Peptide content: difference between revisions
Diff·revision 10 → 11·11:32, 13 Jan 2025
Difference between revision 10 and revision 11 of Peptide content. 9 lines changed; the page grew by 716 bytes.
| Revision 10 — 20:39, 26 Dec 2024 LipidLedgerLou (talk) fix a dangling clause 4,094 bytes +142 | Revision 11 — 11:32, 13 Jan 2025 Chromatokid (talk) clarify that mass spectrometry confirms identity, not purity 4,810 bytes +716 | ||
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| 8 | | Units = Per cent by mass | 8 | | Units = Per cent by mass |
| 9 | | Typical range = 70–90% for a lyophilised trifluoroacetate salt | 9 | | Typical range = 70–90% for a lyophilised trifluoroacetate salt |
| + | 10 | <!-- Determined by --> | |
| + | 11 | | Direct = Amino acid analysis; quantitative nitrogen determination | |
| + | 12 | | By difference = Water plus counterion plus residual solvent subtracted | |
| + | 13 | | Not by = Chromatographic purity, which is a different quantity | |
| 10 | }} | 14 | }} |
| 11 | {{hatnote|For the relative chromatographic measure usually reported as "purity", see [[Area percent purity]].}} | 15 | {{hatnote|For the relative chromatographic measure usually reported as "purity", see [[Area percent purity]].}} |
| ⋮ | ⋮ | ||
| 32 | 36 | ||
| 33 | Water is the term that varies most between vials of the same lot, because a lyophilised cake takes up moisture from the atmosphere on any exposure. That is what the desiccant sachet in a well-packed consignment is for, and it is why a content figure carries a date. | 37 | Water is the term that varies most between vials of the same lot, because a lyophilised cake takes up moisture from the atmosphere on any exposure. That is what the desiccant sachet in a well-packed consignment is for, and it is why a content figure carries a date. |
| + | 38 | ||
| + | 39 | == How content is determined == | |
| + | 40 | Two routes are in ordinary use and they are not equivalent. | |
| + | 41 | ||
| + | 42 | '''Direct determination.''' Amino acid analysis hydrolyses the peptide and quantifies the released residues against a calibrated standard, giving the peptide mass directly. It is the reference approach and it is slow and comparatively expensive. Quantitative nitrogen determination is a faster direct route and is less specific, because any nitrogen-containing impurity contributes. | |
| 34 | 43 | ||
| 35 | == References == | 44 | == References == |