If you have been reading about sublimation and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-01-21. Numbers and descriptions here follow the published literature rather than marketing material.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
The physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying; lyophilisation; cryodesiccation | Regional spelling and historical terms. |
| Primary drying pressure | 0.05-0.5 mbar (5-50 Pa) | Kept below the triple point of water; product-specific. |
| Shelf temperature range | -40 to +40 °C | Freezing, primary, and secondary stages use different set points. |
| Cycle duration | 12-72 hours | Depends on fill volume, formulation, and equipment. |
| Condenser temperature | -50 to -80 °C | Must remain below the product's ice temperature. |
Lyophilization is a drying process in which a solvent, usually water, is removed from a frozen material by sublimation under reduced pressure. The material is first solidified, then placed under vacuum so that ice transitions directly to vapor without a bulk liquid phase. This approach suits heat-sensitive substances that would degrade during conventional evaporation. Primary drying removes unbound ice, while secondary drying reduces water that remains adsorbed to the solid matrix. The result is a porous, lightweight solid that can be reconstituted later.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
Lyophilized products are typically stored as sealed solids in vials or syringes. Moisture ingress is a major concern because many dried cakes are hygroscopic and can lose stability when exposed to humid air. Storage temperature depends on the formulation; some products are kept refrigerated, while others are stable at room temperature. Container closure integrity and headspace moisture are often monitored. Light protection may also be required for some photosensitive materials.
Quality control for lyophilized materials includes visual inspection, residual moisture measurement, and reconstitution testing. Cake appearance can reveal process problems such as collapse, shrinkage, or meltback, although appearance alone does not prove potency. Residual moisture is commonly measured by Karl Fischer titration or by loss on drying. Reconstitution time is checked because a slow or incomplete dissolve can indicate a change in pore structure. Stability studies track these attributes over time under defined temperature and humidity conditions.
=== Inflammatory bowel disease === High red and processed meat consumption is associated with an increased risk of inflammatory bowel disease. The American Gastroenterological Association have stated that a diet low in red and processed meat may reduce ulcerative colitis flares.
The Daily Telegraph reported in April 2009 that it was manufactured in China, but it has since been made illegal there. In March 2009, Druglink magazine reported it only cost a "couple of hundred pounds" to synthesise a kilogram of mephedrone, the same month, The Daily Telegraph reported manufacturers were making "huge amounts of money" from selling it. In January 2010, Druglink magazine reported dealers in Britain spent £2,500 to ship one kilogram from China, but could sell it for £10 a gram, making a profit of £7,500. A later report, in March 2010, stated the wholesale price of mephedrone was £4000 per kilogram. In March 2011, the International Narcotics Control Board published a report about designer drugs, noting mephedrone was by then being used recreationally in Europe, North America, Southeast Asia, New Zealand and Australia. After the 2022 Russian invasion of Ukraine, existing street drugs in Russia became more expensive, leading an increasing number of Russians to turn to mephedrone. According to reports, DIY mephedrone-making kits are widely available in the country.
== Occurrence == Protactinium is one of the rarest and most expensive naturally occurring elements. It is found in the form of two isotopes, 231Pa and 234Pa, with the isotope 234Pa occurring in two different energy states. Nearly all natural protactinium is 231Pa. It is an alpha emitter and is formed by the decay of uranium-235, whereas the beta-radiating 234Pa is produced as a result of uranium-238 decay. Nearly all uranium-238 (99.8%) decays first to the shorter-lived 234mPa isomer. Protactinium occurs in uraninite (pitchblende) at concentrations of about 0.3–3 parts 231Pa per million parts (ppm) of ore. Whereas the usual content is closer to 0.3 ppm (e.g. in Jáchymov, Czech Republic), some ores from the Democratic Republic of the Congo have about 3 ppm. Protactinium is homogeneously dispersed in most natural materials and in water, but at much lower concentrations on the order of one part per trillion, corresponding to a radioactivity of 0.1 picocuries (pCi)/g. There is about 500 times more protactinium in sandy soil particles than in water, even when compared to water present in the same sample of soil. Much higher ratios of 2,000 and above are measured in loam soils and clays, such as bentonite.
