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c/coa·submitted 2 years ago by u/coa_collector

purity is the most under-discussed thing on this board

Explainerbranch of 7 comments

purity is the most under-discussed thing on this board. Not a hot take, just something I have not seen said plainly here. 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…

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7 comments, started 2 years ago
u/certified_referenceMOD399 points·2 years ago

Removed — cropped document. Post the whole page or do not post it; the fields people crop are the fields that matter.

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u/bastian_moreau315 points·2 years ago

Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.

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u/dario_boateng170 points·2 years ago

Cosigning. The batch identifier is load-bearing, and a certificate that cannot be tied to the vial in your hand is not about your vial.

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u/low_appetite_lisa192 points·2 years ago·edited

Small fix — 214nm, not 280nm.

This is the sentence to take away. The rest of the thread is footnotes to it.

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u/alcohol_aversion150 points·2 years ago

water content is on there and everyone skips it

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u/tuva_aalto221 points·2 years ago

Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.

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u/amara_halonen133 points·2 years ago

Did you get the chromatogram or only the summary line?

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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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