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c/coa·submitted 1 year ago by u/tidy_vialdrawer_watch28

the water content question that gets asked weekly, answered properly

COAbranch of 7 comments

Posting this as a discussion rather than a claim: the water content question that gets asked weekly, answered properly. 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…

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7 comments, started 1 year ago
u/priya_palacios-25 points·1 year ago

HPLC-UV and LC-MS answer different questions

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u/yannick_haddad1 point·1 year ago

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

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u/gastric_emptying_g1 point·1 year ago

post the whole document, not the headline number

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u/neha_erdogan1 point·1 year ago

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

This is the sentence to take away. The rest of the thread is footnotes to it.

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u/tidy_vialdrawer_watch28OP1 point·1 year ago

The document I was worried about turned out to be a re-issue with a later creation date. Asked, got the original, entirely ordinary.

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u/karma_irrelevant1 point·1 year ago

Asked for the storage condition behind the stability statement. Got it in a sentence. It is a two-line email and almost nobody sends it.

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u/coa_collectorarchivist1 point·1 year 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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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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