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c/coa·submitted 11 days ago by u/cesar_ivaturi

water content is on the COA and everyone skips it

COAbranch of 6 comments

water content is on the COA and everyone skips it — a position I have arrived at slowly and would like tested. Why the same vial can honestly produce three different numbers. Purity by area percent is relative to what the detector saw on one gradient at one wavelength. Net peptide content subtracts counterion, water…

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6 comments, started 10 days ago
u/liv_nkemelu29 points·10 days ago

Related substances itemised individually is a much stronger document than a single total, because it tells you the shape of the impurity profile rather than its size.

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u/yara_antonsen9 points·10 days ago

That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.

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u/santiago_szabo20 points·9 days ago

Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.

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[removed]22 points·10 days ago

[removed by moderator]

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u/zaid_balogun15 points·9 days ago

Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.

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u/ignacio_silva26 points·10 days ago·edited

Agreed — the itemised related substances table is the difference between a document and a receipt.

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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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