A practical reference on primary drying: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-02 and is reviewed periodically as new material appears.
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.
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.
| 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 physics of lyophilization depends on phase boundaries and heat and mass transfer. During primary drying, heat supplied to the product must equal the latent heat of sublimation, while water vapor moves through the drying cake to the condenser. If shelf temperature or pressure is set too high, the ice front can exceed the collapse temperature, causing meltback or pore collapse. If conditions are too cold, drying slows and costs rise. Formulation excipients, vial geometry, and freezing rate alter these limits.
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.
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.
=== Parkinson's disease and Alzheimer's disease === Oxidative stress and lipid peroxidation are believed to be contributing factors leading to neuronal loss and mitochondrial dysfunction in the substantia nigra in Parkinson's disease, and may play an early role in the pathogenesis of Alzheimer's disease. It is reported that CL content in the brain decreases with aging, and a recent study on rat brain shows it results from lipid peroxidation in mitochondria exposed to free radical stress. Another study shows that the CL biosynthesis pathway may be selectively impaired, causing 20% reduction and composition change of the CL content. It is also associated with a 15% reduction in linked complex I/III activity of the electron transport chain, which is thought to be a critical factor in the development of Parkinson's disease.
"When combined with the federal debt (approximately $680 billion), the debt-to-GDP ratio for Ontarians nears 80 percent." In October 2019, the Financial Accountability Office said that the deficit had increased from $ 3.7 billion in 2017—at the end of the Liberal administration—to $7.4 billion in 2018 under Premier Ford. The deficit had almost doubled partly because of "cancelled climate-change initiatives and subsidizing hydro bills" according to the Hamilton Spectator. The government's 2025 budget reported a $14.6 billion deficit; in 2026, the Ford government's budget deficit was nearly double what was projected in 2025, reaching $13.8 billion.
In 1994, world production of H2O2 was around 1.9 million tonnes and grew to 2.2 million in 2006, most of which was at a concentration of 70% or less. In that year, bulk 30% H2O2 sold for around 0.54 USD/kg, equivalent to US$1.50/kg (US$0.68/lb) on a 100% purity basis. Hydrogen peroxide is manufactured almost exclusively by the anthraquinone process, which was originally developed by BASF in 1939. It begins with the reduction of an anthraquinone (such as 2-ethylanthraquinone or the 2-amyl derivative) to the corresponding anthrahydroquinone, typically by hydrogenation on a palladium catalyst. In the presence of oxygen, the anthrahydroquinone then undergoes autoxidation: the labile hydrogen atoms of the hydroxy groups transfer to the oxygen molecule, to give hydrogen peroxide and regenerating the anthraquinone. Most commercial processes achieve oxidation by passing compressed air through a solution of the anthrahydroquinone, with the hydrogen peroxide then extracted from the solution and the anthraquinone recycled back for successive cycles of hydrogenation and oxidation. The net reaction for the anthraquinone-catalyzed process is:
Low-calorie sweeteners are often made of maltodextrin with added sweeteners. Maltodextrin is an easily digestible synthetic polysaccharide consisting of short chains of three or more glucose molecules and is made by the partial hydrolysis of starch. Strictly, maltodextrin is not classified as sugar as it contains more than two glucose molecules, although its structure is similar to maltose, a molecule composed of two joined glucose molecules. Polyols are sugar alcohols and are used in chewing gums where a sweet flavour is required that lasts for a prolonged time in the mouth.
Laurus nobilis is a widespread relict of the laurel forests that originally covered much of the Mediterranean Basin when the climate of the region was more humid. With the drying of the Mediterranean during the Pliocene era, the laurel forests gradually retreated, and were replaced by the more drought-tolerant sclerophyll plant communities familiar today. Most of the last remaining laurel forests around the Mediterranean are believed to have disappeared approximately ten thousand years ago, although some remnants still persist in the mountains of southern Turkey, northern Syria, southern Spain, north-central Portugal, northern Morocco, the Canary Islands and in Madeira.
