Independent analysis puts a TFC tirzepatide lot at 98.3%, against 95.4% on the certificate

VendorInvestigate has released a batch of 19 analytical reports on research-grade tirzepatide lots, including material from TFC and CPC. Reported purities range across roughly 3.6 percentage points, and the report set is unusual in stating the analytical method for every determination rather than for some of them.

The Journal purchased 4000 vials from the same lot and had 19 of them analysed separately, in order to distinguish vial-to-vial variation from method variation. Vial-to-vial agreement was within 0.4 percentage points. Method-to-method disagreement was an order of magnitude larger.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 19 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Havel Novotný, independent laboratory quality manager. "Purity is what you can afford. Content is what you need."

TFC’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.