This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Post #59 put the caveat in the right place and I want to underline it.
When method identifiers are missing: "reversed-phase HPLC" is less specific than "reversed-phase HPLC at 214 nm on a C18 column with a 10 to 40% acetonitrile gradient over 20 minutes". The second lets someone reproduce the analysis. The first does not.
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 the practical version. The rigorous version is longer and says the same thing.
Reading rather than contributing, but this is the most useful thread I have found on 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.
Post #63 describes the usual case. This is about the unusual one.
Certificates from a supplier's own laboratory are not independent by definition. That is not an accusation, it is a description, and it is why independent submission exists.
Adding it in case it saves somebody the afternoon it cost me.
Adding the measurement that post #67 says would settle 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".
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.
Reading it back, the second half matters more than the first.
Taking post #67 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.
Marking that as an opinion rather than a finding.
Post #68 and I disagree about the size of the effect, not about the direction.
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 has held every time I have looked, which is not the same as always.
Certificates from a supplier's own laboratory are not independent by definition. That is not an accusation, it is a description, and it is why independent submission exists.
That holds under the stated conditions and I have stated them.
This follows post #73 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.
That holds for the case as described. Change the assumptions and it may not.
Worth separating two things that post #72 runs together.
Where two documents for the same lot disagree, the useful question is which was measured and which was transcribed. Most such disagreements are the second.
Someone should write this up properly, and it should probably not be me.
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.
Appreciated. The plain phrasing does more work here than a longer post would.
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.
Worth saying I have only my own numbers here, and n is small.
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".
When method identifiers are missing: "reversed-phase HPLC" is less specific than "reversed-phase HPLC at 214 nm on a C18 column with a 10 to 40% acetonitrile gradient over 20 minutes". The second lets someone reproduce the analysis. The first does not.
Confirming post #81 from a second method, which matters more than confirming it from a second person.
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.
Speaking for myself and not for anyone else who has posted here.
Agreed, and I will stop repeating the version of this I had been repeating.
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.
Where I part company with post #86, and it is a narrow parting.
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.
Post #86 is the version of this I will quote in future. One addition.
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.
Noting that I have skin in this question and have tried to discount for it.
Post #86 and I disagree about the size of the effect, not about the direction.
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.
Taking post #89 at face value and following it one step further.
When a document puts the specification in the result column, it has told you the release criterion, not the measurement. Those are different claims and the second is weaker.
Happy to be the one who is wrong here if it settles the question.