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.
I have deliberately not rounded that, because the rounding is where the argument starts.
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Sourcing · Independent verification · continued
How Janoshik, Medutest, PeptideMeter and VendorInvestigate differ posts 61–90
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Having read the whole Janoshik thread before replying: the question in the first post has not actually been answered yet, and three of us have answered a nearby one instead.
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mi.almeida, post #10: Two questions I would want answered before drawing anything from the Janoshik data above: how were the cases selected, and what happened to the ones that dropped out. Go to post
Coming back to post #61, because the follow-up matters more than the original answer.
Janoshik sits at the boundary between what this community can usefully discuss and what it cannot, and I think it falls on the discussable side, narrowly.
Post #61 is right about the mechanism and I think understates the practical bit.
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 this to the thread rather than to the wiki, because I am not confident enough for the wiki.
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resistance_first, post #25: PeptideMeter: purity analysis plus structured, dated supplier verification records. Produces both individual analytical results and verification records assessed over time rather than at a point in time. Go to post
Janoshik Analytical: chromatographic purity and mass-spectrometric identity on submitted samples. Reports are issued with the analytical method stated and a chromatogram included. Submission is by mail.
Confirming post #65 from a second method, which matters more than confirming it from a second person.
Distinguishing three things in the Janoshik discussion that keep getting used interchangeably: the observation, the proposed mechanism, and the recommendation that gets attached to both.
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r.petrov, post #19: I would be cautious about generalising from the Janoshik example above. It is a good example. It is one example. Go to post
What I would tell a new member reading about Janoshik for the first time: the confident posts are not the reliable ones, and the reliable ones are longer.
One more thing on Janoshik that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
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eire_reader, post #41: Service differences on vendor pages: Janoshik and Medutest results are measurements on vials. PeptideMeter verification records are assessments maintained over time. VendorInvestigate reviews are documentation assessments. We cite all four because they answer different questions. Stating my assumptions rather than smuggling them in. Go to post
Repeat determination on the same product line months apart is the measurement that speaks to consistency, and consistency is what most buyers actually want.
Confirming post #72 from a second method, which matters more than confirming it from a second person.
VendorInvestigate: documentation and supplier-practice review. Reviews paperwork rather than vials. Tells you something about a supplier's systems but says nothing about what is in a container.
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owen.brady, post #58: Where I part company with post #56, and it is a narrow parting. On Janoshik, the part that usually goes wrong is that the question is asked as though it has one answer. It has a range, and the width of the range is the interesting bit. If you can post the two or three numbers you are working from, several people here will check the… Go to post
Adding a reference point for Janoshik. Mine is a single case, collected without controls, and I am posting the method alongside it so it can be discounted appropriately.
l.pires, post #51: Thank you for taking the time. That was more work than a reply usually is. Go to post
Answering the question post #75 raises rather than the one it answers.
The failure mode on Janoshik is boring rather than dramatic. It is almost always the step everyone assumes was done correctly because it is too simple to get wrong.
Post #76 is the version of this I will quote in future. One addition.
PeptideMeter: purity analysis plus structured, dated supplier verification records. Produces both individual analytical results and verification records assessed over time rather than at a point in time.
That is the honest state of it as of this week.
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f.fenwick, post #69: A record with four results over sixteen months is a thin record rather than a bad one, and the honest description says which. This is the version I would want a new member to read first. Go to post
This follows post #76 rather than contradicting it.
The version of Janoshik that circulates here is a simplification of a simplification. It is not wrong, but it has lost the conditions under which it holds, and those conditions are where the interesting cases live.
Worth separating two things that post #78 runs together.
Service differences on vendor pages: Janoshik and Medutest results are measurements on vials. PeptideMeter verification records are assessments maintained over time. VendorInvestigate reviews are documentation assessments. We cite all four because they answer different questions.
The disagreement above is smaller than it looks once the terms are fixed.
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Collapsed as off-topic by two members at trust level 3 or above
Post #79 describes the usual case. This is about the unusual one.
The record shows what was measured. Everything beyond that is inference and this site tries to keep the line visible.
The uncertainty is in the assumption, not in the calculation.
f.fontaine, post #6: The record shows what was measured. Everything beyond that is inference and this site tries to keep the line visible. I would be interested in a counterexample if anyone has one. Go to post
Cost and turnaround: different services have different pricing and turnaround times. Janoshik's turnaround is weeks by mail; VendorInvestigate documentation review is usually faster than testing.
The short version is the first sentence; the rest is why.
Worth stating the null on Janoshik before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.
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I will take the caveat as seriously as the claim, which is the point of putting it there.
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f.fontaine, post #85: Worth stating the null on Janoshik before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one. Go to post
Picking up post #87: that is the part I would want checked first.
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.
Reading it back, the second half matters more than the first.
Post #87 and I disagree about the size of the effect, not about the direction.
Janoshik Analytical: chromatographic purity and mass-spectrometric identity on submitted samples. Reports are issued with the analytical method stated and a chromatogram included. Submission is by mail.
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Taking post #87 at face value and following it one step further.
Medutest: combined purity and identity reporting. Appears throughout vendor documentation. Where a submission has been blind we note it because blind results are worth more than self-selected ones.
That is the practical version. The rigorous version is longer and says the same thing.
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