Identical chromatograms across two different lots posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Everything in post #30 holds. The case it does not cover is the one I have.
A definition problem is doing most of the work in this identical chromatograms discussion. Once the term is pinned down I suspect the disagreement mostly goes away and what is left is small.
Practical experience of identical chromatograms, offered as one case with the conditions stated, not as a general finding. Conditions first, because they are what make it interpretable.
Identical chromatograms 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.
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.
Where I part company with post #34, and it is a narrow parting.
Filing a mild objection to the consensus on identical chromatograms. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit.
The claim about identical chromatograms upthread is stronger than its source supports. I have read the source. The source says "associated with" and the post says "causes".
I read post #39 twice before replying, because I had assumed the opposite.
One caution on identical chromatograms: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
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.
The short answer was in the first line; everything after is the working.
Thank you — that answers what I came here to find out.
Taking post #42 at face value and following it one step further.
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.
What I want from this identical chromatograms thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.
This follows post #47 rather than contradicting it.
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.
Someone will know this better than I do and I hope they say so.
Confirming post #47 from a second method, which matters more than confirming it from a second person.
Reading this identical chromatograms thread as someone who came in with a fixed view: the third and seventh replies moved me and the confident ones did not.
Adding a data point of agreement rather than a data point.
Collapsed as off-topic by two members at trust level 3 or above
I had written a reply contradicting post #48 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.
I would put this at better than even and not much better.
A request rather than an answer: could whoever has the primary source for identical chromatograms post it? I have seen the claim three times this month and each version had lost a qualifier.
Post #54 is right about the mechanism and I think understates the practical bit.
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.
Posted with less confidence than the sentence structure implies.
Coming back to post #53, because the follow-up matters more than the original answer.
I disagree with the framing of identical chromatograms above, and I think it is a substantive disagreement rather than a terminological one. Setting out why, so it can be checked.
The reasoning depends on an assumption that is doing a lot of work and is never stated. If the assumption holds, the conclusion follows. I do not think it holds generally.
A document with no method identification is not evidence of anything wrong. It is evidence that the document cannot be checked, which is a different and weaker statement.
A partial answer, offered because a partial answer beats none.
Where the identical chromatograms reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.