secondary drying raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-07-21 and is reviewed periodically as new material appears.
A freeze-dryer consists of a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. Vials, ampoules, or bulk trays hold the product during the cycle. The condenser traps water vapor as ice at a temperature lower than the product. Cycle development balances shelf temperature, chamber pressure, and time. Scale-up can be difficult because heat and mass transfer change with equipment size, so process analytical tools and conservative validation are often used.
Lyophilization is a dehydration technique in which a product is frozen and the solvent is removed under reduced pressure. The low pressure allows ice to sublimate directly into vapor without passing through a bulk liquid phase. This differs from conventional drying, where heat drives evaporation and can damage heat-sensitive structures. The process is used for biological materials, pharmaceutical formulations, and some foods. Its main advantage is preservation of porous structure and rapid reconstitution.
Freezing is the first stage and sets the ice structure that later becomes the pore network. The formulation is cooled below its freezing point, often with a controlled ramp, and solutes concentrate as ice forms. Primary drying then lowers chamber pressure and supplies heat to sublime the ice. The product temperature must stay below its collapse or eutectic temperature to prevent structural loss. Secondary drying raises the temperature modestly to remove bound water and achieve a low residual moisture.
Stability of a lyophilized solid depends on water content, temperature, and the physical state of the formulation. Amorphous products may slowly absorb moisture and drop below their glass transition temperature, causing collapse or crystallization. Some proteins and peptides can aggregate even in a dry state, especially when exposed to heat or moisture. Accelerated stability studies at elevated temperature and humidity help estimate shelf life, but real-time data remain the basis for expiration dating.
After drying, a lyophilized product is usually sealed under vacuum or an inert gas to limit moisture and oxygen exposure. The container closure system matters because stoppers and seals can allow moisture ingress over time. Storage conditions are selected from stability studies that track potency, cake appearance, and reconstitution behavior. Many freeze-dried materials are kept at controlled room temperature, while some require refrigeration or protection from light.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | freeze-drying, lyophilisation, cryodesiccation | Lyophilization is common in pharmaceutical literature. |
| Typical chamber pressure during primary drying | 0.05–0.5 mbar (5–50 Pa) | Must remain below the triple point of water. |
| Typical shelf temperature during freezing | −40 to −20 °C | Lower temperatures may be used for eutectic systems. |
| Typical residual moisture after secondary drying | 0.5–3% w/w | Product-dependent; low moisture improves stability but can cause over-drying. |
| Typical analytical method for residual moisture | Karl Fischer titration or loss on drying | Thermogravimetric methods are also used. |
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.
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
== History == It was developed but not discovered by Organon International; the first patents were issued in The Netherlands in 1967, and it was launched in West Germany in 1975 , in France in 1979 under the brand name Athymil, and in the UK as Norval. Investigators conducting clinical trials in the US submitted fraudulent data, and it was never approved in the US. Mianserin was one of the first antidepressants to reach the UK market that was less dangerous than the tricyclic antidepressants in overdose; as of 2012 it was not prescribed much in the UK.
=== Legal status === In July 2017, the US Food and Drug Administration (FDA) approved guselkumab for the treatment of plaque psoriasis. In November 2017, Health Canada approved guselkumab for the treatment of plaque psoriasis. In September 2020, the approval was expanded to include the treatment of adults with psoriatic arthritis. In April 2018, guselkumab was approved in Japan for the treatment of psoriatic arthritis. In July 2020, the FDA approved guselkumab as the first IL-23 inhibitor to treat active psoriatic arthritis (PsA). In September 2024, the FDA approved guselkumab for the treatment of moderately to severely active ulcerative colitis in adults. In May 2025, the UK Medicines and Healthcare products Regulatory Agency approved guselkumab for Crohn's disease and ulcerative colitis.
During the Ajuran Sultanate period, the city-states and republics of Merca, Mogadishu, Barawa, Hobyo and their respective ports flourished and had a lucrative foreign commerce with ships sailing to and from Arabia, India, Venetia, Persia, Egypt, Portugal, and as far away as China. Vasco da Gama, who passed by Mogadishu in the 15th century, noted that it was a large city with houses several storeys high and large palaces in its centre, in addition to many mosques with cylindrical minarets. The Harla, an early Hamitic group of tall stature who inhabited parts of Somalia, Tchertcher and other areas in the Horn, also erected various tumuli. These masons are believed to have been ancestral to ethnic Somalis. In the 16th century, Duarte Barbosa noted that many ships from the Kingdom of Cambaya in modern-day India sailed to Mogadishu with cloth and spices, for which they in return received gold, wax and ivory. Barbosa also highlighted the abundance of meat, wheat, barley, horses, and fruit on the coastal markets, which generated enormous wealth for the merchants. Mogadishu, the centre of a thriving textile industry known as toob benadir (specialised for the markets in Egypt, among other places), together with Merca and Barawa, also served as a transit stop for Swahili merchants from Mombasa and Malindi and for the gold trade from Kilwa. Jewish merchants from the Hormuz brought their Indian textile and fruit to the Somali coast in exchange for grain and wood.
