Topic summary

Reused chromatograms across lots: how to spot it

Analytics › COA interpretation batch & lot numbers amino acid analysis documentation quality certificate of analysis

This is a generated summary. It shows the 9 most-liked posts from a topic of 61, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

r.erdoganTL223 Oct 2025#1

On the subject in the title: Reused chromatograms across lots: how to spot it Working notes rather than a conclusion.

Something about reused chromatograms across lots does not reconcile and I would like a second pair of eyes before I decide which half is wrong.

Two sources, both reputable, giving figures that cannot both be right unless they are measuring different quantities. My suspicion is that they are, and I cannot see how.

25 likes 9mo

y.adeyemiTL24 Nov 2025 · edited#2

The opening post put the caveat in the right place and I want to underline it.

I would keep reused chromatograms across lots and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly.

27 likes 9mo

c.silvaTL216 Jan 2026#14

r.girard, post #11: 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". Go to post

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 aware this is the third time this month I have made this point.

23 likes in reply to #11 6mo

b.nwosuTL24 Feb 2026#18

Post #15 is the version of this I will quote in future. One addition.

The useful distinction on reused chromatograms across lots is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them has error bars.

31 likes 6mo

z.iyerTL227 Feb 2026#23

bench_notes, post #20: Reused chromatograms across lots 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. Go to post

Adding the measurement that post #20 says would settle it.

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.

30 likes in reply to #20 5mo

l.aaltonenTL3Regular30 Mar 2026 · edited#30

taper_shift, post #26: 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. Go to post

Post #26 put the caveat in the right place and I want to underline it.

On reused chromatograms across lots the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that.

29 likes in reply to #26 4mo

p.iyer_pharmdTL3Pharmacist11 Apr 2026#33

Helpful, and short, which on this subject is harder than long.

29 likes 4mo

i.coelhoTL26 Jun 2026#47

This follows post #46 rather than contradicting it.

The version of reused chromatograms across lots that I was taught turned out to be a teaching simplification. Useful, and not true in the way I had assumed it was.

27 likes 2mo

s.roosTL210 Jul 2026 · edited#56

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".

30 likes 18d

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