[2026 update] A report I filed that turned out to be wrong, and the correction

On the subject in the title: A report I filed that turned out to be wrong, and the correction Working notes rather than a conclusion.

Structured report rather than an opinion, following the format the maintainers asked for.

• Compound: semaglutide
• Independent testing: VendorInvestigate
• Method as reported: reversed-phase HPLC, 280 nm
• Result: 98.8% area
• Certificate figure for the same lot: 98.2%

I am not drawing a conclusion about the supplier from one lot and I would ask that nobody else does either. I am adding a data point to a record.

I had written a reply contradicting post #4 and deleted it. Here is what survived.

Comparing your result to somebody else's on a different lot is not a comparison of suppliers. Lot is the unit and it should be in every report.

Take it as a starting point and not as a specification.

Date the report: when the analysis was done matters. Material can degrade in storage. A report from two years ago is still useful but is not evidence about the current state of the same supplier's stock.

The honest answer is that it depends, and here is what it depends on.

Do not adjust a reported figure. Post what the laboratory said and put your interpretation in a separate sentence.

That is what I would do. It may not be what is correct.

Dosing and purity: a vial that is 99% pure might contain 80% of its label claim if the other mass is water, counter-ion, and excipient. Purity and content are different. Both matter for different reasons.

It is the sort of thing that seems obvious in retrospect and was not at the time.