TFC names the synthesis and fill sites behind its catalogue
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
Testing Dispatch
Janoshik result on a Zhuhai tirzepatide lot lands 2.5 points above the supplier’s stated 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 30 mg tirzepatide vial from FGP has returned 96% of the labelled mass, the balance being the counter-ion and residual water that every lyophilised salt carries. Chromatographic purity on the same vial was above 98.6%. The two numbers measure different things, and this is one of the few certificates in the trade to print both.
Reported figures across the set were: highest 98.6%, lowest 97.6%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 13 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.
Content by elemental nitrogen determination returned 96% of the labelled nominal mass, which on a 30 mg vial corresponds to roughly 7.18 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 — Janoshik, 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.
Marek Doležal, analytical chemist and former QC laboratory manager, 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."
FGP’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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