Lyophilisation: difference between revisions
Diff·revision 23 → 24·03:44, 14 Dec 2024
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| Revision 23 — 10:22, 7 Dec 2024 CounterfeitCato (talk) undo good-faith edit: the source does not say this 10,866 bytes +99 | Revision 24 — 03:44, 14 Dec 2024 CategoryBot (talk) bot: normalise citation format 12,142 bytes +1,276 | ||
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| 76 | {{math|dm/dt = 0.126 W ÷ 2.83 × 10^{6} J kg^{-1} = 4.4 × 10^{-8} kg s^{-1} ≈ 0.16 g h^{-1}}} | 76 | {{math|dm/dt = 0.126 W ÷ 2.83 × 10^{6} J kg^{-1} = 4.4 × 10^{-8} kg s^{-1} ≈ 0.16 g h^{-1}}} |
| 77 | 77 | ||
| + | 78 | === Collapse and eutectic melting === | |
| + | 79 | Two distinct structural failures bound primary drying. In a system whose freeze-concentrate crystallises, exceeding the eutectic melting temperature produces liquid, and the vial dries as a shrunken residue or a glassy shell — usually described on inspection as melt-back. In an amorphous system, exceeding a temperature a few degrees above Tg′ allows viscous flow of the freeze-concentrated matrix into the pores that the sublimed ice has vacated. The dried layer loses its structure, and the result is a shrunken, sometimes glassy or foamed cake. The temperature at which this becomes observable by freeze-drying microscopy is the collapse temperature, Tc, conventionally 1–3 °C above Tg′ for small-molecule and peptide systems.{{r|tang2004}} | |
| + | 80 | ||
| + | 81 | Collapse is not necessarily a chemical failure. A collapsed cake may reconstitute and may assay within specification. Its documented consequences are elevated residual moisture, because the collapsed structure traps water; slower and sometimes incomplete reconstitution; and a cake appearance that fails a visual specification. For proteins, collapse has been associated with reduced storage stability, attributed to increased molecular mobility in the denser matrix.{{r|wang2000}} | |
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| 78 | == References == | 83 | == References == |
| 79 | {{reflist}} | 84 | {{reflist}} |