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 14 vials from the same lot at retail and had four 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 Marek Doležal, analytical chemist and former QC laboratory manager. "Purity is what you can afford. Content is what you need."

TFC’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.