A practical reference on secondary drying: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-26 and is reviewed periodically as new material appears.
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.
After primary drying, secondary drying removes water that remains bound to the material. This stage raises the shelf temperature while maintaining low pressure, which encourages desorption of unfrozen water. Residual moisture can be reduced to a low percentage, improving stability for many products. The process parameters, including freezing rate, shelf temperature, and chamber pressure, influence the final pore structure and reconstitution behavior. Control of these variables helps prevent collapse or meltback during drying.
Storage conditions depend on the formulation and the intended shelf life. Many pharmaceutical and biological freeze-dried products are kept at 2–8 °C, while some stable foods and reagents tolerate room temperature. Others require −20 °C or colder to slow chemical degradation or aggregation. Protection from light and oxygen is common because oxidation can continue in the dry state. Stability studies usually monitor potency, appearance, moisture, and reconstitution time over months or years. Predictions from accelerated studies are useful but may not fully capture real-time changes.
Quality control for freeze-dried lots combines visual inspection with instrumental tests. Cake appearance, color, and shrinkage are recorded against a reference, while residual moisture is measured by Karl Fischer titration or loss on drying. Thermal analysis can reveal phase transitions and crystallization events, and X-ray diffraction distinguishes amorphous from crystalline solids. Microbiological tests and container closure integrity checks are also routine for sterile products. Analytical methods must be validated for the matrix, because excipients and low moisture can affect accuracy. Open questions include how best to predict long-term stability from short-term data.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilization is the American spelling; lyophilisation is British |
| Primary drying mechanism | Sublimation of ice | Occurs under vacuum below the triple point |
| Typical chamber pressure | 0.05-0.5 mbar | Range depends on product and equipment |
| Typical shelf temperature during freezing | -40 to -20 °C | Lower temperatures may be used for labile products |
| Resulting product form | Porous cake or powder | Appearance depends on formulation and cycle |
In February 1917, revolution broke out in Russia in which workers, soldiers and peasants established soviets, the monarchy was forced into exile fell and a provisional government was formed until the election of a constituent assembly. Alexander Kerensky, a Russian lawyer and revolutionary, became a key political figure in the Russian Revolution of 1917. After the February Revolution, Kerensky joined the newly formed Russian Provisional Government, first as Minister of Justice, then as Minister of War and after July as the government's second Minister-Chairman. A leader of the moderate socialist Trudovik faction of the Socialist Revolutionary Party known as the Labour Group, Kerensky was also the vice-chairman of the powerful Petrograd Soviet. After failing to sign a peace treaty with the German Empire to exit from World War I which led to massive popular unrest against the government cabinet, Kerensky's government was overthrown on 7 November by the Bolsheviks led by Vladimir Lenin in the October Revolution. Soon after the October Revolution, the Russian Constituent Assembly elected Socialist-Revolutionary leader Victor Chernov as President of a Russian Republic, but it rejected the Bolshevik proposal that endorsed the Soviet decrees on land, peace and workers' control and acknowledged the power of the Soviets of Workers', Soldiers' and Peasants' Deputies.
== History == AMP was formed in 1995 to provide structure and leadership to the emerging field of molecular diagnostics. The motivation for forming AMP came from numerous discussions and workshops that took place in the late 1980s and early 1990s. As new molecular technologies and applications emerged, questions about their use, standardization, licensing and accreditation, as well as medical training created consensus for a professional focus. At a workshop in November 1993, participants formed working groups that later became the Association’s initial four subdivisions: Hematopathology, Solid Tumors, Genetics, and Infectious Diseases. In 2012, Informatics was added as a fifth concentration, reflecting the new challenges and opportunities that Big Data management and interpretation has brought to the molecular field.
This reaction was hailed as a "revolution" and essentially started the distinct field of synthetic peptide chemistry. It remained unsurpassed in utility for peptide synthesis until the early 1950s when mixed anhydride and active ester methodologies were developed. Although the reaction is no longer commonly used for peptides, it is nonetheless very widespread for amine protection in other applications within organic synthesis and total synthesis. Common procedures to achieve protection starting from benzyl chloroformate include:
Glycine + tetrahydrofolate + NAD+ ⇌ CO2 + NH+4 + N5,N10-methylene tetrahydrofolate + NADH + H+ In the second pathway, glycine is degraded in two steps. The first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase. In the third pathway of its degradation, glycine is converted to glyoxylate by D-amino acid oxidase. Glyoxylate is then oxidized by hepatic lactate dehydrogenase to oxalate in an NAD+-dependent reaction. The half-life of glycine and its elimination from the body varies significantly based on dose. In one study, the half-life varied between 0.5 and 4.0 hours.
Sources: en.wikipedia.org
=== Pharmacokinetics === Melphalan is transported into cancer cells by L-leucine-type transporters (LAT1 and LAT2). Metabolites of melphalan – mono- and dihydroxymelphalan – are pharmacologically inactive. They are created by a substitution of the chlorine atom with a hydroxyl group.
==== 10 Man Operational Ration Pack ==== The UK also fields a larger pack of rations intended to feed ten soldiers for 24 hours from centralised but basic preparation; generally similar in content to the single issue ORP but tending to contain larger quantities of food in cylindrical tin cans to be divided up on preparation, rather than individual retort pouches or packets. Even dry materials like sugar or biscuits are often packed in these cans. They contain ingredients for baking bread and tinned food, including vegetables, corned beef and sausages in lard. Also included are chocolate, pre-cooked chicken or beef in gravy and soya mince. Ten boxed one-man ORPs are supplied in larger boxes identical in shape to the single ten-man pack.
Closely monitoring a patient's condition but withholding treatment until symptoms appear or change. Also called watchful waiting, active surveillance, and expectant management. (NCI) Observational study
All spermatophytes, except for the family of grasses and cereals (Poaceae), contain 7S (vicilin) and 11S (legumin) soy protein-like globulin storage proteins; or only one of these globulin proteins. S denotes Svedberg, sedimentation coefficients. Oats and rice are anomalous in that they also contain a majority of soybean-like protein. Cocoa, for example, contains the 7S globulin, which contributes to cocoa/chocolate taste and aroma, whereas coffee beans (coffee grounds) contain the 11S globulin responsible for coffee's aroma and flavor. Vicilin and legumin proteins belong to the cupin superfamily, a large family of functionally diverse proteins that have a common origin and whose evolution can be followed from bacteria to eukaryotes including animals and higher plants. 2S albumins form a major group of homologous storage proteins in many dicot species and in some monocots but not in grasses (cereals). Soybeans contain a small but significant 2S storage protein. 2S albumin are grouped in the prolamin superfamily. Other allergenic proteins included in this 'superfamily' are the non-specific plant lipid transfer proteins, alpha amylase inhibitor, trypsin inhibitors, and prolamin storage proteins of cereals and grasses. Peanuts, for instance, contain 20% 2S albumin but only 6% 7S globulin and 74% 11S. It is the high 2S albumin and low 7S globulin that is responsible for the relatively low lysine content of peanut protein compared to soy protein.
==== Bretisilocin ==== In March 2026, bretisilocin entered European Medicines Agency's priority medicines (PRIME) scheme for major depressive disorder, while a phase 2 clinical trial was still ongoing.
Sources: en.wikipedia.org
Mrs. Glover, the well-known Scientist, will receive applications for one week from ladies and gentlemen who wish to learn how to heal the sick without medicine, and with a success unequaled by any known method of the present day, at Dr. Kennedy's office, No. 71 South Common Street, Lynn, Mass. Lynn was a center of the shoe industry and most of Eddy's students were factory workers or artisans. She charged $100, raised a few weeks later to $300, for a three-week course of 12 lessons (reduced in 1888 to seven). Eddy based the lessons on a revised version of Quimby's "Questions and Answers" manuscript—now called "The Science of Man, by which the sick are healed, Embracing Questions and Answers in Moral Science"—and on three shorter manuscripts, "The Soul's Inquiry of Man", "Spiritualism", and "Individuality", which she had written for her classes. "Questions and Answers" began: "What is God?" The answer: "Principle, wisdom, love, and truth." Two books on mental healing appeared around that time that may have influenced Eddy's thinking: The Mental Cure (1869) and Mental Medicine (1872), both by Warren Felt Evans, another former patient of Quimby's. Eddy allowed her students to make copies of the manuscripts, but they were forbidden, under a $3,000 bond, from showing them to anyone. The students agreed to pay Eddy 10 percent annually of income derived from her work, and $1,000 if they failed to practice or teach it.
== Further reading == Reiter, Nadine; El-Shabrawi, Laila; Leinweber, Bernd; Berghold, Andrea; Aberer, Elisabeth (2011). "Calcinosis cutis". Journal of the American Academy of Dermatology. 65 (1): 15–22. doi:10.1016/j.jaad.2010.08.039. PMID 21679811. Róbert, Lili; Kiss, Norbert; Medvecz, Márta; Kuroli, Enikő; Sárdy, Miklós; Hidvégi, Bernadett (2020). "Epidemiology and treatment of calcinosis cutis: 13 years of experience". Indian Journal of Dermatology. 65 (2). Medknow: 105–111. doi:10.4103/ijd.ijd_527_18. ISSN 0019-5154. PMC 7059479. PMID 32180595.
This process continues until the entire chain is cleaved into acetyl CoA units. The final cycle produces two separate acetyl CoAs, instead of one acyl CoA and one acetyl CoA. For every cycle, the Acyl CoA unit is shortened by two carbon atoms. Concomitantly, one molecule of FADH2, NADH and acetyl CoA are formed.
== Current status == In October 1998, the United States Navy fleet of E-6Bs replaced the EC-135C in performing the "Looking Glass" mission, previously carried out for 37 years by the U.S. Air Force. Unlike the original Looking Glass aircraft, the E-6Bs are modified Boeing 707 aircraft, not the military-only KC-135. The E-6B provides the National Command Authority with the same capability as the EC-135 fleet to control the nation's intercontinental ballistic missile (ICBM) force, nuclear-capable bombers and submarine-launched ballistic missiles (SLBM). With the assumption of this mission, a USSTRATCOM battle staff now flies with the TACAMO crew. If the USSTRATCOM Global Operations Center (GOC) is unable to function in its role, the E-6B Looking Glass can assume command of all U.S. nuclear-capable forces. Flying aboard each ABNCP is a crew of 22, which includes an air crew, a Communications Systems Officer and team, an Airborne Emergency Action Officer (an Admiral or General officer), a Mission Commander, a Strike Advisor, an Airborne Launch Control System/Intelligence Officer, a Meteorological Effects Officer, a Logistics Officer, a Force Status Controller, and an Emergency Actions NCO. In addition to being able to direct the launch of ICBMs using the Airborne Launch Control System, the E-6B can communicate Emergency Action Messages (EAM) to nuclear submarines running at depth, by extending a two and a half-mile-long (4 km) trailing wire antenna (TWA) for use with the Survivable Low Frequency Communications System (SLFCS), as the EC-135C could.
Sources: en.wikipedia.org
Lyophilization removes water by sublimation from a frozen material, while evaporation changes liquid water into vapor. The low-pressure freezing step avoids the liquid phase and can preserve heat-sensitive structures.
Vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor. It also helps remove water vapor from the product chamber and shortens primary drying.
Many aqueous solutions and suspensions can be freeze-dried, but some formulations collapse or do not form a stable cake. The process requires careful formulation and cycle development.
Karl Fischer titration is widely used because it is specific for water and works at low levels. Loss on drying is simpler but less specific, since volatile solvents or decomposition products can also be lost.