Lyophilisation: difference between revisions
Diff·revision 10 → 11·23:01, 12 Dec 2024
Difference between revision 10 and revision 11 of Lyophilisation. 8 lines changed; the page grew by 1,563 bytes.
| Revision 10 — 08:35, 27 Nov 2024 CrossRefCleve (talk) state that overlay gas is used and name it 10,767 bytes +508 | Revision 11 — 23:01, 12 Dec 2024 DiagramDelphine (talk) copyedit 12,330 bytes +1,563 | ||
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| 13 | | Shelf temperature, secondary drying = 20–40 °C | 13 | | Shelf temperature, secondary drying = 20–40 °C |
| 14 | }} | 14 | }} |
| + | 15 | {{hatnote|For the reverse operation performed by the end user, see [[Reconstitution of lyophilised peptides]]. For measurement of the water that remains, see [[Karl Fischer titration]].}} | |
| 15 | 16 | ||
| 16 | '''Lyophilisation''', also called '''freeze-drying''', is a dehydration process in which a solution is frozen and the ice is then removed by sublimation at a pressure below the triple point of water, leaving a porous solid whose volume approximates that of the original fill. It is the standard final step in the isolation of synthetic [[peptide|peptides]] after [[Preparative HPLC purification|preparative purification]], and the reason a research peptide is distributed as a dry cake in a sealed [[vial]] rather than as a solution.{{r|nail2002}} | 17 | '''Lyophilisation''', also called '''freeze-drying''', is a dehydration process in which a solution is frozen and the ice is then removed by sublimation at a pressure below the triple point of water, leaving a porous solid whose volume approximates that of the original fill. It is the standard final step in the isolation of synthetic [[peptide|peptides]] after [[Preparative HPLC purification|preparative purification]], and the reason a research peptide is distributed as a dry cake in a sealed [[vial]] rather than as a solution.{{r|nail2002}} |
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| 73 | 74 | ||
| 74 | and the sublimation rate is | 75 | and the sublimation rate is |
| + | 76 | ||
| + | 77 | {{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}}} | |
| + | 78 | ||
| + | 79 | === Collapse and eutectic melting === | |
| + | 80 | 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}} | |
| + | 81 | ||
| + | 82 | 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}} | |
| 75 | 83 | ||
| 76 | == References == | 84 | == References == |