This is a working overview of sublimation, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Analytical methods for lyophilized solids must account for the low moisture content and the fragile cake. Karl Fischer titration is widely used for water content, while near-infrared spectroscopy can measure moisture non-destructively in sealed containers. X-ray diffraction and modulated differential scanning calorimetry help identify crystalline or amorphous phases. Residual solvent analysis may be needed if organic solvents were used during formulation. The combination of these methods supports batch release and long-term stability assessment.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Storage temperature | 2–8 °C or 20–25 °C | Depends on product stability; some require frozen storage. |
| Moisture content | 0.5–3% w/w | Higher values may reduce stability; target set per product. |
| Moisture method | Karl Fischer titration | Coulometric for low levels; volumetric for higher levels. |
| Cake appearance | Uniform, intact, no collapse | Visual inspection is qualitative and not a potency measure. |
| Reconstitution time | Seconds to several minutes | Depends on cake density, excipients, and diluent. |
Handling practices aim to prevent moisture ingress and mechanical damage. Vials should remain stoppered and crimped until use, and reconstitution should follow the labeled diluent and volume. Shipping may involve temperature-controlled containers and desiccants, but direct contact between desiccant and product is avoided. Regulatory guidance expects documented storage conditions, excursion assessments, and stability commitments. Open questions remain about how best to predict long-term stability from short accelerated studies for every formulation class.
After lyophilization, the product is usually a porous cake or powder with a large internal surface area. This structure can absorb moisture quickly if exposed to humid air, so vials are sealed under vacuum or an inert gas. Moisture uptake may lower the glass transition temperature of the dried matrix and accelerate chemical or physical degradation. Storage conditions therefore depend on the formulation, container, and intended shelf life. Some products remain stable at room temperature, while others require refrigeration or freezing.
Quality control for lyophilized products includes appearance, cake structure, reconstitution time, pH, residual moisture, and potency. Residual moisture is a key attribute because excess water can reduce stability, while excessively low moisture may cause structural changes or aggregation in some systems. Stability studies compare real-time and accelerated conditions to estimate shelf life. Analytical methods must be validated for the specific matrix, container, and moisture range. Sterility and container integrity are also monitored for sterile products.
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.
==== Merchant wholesalers ==== These firms take ownership of inventory and earn a margin by buying and reselling. They can specialize by product (food, pharmaceuticals, industrial inputs) or by customer segment (construction trades, hospitality, public sector).
It was determined that long-term exposure to low levels of confirmed mycotoxins could pose chronic health risks. For all the above reasons, a trend away from feed ingredients and toward USDA-certified ingredients fit for human consumption has developed. In 1999, another fungal toxin triggered the recall of dry dog food made by Doane Pet Care at one of its plants, including Ol' Roy, Wal-Mart's brand, as well as 53 other brands. This time the toxin killed 25 dogs. A 2005 consumer alert was released for contaminated Diamond Pet Foods for dogs and cats. Over 100 canine deaths and at least one feline fatality have been linked to Diamond Pet Foods contaminated by potentially deadly aflatoxin, according to Cornell University veterinarians.
== Industrial sources == β-carotene is industrially made either by total synthesis (see Retinol § Industrial synthesis) or by extraction from biological sources. Natural sources primarily include carrot, crude palm oil, and microalgae (such as Dunaliella salina), and genetically-engineered microbes. The synthetic path is low-cost and high-yield.
== External links == "Erythropoietin". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on 7 April 2020. Overview of all the structural information available in the PDB for UniProt: P01588 (Erythropoietin) at the PDBe-KB.
==== Fats ==== The fat content of the dry weight of mashua is between 0.1–0.4%. The investigation of the fatty acid composition of mashua flour by Ramallo (2004) showed a significant content of polyunsaturated fatty acids of 70.8%. The most abundant fatty acids are linoleic acid (48.7%), α-linolenic acid (22.13%), palmitic acid (21.2%) and oleic acid (3.96%). Ideally, the omega-6 to omega-3 fatty acid ratio should be between 1 and 4. For mashua the ratio between linoleic acid (omega-6) and the α-linolenic acid (omega-3) is 2.2 and therefore in the optimum range.
