A practical reference on sublimation: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-07-15 and is reviewed periodically as new material appears.
Lyophilization, also called freeze-drying, removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts free water into ice and may also produce a glassy phase. Primary drying then lowers chamber pressure so ice sublimes directly to vapor without passing through a liquid stage. Secondary drying raises the temperature modestly to remove bound water. The result is a porous, dry solid that usually reconstitutes quickly. Each stage influences pore structure, residual moisture, and stability.
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.
Quality control for lyophilized materials includes visual inspection of the cake, measurement of residual moisture, and tests for reconstitution time. An acceptable cake is typically uniform and may be slightly porous; shrinkage, meltback, or cracks can indicate process deviations. Analytical methods such as Karl Fischer titration, thermogravimetric analysis, and near-infrared spectroscopy quantify water content. Reconstitution time is recorded because a very slow or incomplete dissolution can signal collapse or aggregation. Stability studies compare samples stored under defined temperature and humidity conditions over months or years.
Regulatory expectations for lyophilized products focus on consistent manufacture and documented stability. Batches are often monitored for moisture, appearance, potency, and sterility where applicable. Process parameters such as shelf temperature, chamber pressure, and drying time are recorded and controlled within validated ranges. Open questions remain about how best to predict long-term stability from short accelerated studies, especially for complex biologics. Variations in freezing rate and ice crystal size can produce differences that are not always visible but may affect performance.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying; lyophilisation; cryodesiccation | Regional spelling and historical terms. |
| Primary drying pressure | 0.05-0.5 mbar (5-50 Pa) | Kept below the triple point of water; product-specific. |
| Shelf temperature range | -40 to +40 °C | Freezing, primary, and secondary stages use different set points. |
| Cycle duration | 12-72 hours | Depends on fill volume, formulation, and equipment. |
| Condenser temperature | -50 to -80 °C | Must remain below the product's ice temperature. |
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.
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.
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.
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.
=== Cardiovascular === Heat shock proteins appear to serve a significant cardiovascular role. Hsp90, hsp84, hsp70, hsp27, hsp20, and alpha B crystallin all have been reported as having roles in the cardiovasculature. Hsp90 binds both endothelial nitric oxide synthase and soluble guanylate cyclase, which in turn are involved in vascular relaxation. The subset of hsp70, extracellular hsp70 (ehsp70) and intracellular hsp70 (ihsp70), has been shown to have a pivotal role in managing oxidative stress and other physiological factors. Krief et al. referred hspb7 (cvHSP - cardiovascular Heat shock protein) as cardiac heat shock protein. Gata4 is an essential gene responsible for cardiac morphogenesis. It also regulates the gene expression of hspb7 and hspb12. Gata4 depletion can result in reduced transcript levels of hspb7 and hspb12 and this could result in cardiac myopathies in zebrafish embryos as observed by Gabriel et al. hspb7 also acts in the downregulation of Kupffer vesicles which is responsible for regulation of left-right asymmetry of heart in zebrafish. Along with hspb7, hspb12 is involved in cardiac laterality determination. A kinase of the nitric oxide cell signalling pathway, protein kinase G, phosphorylates a small heat shock protein, hsp20. Hsp20 phosphorylation correlates well with smooth muscle relaxation and is one significant phosphoprotein involved in the process. Hsp20 appears significant in development of the smooth muscle phenotype during development.
Until late 1976, black Rhodesians could not hold ranks higher than Sub-Inspector in the BSAP, only white Rhodesians could gain commissioned rank. After moderate black leader Bishop Abel Muzorewa was elected in the 1979 elections the promotion of African members hastened. After Robert Mugabe took power, the force followed a racial policy of "Africanisation", in which senior white officers were forcibly retired and their positions filled by black officers. The rank structure was unique; black policemen (known colloquially as "Mapolisa") were Constables, Sergeants, Senior Sergeants, Sergeant Majors, and Sub Inspectors. The white police (known colloquially as 'Majoni') ranks began at Patrol Officer (single gold bar on each shoulder), proceeding to Senior Patrol Officer (two gold bars), Section Officer (three gold bars), and thereafter to Inspector, Chief Inspector and commissioned ranks, etc., as per UK police rank structures. From 1977 Inspector and Chief Inspector became commissioned ranks to better align the Police ranks with those of the rest of the Security Forces. Lance and Staff rank prefixes were also used were appropriate in a similar manner to most Commonwealth armed forces. Members serving under CID had the prefix 'Detective' to their rank e.g. Detective Section Officer, abbreviated to D/SO. The prefix was dropped once a member attained the rank of Superintendent. White officers were assigned separate mess facilities to the black police and were obliged to employ black 'batmen'.
=== Museums === Abbey House Museum, Leeds Armley Mills Industrial Museum, Leeds Bagshaw Museum, Batley Bankfield Museum, Halifax Bradford Industrial Museum, Eccleshill/Fagley, Bradford Brontë Parsonage Museum, Haworth Colne Valley Museum, Golcar, Huddersfield Eureka, Halifax Leeds City Museum, Leeds National Coal Mining Museum for England Overton, Wakefield National Media Museum, Bradford Pennine Farm Museum, Ripponden, Halifax Pontefract Museum Royal Armouries Museum, Leeds Thackray Museum, Leeds The Hepworth Wakefield Thwaite Mills, Leeds Tolson Museum, Dalton, Huddersfield Wakefield Museum, Wakefield West Yorkshire Folk Museum, Shibden Hall, Halifax Yorkshire Sculpture Park, West Bretton, Wakefield
== Related compounds == N-Methyliminodiacetic acid (MIDA), the N-methyl derivative of IDA Imidodiacetic acid, the amino diacetic acid N-(2-Carboxyethyl)iminodiacetic acid, a more biodegradable analogue of NTA N-hydroxyiminodiacetic acid (HIDA), HON(CH2CO2H)2 (registry number = 87339-38-6) See HIDA scan.
