What “LC-MS: conforms” tells a reader, which is almost nothing
What the Journal asks for when it writes to a supplier about an identity claim, and how often it gets it.
TheCompound Journal
Reporting on incretins, compounding & the peptide supply chain
Testing Dispatch
The supplier confirmed the determination and supplied the method behind its own figure inside a week.
Two laboratories analysing vials from the same semaglutide lot have returned figures 0.8 percentage points apart. Janoshik reported 95.2%; PeptideMeter reported a lower number on a shallower gradient with a tighter integration threshold. Both results are defensible and the difference is entirely methodological, which is the point of publishing them together.
The Journal purchased 20 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 20 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 wider context is that material sold for research use carries no regulatory release specification in any jurisdiction the Journal has examined. A certificate is a commercial document, not a compliance one, and its content is whatever the issuer chooses to put on it. That is the gap independent testing fills, and it fills it imperfectly.
Havel Novotný, independent laboratory quality 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."
BCH’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.
What the Journal asks for when it writes to a supplier about an identity claim, and how often it gets it.
A reminder that a purity figure is the output of a method, and that methods differ.
Statements of conformity are supposed to rest on a stated decision rule. Almost nothing in this trade states one.
Follow the resin, not the catalogue.
The report states the gradient, the wavelength and the integration threshold, which is more than most.
The supplier confirmed the determination and supplied the method behind its own figure inside a week.