Adding the measurement that the opening post says would settle it. Peptide content and chromatographic purity are separate determinations and a certificate that reports only one has answered only one question. Content is the one that tells you how much is in the vial. The rule of thumb is fine; the edge cases are…
Counter-ion form: the field almost nobody reports Writing it up because I had to work it out twice and would rather nobody else did.
Counter-ion form, from the point of view of someone who has read the documentation and is still stuck.
Saying which parts I have understood so that nobody wastes time re-explaining them, and where exactly the understanding stops.
Adding the measurement that the opening post says would settle it.
Peptide content and chromatographic purity are separate determinations and a certificate that reports only one has answered only one question. Content is the one that tells you how much is in the vial.
The rule of thumb is fine; the edge cases are where it earns its keep.
Counter-ion form belongs on the document and almost never is. Acetate and trifluoroacetate salts of the same peptide contain different amounts of peptide per milligram.
Purity and content are different measurements: purity tells you what proportion of the detected material is the intended species. Content tells you how much of the intended species is present in the container. A lyophilised vial can be 99% pure and contain considerably less than the label claims because the remainder is water, counter-ion and excipient.
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