This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Post #29 describes the usual case. This is about the unusual one.
What would change my mind on reused chromatograms across lots 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.
Helpful, and short, which on this subject is harder than long.
Confirming post #32 from a second method, which matters more than confirming it from a second person.
A chromatogram supplied as a small image is legible for peak shape and not for baseline detail. That is enough to sanity-check an integration and not enough to reproduce it.
I disagree with the framing of reused chromatograms across lots 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.
Coming back to post #34, because the follow-up matters more than the original answer.
The distinction between release testing and characterisation is one industrial documents make and retail ones usually do not. It is the difference between "we tested every lot for this" and "we established this once".
Happy to be corrected if someone holds better data than mine.
Post #37 is right about the mechanism and I think understates the practical bit.
Practical note on reused chromatograms across lots: 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.
A chromatogram supplied as a small image is legible for peak shape and not for baseline detail. That is enough to sanity-check an integration and not enough to reproduce it.
I read post #40 twice before replying, because I had assumed the opposite.
I have been on both sides of the reused chromatograms across lots argument in this category within eighteen months, which should tell you how strong the evidence for either side is.
Adding a small correction to the reused chromatograms across lots summary above rather than a disagreement with it. The substance holds; one of the figures is out by a factor that matters.
A chromatogram supplied as a small image is legible for peak shape and not for baseline detail. That is enough to sanity-check an integration and not enough to reproduce it.
Coming back to post #44, because the follow-up matters more than the original answer.
Whatever the answer on reused chromatograms across lots turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, invite the correction.
The distinction between release testing and characterisation is one industrial documents make and retail ones usually do not. It is the difference between "we tested every lot for this" and "we established this once".
Second-hand, so weight it accordingly.
An itemised related-substances table with retention times says considerably more about the synthesis than a single total. A total tells you how much is not the main peak and nothing about what it is.
I read post #47 twice before replying, because I had assumed the opposite.
The honest answer on reused chromatograms across lots is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter.
Most people get the first two right and then argue about the fourth.
Post #51 answers the question as asked. The question underneath it is different.
Checked the reused chromatograms across lots claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
A chromatogram supplied as a small image is legible for peak shape and not for baseline detail. That is enough to sanity-check an integration and not enough to reproduce it.
On reused chromatograms across lots I would separate what is worth knowing from what is worth acting on. The first list is long and the second is short, and conflating them is how threads get heated.
Coming back to post #51, because the follow-up matters more than the original answer.
Counterpoint on reused chromatograms across lots, offered without confidence: the same observation is consistent with a much duller explanation, and nobody has ruled the dull one out.
Since reused chromatograms across lots keeps coming up, it should probably be a maintained page rather than a recurring thread. I am happy to draft it if someone with more direct experience will review it.
Adding a note of thanks rather than an opinion. I did not know most of that.
Summarising the reused chromatograms across lots 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.
An itemised related-substances table with retention times says considerably more about the synthesis than a single total. A total tells you how much is not the main peak and nothing about what it is.
I am confident about the direction and much less about the magnitude.