Sources: en.wikipedia.org
==== Dry ice ==== The Santa Fe Refrigerator Despatch (SFRD) briefly experimented with dry ice as a cooling agent in 1931. The compound was readily available and seemed like an ideal replacement for frozen water. Dry ice melts at −109 °F or −78.33 °C (versus 32 °F or 0 °C for conventional ice) and was twice as effective thermodynamically. Overall weight was reduced as the need for brine and water was eliminated. While the higher cost of dry ice was certainly a drawback, logistical issues in loading long lines of cars efficiently prevented it from gaining acceptance over conventional ice. Worst of all, it was found that dry ice can adversely affect the color and flavor of certain foods if placed too close to them.
=== Unit operations and unit processes === Food processing results in physical and (bio)chemical changes in food materials independently whether processing involves home cooking, food services or industrial food manufacturing. Food processing is typically covered by food engineering, biochemical engineering and chemical engineering disciplines. Description of processes relies on understanding physical phenomena occurring in unit operations and kinetics of (bio)chemical reactions in unit processes which form the building blocks of food processing. Unit operations in food processing are building blocks of operations resulting in physical changes in food materials. Unit operations are governed by general physical laws and include heat transfer and mass transfer required in different operations, such as separation processes, mixing and crystallization. Unit processes in food processing consist of unit operations and biochemical processes and chemical reactions resulting in (bio)chemical changes in food materials. In chemical reaction engineering multiple unit operations are combined with unit processes to achieve the desired chemical changes. Unit operations and unit processes are the premise of food processing systems. Multiple unit operations are often needed to carry out food processing designed to result in physical changes. Biochemical and chemical changes during food processing, such as loss of vitamin C, can accompany intended physical modifications, e.g., during heat treatments.
An insulin pump allows the replacement of slow-acting insulin for basal needs with a continuous infusion of rapid-acting insulin. The insulin pump delivers a single type of rapid-acting insulin in two ways:
=== Biosynthesis === Like other steroid hormones, testosterone is derived from cholesterol (Figure 1). The first step in the biosynthesis involves the oxidative cleavage of the side-chain of cholesterol by cholesterol side-chain cleavage enzyme (P450scc, CYP11A1), a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In the next step, two additional carbon atoms are removed by the CYP17A1 (17α-hydroxylase/17,20-lyase) enzyme in the endoplasmic reticulum to yield a variety of C19 steroids. In addition, the 3β-hydroxyl group is oxidized by 3β-hydroxysteroid dehydrogenase to produce androstenedione. In the final and rate limiting step, the C17 keto group androstenedione is reduced by 17β-hydroxysteroid dehydrogenase to yield testosterone. The largest amounts of testosterone (>95%) are produced by the testes in men, while the adrenal glands account for most of the remainder. Testosterone is also synthesized in far smaller total quantities in women by the adrenal glands, thecal cells of the ovaries, and, during pregnancy, by the placenta. In the testes, testosterone is produced by the Leydig cells. The male generative glands also contain Sertoli cells, which require testosterone for spermatogenesis. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific plasma protein, sex hormone-binding globulin (SHBG).
==== International law ==== Law professor Mary Ellen O'Connell said that the strike "violated fundamental principles of international law". Luke Moffett of Queen's University Belfast, also a law professor, stated that striking the ship without grounds of self-defense could be extrajudicial killing. In October, the Associated Press stated that the Trump administration is "treating alleged drug traffickers as unlawful combatants who must be met with military force". Regarding the 2 September strike, Geoffrey Corn, former senior adviser on the law of war to the US Army, said "I don't think there is any way to legitimately characterize a drug ship heading from Venezuela, arguably to Trinidad, as an actual or imminent armed attack against the United States, justifying this military response." George W. Bush administration legal figure John Yoo has also questioned the legality of the strikes arguing that "There has to be a line between crime and war." Obama era legal figure Harold Hongju Koh said that the strikes were "lawless, dangerous and reckless". Former chief White House ethics lawyer Richard Painter called the strikes a violation of international and federal law. Unnamed sources told The New York Times and the Washington Post that the US military used a plane during the first strike in September 2025 that was part of a US Air Force fleet painted to look like civilian aircraft.