=== History === Cornish-Bowden, Athel (1997). New Beer in an Old Bottle. Eduard Buchner and the Growth of Biochemical Knowledge. Valencia: Universitat de Valencia. ISBN 978-84-370-3328-0. Archived from the original on 13 December 2010. Retrieved 8 December 2007., A history of early enzymology. Williams, Henry Smith (1904). Modern Development of the Chemical and Biological Sciences. A History of Science: in Five Volumes. Vol. IV. New York: Harper and Brothers. Archived from the original on 9 May 2012. Retrieved 8 December 2007., a textbook from the 19th century.
=== Detection in body fluids === Modafinil and/or its major metabolite, modafinil acid, may be quantified in Plasma, serum, or urine to monitor dosage in those receiving modafinil therapeutically, to confirm a diagnosis of poisoning in hospitalized patients, or to assist in the forensic investigation of a vehicular traffic violation. Instrumental techniques involving gas or liquid chromatography are usually employed for these purposes. In 2011, modafinil was not tested for by common drug screens (except for anti-doping screens) and is unlikely to cause false positives for other chemically unrelated drugs such as substituted amphetamines. Reagent testing can screen for the presence of modafinil in samples.
Sources: en.wikipedia.org
=== 24 January === At least 70 people were killed in an RSF drone strike on the maternity ward of the Saudi Hospital in El Fasher that also destroyed its emergency department. The SAF claimed to have broken the siege around the Signal Corp's base in Khartoum. The RSF denied the claims. The SAF also claimed to have broken the siege around its General Headquarters in Khartoum and retook the El-Jeili oil refinery. The SAF and allied militias repelled an RSF attack on El Fasher following the expiration of the latter's ultimatum for the SAF to withdraw. The JDF claimed it had killed more than 400 RSF militants, destroyed more than 25 vehicles and captured 30 others. Ayub Osman Nahar resigned as an advisor to Hemedti, saying that he refused to be part of the RSF's atrocities against civilians and accusing the group of burning villages and killing civilians in North Darfur and Gezira State.
== History == Originally, the name "Medicare" in the United States referred to a program providing medical care for families of people serving in the military as part of the Dependents' Medical Care Act, which was passed in 1956. President Dwight D. Eisenhower held the first White House Conference on Aging in January 1961, in which creating a health care program for social security beneficiaries was proposed. President Lyndon B. Johnson signed the Social Security Amendments on July 30, 1965, establishing both Medicare and Medicaid. Arthur E. Hess, a deputy commissioner of the Social Security Administration, was named as first director of the Bureau of Health Insurance in 1965, placing him as the first executive in charge of the Medicare program. At the time, the program provided health insurance to 19 million Americans. The Social Security Administration (SSA) became responsible for the administration of Medicare and the Social and Rehabilitation Service (SRS) became responsible for the administration of Medicaid. Both agencies were organized under what was then known as the Department of Health, Education, and Welfare (HEW), in 1965. Since then, HEW, has been reorganized as the Department of Health and Human Services (HHS) in 1980. This consequently brought Medicare and Medicaid under the jurisdiction of the HHS. In March 1977, the Health Care Financing Administration (HCFA) was established under HEW. HCFA became responsible for the coordination of Medicare and Medicaid.
Analytical application of the radiotracer method is a forerunner of isotope dilution. This method was developed in the early 20th century by George de Hevesy for which he was awarded the Nobel Prize in Chemistry for 1943. An early application of isotope dilution in the form of radiotracer method was determination of the solubility of lead sulphide and lead chromate in 1913 by George de Hevesy and Friedrich Adolf Paneth. In the 1930s, US biochemist David Rittenberg pioneered the use of isotope dilution in biochemistry enabling detailed studies of cell metabolism.
