Lyophilisation: difference between revisions
Diff·revision 41 → 42·00:14, 1 May 2025
Difference between revision 41 and revision 42 of Lyophilisation. 4 lines changed; the page grew by 873 bytes.
| Revision 41 — 13:00, 21 Apr 2025 CrudePeptidePearl (talk) promote subsection to section 20,027 bytes ±0 | Revision 42 — 00:14, 1 May 2025 CagriCass (talk) convert list to prose 20,900 bytes +873 | ||
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| 118 | Stoppers contribute to the final moisture in a way that is easy to overlook. Elastomeric closures absorb water during steam sterilisation and release it slowly into the sealed headspace, so a vial can gain moisture during storage from its own closure. Post-sterilisation drying of stoppers, and the choice of a low-moisture-transmission elastomer, are the usual mitigations; the phenomenon is discussed further at [[vial]].{{r|iso8362_5}} | 118 | Stoppers contribute to the final moisture in a way that is easy to overlook. Elastomeric closures absorb water during steam sterilisation and release it slowly into the sealed headspace, so a vial can gain moisture during storage from its own closure. Post-sterilisation drying of stoppers, and the choice of a low-moisture-transmission elastomer, are the usual mitigations; the phenomenon is discussed further at [[vial]].{{r|iso8362_5}} |
| 119 | 119 | ||
| + | 120 | {{figure|vial|A stoppered vial after drying. The closure is seated by the shelves at the end of the cycle while the chamber is still under partial vacuum, so the headspace composition is set by the process rather than by the room.}} | |
| + | 121 | ||
| 120 | == Formulation == | 122 | == Formulation == |
| 121 | A pure peptide dried from water alone often produces an unsatisfactory solid: a thin film at the vial base, a cake that shrinks away from the wall, or a residue that is difficult to see and easy to mistake for an empty vial. Formulation addresses cake structure, chemical stability and reconstitution behaviour simultaneously. | 123 | A pure peptide dried from water alone often produces an unsatisfactory solid: a thin film at the vial base, a cake that shrinks away from the wall, or a residue that is difficult to see and easy to mistake for an empty vial. Formulation addresses cake structure, chemical stability and reconstitution behaviour simultaneously. |
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| 125 | ; Buffers : Buffer salts can crystallise selectively during freezing and shift pH substantially. Sodium phosphate is the classic example: crystallisation of the disodium salt during freeze concentration has been reported to drive pH down by several units, a change more than sufficient to accelerate hydrolytic degradation. Histidine and citrate buffers are less prone to this behaviour.{{r|carpenter1997}} | 127 | ; Buffers : Buffer salts can crystallise selectively during freezing and shift pH substantially. Sodium phosphate is the classic example: crystallisation of the disodium salt during freeze concentration has been reported to drive pH down by several units, a change more than sufficient to accelerate hydrolytic degradation. Histidine and citrate buffers are less prone to this behaviour.{{r|carpenter1997}} |
| 126 | ; Surfactants : Polysorbate 20 or 80 at low concentration reduces adsorption at the ice-water and air-water interfaces, a recognised route to aggregation during freezing.{{r|wang2000}} | 128 | ; Surfactants : Polysorbate 20 or 80 at low concentration reduces adsorption at the ice-water and air-water interfaces, a recognised route to aggregation during freezing.{{r|wang2000}} |
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| + | 130 | For research peptides the formulation is frequently minimal — the peptide, its counterion, and whatever residue survives purification — because the material is sold as a chemical rather than as a dosage form. This has two consequences an encyclopedia should record. The cake is often small and poorly formed relative to a pharmaceutically formulated product, so cake appearance carries little information about quality; and the absence of a bulking agent means the mass in the vial is dominated by peptide, counterion and water, making [[Peptide content|peptide content]] rather than fill weight the meaningful quantity.{{r|usp1207}} | |
| 127 | 131 | ||
| 128 | == References == | 132 | == References == |