How to read a Certificate of Analysis — complete guide

OP back with an update, since a thread like this is useless without one.

Closing this out. What actually changed my mind was the point about waiting for a trend instead of reading a single measurement, which is embarrassing in hindsight and worth saying anyway.

JenPlateau said:

If two explanations both fit, the useful question is which one predicts something the other does not.

Coming at JenPlateau’s question from a different direction. The distinction that resolves most of these threads is between what is true on average and what is true for one person. Both are real; they answer different questions and get quoted as if they were the same one.

Correct me if the detail matters more than I have assumed.

One concrete data point for the thread. One habit that pays for itself: post the method alongside the number. A figure without its method cannot be checked, and an unchecked figure is how this community accumulates folklore.

Following on from JenPlateau — and this may be the naive question:

How long did you give it before you decided it was working?

HPLC_Greg said:

One habit that pays for itself: post the method alongside the number.

Pushing back on HPLC_Greg here. The counter-case has not been addressed. Somebody upthread described the situation that does not fit, and the thread moved on rather than engaging with it, which is the failure mode this board is supposed to avoid.