Lyophilisation: difference between revisions
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| Revision 18 — 04:46, 8 Nov 2024 PharmDrafts (talk) copyedit 9,352 bytes +1,105 | Revision 19 — 00:08, 14 Nov 2024 COA_Colwyn (talk) move unsourced paragraph to talk 10,221 bytes +869 | ||
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| 1 | {{Infobox method | 1 | {{Infobox method |
| 2 | | name = Lyophilisation | 2 | | name = Lyophilisation |
| + | 3 | | image = vial.svg | |
| + | 4 | | caption = A lyophilised cake occupies approximately the volume of the original fill. Cake structure is a recorded quality attribute. | |
| 3 | | Also known as = Freeze-drying | 5 | | Also known as = Freeze-drying |
| 4 | | Class = Dehydration by sublimation | 6 | | Class = Dehydration by sublimation |
| ⋮ | ⋮ | ||
| 60 | | Glycine | Eutectic ≈ −3.6 °C | Crystallises | | 62 | | Glycine | Eutectic ≈ −3.6 °C | Crystallises | |
| 61 | | Sodium chloride | Eutectic ≈ −21.1 °C | Crystallises | | 63 | | Sodium chloride | Eutectic ≈ −21.1 °C | Crystallises | |
| + | 64 | ||
| + | 65 | == Primary drying == | |
| + | 66 | Primary drying removes the ice, which for a typical aqueous fill is 90–98% of the water present. Its duration is set by the sublimation rate, which in the simplest treatment follows from an energy balance across the vial base: the mass flow equals the heat flow divided by the enthalpy of sublimation. | |
| + | 67 | ||
| + | 68 | A worked estimate for a single 6R vial illustrates the magnitudes involved. Taking a vial cross-sectional area of 3.14 cm², a vial heat transfer coefficient of 20 W·m⁻²·K⁻¹, a shelf temperature of −10 °C and a product temperature of −30 °C, the heat flow is | |
| + | 69 | ||
| + | 70 | {{math|Q = 20 W m^{-2} K^{-1} × 3.14 × 10^{-4} m^{2} × 20 K = 0.126 W}} | |
| + | 71 | ||
| + | 72 | and the sublimation rate is | |
| 62 | 73 | ||
| 63 | == References == | 74 | == References == |