Lyophilisation: difference between revisions
Diff·revision 44 → 45·07:19, 26 May 2025
Difference between revision 44 and revision 45 of Lyophilisation. 7 lines changed; the page grew by 1,070 bytes.
| Revision 44 — 03:01, 18 May 2025 AnalyticalAnnie (talk) expand §Primary drying 21,545 bytes ±0 | Revision 45 — 07:19, 26 May 2025 CapitalisationCaz (talk) typo 22,615 bytes +1,070 | ||
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| 133 | Peptides purified by reverse-phase chromatography with trifluoroacetic acid as ion-pairing agent are isolated as trifluoroacetate salts unless a salt exchange is performed. Trifluoroacetate is hygroscopic, contributes appreciable mass, and lowers the pH of the reconstituted solution. Its presence also depresses the critical temperature of the freeze concentrate, lengthening the cycle. Acetate exchange is the usual remedy and is one of the routine differences between material intended as an [[Active pharmaceutical ingredient|active pharmaceutical ingredient]] and material sold for laboratory use.{{r|nail2002}} | 133 | Peptides purified by reverse-phase chromatography with trifluoroacetic acid as ion-pairing agent are isolated as trifluoroacetate salts unless a salt exchange is performed. Trifluoroacetate is hygroscopic, contributes appreciable mass, and lowers the pH of the reconstituted solution. Its presence also depresses the critical temperature of the freeze concentrate, lengthening the cycle. Acetate exchange is the usual remedy and is one of the routine differences between material intended as an [[Active pharmaceutical ingredient|active pharmaceutical ingredient]] and material sold for laboratory use.{{r|nail2002}} |
| 134 | 134 | ||
| + | 135 | == Cake attributes and their interpretation == | |
| + | 136 | The attributes recorded for a lyophilised product are appearance, residual moisture, reconstitution time and the assay of the reconstituted solution. Each answers a different question, and none substitutes for another. | |
| + | 137 | ||
| + | 138 | Appearance is judged against a description in the specification — for instance a white to off-white cake occupying substantially the volume of the fill, free of melt-back and of visible particulate. Appearance detects gross process failure and is the only attribute observable without instruments. It does not detect chemical degradation, and a cosmetically perfect cake carries no information about purity. | |
| + | 139 | ||
| + | 140 | Residual moisture is measured by [[Karl Fischer titration]] or, less specifically, by [[Loss on drying|loss on drying]]. A discrepancy between the two on the same lot is informative: loss on drying substantially exceeding the Karl Fischer figure suggests [[Residual solvent|residual solvent]], whereas the reverse suggests water bound too tightly to be driven off at the drying temperature. | |
| + | 141 | ||
| 135 | == References == | 142 | == References == |
| 136 | {{reflist}} | 143 | {{reflist}} |