Sources: en.wikipedia.org
In Chadwick's words, "...In order to explain the great penetrating power of the radiation we must further assume that the particle has no net charge..." The existence of the neutron was first postulated by Rutherford in 1920, and in the words of Chadwick, "...how on earth were you going to build up a big nucleus with a large positive charge? And the answer was a neutral particle." Subsequently, he communicated his findings in more detail. In the words of Richard Rhodes, referring to the neutron, "It would therefore serve as a new nuclear probe of surpassing power of penetration." Philip Morrison stated, "A beam of thermal neutrons moving at about the speed of sound...produces nuclear reactions in many materials much more easily than a beam of protons...traveling thousands of times faster." According to Rhodes, "Slowing down a neutron gave it more time in the vicinity of the nucleus, and that gave it more time to be captured." Fermi's team, studying radiative capture which is the emission of gamma radiation after the nucleus captures a neutron, studied sixty elements, inducing radioactivity in forty. In the process, they discovered the ability of hydrogen to slow down the neutrons. Enrico Fermi and his colleagues in Rome studied the results of bombarding uranium with neutrons in 1934. Fermi concluded that his experiments had created new elements with 93 and 94 protons, which the group dubbed ausenium and hesperium.
==== Dopamine precursors and related ==== Carbidopa (Lodosyn) – aromatic L-amino acid decarboxylase (AAAD) inhibitor Carbidopa/levodopa (Crexont; IPX-203; IPX203) – combination of carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and levodopa (dopamine precursor) [324] Foscarbidopa/foslevodopa (ABBV-951; foslevodopa/foscarbidopa; levodopa/carbidopa prodrug; Produodopa; Vyalev) – combination of foscarbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) and foslevodopa (dopamine precursor) [325] Levodopa (CVT-301; CXG-89; Inbrija) – dopamine precursor and indirect non-selective dopamine receptor agonist [326] Levodopa/benserazide (co-beneldopa) (Madopar, Prolopa) – combination of levodopa (dopamine precursor) and benserazide (aromatic L-amino acid decarboxylase (AAAD) inhibitor) Levodopa/carbidopa extended-release (GSK-587124; IPX-066; Numient; Patrome; Rytary) – combination of levodopa (dopamine precursor) and carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) [327] Levodopa/carbidopa intraduodenal (ABT-SLV187; carbidopa/levodopa enteral suspension; Duodopa; Duopa; LCIG; levodopa/carbidopa intestinal gel) – combination of levodopa (dopamine precursor) and carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) [328] Melevodopa/carbidopa (carbidopa/melevodopa; CHF-1512; CNP-1512; GT-1512; levodopa methyl ester/carbidopa; Sirio; V-1512) – combination of melevodopa (dopamine precursor) and carbidopa (aromatic L-amino acid decarboxylase (AAAD) inhibitor) [329]
Air knife coating Anilox coater Flexo coater Gap Coating Knife-over-roll coating Gravure coating Hot melt coating – when the necessary coating viscosity is achieved by temperature rather than solution of the polymers etc. This method commonly implies slot-die coating above room temperature, but it also is possible to have hot-melt roller coating; hot-melt metering-rod coating, etc. Immersion dip coating Kiss coating Metering rod (Meyer bar) coating Roller coating Forward roller coating Reverse roll coating Silk Screen coater Rotary screen Slot Die coating – Slot die coating was originally developed in the 1950s. Slot die coating has a low operational cost and is an easily scaled processing technique for depositing thin and uniform films rapidly, while minimizing material waste. Slot die coating technology is used to deposit a variety of liquid chemistries onto substrates of various materials such as glass, metal, and polymers by precisely metering the process fluid and dispensing it at a controlled rate while the coating die is precisely moved relative to the substrate. The complex inner geometry of conventional slot dies require machining or can be accomplished with 3D printing. Extrusion coating – generally high pressure, often high temperature, and with the web travelling much faster than the speed of the extruded polymer Curtain coating – low viscosity, with the slot vertically above the web and a gap between slot-die and web. Slide coating – bead coating with an angled slide between the slot-die and the bead.
In other cases, topical is defined as applied to a localized area of the body or to the surface of a body part regardless of the location of the effect. By this definition, topical administration also includes transdermal application, where the substance is administered onto the skin but is absorbed into the body to attain systemic distribution. Such medications are generally hydrophobic chemicals, such as steroid hormones. Specific types include transdermal patches which have become a popular means of administering some drugs for birth control, hormone replacement therapy, and prevention of motion sickness. One example of an antibiotic that may be applied topically is chloramphenicol. If defined strictly as having a local effect, the topical route of administration can also include enteral administration of medications that are poorly absorbable by the gastrointestinal tract. One poorly absorbable antibiotic is vancomycin, which is recommended by mouth as a treatment for severe Clostridioides difficile colitis.
