Independent analysis puts a BCH tirzepatide lot at 98.3%, against 94.9% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Testing Dispatch
PeptideMeter result on a Tianjin retatrutide lot lands 3.7 points above the supplier’s stated figure
A reminder that a purity figure is the output of a method, and that methods differ.
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 95% 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 95% 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.
Dr Emiko Tanabe, mass spectrometrist, 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."GL Biochem’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.
Related coverage
What changed at KP in February, and what the company says prompted it
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
GL Biochem names the synthesis and fill sites behind its catalogue
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
Sending the same vial twice, under two names
Duplicate submissions under different names test within-laboratory repeatability, which is a different quantity from between-laboratory reproducibility.
VendorInvestigate result on a Changsha orforglipron lot lands 1.6 points above the supplier’s stated figure
The result is unremarkable. What the report states alongside it is not.
Independent analysis puts a SGN survodutide lot at 97.0%, against 92.8% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.