PeptideMeter result on a Tianjin retatrutide lot lands 3.7 points below the supplier’s figure

PeptideMeter has published a purity determination of 96.8% on a 20 mg vial of retatrutide supplied by GL Biochem, against a figure of 93.8% on the certificate that accompanied the vial. The sample was submitted by the Journal in November 2025 as part of a continuing programme of arm’s-length purchasing, and the vendor was told before the order was placed that any result would be published.

Content by elemental nitrogen determination returned 89% of the labelled nominal mass, which on a 20 mg vial corresponds to roughly 14.13 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 89% of the labelled nominal mass, which on a 20 mg vial corresponds to roughly 14.13 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.

Four independent services — PeptideMeter, VendorInvestigate, and the two others operating in this market — carry the analytical burden for a trade that has no release-testing obligation of its own. Each is paid by whoever submits the sample, which is usually the vendor. The Journal’s position is that a submitter-pays model is workable but that its incentive structure has to be stated whenever a result is quoted as verification.

"The figure is not wrong and neither is theirs," said Rowena Ashcombe, community pharmacist and diabetes educator. "They are answers to two different questions and the trade has decided to pretend there is only one question. Print the gradient and the argument disappears."

GL Biochem’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.