Vegetables have been part of the human diet from time immemorial. Some are staple foods but most are accessory foodstuffs, adding variety to meals with their unique flavors and at the same time, adding nutrients necessary for health. Some vegetables are perennials but most are annuals and biennials, usually harvested within a year of sowing or planting. Whatever system is used for growing crops, cultivation follows a similar pattern; preparation of the soil by loosening it, removing or burying weeds, and adding organic manures or fertilisers; sowing seeds or planting young plants; tending the crop while it grows to reduce weed competition, control pests, and provide sufficient water; harvesting the crop when it is ready; sorting, storing, and marketing the crop or eating it fresh from the ground. Different soil types suit different crops, but in general in temperate climates, sandy soils dry out fast but warm up quickly in the spring and are suitable for early crops, while heavy clays retain moisture better and are more suitable for late season crops. The growing season can be lengthened by the use of fleece, cloches, plastic mulch, polytunnels, and greenhouses. In hotter regions, the production of vegetables is constrained by the climate, especially the pattern of rainfall, while in temperate zones, it is constrained by the temperature and day length.
Sources: en.wikipedia.org
Stoney River Steakhouse & Grill is a chain of steakhouses in the United States. In 2008, the company had 12 locations. As of 2025, there are ten Stoney River restaurants. In 2007, O'Charley's filed a lawsuit against competitor Darden claiming their Rocky River Grillhouse restaurant was too similar of a trademark to their Stoney River Legendary Steaks brand.
==== BLM10/PA200 ==== Yet another type of non-ATPase regulatory particle is the Blm10 (yeast) or PA200/PSME4 (human). It opens only one α subunit in the 20S gate and itself folds into a dome with a very small pore over it.
intensive property A physical quantity whose value does not depend on the size of the system or the quantity of matter for which it is measured. Examples include density, temperature, and pressure. Contrast extensive property.
Asn, followed by anything but Pro, followed by either Ser or Thr, followed by anything but Pro This pattern may be written as N{P}[ST]{P} where N = Asn, P = Pro, S = Ser, T = Thr; {X} means any amino acid except X; and [XY] means either X or Y. The notation [XY] does not give any indication of the probability of X or Y occurring in the pattern. Observed probabilities can be graphically represented using sequence logos. Sometimes patterns are defined in terms of a probabilistic model such as a hidden Markov model.
The buildup of South African armour and artillery on the border did not go unnoticed; by late November the Soviet Union had enough satellite reconnaissance photographs and other intelligence to deduce that the SADF was preparing for another major incursion into Angola. During a private meeting arranged at the Algonquin Hotel by UN Secretary-General Javier Pérez de Cuéllar at Moscow's request, Soviet diplomats informed their South African counterparts that further aggression towards FAPLA would not be tolerated. The Soviets threatened unspecified retaliation if FAPLA's grip on Angola disintegrated further as a result of Askari. Simultaneously, in a direct show of force, a Soviet aircraft carrier and three surface ships called at Luanda before rounding the Cape of Good Hope. This constituted the most powerful Soviet naval detachment which had ever approached within striking distance of South African waters. Botha was unmoved, and Askari proceeded as scheduled on 9 December. Its targets were several large PLAN training camps, all of which were located no more than five kilometres from an adjacent FAPLA brigade headquarters. The four local FAPLA brigades represented one-seventh of the entire Angolan army, and three had substantial Soviet advisory contingents. Soviet General Valentin Varennikov, who was instrumental in directing the Angolan defence, was confident that "given their numerical strength and armament, the brigades...[would] be able to repel any South African attack".
Sources: en.wikipedia.org
Yes, the terms are generally interchangeable. Lyophilization is more common in pharmaceutical and laboratory contexts, while freeze-drying appears widely in food science and general writing. Both describe removal of solvent by sublimation under vacuum after freezing.
Reduced pressure keeps the process below the triple point of water, so ice can sublimate directly to vapor. It also lowers the temperature needed for drying, which helps preserve heat-sensitive materials. Without vacuum, melting or boiling could occur instead of controlled sublimation.
The rate depends on heat transfer to the product and mass transfer of vapor through the dried layer. A cold condenser, adequate vacuum, and suitable shelf temperature all influence speed. Formulation properties such as solid content and collapse temperature also set practical limits.
Sealed vials or containers should be kept at the temperature specified by stability data, often controlled room temperature or 2–8 °C. Moisture and oxygen barriers are important because both can degrade sensitive materials. Opened containers may need immediate use or protection from ambient humidity.