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c/coa·submitted 2 months ago by u/first_hundred

[PSA] certificate of analysis is not what most of this community thinks it is

COAbranch of 6 comments

certificate of analysis is not what most of this community thinks it is. Two minutes of reading now saves an argument later. My first certificate had a compound name, a percentage and a logo. I thought that was normal. It is not, and now I know what to ask for. How to ask for a batch record without it turning into a…

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6 comments, started 2 months ago
u/camila_lindqvist52 points·2 months ago

The PDF creation date being later than the analysis date is usually a re-issue or a re-export. It is worth one question and it is not evidence of anything on its own.

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u/anders_kuusela40 points·2 months ago

I would not read a rounded figure as evasive. Plenty of documents round to one decimal as house style.

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u/dead_space_doug14 points·2 months ago

Yes — and the reason to ask for the whole page is that the interesting parts are the ones people crop out to fit a screenshot.

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u/rohan_steiner12 points·2 months ago

Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.

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u/first_hundredOP7 points·2 months ago·edited

Does the lot on the vial match the lot on the page?

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u/cormac_pereira13 points·2 months ago

Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.

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About c/coa

How to read a certificate of analysis and what it does and does not tell you. Area% versus mass%, identity versus quantity, water content, related substances, acetate counterions, and the difference between a vendor-supplied COA and an independent test on the vial you actually received.

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