Sources: en.wikipedia.org
== Insulin == Agonists: Chaetochromin (4548-G05) Insulin-like growth factor 1 Insulin-like growth factor 2 Insulin Insulin aspart Insulin degludec Insulin detemir Insulin glargine Insulin glulisine Insulin lispro Mecasermin Mecasermin rinfabate Antagonists: BMS-754807 S661 S961 Kinase inhibitors: Linsitinib Antibodies: Xentuzumab (against IGF-1 and IGF-2)
== Pharmacokinetics == Synthetic cannabinoids are delivered by smoking. In a human study, after 50 μg/kg smoked JWH-018 are delivered, one male and a female have their serum concentration of 8.1 and 10.2 μg/L respectively after 5 minutes, down to 4.6 and 6.1 μg/L after 15 minutes, suggesting the biological half-life of JWH-018 is short. 13 phase 1 metabolites are identified. Monohydroxylated and dihydrodiol metabolites are most prevalent metabolites of synthetic cannabinoids. UGT1A1, UGT1A3, UGT1A9, UGT1A10 and UGT2B7 isoenzymes were primarily responsible for JWH-018 and JWH-073 metabolites' conjugation and had high affinity for hydroxylated metabolites (Km=12–18 mmol/L). Generation of JWH-018-N-4- and 5-hydroxypentyl (JWH-018 metabolites) was primarily mediated by CYP2C9 followed by CYP1A2 and CYP2C19. CYP3A4 catalyzed JWH-018-N-4-hydroxypentyl production but with lower activity than CYP1A2 and CP2C19. The drugs are mainly excreted as urine. Phenethylamines are first-order kinetics with half life of 5 to 10 minutes which are absorbed by ingestion. The drugs have low concentration in the brain due to low biological half-life. It is difficult to measure the plasma concentration due to low stability of Phenethylamine. There are two possible metabolism pathways. The first possible pathway is metabolism by MAO-B (an intracellular enzyme mainly in the brain and tightly bound to the outer membrane of mitochondria which deaminates free primary and secondary amines) to form phenylacetic acid due to MAO-B selectivity on non-polar aromatic amines.
== History == Nearing the completion of the Human Genome Project, the field of genetics was shifting its focus toward determining the functions of genes. This involved cataloguing other collections of biological materials, like RNA and proteins in cells. These collections of materials were called -omes, evoking the widespread excitement surrounding the sequencing of the human genome. The term translatome was first proposed in 2001 by Greenbaum et al. The translatome was intended to describe the relative quantities of proteins in a proteome. The term translatome now generally refers to the collection of proteins actively being created in a cell. Translatomics, in combination with degradomics, aims to describe the net change to the proteome under different conditions.
== Organizations == Historically, pharmacometrics has been represented in related clinical pharmacology and statistics organizations. A number of smaller local organizations in Europe, the United States, and New Zealand/Australia held local meetings. In the early 1990s, the PAGE meeting was organized and has been held yearly since then, although no official organization was present. Ette and Williams have provided a historical context from which the evolution of pharmacometrics can be appreciated.
The following figures were averaged from 2005 to 2007 adult data compiled by the CDC BRFSS program and 2003–2004 child data[A] from the National Survey of Children's Health. There is also data from a more recent 2016 CDC study of the 50 states plus the District of Columbia, Puerto Rico, the U.S. Virgin Islands and Guam. Care should be taken in interpreting these numbers, because they are based on self-report surveys which asked individuals (or, in case of children and adolescents, their parents) to report their height and weight. Height is commonly overreported and weight underreported, sometimes resulting in significantly lower estimates. One study estimated the difference between actual and self-reported obesity as 7% among males and 13% among females as of 2002, with the tendency to increase. The long-running REGARDS study, published in the journal of Obesity in 2014, brought in individuals from the nine census regions and measured their height and weight. The data collected disagreed with the data in the CDC's phone survey used to create the following chart. REGARDS found that the West North Central region (North Dakota, South Dakota, Minnesota, Missouri, Nebraska, and Iowa), and East North Central region (Illinois, Ohio, Wisconsin, Michigan, and Indiana) were the worst in obesity numbers, not the East South Central region (Tennessee, Mississippi, Alabama, Kentucky) as had been previously thought. Dr.
Sources: en.wikipedia.org
Simple drying usually removes water by evaporation from a liquid or solid, often with heat. Lyophilization first freezes the material and then removes ice by sublimation under vacuum. This avoids prolonged exposure to liquid water and high temperatures.
Reduced pressure lowers the boiling point of water and allows ice to sublime at temperatures below freezing. It also helps remove water vapor from the product toward the condenser. The exact pressure is chosen to stay below the triple point of water.
No. Materials with low solids content or high volatile solvents may form weak or collapsed cakes. Some proteins and cells require stabilizers to survive freezing and drying stresses. Feasibility depends on formulation and process design.
Most are held in sealed containers at controlled temperatures, often 2–8 °C, while some require frozen storage. Protection from moisture and light helps preserve the dry matrix. Exact conditions are set by the manufacturer or study protocol.