Lyophilisation: difference between revisions
Diff·revision 22 → 23·17:33, 10 Jul 2025
Difference between revision 22 and revision 23 of Lyophilisation. 7 lines changed; the page grew by 1,596 bytes.
| Revision 22 — 11:15, 19 Jun 2025 SupplyWatchSuri (talk) add the light-exposure point for photosensitive material 23,183 bytes +568 | Revision 23 — 17:33, 10 Jul 2025 DeadSpaceDot (talk) state that a phase-change pack and a gel pack behave differently 24,779 bytes +1,596 | ||
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| 142 | 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. | 142 | 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. |
| 143 | 143 | ||
| + | 144 | Reconstitution time and clarity detect collapse, over-concentration and incipient aggregation. A cake that requires prolonged agitation, or that yields a hazy solution, is a documented indicator of physical instability even when chemical assay is within specification.{{r|wang2000}} | |
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| + | 146 | == Why lyophilised material tolerates ambient shipping == | |
| + | 147 | The practical significance of lyophilisation for distribution is that it removes the dominant degradation pathway. Hydrolytic reactions require water and molecular mobility; a dry amorphous glass held below its glass transition temperature provides neither in quantity. Reported consequences are large. Degradation rates for peptides in the dry state are commonly two to three orders of magnitude below rates for the same peptide in solution at the same temperature, and the temperature sensitivity of the residual degradation is correspondingly lower.{{r|chang2009,wang2000}} | |
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| + | 149 | This is the basis for the common practice of shipping lyophilised research peptides at ambient temperature without refrigeration, and for manufacturers' statements that a lyophilised product tolerates transient warming. It is not a licence to disregard temperature entirely. The glass transition temperature of a dry peptide-sucrose matrix may be only 40–70 °C; a parcel left in a vehicle in summer can plausibly approach that range, and above it the matrix devitrifies and mobility rises sharply. Moisture ingress through a compromised seal has the same effect, because water plasticises the glass and lowers its transition temperature by tens of degrees.{{r|chang2009}} | |
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| 144 | == References == | 151 | == References == |
| 145 | {{reflist}} | 152 | {{reflist}} |