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

reading related substances threads from 2024 and half of it aged badly

Suspiciousbranch of 7 comments

The title is the argument: reading related substances threads from 2024 and half of it aged badly. Here is the rest of it. Started keeping a folder of every certificate I have been sent. The ones that itemise impurities are a small group and they are mostly the same suppliers. Water content 3.8%, acetate 6.2%, purity…

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7 comments, started 7 months ago
u/low_appetite_lisa38 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/anders_kuusela11 points·7 months ago

Agreed on asking for the storage condition. It is one line and it changes how you read the entire stability claim.

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u/fatima_wojcik6 points·7 months ago

Asked GL Biochem 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.

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u/purity_pedantanalytical4 points·7 months ago

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

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u/wrong_network_w0 points·7 months ago

Area percent or net peptide content? They answer different questions.

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u/tuva_aalto1 point·7 months ago·edited

redact your own name, never the batch details

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u/certified_referenceQC1 point·7 months ago

Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.

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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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