Peptide content: difference between revisions
Diff·revision 4 → 5·18:31, 6 Oct 2024
Difference between revision 4 and revision 5 of Peptide content. 2 lines changed; the page grew by 425 bytes.
| Revision 4 — 08:38, 1 Oct 2024 StubSorterBot (talk) bot: flag bare reference 2,529 bytes +574 | Revision 5 — 18:31, 6 Oct 2024 FigureFerdinand (talk) add the ionisation mode to the mass-spectrometry description 2,954 bytes +425 | ||
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| 7 | Content is the determination that makes a mass statement possible. A purchaser reconstituting a nominally 5 mg vial and calculating a concentration is implicitly assuming a content figure, and in the ordinary case the assumption made is 100%, which is never correct for a lyophilised peptide salt. Typical content for such material falls between roughly 70% and 90%, so the assumption is wrong by an amount that matters.{{r|usp1503}} | 7 | Content is the determination that makes a mass statement possible. A purchaser reconstituting a nominally 5 mg vial and calculating a concentration is implicitly assuming a content figure, and in the ordinary case the assumption made is 100%, which is never correct for a lyophilised peptide salt. Typical content for such material falls between roughly 70% and 90%, so the assumption is wrong by an amount that matters.{{r|usp1503}} |
| 8 | 8 | ||
| + | 9 | The relationship between content and [[Area percent purity|area percent purity]] is the single most-misread pairing in research-peptide documentation. They are independent quantities: purity is a ratio among the species that eluted, and content is a fraction of the vial. A certificate reporting 99% purity and 83% content is internally consistent, and the two figures together say considerably more than either says alone. | |
| + | 10 | ||
| 9 | == What occupies the rest of the mass == | 11 | == What occupies the rest of the mass == |
| 10 | For a lyophilised peptide purified by reverse-phase chromatography and freeze-dried from an aqueous acetonitrile mobile phase, four components account for essentially all of the non-peptide mass. | 12 | For a lyophilised peptide purified by reverse-phase chromatography and freeze-dried from an aqueous acetonitrile mobile phase, four components account for essentially all of the non-peptide mass. |