Lyophilisation: difference between revisions
Diff·revision 31 → 32·12:03, 10 Feb 2025
Difference between revision 31 and revision 32 of Lyophilisation. 2 lines changed; the page grew by 237 bytes.
| Revision 31 — 23:17, 31 Jan 2025 StopperingSteff (talk) add citation 16,876 bytes ±0 | Revision 32 — 12:03, 10 Feb 2025 ParentCatPansy (talk) correct percentage: source reports placebo-adjusted 17,113 bytes +237 | ||
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| 89 | Vials do not all behave alike. Those at the edge of a shelf receive additional radiant heat from chamber walls and door, sublime faster, and reach higher product temperatures; this edge-vial effect can amount to several degrees and is the usual reason a cycle validated on a laboratory dryer fails at production scale.{{r|rambhatla2003}} | 89 | Vials do not all behave alike. Those at the edge of a shelf receive additional radiant heat from chamber walls and door, sublime faster, and reach higher product temperatures; this edge-vial effect can amount to several degrees and is the usual reason a cycle validated on a laboratory dryer fails at production scale.{{r|rambhatla2003}} |
| 90 | 90 | ||
| + | 91 | {{note|Product temperature during primary drying is below shelf temperature, sometimes by 20 °C or more. Shelf temperature is not a proxy for product temperature, and a cycle described only by its shelf settings cannot be evaluated.}} | |
| + | 92 | ||
| 91 | === Collapse and eutectic melting === | 93 | === Collapse and eutectic melting === |
| 92 | 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}} | 94 | 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}} |