This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Narrowing post #30, because the general version has more than one answer.
Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method.
It took me longer than it should have to see that.
Post #32 and I disagree about the size of the effect, not about the direction.
A record with four results over sixteen months is a thin record rather than a bad one, and the honest description says which.
Filing this under things that are true until someone shows me otherwise.
Purity-only: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
This follows post #34 rather than contradicting it.
Careful with the language on purity-only. "Not detected" and "not present" are different findings and the first is a statement about the method.
Worth separating two things that post #36 runs together.
It does not extend to lots nobody has seen, it is not a recommendation, and it says nothing about anything other than what was measured.
One of those cases where knowing the mechanism does not help the decision.
Purity-only was covered in the wiki last year and the page has a review date on it, which is a better starting point than my memory of a thread.
I keep a log for purity-only specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.
Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method.
Adding a source would improve this post and I do not have one to hand.
A record with four results over sixteen months is a thin record rather than a bad one, and the honest description says which.
It is worth stating the boring hypothesis before the interesting one.
This follows post #45 rather than contradicting it.
Source for the purity-only figure, since it was asked for. It is in the discussion rather than the abstract, which is why the version circulating is stronger than the paper is.
Reading the surrounding paragraph is worth the two minutes. The authors are more careful than their summarisers.
Repeat determination on the same product line months apart is the measurement that speaks to consistency, and consistency is what most buyers actually want.
This has been discussed before and I could not find the thread, so, again.
Summarising the purity-only thread so far, since it is long and the answer is buried: the first reply has the method, the fourth has the correction to it, and the rest is people agreeing at length.
Coming back to post #50, because the follow-up matters more than the original answer.
The most useful reply I ever got about purity-only was a request to state my units. It sounds like pedantry and it has saved me twice.
This follows post #52 rather than contradicting it.
Repeat testing: if you want to verify the same lot a second time, testing with a different service strengthens the conclusion. Testing with the same service verifies reproducibility but uses the same method.
Posted with less confidence than the sentence structure implies.
Checked the purity-only claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
The record shows what was measured. Everything beyond that is inference and this site tries to keep the line visible.
Picking up post #56: that is the part I would want checked first.
I read the earlier replies on purity-only twice before writing this, because I had assumed the opposite and wanted to be sure I was disagreeing with what was said rather than what I expected.
On post #54 — agreed on the reasoning, with one qualification.
Purity-only came up in a thread eighteen months ago and was answered well. I cannot find it, which is itself the problem, so here is the reconstruction.
It does not extend to lots nobody has seen, it is not a recommendation, and it says nothing about anything other than what was measured.
Happy to be corrected if someone holds better data than mine.