Analytics · COA interpretation · continued

A field-by-field walk through a certificate of analysis posts 91–120

Analytics › COA interpretation documentation quality amino acid analysis certificate of analysis batch & lot numbers Solved

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.

formulary_notesTL3Regular17 Jul 2025#91

p.onwuka, post #6: Worth separating two things that post #2 runs together. I changed my mind about field-by-field walk through a certificate after someone here asked me for the source and I could not produce one. That is worth saying out loud because it is the ordinary way it happens. Go to post

Where I part company with post #89, and it is a narrow parting.

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.

24 likes in reply to #6 12mo

r.bruunTL217 Jul 2025#92

Collapsed as off-topic by two members at trust level 3 or above

Post #89 is the version of this I will quote in future. One addition.

Checked the field-by-field walk through a certificate claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.

TL4_HalvorsenTL4Leader · Journal club17 Jul 2025#93

"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.

The number is defensible. The precision I gave it is not.

3 likes 12mo

ch.correiaTL217 Jul 2025#94

n.cardoso, post #37: Post #36 and I disagree about the size of the effect, not about the direction. Practical note on field-by-field walk through a certificate: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow. Go to post

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 strength of my opinion here exceeds the strength of my evidence.

0 likes in reply to #37 12mo

quiet_lurkerTL2Regular17 Jul 2025#95

formulary_notes, post #91: Where I part company with post #89, and it is a narrow parting. 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. Go to post

A note on how field-by-field walk through a certificate gets discussed rather than on field-by-field walk through a certificate itself: the confident posts get the replies and the careful ones get ignored, and the careful ones have been right more often.

18 likes in reply to #91 12mo

j.bhattacharyaTL217 Jul 2025#96

Confirming post #93 from a second method, which matters more than confirming it from a second person.

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".

7 likes 12mo

s.chowdhuryTL3Regular17 Jul 2025#97

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.

1 like 12mo

an.ibarraTL217 Jul 2025#98

Marking my place. If it changes for me I will come back and say so.

0 likes 12mo

s.leclercTL417 Jul 2025#99

Collapsed as off-topic by two members at trust level 3 or above

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.

I would treat that as a working assumption and revisit it.

l.salinasTL217 Jul 2025#100

One more thing on field-by-field walk through a certificate that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.

23 likes 12mo

k.redgraveTL2Member17 Jul 2025#101

I read post #97 twice before replying, because I had assumed the opposite.

Field-by-field walk through a certificate looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.

1 like 12mo

v.bruunTL217 Jul 2025#102

IHollingworth, post #67: 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

Post #101 answers the question as asked. The question underneath it is different.

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.

Take the reasoning and check the arithmetic; I do not always get it right.

0 likes in reply to #67 12mo

citation_peakTL3Regular17 Jul 2025#103

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

22 likes 12mo

s.ivaturiTL217 Jul 2025 · edited#104

On field-by-field walk through a certificate the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that.

10 likes 12mo

erratum_fileTL3Regular17 Jul 2025#105

Everything in post #101 holds. The case it does not cover is the one I have.

An honest declaration on field-by-field walk through a certificate: I have a prior here and it is strong enough that you should weight what I say downward. Stating it rather than hiding it.

0 likes 12mo

a.cabreraTL217 Jul 2025#106

baseline_table, post #59: The reason field-by-field walk through a certificate is hard to answer is that the obvious measurement and the relevant quantity are not the same thing, and substituting one for the other is silent. Go to post

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 looked this up rather than remembered it, which is the right order.

31 likes in reply to #59 12mo

RidgewayTL3Regular17 Jul 2025#107

a.pereira, post #35: Helpful, and easy to find again, which is half of what a good reply 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.

16 likes in reply to #35 12mo

i.grimaldiTL217 Jul 2025#108

Collapsed as off-topic by two members at trust level 3 or above

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

q.zhao_qaTL3Quality assurance17 Jul 2025#109

w.moreau, post #10: 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. That is the honest state of it as of this week. Go to post

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 has been true for the cases I have seen and I have not seen many.

5 likes in reply to #10 12mo

s.antonsenTL217 Jul 2025#110

On field-by-field walk through a certificate I would separate what is worth knowing from what is worth acting on. The first list is long and the second is short, and conflating them is how threads get heated.

1 like 12mo

r.aldana_pharmdTL4Pharmacist17 Jul 2025#111

v.malinowski, post #2: On the opening post — agreed on the reasoning, with one qualification. The most useful thing anyone has posted about field-by-field walk through a certificate in this category was a table of what had been measured and by whom. That is what I would want again. Go to post

Confirming post #109 from a second method, which matters more than confirming it from a second person.

I am aware this is the third time this month I have made this point.

3 likes in reply to #2 12mo

s.okaforTL217 Jul 2025#112

Collapsed as off-topic by two members at trust level 3 or above

I had written a reply contradicting post #110 and deleted it. Here is what survived.

The confident answers on field-by-field walk through a certificate and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.

bench_notesTL4 Moderator17 Jul 2025#113

Where I have landed on field-by-field walk through a certificate, having got it wrong once in public: the direction is clear, the magnitude is not, and anyone quoting a precise magnitude has borrowed it from somewhere that did not measure it.

24 likes 12mo

e.vargaTL217 Jul 2025#114

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.

0 likes 12mo

a.batistaTL217 Jul 2025#115

s.ivaturi, post #104: On field-by-field walk through a certificate the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that. Go to post

I will take the caveat as seriously as the claim, which is the point of putting it there.

1 like in reply to #104 12mo

a.novakTL217 Jul 2025#116

The question underneath field-by-field walk through a certificate is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.

Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.

7 likes 12mo

d.tammTL217 Jul 2025#117

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.

A qualification I should have led with rather than closed on.

17 likes 12mo

a.nwosuTL217 Jul 2025#118

t.marchetti, post #68: I came in to disagree and I am leaving without a disagreement. Go to post

Worth separating two things that post #114 runs together.

"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.

33 likes in reply to #68 12mo

titration_diaryTL317 Jul 2025#119

Collapsed as off-topic by two members at trust level 3 or above

Answering the field-by-field walk through a certificate question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.

i.guerreroTL217 Jul 2025#120

j.delacroix, post #53: 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. Second-hand, so weight it accordingly. Go to post

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 have deliberately not rounded that, because the rounding is where the argument starts.

23 likes in reply to #53 12mo