Batch date after test date, and other internal inconsistencies — setting out what I have, and where I think it stops being reliable.
Proposing that batch date deserves a maintained page rather than a recurring topic, and drafting the skeleton here so that the argument about scope happens before the writing rather than after.
What I think belongs on it, what does not, and the three claims that would need a citation each.
The fields that make one usable: lot identifier matching the container, test date, method identification specific enough to reproduce, the result as a number, and the acceptance criterion stated separately from the result.
Coming back to the opening post, 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".
Post #3 answers the question as asked. The question underneath it is different.
I read the earlier replies on batch date twice before writing this, because I had assumed the opposite and wanted to be sure I was disagreeing with what was said rather than what I expected.
Picking up post #3: that is the part I would want checked first.
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.
Coming back to post #3, because the follow-up matters more than the original answer.
Reporting rather than recommending, on batch date. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
On batch date 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.
Post #7 and I disagree about the size of the effect, not about the direction.
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.
The bit of batch date 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.
A test date preceding a manufacturing date is a clerical error until somebody explains otherwise, and asking is cheap. Most such things are transcription.
Two people can read the same figure differently here and both be reasonable.
One caution on batch date: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
Answering the question post #10 raises rather than the one it answers.
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 have written this out at length because the short version keeps being misread.
Right, and stated more narrowly than I would have dared to state it.
The signature block matters more than it appears to. A named individual with a date is a different kind of document from an unsigned one, whatever the numbers say.
On balance I think that is right, and I would not bet much on it.
Everything in post #14 holds. The case it does not cover is the one I have.
Batch date is a good example of a question where the honest answer is boring and the interesting answers are unsupported. I would go with boring.
This follows post #16 rather than contradicting it.
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".
The general case is well covered; this is the awkward specific one.
Careful with the language on batch date. "Not detected" and "not present" are different findings and the first is a statement about the method.
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.
Not the answer, but possibly the question that gets there.
Worth separating two things that post #19 runs together.
Nobody has said the unglamorous part of batch date yet, so: most of the variation is explained by things that are boring to write about and easy to check.
This follows post #23 rather than contradicting it.
What fields matter on a certificate: lot number matching the vial, test date, the analytical method stated specifically, the measured result as a number, and the acceptance limit stated separately. A certificate missing any of these is weaker.
I had written a reply contradicting post #23 and deleted it. Here is what survived.
On batch date: 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.
Thank you for the correction. I would rather find out here than later.
Counter-ion form is crucial: peptides are isolated as salts, most often trifluoroacetate from reversed-phase purification or acetate after salt exchange. The counter-ion is part of the mass in the vial and is not part of the peptide. Two vials of the same purity, one as TFA and one as acetate, contain different amounts of peptide per milligram.
Written from notes rather than memory, which is why the numbers are specific.
Picking up post #27: that is the part I would want checked first.
Small correction to my own earlier position on batch date. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
Everything in post #27 holds. The case it does not cover is the one I have.
Asking for the batch record rather than the certificate is a reasonable request and the response to it is informative whichever way it goes.
Narrowing post #27, because the general version has more than one answer.
A certificate of analysis is a statement by its issuer that a defined test was performed on a defined lot and produced a defined result. That is all it is, and it is not nothing. What makes it usable: lot identifier matching the container, test date, method identification specific enough to reproduce, the actual result as a number, and the acceptance criterion stated separately from the result.