PeptideMeter result on a Tianjin mazdutide lot lands 4.3 points above the supplier’s stated figure
The supplier confirmed the determination and supplied the method behind its own figure inside a week.
Testing Dispatch
Independent analysis puts a TFC cagrilintide lot at 95.9%, against 95.2% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
VendorInvestigate has published a purity determination of 95.9% on a 5 mg vial of cagrilintide supplied by TFC, against a figure of 95.2% on the certificate that accompanied the vial. The sample was submitted by the Journal in September 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.
The Journal purchased 9 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.
The Journal purchased 9 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.
Purity became this trade’s single figure of merit because it is the cheapest measurement to obtain and the easiest to compare. Peptide content, which determines how much drug is actually in a vial, costs several times as much and is quoted as a priced addition by most of the twenty companies in the Journal’s dossier programme rather than carried as a standard release test. Sterility and endotoxin are separate disciplines again, and are neither tested nor claimed.
Dr Emiko Tanabe, mass spectrometrist, 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."
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.
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Who signed this, and what did they undertake by signing it
Accreditation is granted for a defined scope of methods. A laboratory can be properly accredited and the test on your certificate can sit outside it.