The arithmetic in post #5 is right; the assumption feeding it is the part to check. Worth stating the null on field-by-field walk through a certificate before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.
Second pass at: A field-by-field walk through a certificate of analysis Writing it up because I had to work it out twice and would rather nobody else did.
The question about field-by-field walk through a certificate that I actually want answered is the second one below. The first is context and I have kept it short.
Both are stated with units, and I have said what I already checked so that nobody repeats it.
Narrowing the opening post, because the general version has more than one answer.
If you are new and reading this thread for the answer to field-by-field walk through a certificate: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping.
The bit of field-by-field walk through a certificate 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.
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.
Answering the question the opening post raises rather than the one it answers.
My position on field-by-field walk through a certificate is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.
The arithmetic in post #5 is right; the assumption feeding it is the part to check.
Worth stating the null on field-by-field walk through a certificate before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.
Grateful for the specificity. Vague answers to this question are what sent me looking.
Post #5 describes the usual case. This is about the unusual one.
Adding what did not work for me on field-by-field walk through a certificate, since the failures never get written up and they are half the useful information.
Post #8 and I disagree about the size of the effect, not about the direction.
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 will know this better than I do and I hope they say so.
Peptide content and chromatographic purity are separate determinations and a certificate that reports only one has answered only one question. Content is the one that tells you how much is in the vial.
This is where my knowledge stops and I would rather mark the edge than blur it.
Where the field-by-field walk through a certificate reasoning breaks down for me is the step from the group result to the individual case. That step is almost never argued for.
Worth separating two things that post #13 runs together.
A note on scope: what I am saying about field-by-field walk through a certificate applies to the case in the first post and I would not extend it further without checking.
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.
Amino acid analysis gives content: it hydrolyses the peptide and quantifies the residues. It measures the peptide content independent of chromatographic purity. Very few supplier certificates report it.
One case, stated as one case.
Confirming post #21 from a second method, which matters more than confirming it from a second person.
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 interesting part of this is the exception, and I do not understand the exception.
Asking for the batch record rather than the certificate is a reasonable request and the response to it is informative whichever way it goes.
Worth one more sentence than it usually gets.
Coming back to post #21, because the follow-up matters more than the original answer.
Trying to state the field-by-field walk through a certificate position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Endotoxin testing is separate: a certificate of purity says nothing about endotoxin. A chemically pure preparation can carry a clinically significant endotoxin load. If endotoxin matters, it needs to be tested and reported.
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.
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.
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.