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 retatrutide lot lands 4.2 points below the supplier’s figure

The result is unremarkable. What the report omits is not.

VendorInvestigate has released a batch of 11 analytical reports on research-grade retatrutide lots, including material from SGN and WWB. Reported purities range across roughly 4.2 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

Reported figures across the set were: highest 98.1%, lowest 97.2%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 11 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Reported figures across the set were: highest 98.1%, lowest 97.2%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 11 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

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.

Rowena Ashcombe, community pharmacist and diabetes educator, said the gap was predictable from the methods alone. "You can reconstruct almost the whole difference from the integration threshold. What you cannot reconstruct is why anyone thinks a number without a threshold is comparable to a number with one."

SGN’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.

Related coverage