. 6 — June 2026Independent since 2024

TheCompound Journal

Reporting on incretins, compounding & the peptide supply chain

A monthly journal of record.
30 issues · 32 contributors
Not medical advice. We sell nothing.

Testing Dispatch

VendorInvestigate result on a Guangzhou liraglutide lot lands 3.6 points above the supplier’s stated figure

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 ERP has returned 99.2%, a figure 3.6 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 VendorInvestigate on a vial the Journal bought as an ordinary retail customer in September 2024 and posted unopened.

Content by elemental nitrogen determination returned 92% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 10.72 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.

Content by elemental nitrogen determination returned 92% of the labelled nominal mass, which on a 15 mg vial corresponds to roughly 10.72 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.

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.

Dr Wenjun Xie, process chemist and peptide manufacturing consultant, wanted the wavelength printed. "A method reading at 280 nanometres cannot see a fragment that has lost its aromatic residue. That is not a failure of the laboratory, it is a fact about the question they were asked."

ERP’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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