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

[Question] area percent — what am I missing here

Questionbranch of 7 comments

area percent — what am I missing here. Searched first, found three threads that contradict each other, hence the post. Asked QSC for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody. Ask what the stability…

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7 comments, started 1 year ago
u/laila_wojcik-32 points·1 year 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/camila_lindqvist1 point·1 year ago

The PDF creation date being later than the analysis date is usually a re-issue or a re-export.

laila_wojcik has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.

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[removed]1 point·1 year ago

[removed by moderator]

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u/first_hundredMOD1 point·1 year ago

Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.

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u/marisol_frisk1 point·1 year ago

a total of 0.4% tells you less than four named impurities adding to 0.6%

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u/chidi_demirOP1 point·1 year ago

identity and quantity are two questions and most documents answer one

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u/laila_yilmaz1 point·1 year 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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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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