The short version of Collapse temperature fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-14. Anything still debated is marked as such rather than presented as settled.
A formulation often contains excipients that protect the active ingredient during freezing and drying. Bulking agents provide structure, while lyoprotectants stabilize sensitive molecules. The freezing step can produce ice crystals whose size and distribution affect the drying rate, and cycle design includes freezing, annealing, and drying phases. If the product temperature rises above a critical value, the cake may collapse or lose its porous structure. Successful lyophilization therefore depends on the interaction between formulation, equipment, and cycle design.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen to convert liquid water into ice. Next, the pressure is reduced below the triple point of water so that ice changes directly into vapor without passing through a liquid phase. This step is called primary drying. The result is a porous solid or cake that retains the original shape of the frozen solution.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
The process generally proceeds in three stages: freezing, primary drying, and secondary drying. During freezing, controlled cooling converts water into ice and may also crystallize or vitrify solutes. In primary drying, the pressure is lowered below the triple point, and heat is supplied so ice sublimes directly to vapor. Secondary drying removes water that remains bound to the solid matrix, yielding a low final water content. Product temperature must stay below the collapse or glass transition temperature to maintain structure. Cycle design therefore balances shelf temperature, chamber pressure, and time.
Freeze-drying is used for materials whose activity or structure depends on low temperature and low water content. Examples include certain biologics, diagnostic reagents, starter cultures, coffee, and porous inorganic precursors. The dried product forms a cake whose porosity aids rapid wetting and dissolution. Main drawbacks are high energy use, long cycle times, and sensitivity to formulation and equipment variation. Questions remain about how freezing rates and ice morphology affect batch uniformity, especially when moving from laboratory to production scale.
Lyophilization, also called freeze-drying, is a dehydration process in which a solvent, usually water, is frozen and then removed by sublimation under reduced pressure. The method preserves heat-sensitive materials that would degrade in conventional drying. Large-scale use grew during the mid-twentieth century for blood plasma and antibiotics, and it later expanded to vaccines, enzymes, foods, and advanced materials. The process produces a dry, porous solid that usually reconstitutes rapidly. It is distinct from simple evaporation because the solvent bypasses the liquid phase during primary removal.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
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 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.
Phosphocreatine, also known as creatine phosphate (CP) or PCr (Pcr), is a phosphorylated form of creatine that serves as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle, myocardium and the brain to recycle adenosine triphosphate (ATP), the energy currency of the cell.
Interferon beta-1a is available only in injectable forms, and can cause skin reactions at the injection site that may include cutaneous necrosis. Skin reactions with interferon beta are more common with subcutaneous administration and vary greatly in their clinical presentation. They usually appear within the first month of treatment albeit their frequence and importance diminish after six months of treatment. Skin reactions are more prevalent in women. Mild skin reactions usually do not impede treatment whereas necroses appear in around 5% of patients and lead to the discontinuation of the therapy. Also over time, a visible dent at the injection site due to the local destruction of fat tissue, known as lipoatrophy, may develop, however, this rarely occurs with interferon treatment. Interferons, a subclass of cytokines, are produced in the body during illnesses such as influenza in order to help fight the infection. They are responsible for many of the symptoms of influenza infections, including fever, muscle aches, fatigue, and headaches. Many patients report influenza-like symptoms hours after taking interferon beta that usually improve within 24 hours, being such symptoms related to the temporary increase of cytokines. This reaction tends to disappear after 3 months of treatment and its symptoms can be treated with over-the-counter nonsteroidal anti-inflammatory drugs, such as ibuprofen, that reduce fever and pain. Another common transient secondary effect with interferon-beta is a functional deterioration of already existing symptoms of the disease.
An androgen prohormone, or proandrogen, is a prohormone (or prodrug) of an anabolic-androgenic steroid (AAS). They can be prohormones of testosterone or of synthetic AAS, for example, nandrolone (19-nortestosterone). Dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), and androstenedione may all be considered proandrogens of testosterone. Since 2005, the use of steroid precursors (prohormones) has been illegal in the U.S.
Although mild hypokalemia does not cause distinct symptoms, it is a risk factor for hypertension and cardiac arrhythmia. Severe hypokalemia usually presents with hypertension, arrhythmia, muscle cramps, fatigue, weakness and constipation. Causes of hypokalemia include vomiting, diarrhea, medications like furosemide and steroids, kidney dialysis, diabetes insipidus, hyperaldosteronism, and hypomagnesemia.
The latter showed yields for LPC extraction from 1% to 7.5% and toxicity screenings confirm that coniferous trees may contain toxins that can be consumed in small amounts, and additional studies including measuring the quantity of each toxin are needed.
Sources: en.wikipedia.org
acts as a self-standard. Ultramicroporous, microporous, and mesoporous conditions may be analyzed using this technique. Typical standard deviations for full isotherm fits including porous samples are less than 2%. Notice that in this description of physical adsorption, the entropy of adsorption is consistent with the Dubinin thermodynamic criterion, that is the entropy of adsorption from the liquid state to the adsorbed state is approximately zero.
=== 1 April === Ukraine reported shooting down two of three Shahed drones. A power substation in Zaporizhzhia Oblast was damaged by a drone strike. Ukrainian border guards intercepted a Russian sabotage group trying to enter Sumy Oblast. Valeriy Chaika, a Russian-appointed official in Starobilsk, Luhansk Oblast was killed after a bomb exploded in his car. The Security Service of Ukraine (SBU) arrested a resident of Kharkiv on suspicion of spying for Russia and a businessman from Berdiansk on suspicion of selling construction material for Russian fortifications. It also charged RT chief editor Margarita Simonyan in absentia with promoting genocide, spreading propaganda, justifying the Russian invasion and encouraging the violation of Ukraine's territorial integrity.
Fellowship of the Australian Academy of Science is made up of about 500 Australian scientists. Scientists judged by their peers to have made an exceptional contribution to knowledge in their field may be elected to Fellowship of the Academy. Fellows are often denoted using the post-nominal FAA (Fellow of the Australian Academy of Science). A small number of distinguished foreign scientists with substantial connections to Australian science are elected as Corresponding Members. Fellows are appointed for life; this table also contains deceased fellows.
== Alternative Medical Causes of Altered Turgor == Altered skin turgor can be caused by chronic medical conditions completely unrelated to an individual's immediate hydration status. Systemic sclerosis, or scleroderma, is an autoimmune disorder that triggers excessive collage production, resulting in abnormally tight, hard, and shiny skin that exhibits high turgor and cannot be pinched at all. On the other hand, genetic connective tissue disorders can drastically lower baseline skin tension, making the skin hyper-elastic. Additionally, localized fluid retention or severe edema stretches the dermis tightly, masking underlying systemic dehydration by artificially inflating skin turgor measurements.
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.