The short version of Sublimation fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-02-11 and is reviewed periodically as new material appears.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
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.
Regulatory expectations for lyophilized products focus on consistent manufacture and documented stability. Batches are often monitored for moisture, appearance, potency, and sterility where applicable. Process parameters such as shelf temperature, chamber pressure, and drying time are recorded and controlled within validated ranges. Open questions remain about how best to predict long-term stability from short accelerated studies, especially for complex biologics. Variations in freezing rate and ice crystal size can produce differences that are not always visible but may affect performance.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture uptake. Residual water content is measured because small changes can alter chemical stability and cake appearance. Storage temperature depends on the material; many biological products are kept at 2–8 °C, while some require −20 °C or colder. Exposure to ambient humidity during handling can cause the porous solid to absorb water and collapse. Container closures and stoppers are therefore selected for low moisture transmission and compatibility.
Quality control for lyophilized materials includes visual inspection of the cake, measurement of residual moisture, and tests for reconstitution time. An acceptable cake is typically uniform and may be slightly porous; shrinkage, meltback, or cracks can indicate process deviations. Analytical methods such as Karl Fischer titration, thermogravimetric analysis, and near-infrared spectroscopy quantify water content. Reconstitution time is recorded because a very slow or incomplete dissolution can signal collapse or aggregation. Stability studies compare samples stored under defined temperature and humidity conditions over months or years.
| Property | Value | Notes |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
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.
The low pressure used during drying allows water vapor to move from the ice surface to a cold condenser. Energy supplied as heat drives sublimation but must stay below the collapse temperature of the frozen matrix. If the product becomes too warm, the frozen structure may soften or melt, reducing pore formation and slowing drying. Formulations often include bulking agents, stabilizers, or buffers to support a rigid cake. The final moisture content depends on formulation, freezing rate, and the length of secondary drying.
Freeze-drying is distinct from simple evaporation and from spray drying. Evaporation removes water at temperatures above freezing, while spray drying rapidly dries droplets in a heated gas stream. Lyophilization avoids high temperatures, which can be useful for heat-sensitive materials such as proteins, vaccines, and some foods. The porous cake produced by sublimation dissolves or rehydrates more quickly than a dense dried mass. Not all materials tolerate freezing or the pH shifts that can occur as solutes concentrate during ice formation.
Lyophilization removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
== Interactions == Concomitant use of tizanidine and moderate or potent CYP1A2 inhibitors (such as zileuton, certain antiarrhythmics (amiodarone, mexiletine, propafenone, verapamil), cimetidine, famotidine, aciclovir, ticlopidine and oral contraceptives) is contraindicated. Concomitant use of tizanidine with fluvoxamine, a potent CYP1A2 inhibitor in humans, resulted in a 33-fold increase in the tizanidine AUC (plasma drug concentration-time curve). For this reason fluvoxamine and tizanidine should not be taken at the same time. Fluoroquinolone antibiotics such as moxifloxacin, levofloxacin, and ciprofloxacin should also be avoided due to an increased serum concentration of tizanidine when administered concomitantly. Tizanidine has the potential to interact with other central nervous system depressants. Alcohol should be avoided, particularly as it can upset the stomach. The CNS-depressant effects of tizanidine and alcohol are additive. Caution with the following interactions:
== See also == Common beta emitters Neutrino Betavoltaics Particle radiation Radionuclide Tritium illumination, a form of fluorescent lighting powered by beta decay Pandemonium effect Total absorption spectroscopy
== Parry Island seaplane base == The Imperial Japanese Navy had developed a seaplane base on Parry Island. Following its capture on 22 February, Seabees from the 110th Naval Construction Battalion expanded the base, building a coral-surfaced parking area and shops for minor aircraft and engine overhaul. A marine ways was installed on a Japanese pier and boat-repair shops were also erected. US Navy and Marine units based at Parry Island included:
== Further reading == Wainwright, Dylan K.; Lauder, George V. (2017). "Mucus Matters: The Slippery and Complex Surfaces of Fish" (PDF). In Gorb, Stanislav N.; Gorb, Elena V. (eds.). Functional Surfaces in Biology III: Diversity of the Physical Phenomena. Biologically-Inspired Systems. Vol. 10. Springer, Cham. pp. 223–246. doi:10.1007/978-3-319-74144-4_10. ISBN 978-3-319-74144-4. Retrieved 2021-09-13.
== Discovery == The protein was first isolated in 1987 by Thomas J. Martin's team at the University of Melbourne. Miao et al. showed that disruption of the PTHrP gene in mice caused a lethal phenotype and distinct bone abnormalities, suggesting that PTHrP has a physiological function.
Sources: en.wikipedia.org
The numbered divisions were organised so that on mobilisation they could deploy a complete infantry division, a cavalry brigade, and a number of troops for internal security or local frontier defence. Permanent divisional commands were formed with an establishment of staff officers under a major general.
Drosophila melanogaster is a species of fly (an insect of the order Diptera) in the family Drosophilidae. The species is often referred to as the fruit fly or lesser fruit fly, or less commonly the "vinegar fly", "pomace fly", or "banana fly". D. melanogaster is attracted to rotting fruit and fermenting beverages and is often found in orchards, kitchens, and pubs. Starting with Charles W. Woodworth's 1901 proposal of the use of this species as a model organism, D. melanogaster continues to be widely used for biological research in genetics, physiology, microbial pathogenesis, and life history evolution. In 1946 D. melanogaster was the first animal to be launched into space. As of 2017, six Nobel Prizes have been awarded to drosophilists for their work using the insect. Drosophila melanogaster is typically used in research owing to its rapid life cycle, relatively simple genetics with only four pairs of chromosomes, and large number of offspring per generation. It was originally an African species, with all non-African lineages having a common origin. Its geographic range includes all continents, including islands. D. melanogaster is a common pest in homes, restaurants, and other places where food is served. Flies belonging to the family Tephritidae are also called "fruit flies". This can cause confusion, especially in the Mediterranean, Australia, and South Africa, where the Mediterranean fruit fly Ceratitis capitata is an economic pest.
Myoglobin and hemoglobin, the first two proteins whose structures were solved by X-ray crystallography, have very similar folds made up of about 70% α-helix, with the rest being non-repetitive regions, or "loops" that connect the helices. In classifying proteins by their dominant fold, the Structural Classification of Proteins database maintains a large category specifically for all-α proteins. Hemoglobin then has an even larger-scale quaternary structure, in which the functional oxygen-binding molecule is made up of four subunits.
That's exactly what I didn't want to happen." One of Staley's last shows with Alice in Chains was the MTV Unplugged performance in New York on April 10, 1996. The recording of Unplugged came after a long period of inactivity for the band; it was their first concert in two-and-a-half years. Staley made his last performance on July 3, 1996, in Kansas City, Missouri, while Alice in Chains was touring with Kiss.
Sources: en.wikipedia.org
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
Most are held in sealed containers at controlled temperatures, often 2–8 °C, while some require frozen storage. Protection from moisture and light helps preserve the dry matrix. Exact conditions are set by the manufacturer or study protocol.