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c/coa·submitted 7 months ago by u/yusuf_nakamura

how much of what we believe about related substances actually comes from certificate of analysis threads

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how much of what we believe about related substances actually comes from certificate of analysis threads. Searched first, found three threads that contradict each other, hence the post. Asked for the storage condition behind the stability statement. Got it in a sentence. It is a two-line email and almost nobody sends…

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6 comments, started 7 months ago
u/santiago_szabo71 points·7 months ago

Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for. A 99% pure acetate salt can still be about 85% peptide by mass.

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u/nabila_espinoza33 points·7 months ago

UV at 214nm sees the peptide bond and picks up almost everything; at 280nm you are looking at aromatics only. Which wavelength the number came from is part of the number.

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u/alcohol_aversion-9 points·7 months ago

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

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u/yusuf_nakamuraOP102 points·7 months ago

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

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u/ismael_eriksen47 points·7 months ago

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

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u/yara_antonsen17 points·7 months ago

redact your own name, never the batch details

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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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