primary drying raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-02-11. Anything still debated is marked as such rather than presented as settled.
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.
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 |
|---|---|---|
| Primary phase change | Sublimation | Ice changes directly to vapor under reduced pressure |
| Typical chamber pressure | 0.01–0.5 mbar (1–50 Pa) | Below the triple point of water; product-specific |
| Typical product temperature during primary drying | −40 °C to −10 °C | Kept below collapse temperature |
| Typical residual moisture | 0.5–3% w/w | Target range varies by formulation and use |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilization is the US spelling |
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.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
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.
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.
== Personal life == In 1993, Pritzker married Mary Kathryn "M. K." Muenster, whom he had met in Washington, D.C., when she worked as an aide to U.S. senator Tom Daschle. She is one of three children of Theodore and Karen Muenster. Her father unsuccessfully ran for the U.S. Senate in 1990 and her mother served in the South Dakota Senate. They live in Chicago's Gold Coast neighborhood with their two children. During the 2018 campaign, the Chicago Sun-Times reported that Pritzker and his wife had purchased a mansion next door to their home in 2017. The mansion remained vacant and the interior was in disrepair. He then appealed his original property tax assessment because the newly built property was uninhabitable, in part because it had "no functioning bathrooms or kitchen"; the Cook County assessor reduced the home's value from $6.25 million to about $1.1 million, which granted Pritzker an 83% property tax reduction, equal to about $230,000. The Cook County inspector general accused Pritzker of a scheme to defraud the county. Pritzker called the controversy a political attack and stressed that the county regulations had been followed, but paid the county treasurer $330,000 to reimburse the amount of the property tax reduction. To defend his claim that regulations were followed, Pritzker's campaign pointed to notes from an appraiser in the inspector general report that said the property was in "very poor condition", noting that the staircase was "structurally unsound" and "dangerous".
=== Operation Epic Fury, 2026 === It was announced on 24 March 2026 that the Pentagon had ordered the commander of the 82nd Airborne Division, Major General Brandon R. Tegtmeier, and his headquarters staff to the Middle East, ahead of a potential deployment of a brigade combat team of around 3,000 troops to support operations against Iran. The U.S. Army extended the 82nd Airborne Division’s deployment to the Middle East to a full year, due to “operational requirements”. The extended deployment was announced by Major General Tegtmeier in a letter to military families.
=== Post-settlement activity === In 1991, the local Bhopal authorities charged Anderson, who had retired in 1986, with manslaughter, a crime that carries a maximum penalty of 10 years in prison. He was declared a fugitive from justice by the Chief Judicial Magistrate of Bhopal on 1 February 1992 for failing to appear at the court hearings in a culpable homicide case in which he was named the chief defendant. Orders were passed to the Government of India to press for an extradition from the United States. The United States declined to extradite him citing a lack of evidence. The U.S. Supreme Court refused to hear an appeal of the decision of the lower federal courts in October 1993 against allowing victims of the Bhopal disaster to seek damages in a U.S. court. In 2004, the Indian Supreme Court ordered the Indian government to release any remaining settlement funds to victims. And in September 2006, the Welfare Commission for Bhopal Gas Victims announced that all original compensation claims and revised petitions had been "cleared". In 2006, the U.S. Court of Appeals for the Second Circuit in New York City upheld the dismissal of remaining claims in the case of Bano v. Union Carbide Corporation. This move blocked plaintiffs' motions for class certification and claims for property damages and remediation.
== Organic synthesis == Cyanogen bromide is a common reagent in organic synthesis. In most reactions, it acts as a source of electrophilic cyanogen and nucleophilic bromide; carbocations preferentially attack the nitrogen atom. In the presence of a Lewis acid, it cyanidates arenes. BrCN converts alcohols to cyanates; amines to cyanamides or dicyanamides. Excess BrCN continues the reaction to guanidines; hydroxylamines yield hydroxyguanidines similarly. The cyanamides so formed umpole the original amine, and tends to eliminate alkyl substituents. In the von Braun reaction, tertiary amines react with cyanogen bromide to yield disubstituted cyanamides and an alkyl bromide. That net reaction is similar to the Polonovski elimination, but does not require N-oxidation. In bromocyanation, BrCN adds across multiple bonds to give a vicinal cyanobromide. Bromocyanated enols spontaneously undergo a Darzens-like elimination to an epoxynitrile. Cyanogen bromide is also a dehydrating agent, hydrolyzing to hydrogen bromide and cyanic acid. The compound is used in the synthesis of the pharmaceuticals 4-methylaminorex and viroxime.
