Peptide content: difference between revisions
Diff·revision 2 → 3·17:34, 15 Sep 2024
Difference between revision 2 and revision 3 of Peptide content. 11 lines changed; the page grew by 682 bytes.
| Revision 2 — 04:05, 9 Sep 2024 AAA_Analyst (talk) give the injection volume, without which the loading cannot be judged 1,273 bytes ±0 | Revision 3 — 17:34, 15 Sep 2024 AnalyticalAnnie (talk) clarify that area percent is not mass percent 1,955 bytes +682 | ||
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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 | == 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. | |
| + | 11 | ||
| + | 12 | | Component | Typical share | Determined by | | |
| + | 13 | |---|---|---| | |
| + | 14 | | Water | 3–10% | [[Karl Fischer titration]] or [[Loss on drying]] | | |
| + | 15 | | Counterion (usually trifluoroacetate) | 5–20% | Ion chromatography; inferred from the synthesis route only as a last resort | | |
| + | 16 | | Residual solvent | below 1% | Headspace gas chromatography | | |
| + | 17 | | Peptide-related impurities | 0.5–3% | The complement of [[Area percent purity]] | | |
| + | 18 | ||
| 9 | == References == | 19 | == References == |
| 10 | {{reflist}} | 20 | {{reflist}} |
| ⋮ | ⋮ | ||
| 14 | [[Category:Analytical methods]] | 24 | [[Category:Analytical methods]] |
| 15 | [[Category:Compendial testing]] | 25 | [[Category:Compendial testing]] |
| + | 26 | [[Category:Testing methodology]] | |
| 16 | 27 |