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".
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Analytics · COA interpretation · continued
Specification in the result column: why that is a meaningful error posts 31–60
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
fr.translation_mo, post #25: 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. Go to post
Narrowing post #31, 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.
Post #31 and I disagree about the size of the effect, not about the direction.
"Not less than 98 per cent" is a specification. "98.3 per cent" is a result. A certificate carrying only the first has not told you what was measured.
Adding this to the thread rather than to the wiki, because I am not confident enough for the wiki.
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A test date preceding a manufacturing date is a clerical error until somebody explains otherwise, and asking is cheap. Most such things are transcription.
I would put this at better than even and not much better.
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h.kimani, post #32: Narrowing post #31, 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. Go to post
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.
Posted with less confidence than the sentence structure implies.
fr.translation_mo, post #25: 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. Go to post
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".
This follows post #35 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.
The short version is the first sentence; the rest is why.
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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.
I would treat the number as indicative rather than as a measurement.
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That is clearer than the version I had in my head. Thank you.
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j.moreau, post #6: 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". That holds for the case as described. Change the assumptions and it may not. Go to post
Coming back to post #38, because the follow-up matters more than the original answer.
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.
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 conclusion is tentative; the arithmetic underneath it is not.
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r.vukovic, post #2: 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. The honest answer is that it depends, and here is what it depends on. Go to post
I had written a reply contradicting post #42 and deleted it. Here is what survived.
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.
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.
I would put a moderate confidence on that and no more.
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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 uncertainty is in the assumption, not in the calculation.
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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 have separated what I observed from what I concluded, which does not always happen.
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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.
Caveat: everything above assumes the paperwork is what it says it is.
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chromatogram, post #29: 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. Noting that I have skin in this question and have tried to discount for it. Go to post
The arithmetic in post #49 is right; the assumption feeding it is the part to check.
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.
Written from notes rather than memory, which is why the numbers are specific.
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 interesting part of this is the exception, and I do not understand the exception.
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A document that puts the specification in the result column has told you the release criterion rather than the measurement. Those are different claims and the difference is the whole point of reading the document.
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Adding the measurement that post #53 says would settle it.
Method identification means enough to reproduce: column chemistry, dimensions, gradient, flow, wavelength. A method name alone identifies a family of methods.
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Collapsed as off-topic by two members at trust level 3 or above
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 a description of practice, not a recommendation of 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".
I have kept the units in throughout, for the obvious reason.
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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.
If it helps: the failure mode here is usually boring rather than dramatic.
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