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c/coa·submitted 11 months ago by u/purity_pedant

[Question] how do you actually verify area percent

Questionbranch of 11 comments

Right, the COA question again, but with numbers this time. I have 5 data points over 26 weeks. The pattern is consistent enough that I do not think it is chance, and boring enough that nobody is going to screenshot it, which is usually a good sign. The thing I would flag for anyone new: the effect I am describing…

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11 comments, started 11 months ago
u/amara_halonen156 points·11 months ago

the related substances line is where the story is

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u/wanjiru_varga-13 points·11 months ago

Disagree but this is the good kind of wrong — it is specific enough to be checked.

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u/priya_palacios0 points·11 months ago

axis labels included, always

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u/purity_pedantanalytical1 point·11 months ago

the counterion is part of the mass you paid for

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u/yannick_haddad1 point·11 months ago

post the whole document, not the headline number

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u/katrin_girard1 point·11 months ago

chromatogram or it did not happen

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u/karma_irrelevant1 point·11 months ago

Yeah, 96.8% area is not the problem, the missing impurity breakdown is the problem.

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u/kavya_verhoeven96 points·11 months ago

The chromatogram trace is where the real information lives. The summary number is just a headline.

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u/anya_moreau68 points·11 months ago

Dead space in the needle hub holds a small but non-trivial volume. On low-volume draws that can be several units.

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u/aurel_boateng19 points·11 months ago

the batch number or it did not happen

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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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