This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
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 variance between people here is larger than the effect being discussed.
This is the sort of exchange that makes the archive worth searching.
Post #60 and I disagree about the size of the effect, not about the direction.
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.
Speaking for myself and not for anyone else who has posted here.
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.
This follows post #66 rather than contradicting it.
A certificate 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.
I am reporting what happened, not recommending it.
Worth separating two things that post #64 runs together.
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.
Someone should write this up properly, and it should probably not be me.
I had read the opposite somewhere and cannot now find where, which tells me something.
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.
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.
That is one dataset and I would not build a rule on it.
Post #71 put the caveat in the right place and I want to underline it.
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.
Stating my assumptions rather than smuggling them in.
Building on post #71 rather than restating 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.
The confident version of this sentence would be wrong, so here is the hedged one.
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.
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 is consistent with mine, for whatever one more account is worth.
Taking post #75 at face value and following it one step further.
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.
The mechanism is plausible, which is not the same as established.
I read post #75 twice before replying, because I had assumed the opposite.
A stability statement tied to a named storage condition can be evaluated. One without a condition attached cannot be evaluated at all and is decoration.
Anyone who has looked at this more carefully, please correct the record.
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.
The arithmetic in post #80 is right; the assumption feeding it is the part to check.
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.
It is worth checking rather than assuming, which costs nothing.
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.
This has been discussed before and I could not find the thread, so, again.
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.
Scoping that to what I have actually seen rather than what I have read.
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.
Narrowing post #84, because the general version has more than one 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.
Posting it because the silence on this was starting to look like agreement.
Thank you for the correction. I would rather find out here than later.
Taking post #87 at face value and following it one step further.
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.
It is the kind of thing that is obvious once and never again.
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.
Where I would look next, rather than where I would stop.