If you are new and reading this thread for the answer to Identical chromatograms: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping.
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Sourcing · Red flags · continued
Second pass at: Identical chromatograms across two different lots posts 61–90
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
j.delacroix, post #13: Where somebody posts a concern, ask what would resolve it before arguing about it. Half of these threads end with a document nobody had asked for. That is the shape of it. The detail is where I would expect to be corrected. Go to post
Thank you for the correction. I would rather find out here than later.
The arithmetic in post #61 is right; the assumption feeding it is the part to check.
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 right answer here may simply be that it has not been measured.
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Answering the question post #60 raises rather than the one it answers.
The bit of Identical chromatograms that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge.
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Collapsed as off-topic by two members at trust level 3 or above
Where somebody posts a concern, ask what would resolve it before arguing about it. Half of these threads end with a document nobody had asked for.
That is all the detail I have. Someone else will have more.
a.molnar, post #20: Where the same certificate image appears with different lot numbers, that is a documentation finding worth reporting with the images attached. Adding it because I spent an afternoon working it out and nobody should have to twice. Go to post
Post #64 and I disagree about the size of the effect, not about the direction.
My position on Identical chromatograms is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.
a.weiss, post #42: I have been on both sides of the Identical chromatograms argument in this category within eighteen months, which should tell you how strong the evidence for either side is. Go to post
Narrowing post #66, because the general version has more than one answer.
Where the same certificate image appears with different lot numbers, that is a documentation finding worth reporting with the images attached.
This is where my knowledge stops and I would rather mark the edge than blur it.
Reporting something here requires the batch, the date, the method and the document, which is exactly what makes the reports worth reading two years later.
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Confirming post #66 from a second method, which matters more than confirming it from a second person.
Pricing patterns: unusually low prices for what are otherwise consistent with market rates might indicate lower quality, stolen goods, or a scam. Unusually high prices without justification raise different flags.
Worth checking against a second source before it gets quoted onward.
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ka.batista, post #33: On Identical chromatograms the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that. Go to post
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.
Post #72 describes the usual case. This is about the unusual one.
Inconsistency across documents: a certificate stating one purity, a website claiming another, and a supplier's verbal representation claiming a third, all on the same product, is a red flag for either incompetence or deception.
That has been true for the cases I have seen and I have not seen many.
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k.roos, post #43: Confirming post #40 from a second method, which matters more than confirming it from a second person. On Identical chromatograms, I would rather understate and be corrected upward than overstate and be quoted. That is a house style here and it is a good one. Go to post
Nothing here should be read as an accusation against a named company, and the guidelines exist so that reports remain reports.
Written from notes rather than memory, which is why the numbers are specific.
m.broberg, post #27: Pricing patterns: unusually low prices for what are otherwise consistent with market rates might indicate lower quality, stolen goods, or a scam. Unusually high prices without justification raise different flags. The step people skip is the one I have spelled out. Go to post
Reading rather than answering, but this is the post I would point somebody at.
The arithmetic in post #75 is right; the assumption feeding it is the part to check.
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.
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a.stephanopoulos, post #38: Picking up post #36: that is the part I would want checked first. Identical chromatograms is worth one more sentence than it usually gets, and the sentence is the one about how the number was arrived at. Go to post
I read post #75 twice before replying, because I had assumed the opposite.
Reporting something here requires the batch, the date, the method and the document, which is exactly what makes the reports worth reading two years later.
That holds under the stated conditions and I have stated them.
a.molnar, post #20: Where the same certificate image appears with different lot numbers, that is a documentation finding worth reporting with the images attached. Adding it because I spent an afternoon working it out and nobody should have to twice. Go to post
Post #79 answers the question as asked. The question underneath it is different.
Inconsistency across documents: a certificate stating one purity, a website claiming another, and a supplier's verbal representation claiming a third, all on the same product, is a red flag for either incompetence or deception.
Same conclusion as the reply above, reached differently, which is mildly reassuring.
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.
I looked this up rather than remembered it, which is the right order.
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Collapsed as off-topic by two members at trust level 3 or above
Coming back to post #78, because the follow-up matters more than the original answer.
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.
That is what I would do. It may not be what is correct.
m.ibarra, post #25: Adding the boring version of Identical chromatograms, because the interesting version keeps getting posted and the boring one is usually right. Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does. Go to post
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.
The confident answers on Identical chromatograms and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.
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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.
I am aware this is the third time this month I have made this point.
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m.lindqvist, post #17: Post #13 and I disagree about the size of the effect, not about the direction. Where I would push back on the Identical chromatograms consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed. Go to post
Adding the measurement that post #84 says would settle it.
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.
Narrowing post #88, because the general version has more than one answer.
Nothing here should be read as an accusation against a named company, and the guidelines exist so that reports remain reports.
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n.petrov, post #78: The arithmetic in post #75 is right; the assumption feeding it is the part to check. 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. Go to post
Practical note on Identical chromatograms: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow.