The short version of secondary drying fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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 |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
The process relies on the phase diagram of water, where the triple point marks the conditions at which ice, liquid water, and vapor coexist. By maintaining pressure below this point, typically around 0.01 to 0.1 millibar, sublimation becomes the dominant mechanism. Formulations often include excipients such as sugars or polymers that act as lyoprotectants and bulking agents. These additives help preserve the structure of the active ingredient and prevent collapse during drying. The choice of excipient and freezing rate influences the final cake morphology and stability.
Industries use lyophilization for pharmaceuticals, biological products, and food preservation. In the pharmaceutical sector, it extends the shelf life of injectable drugs, vaccines, and proteins that are unstable in aqueous solution. Food manufacturers apply freeze-drying to coffee, fruits, and ready meals to retain flavor and texture. The process is energy-intensive and requires specialized equipment, which limits its use to high-value products. Ongoing research examines how formulation and process parameters affect the quality of the final dried product.
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.
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.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
Lyophilized products are typically hygroscopic and require protection from moisture during storage. Manufacturers seal them in glass vials, often under vacuum or an inert gas such as nitrogen. The container closure system, including the stopper and crimp seal, must prevent water vapor ingress. Storage temperature varies from controlled room temperature to refrigerated or frozen conditions, depending on the formulation. Humidity-controlled environments are essential because even brief exposure to ambient air can degrade the product.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
Bergamot essential oil (pronounced ), is a cold-pressed essential oil produced by cells inside the rind of a bergamot orange fruit. It is a common flavouring and top note in perfumes. The scent of bergamot essential oil is similar to a sweet light orange peel oil with a floral note.
== Cultivation == Successful cultivation requires warm to hot summers with high sunshine levels; even partial shade will reduce the yield substantially. It also prefers rich, well-drained soil. The seed is harvested by cutting the flower heads off the stalks when the seed is beginning to ripen. The seed heads are placed upside down in a paper bag and left in a warm, dry place for a week. The seeds then separate from the stems easily for storage in an airtight container. These plants, like their fennel and parsley relatives, often are eaten by black swallowtail caterpillars in areas where that species occurs. For this reason, they may be included in some butterfly gardens.
A detailed report of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some demographic information about the patient (for example, age, gender, ethnic origin). (NCI) Case report form
== Applications == Applications of phage display technology include determination of interaction partners of a protein (which would be used as the immobilised phage "bait" with a DNA library consisting of all coding sequences of a cell, tissue or organism) so that the function or the mechanism of the function of that protein may be determined. Phage display is also a widely used method for in vitro protein evolution (also called protein engineering). As such, phage display is a useful tool in drug discovery. It is used for finding new ligands (enzyme inhibitors, receptor agonists and antagonists) to target proteins. The technique is also used to determine tumour antigens (for use in diagnosis and therapeutic targeting) and in searching for protein-DNA interactions using specially-constructed DNA libraries with randomised segments. Recently, phage display has also been used in the context of cancer treatments - such as the adoptive cell transfer approach. In these cases, phage display is used to create and select synthetic antibodies that target tumour surface proteins. These are made into synthetic receptors for T-Cells collected from the patient that are used to combat the disease. Recently, M13 bacteriophages were genetically engineered to display an anti-GD2 single-chain variable fragment (scFv) derived from the FDA-approved antibody Dinutuximab on their pIII coat protein. The engineered phages were subsequently loaded with hundreds of photosensitizer molecules to selectively deliver the payload to GD2-positive neuroblastoma cells.
A live album and DVD, Rush in Rio, was released in October 2003, featuring the last performance of the band's Vapor Trails tour on November 23, 2002, at Maracanã Stadium in Rio de Janeiro, Brazil. To celebrate the band's 30th anniversary, June 2004 saw the release of Feedback, an extended play work recorded in suburban Toronto featuring eight covers of artists including Cream, The Who and The Yardbirds, bands the members of Rush cite as being their inspiration around the time of their inception. Helping to support Feedback and continue celebrating their 30th anniversary as a band, Rush launched the 30th Anniversary Tour in the summer of 2004, playing dates in the United States, Canada, the United Kingdom, Germany, Italy, Sweden, the Czech Republic, and the Netherlands. On September 24, 2004, the concert at The Festhalle in Frankfurt, Germany was filmed for a DVD titled R30: 30th Anniversary World Tour, which was released on November 22, 2005. The release omitted eight songs also included on Rush in Rio; the complete concert was released on Blu-ray on December 8, 2009. During promotional interviews for the R30 DVD, the band members revealed their intention to begin writing new material in early 2006. While in Toronto, Lifeson and Lee began writing songs in January 2006. During that time, Peart assumed the role of lyric writing while living in Southern California. In September 2007, Rush hired American producer Nick Raskulinecz to co-produce the album. The band went to Allaire Studios in Shokan, New York in November 2006 to record the bulk of the material.
Sources: en.wikipedia.org
Command of the newly formed regiment passed from Allen to Seth Warner. Allen joined the staff of the Northern Army of New York's Major General Philip Schuyler and was given the rank of lieutenant colonel. Under Warner the regiment fought at the battles of Hubbardton and Bennington in 1777. The regiment was disbanded in 1779.
== Production == Selenium is most commonly produced from selenide in many sulfide ores, such as those of copper, nickel, or lead. Electrolytic metal refining is particularly productive of selenium as a byproduct, obtained from the anode mud of copper refineries. Dissolved selenite anions present in the electrolysis solution are also known to interfere with the electrorefining process of copper. Another source was the mud from the lead chambers of sulfuric acid plants, a process that is no longer used. Selenium can be refined from these muds by a number of methods. However, most elemental selenium comes as a byproduct of refining copper or producing sulfuric acid. Since its invention, solvent extraction and electrowinning (SX/EW) production of copper produces an increasing share of the worldwide copper supply. This changes the availability of selenium because only a comparably small part of the selenium in the ore is leached with the copper. Industrial production of selenium usually involves the extraction of selenium dioxide from residues obtained during the purification of copper. Common production from the residue then begins by oxidation with sodium carbonate to produce selenium dioxide, which is mixed with water and acidified to form selenous acid (oxidation step). Selenous acid is bubbled with sulfur dioxide (reduction step) to give elemental selenium. About 2,000 tonnes of selenium were produced in 2011 worldwide, mostly in Germany (650 t), Japan (630 t), Belgium (200 t), and Russia (140 t), and the total reserves were estimated at 93,000 tonnes.
Tetrahydrocannabinol (THC) is a cannabinoid found in cannabis. It is the principal psychoactive constituent of Cannabis and one of at least 113 total cannabinoids identified on the plant. Although the chemical formula for THC (C21H30O2) describes multiple isomers, the term THC usually refers to the delta-9-THC isomer with chemical name (−)-trans-Δ9-tetrahydrocannabinol. THC, also known pharmaceutically as dronabinol, is used medically to relieve chemotherapy-induced nausea and HIV/AIDS-related anorexia. Nabiximols, a botanical drug which contains THC, is used medically to treat symptoms of multiple sclerosis, including spasticity and neuropathic pain. THC acts as a partial agonist at CB1 and CB2 cannabinoid receptors. THC can be administered orally, inhaled, or transdermally, with bioavailability and onset varying by route, and is extensively metabolized in the liver to active and inactive metabolites before being excreted in feces and urine. Side effects include red eyes, dry mouth, drowsiness, memory impairment, anxiety, and, with chronic use, cannabinoid hyperemesis syndrome. While human overdose is rare, THC can interact with other drugs and has a complex pharmacokinetic profile.
In North America: Alphora, Delmar and NAEJA, all Canada. AMRI, Aptuit, Cambridge Major, ChemBridge, Innocentive, Irix Pharmaceuticals and PharmEco, all USA. In Europe: Carbogen-Amcis, Switzerland; Chemcomm, Germany; ChemDiv, Russia; Clauson-Kaas, Denmark; Enamine Ltd, Ukraine; Girindus, Germany; Nerviano Medical Sciences, Italy; Recipharm, Sweden; Serichim, Italy; Solvias, Switzerland, Netherlands. In Asia: BioDuro, Medicilon, Pharmaron and WuXi AppTec, all China; Acoris, Aptuit Laurus, Biocon/Syngene, Chembiotek, Chempartner and ProCitius, all India; NARD Institute and Riken, both Japan. The business of CROs is usually done through a "pay for service" arrangement. Unlike manufacturing companies, invoicing of CROs is not based on unit product price, but on full-time equivalents (FTEs), or the cost of a scientist working one year on a given customer assignment. Companies offering both contract research and manufacturing services (CRAMS) combine the activities of CROs and CMOs. Their history is either a forward integration of a CRO, which adds industrial scale capabilities, or backwards integration of a CMO. As there are only limited synergies (>90% of the projects end at the sample preparation stage), it is questionable if one-stop shops really fulfil a need. Large fine chemical companies consider the preparation of samples more as marketing tool (and expense) rather than a profit contributor.
Sources: en.wikipedia.org
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
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.