[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.

Multiple services on one lot: agreement across two independent laboratories is stronger than a high number from one. Our vendor pages deliberately mix services for that reason.

post #2 answers the question as asked. The question underneath it is different.

Testing service selection: Janoshik gives purity with chromatogram. Medutest gives combined purity and identity. PeptideMeter gives verification records as well as results. VendorInvestigate reviews documentation. They answer different questions.

Lot matching: confirm the lot number on the certificate matches the lot number on the vial. A result from a different lot is not evidence about your vial.

Pattern across lots: a single result is a data point. Three or four results from the same supplier showing a consistent pattern becomes a record worth discussing. Two results that disagree might just be measurement variation.

I read post #4 twice before replying, because I had assumed the opposite.

Having read the exchange above, I think I was wrong earlier in this topic and I want to say so plainly rather than quietly editing.

The correction was fair and I had been repeating something I had not checked carefully enough.

Disputed records: when a result disagreed and was not explained, the record says disputed and stays that way. We do not remove inconvenient history; we document it.

Picking up post #6: that is the part I would want checked first.

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.

Coming back to post #8, because the follow-up matters more than the original answer.

Temporal patterns: if results from a supplier were good two years ago but have deteriorated recently, that is information. If they have been consistent over years, that is also information.

On post #7 — agreed on the reasoning, with one qualification.

Practical note that does not fit anywhere else. Whatever you conclude from this topic, write down what you did and when. The single most useful thing in your own records is not any individual result; it is that they are dated and consecutive.

post #11 answers the question as asked. The question underneath it is different.

Blind submission is worth the effort: have someone else relabel the sample so neither you nor the laboratory knows which supplier it came from until the result is back. Blind results change minds; self-selected results do not.

Structured report format: compound, lot, independent testing service, method as reported, result, and the certificate figure for the same lot. One lot is one lot. It becomes a pattern at three or four, and it becomes a disputed record when asked and not explained.

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.