Sources: en.wikipedia.org
In 2005, an animated short film of the nanofactory concept was produced by John Burch, in collaboration with Drexler. Such visions have been the subject of much debate, on several intellectual levels. No one has discovered an insurmountable problem with the underlying theories and no one has proved that the theories can be translated into practice. However, the debate continues, with some of it being summarized in the molecular nanotechnology article. If nanofactories could be built, severe disruption to the world economy would be one of many possible negative impacts, though it could be argued that this disruption would have little negative effect, if everyone had such nanofactories. Great benefits also would be anticipated. Various works of science fiction have explored these and similar concepts. The potential for such devices was part of the mandate of a major UK study led by mechanical engineering professor Dame Ann Dowling.
=== 2024–present: I'm a Celebrity... South Africa and Everything. All At Once === In April 2024, Collins made a guest appearance on the E4 reality series The Underdog: Josh Must Win, in which contestants believe they are competing on a reality show called The Favourite, however unbeknownst to them, the game is being controlled by Amber Gill, Nick Grimshaw, Pete Wicks and Vicky Pattison who must ensure that Josh, a non-typical reality show contestant, is declared the winner. Collins was enlisted to help with a photoshoot in which she assigned costumes to the contestants and advised them on various different poses. In May 2024, Collins appeared on the Daily Mail's podcast series Everything I Know About Me where she spoke about her life and career. In September 2024, Collins appeared on the BBC genealogy documentary series Who Do You Think You Are?. Collins was keen to learn more about her mother's side of the family, after she was fostered at birth and ultimately discovered that her grandmother was a diagnosed chronic schizophrenic who spent time in two psychiatric hospitals. Throughout the episode, she meets her distant cousins who reside in Dagenham near to where Collins grew up, and sees a photo of her grandmother for the first time. She also discovers that her ancestors lived on Dorset Street in Spitalfields, where Jack the Ripper is believed to have murdered his final victim Mary Jane Kelly in November 1888. In January 2025, she appeared on an episode of Pointless Celebrities alongside Hayley Hasselhoff, filmed two years prior.
== Contraindications == Benzodiazepines require special precaution if used in children and in alcohol- or other drug-dependent individuals. Particular care should be taken in pregnant or elderly people, people with substance use disorder history, particularly alcohol dependence, and people with comorbid psychiatric disorders. Alprazolam should be avoided or carefully monitored by medical professionals in individuals with myasthenia gravis, acute narrow-angle glaucoma, severe liver deficiencies such as cirrhosis, severe sleep apnea, pre-existing respiratory depression, marked neuromuscular respiratory, acute pulmonary insufficiency, chronic psychosis, hypersensitivity, allergy to alprazolam or other benzodiazepines, and borderline personality disorder, where it may induce suicidality and dyscontrol. Like all central nervous system depressants, alprazolam in larger-than-normal doses can cause significant deterioration in alertness and increase drowsiness, especially in those unaccustomed to the drug's effects.
'Watch Men Fall') took place at Le Trianon in Paris on 25 September 2019 during the Major Arcana evening as part of the Red Bull Music Festival. Bus de Nuit, featuring two previously unreleased tracks and two remixes, was released in October.
Sources: en.wikipedia.org
Most lyophilized products are stored in sealed containers at controlled temperature and humidity. Some require refrigeration, while others are stable at room temperature. Protection from light and moisture is often necessary.
Cake collapse indicates that the porous structure was lost during drying. It can result from excessive product temperature or an unsuitable formulation. Collapsed cakes may have slower reconstitution and are often rejected by visual inspection.
Residual moisture affects the chemical and physical stability of a lyophilized solid. High moisture can promote degradation, aggregation, or cake shrinkage. The acceptable range is set for each product based on stability data.
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.