== See also == Chicken restaurant List of fast-food chicken restaurants Oporto – Australian-based Portuguese themed chicken restaurant TASTE Holdings – management group in which Chickenland (Pty) Ltd has significant shareholding
Sources: en.wikipedia.org
Locals are "Districts"; national convention meets quadrennially; headquarters in Pittsburgh; in 1979 had $120,000,000 in insurance; also sponsored outings, baseball games, etc. While originally for German men and women, by 1979 the Union was open to men and women of all ethnic backgrounds. In 1923 the Union had 54,000 members, 50,000 in 1965, and 37,000 in 1979. Improved Order, Knights of Pythias Independent Order of Red Men North American Swiss Alliance - Founded July 14, 1865, as the Grütli Bund der Vereinigten Staaten von Nord Amerika in Cincinnati. Became Nordamerikanishcher Schweizerbund in July 1911. National convention meets quadrennially, locals are called branches or lodges. Open to Swiss, Swiss descendants, or spouses of Swiss. Membership 2,000 in 1965, 4,000 in 1978 and 3,350 in 1994, about 10 to 15% are social, uninsured members. Periodical originally called Gruetlianer changed to Der Schweizer in 1911. Headquarters in Cleveland in 1979, but it was an "organization on wheels" moving to several places every few years in the late 19th century Schwarzer Ritter, Deutscher Orden - Claimed great antiquity, though in 1899 it was said to have been present in the United States for about 30 years. Active in New York, New Jersey, Pennsylvania, and the District of Columbia. Sons of Hermann United League of America Workmen's Benefit Fund - Founded as the Workmen's Sick and Death Benefit Fund in 1884, this organization was licensed to provide insurance in February 1899. The current name was adopted in 1939. Membership opened to non-Germans in 1976.
== Further reading == Goldman, Lee (15 April 2001). "Key challenges confronting internal medicine in the early twenty-first century". The American Journal of Medicine. 110 (6): 463–470. doi:10.1016/S0002-9343(01)00649-0. PMID 11331058. Meltzer, David; Manning, WG; Morrison, J; Shah, MN; Jin, L; Guth, T; Levinson, W (Dec 3, 2002). "Effects of Physician Experience on Costs and Outcomes on an Academic General Medicine Service: Results of a Trial of Hospitalists". Annals of Internal Medicine. 137 (11): 866–74. doi:10.7326/0003-4819-137-11-200212030-00007. PMID 12458986. S2CID 31987327. Salerno, Stephen M; Landry, Francis J; Kaboli, Peter J (Feb 1, 2001). "Patient perceptions of the capabilities of internists: a multi-center survey". The American Journal of Medicine. 110 (2): 111–117. doi:10.1016/S0002-9343(00)00666-5. PMID 11165552. Sox, Harold C (Jun 15, 2001). "Supply, demand, and the workforce of internal medicine". The American Journal of Medicine. 110 (9): 745–749. doi:10.1016/S0002-9343(01)00756-2. PMID 11403763. Wetterneck, Tosha B.; Linzer, M; McMurray, JE; Douglas, J; Schwartz, MD; Bigby, J; Gerrity, MS; Pathman, DE; et al. (Mar 25, 2002). "Worklife and Satisfaction of General Internists". Archives of Internal Medicine. 162 (6): 649–56. doi:10.1001/archinte.162.6.649. PMID 11911718.
(1) Most often, 5'-DMT group is removed at the end of the oligonucleotide chain assembly. The oligonucleotides are then released from the solid phase and deprotected (base and phosphate) by treatment with aqueous ammonium hydroxide, aqueous methylamine, their mixtures, gaseous ammonia or methylamine or, less commonly, solutions of other primary amines or alkalies at ambient or elevated temperature. This removes all remaining protection groups from 2'-deoxyoligonucleotides, resulting in a reaction mixture containing the desired product. If the oligonucleotide contains any 2'-O-protected ribonucleotide residues, the deprotection protocol includes the second step where the 2'-O-protecting silyl groups are removed by treatment with fluoride ion by various methods. The fully deprotected product is used as is, or the desired oligonucleotide can be purified by a number of methods. Most commonly, the crude product is desalted using ethanol precipitation, size exclusion chromatography, or reverse-phase HPLC. To eliminate unwanted truncation products, the oligonucleotides can be purified via polyacrylamide gel electrophoresis or anion-exchange HPLC followed by desalting. (2) The second approach is only used when the intended method of purification is reverse-phase HPLC. In this case, the 5'-terminal DMT group that serves as a hydrophobic handle for purification is kept on at the end of the synthesis. The oligonucleotide is deprotected under basic conditions as described above and, upon evaporation, is purified by reverse-phase HPLC.
==== Distribution ==== Sertraline is highly plasma protein bound (98.5%) across a concentration range of 20 to 500 ng/mL. Despite the high plasma protein binding, sertraline and its metabolite desmethylsertraline at respective tested concentrations of 300 ng/mL and 200 ng/mL were found not to interfere with the plasma protein binding of warfarin and propranolol, two other highly plasma protein-bound drugs.
Sources: en.wikipedia.org
Lyophilization relies on sublimation, so water moves from solid ice to vapor without becoming liquid. The material is frozen, pressure is reduced, and controlled heat is supplied. Vapor is captured on a cold condenser, leaving a dry porous solid.
The process has three main stages: freezing, primary drying, and secondary drying. Freezing sets the ice structure, primary drying removes free ice, and secondary drying removes bound water. Each stage uses specific temperature, pressure, and time settings.
No, it is a drying method rather than a sterilization method. Removing water can limit microbial growth, but it does not reliably kill microorganisms. Sterility must come from separate steps such as filtration, heat treatment, or aseptic processing.
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.