Topic summary

A checklist for reading a certificate in under two minutes

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

This is a generated summary. It shows the 7 most-liked posts from a topic of 47, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

cannula_traceTL3Regular1 Apr 2026#1

A checklist for reading a certificate in under two minutes — setting out what I have, and where I think it stops being reliable.

I would like to understand what this number means before I repeat it anywhere.

A PeptideMeter report on a semaglutide lot gives 96.8% purity. The supplier certificate for the same lot states 98.1%. Both documents name a reversed-phase method; neither states the same gradient.

My question is not "who is right". It is: given that those two figures were produced by different methods, what is the largest difference I should expect from method alone, and at what point does a gap stop being explainable that way?

60 likes 4mo

m.strand_rphTL3Pharmacist Solution11 Apr 2026#4

ppm_error, post #2: 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… Go to post

Purity and content are different measurements: purity tells you what proportion of the detected material is the intended species. Content tells you how much of the intended species is present in the container. A lyophilised vial can be 99% pure and contain considerably less than the label claims because the remainder is water, counter-ion and excipient.

8 likes in reply to #2 4mo

r.lundgrenTL2 Moderator13 Apr 2026#5

I read post #3 twice before replying, because I had assumed the opposite.

Water content (residual moisture) matters: lyophilised peptide is not dry. A few percent water is normal. The difference between a TFA salt and an acetate salt can be several percent. Content calculations need the water content to be accurate.

24 likes in reply to #2 3mo

t.nardoneTL3Regular28 Apr 2026#12

Sterility testing is separate: chromatographic purity, mass spectrometry, and endotoxin testing all say nothing about whether a solution is sterile. If sterility matters, it needs to be tested and reported.

22 likes 3mo

s.teixeiraTL2 Moderator8 May 2026 · edited#17

forest_plot, post #8: 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. Go to post

post #16 is right about the mechanism and I think understates the practical bit.

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.

31 likes in reply to #8 3mo

impurity_tableTL3Analytical chemist20 May 2026#24

32 likes 2mo

i.balogunTL2 Moderator21 May 2026#25

r.lundgren, post #5: I read post #3 twice before replying, because I had assumed the opposite. Water content (residual moisture) matters: lyophilised peptide is not dry. A few percent water is normal. The difference between a TFA salt and an acetate salt can be several percent. Content calculations need the water content to be accurate. Go to post

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.

23 likes in reply to #5 2mo

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