Which fields on a certificate actually matter, ranked

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.

Happy to expand any of that if it is the useful part.

This follows post #13 rather than contradicting it.

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.

Worth checking against a second source before it gets quoted onward.

Nothing to add, except that this is the answer I would give if asked.

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".

I would want a second opinion before relying on that.

Asking for the batch record rather than the certificate is a reasonable request and the response to it is informative whichever way it goes.

Not disagreeing with anyone above, just adding the bit I keep having to look up.

That is a fair summary of where the discussion has got to.

Agreed on all of that, and I have nothing to add to it.

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.

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.

On post #22 — agreed on the reasoning, with one qualification.

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.

This follows post #22 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".

A weak preference rather than a position.

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.

That matches what I was told, which is not the same as knowing 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.

Adding the caveat now so it does not have to be extracted later.

Reading old certificates: if a certificate is dated years ago, the lot it describes might be old. That is not automatically a problem but it is worth noting. Fresh testing on the current lot is stronger than old testing on an older lot.

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".

Coming back to post #28, because the follow-up matters more than the original answer.

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.

Happy to be the one who is wrong here if it settles the question.