Sources: en.wikipedia.org
By 1830, the German mathematician Carl Friedrich Gauss had determined the boundary conditions governing capillary action (i.e., the conditions at the liquid-solid interface). In 1871, the British physicist Sir William Thomson (later Lord Kelvin) determined the effect of the meniscus on a liquid's vapor pressure—a relation known as the Kelvin equation. German physicist Franz Ernst Neumann (1798–1895) subsequently determined the interaction between two immiscible liquids. Albert Einstein's first paper, which was submitted to Annalen der Physik in 1900, was on capillarity.
== Pharmacological targets == Recombinant forms of human relaxin-2 such as volenrelaxin (LY3540378) and serelaxin (RLX030) have been developed as investigational drugs. It is suggested that relaxin could be used as a therapeutic target when it comes to gynaecological disorders.
== Awards == Broadbent was elected as a Fellow of the Royal Society Te Apārangi in 2021. The Society said "One of her most notable contributions is the development and testing of healthcare robots, especially for improving outcomes in rest-home and dementia care and chronic illness...this is innovative interdisciplinary work of exceptional quality".
Sources: en.wikipedia.org
=== Advantages === Like iTDP, the main advantage of MSi-TDP is the capacity, within limits, to fully assess given proteoforms, including isotopic variants. Different front-end fractionation techniques can first be used to broadly resolve proteoforms (e.g. gel, LC, and capillary) in proteome extracts, enabling the subsequent MS/MS analysis of intact species to focus on those that are most compatible with the method (i.e. generally those <20-30 kDa). MSi-TDP can complement BUP approaches. Characterization of small proteins can be a significant challenge in BUP if an insufficient number of tryptic peptides are generated for analysis. MSi-TDP enables low mass protein detection, thus providing more detailed coverage of proteoforms in the lower MW range. Sequentially combining any number of fractionation techniques available to the researcher, such as chromatography (gel filtration and ion exchange), density-gradient ultrafiltration, or electrophoresis, dramatically increases the depth and quality of proteoform and proteome analysis.
Because PAI-2 is not properly secreted it accumulates in the cell where it remains unglycosylated. The exposed RCL loop on the PAI-2 contains the sequence Arg380-Thr381 which is identical to the cleavage site uPA/tPA identity. When uPA/tPA bind and cleave the bond between Arg-380 and Thr381 the RCL loop inserts itself into a β-sheet A slot in the enzyme(s) and conformationally alters the active site of the enzyme allowing it to no longer function.
The incompressible Navier–Stokes equations with uniform density and viscosity and conservative external field is the fundamental equation of hydraulics. The domain for these equations is commonly a 3 or fewer dimensional Euclidean space, for which an orthogonal coordinate reference frame is usually set to explicit the system of scalar partial differential equations to be solved. In 3-dimensional orthogonal coordinate systems are 3: Cartesian, cylindrical, and spherical. Expressing the Navier–Stokes vector equation in Cartesian coordinates is quite straightforward and not much influenced by the number of dimensions of the euclidean space employed, and this is the case also for the first-order terms (like the variation and convection ones) also in non-cartesian orthogonal coordinate systems. But for the higher order terms (the two coming from the divergence of the deviatoric stress that distinguish Navier–Stokes equations from Euler equations) some tensor calculus is required for deducing an expression in non-cartesian orthogonal coordinate systems. A special case of the fundamental equation of hydraulics is the Bernoulli's equation. The incompressible Navier–Stokes equation is composite, the sum of two orthogonal equations,
Sources: en.wikipedia.org
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.
Reduced pressure lowers the boiling point of water and allows ice to sublime at temperatures below freezing. It also helps remove water vapor from the product toward the condenser. The exact pressure is chosen to stay below the triple point of water.
No. Materials with low solids content or high volatile solvents may form weak or collapsed cakes. Some proteins and cells require stabilizers to survive freezing and drying stresses. Feasibility depends on formulation and process design.
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.