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c/coa·submitted 5 months ago by u/laila_wojcik

related substances are the most under-discussed thing on this board

Explainerbranch of 7 comments

related substances are the most under-discussed thing on this board. Change my mind, genuinely — I have no stake in being right about this. Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label weight. All four numbers honest, and I had to read it twice. Spent four months confusing area% and…

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7 comments, started 5 months ago
u/aleksi_eriksen79 points·5 months ago

Area percent is the peak area of your compound over the total integrated area, at one wavelength, on one gradient. It is a relative measure of what the detector saw, not a mass fraction of the vial.

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u/honest_syringe2433 points·5 months ago

Did you get the chromatogram or only the summary line?

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u/yusuf_nakamura23 points·5 months ago

water content is on there and everyone skips it

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u/laila_wojcikOP-31 points·5 months ago·edited

What does the method line actually say? Not the technique — the column and the gradient.

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u/karma_irrelevant26 points·5 months ago

area% is not mass%, and the difference is the whole game

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u/liv_nkemelu11 points·5 months ago

Same view. QYB prints the column and the gradient, which means somebody could actually reproduce the run.

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[deleted]15 points·5 months ago

[deleted]

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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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