Sources: en.wikipedia.org
Cube sugar (sometimes called sugar lumps) are white or brown granulated sugars lightly steamed and pressed together in block shape. They are used to sweeten drinks. Sugarloaf was the usual cone-form in which refined sugar was produced and sold until the late 19th century.
A Study published by Altus Group indicates that 383 pubs closed in England during the first six months of 2023, including 46 in London. 9 October – Medway Council in Kent cancels its 2023 Christmas lights due to what it describes as a "challenging financial situation". 11 October – South Yorkshire Police says it is making "ongoing" inquiries after video footage emerged of a man climbing onto the roof of Sheffield Town Hall to replace an Israeli flag with a Palestinian one. An Independent Monitoring Board report into Wandsworth Prison has concluded that the prison is "unsafe and inhumane"; the report was prepared before the escape of Daniel Khalife in September. 12 October – Following reports that some student societies have been distributing leaflets in support of Hamas, education ministers Gillian Keegan and Robert Halfon have written to university vice chancellors in England urging them to "act swiftly and decisively against any threats" to students' safety and welfare. The number of people waiting for planned NHS treatment in England rises to 7.75 million. 13 October – Three Jewish schools in north London have closed for the day amid safety concerns for their students because of the ongoing conflict between Israel and Hamas. Police have detailed a 22-year-old woman on suspicion of supporting Hamas, which is a prescribed terrorist organisation in the UK, following a speech given at a protest in Brighton on 8 October.
Formylglycine-generating enzyme (FGE), located at 3p26.1 in humans, is the name for an enzyme present in the endoplasmic reticulum that catalyzes the conversion of cysteine to formylglycine (fGly). There are two main classes of FGE, aerobic and anaerobic. FGE activates sulfatases, which are essential for the degradation of sulfate esters. The catalytic activity of sulfatases is dependent upon a formylglycine (sometimes called oxoalanine) residue in the active site.
==== Type 2 ==== The SCFAs excreted by the soluble dietary fiber-consuming bacteria in the intestine activate FFAR2 on nearby intestinal L-cells. This stimules these cells to secrete GLP-1 (i.e., glucagon-like peptide-1) and PYY (i.e., peptide YY) into the blood. GLP-1 stimulates pancreatic beta cells to secrete insulin into the blood and inhibits pancreatic alpha cells from secreting glucagon into the blood. Since insulin causes cells to take up blood glucose and glucagon causes the liver to release glucose into the blood, FFAR2 activation of L cells lowers blood glucose levels. In addition, PYY and GLP-1 reduce appetite and food consumption. The excreted SCFAs also activate FFAR2 on nearby intestinal K cells to simulate their secretion of GIP (i.e., glucose-dependent insulinotropic polypeptide). GIP stimulates insulin secretion but, perhaps paradoxically, also stimulates glucagon secretion; however, the net effect of GIP is to reduce blood glucose levels. GIP also slows gastric motility. In addition, both GLP-1 and GIP protect pancreatic beta cells from dying by apoptosis (see programmed cell death). The SCFAs excreted by the gut microorganisms also pass through the intestinal epithelium to enter the blood stream and activate FFAR2 on cells located in distant tissues such as pancreas beta cells and adipose tissue fat cells. Individuals with type 2 diabetes, particularly in advanced cases, have nearly completely lost the incretin effect.
LGD-4033 has not yet completed clinical development or been approved for any use. As of 2023, it is in phase 2 clinical trials for the treatment of hip fracture and muscle atrophy. LGD-4033 was developed by Ligand Pharmaceuticals, and is now being developed by Viking Therapeutics. Aside from its development as a potential pharmaceutical drug, LGD-4033 is on the World Anti-Doping Agency list of prohibited substances and is sold for physique- and performance-enhancing purposes by black-market Internet suppliers. LGD-4033 is often used in these contexts at doses greatly exceeding those evaluated in clinical trials, with unknown effectiveness and safety. Many products sold online that are purported to be LGD-4033 either contain none or contain other unrelated substances. Social media has played an important role in facilitating the widespread non-medical use of SARMs.
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.
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.