Identical chromatograms across two different lots Writing it up because I had to work it out twice and would rather nobody else did.
Collecting what is known about identical chromatograms in one place, because it is currently spread across a category, two tag pages and a thread that is hard to find.
This is a summary rather than new work, and I have attributed each part to where I found it.
The opening post answers the question as asked. The question underneath it is different.
For anyone finding this later: the short answer on identical chromatograms is that it depends on one thing, and the rest of the thread is people identifying which thing.
Before the thread moves on from identical chromatograms — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of four and from an n of four hundred.
Clear enough that I do not think I have a follow-up, which is unusual.
Narrowing post #4, because the general version has more than one answer.
Source for the identical chromatograms 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.
Identical chromatograms is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which one is being asked for.
Inability to trace lots: if you ask "where was this synthesised, by whom, under what conditions" and cannot get a clear answer, that is a red flag. Traceability is not glamorous but it is foundational.
Adding this to the thread rather than to the wiki, because I am not confident enough for the wiki.
What would change my mind on identical chromatograms is a second dataset collected by someone with no stake in the first. Until then I hold it loosely and I would rather say so than pretend to more.
Post #9 is right about the mechanism and I think understates the practical bit.
The strongest single signal available cheaply is what happens when you ask a technical question. A quantitative answer inside a working day is difficult to fake at scale.
The answer changed when I changed how I was measuring, which was informative.
Coming back to post #8, because the follow-up matters more than the original answer.
I would put moderate confidence on the mainstream reading of identical chromatograms and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.
On identical chromatograms: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.
Keep the two claims separate. "The result on this lot did not match the certificate" is a report that can be checked. "This supplier is dishonest" is an allegation about intent and nothing in a chromatogram supports it.
The mechanism is plausible, which is not the same as established.
I had written a reply contradicting post #12 and deleted it. Here is what survived.
The most useful contribution to this subcategory is a resolved case written up with the resolution, because the unresolved ones are all anyone remembers.
A single observation, in a thread that deserves better than single observations.
Small correction to my own earlier position on identical chromatograms. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
Where the same certificate image appears with different lot numbers, that is a documentation finding worth reporting with the images attached.
That is what the documentation says. What happens in practice is usually close.
The reason identical chromatograms keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is unknown.
Post #17 describes the usual case. This is about the unusual one.
I would call the community position on identical chromatograms likely rather than established, and I would be comfortable defending that hedge.
Nothing here should be read as an accusation against a named company, and the guidelines exist so that reports remain reports.
Prices well below the rest of the market are a fact rather than a finding. They are worth noting and they do not establish anything on their own.
Practical answer on identical chromatograms, since the theoretical one is upthread: do the simplest check first, write down the result, and only then decide whether the complicated explanation is needed. It usually is not.
Sensible. I would want the same detail before I acted on it either.
A stock listing that never changes and a lead time that never varies are both worth noticing. Real operations have variation in them.
If this contradicts something upthread, the upthread version may well be the better one.