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 Chengdu retatrutide lot lands 3.0 points below the supplier’s figure

A reminder that a purity figure is the output of a method, and that methods differ.

A peptide content determination commissioned by the Journal on a 5 mg retatrutide vial from SWB has returned 95% of the labelled mass. Chromatographic purity on the same vial was above 96.5%. The two numbers measure different things and only one of them was on the certificate.

Reported figures across the set were: highest 96.5%, lowest 94.8%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 18 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

Purity became this trade’s single figure of merit because it is the cheapest measurement to obtain and the easiest to compare. Peptide content, which determines how much drug is actually in a vial, costs several times as much and is not offered as a standard release test by any of the twenty companies in the Journal’s dossier programme. Sterility and endotoxin are separate disciplines again, and are neither tested nor claimed.

Sinéad Corrigan, patient advocate and former trial participant, was more cautious. "One lot tells you about one lot. I would not draw a conclusion about a company from a single determination, and I would not let a company draw one either."

SWB’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.

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