Everything below concerns freeze-drying. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-05-14. Where a claim depends on a specific study, the study is described rather than over-claimed.
Lyophilization, also known as freeze-drying, is a process that removes water from a material by freezing it and then reducing pressure to allow ice to sublimate directly into vapor. The method begins with a freezing step that solidifies the water content. Next, primary drying lowers the pressure below the triple point of water, enabling sublimation without passing through a liquid phase. A final secondary drying step removes bound water through desorption. This sequence produces a dry, porous cake that can be reconstituted later.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Freeze-drying | Lyophilization is the technical synonym. |
| Typical chamber pressure | 0.01–0.1 mbar | Below the triple point of water. |
| Primary drying temperature | −40 to −10 °C | Depends on formulation and equipment. |
| Residual moisture | 1–5% | Target for many pharmaceutical products. |
| Typical equipment | Vacuum freeze-dryer | Includes drying chamber and condenser. |
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 freeze-dried forms includes visual inspection, water content measurement, and reconstitution time. A satisfactory cake is typically uniform, porous, and intact, although minor shrinkage or cracking may be acceptable if specifications allow. Karl Fischer titration, thermal gravimetric analysis, and near-infrared spectroscopy are used to measure water content. Reconstitution is assessed by adding a specified diluent and recording the time and ease of dissolution. Microbiological and particulate tests are added when the product is sterile or intended for injection.
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.
Lyophilization, or freeze-drying, removes water from a material by freezing it and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intervening liquid state. It is used for heat-sensitive materials that would degrade in conventional drying. The three stages are freezing, primary drying, and secondary drying, each with distinct temperature and pressure requirements. In practice, cycle design balances these variables.
Freezing determines ice crystal structure and pore size, which affect drying speed and product uniformity. Rapid freezing creates small crystals, while slow freezing creates larger crystals and often faster sublimation. During primary drying, chamber pressure is held below the vapor pressure of ice, and shelf temperature supplies heat for sublimation. The ice front recedes, leaving a porous matrix. Thermal limits such as collapse and eutectic temperatures set safe boundaries for formulation. These limits vary with solute composition and concentration.
Secondary drying removes bound water that remains after ice sublimation. Shelf temperature is raised gradually while pressure remains low, reducing water content to a target range. Over-drying can cause brittleness or electrostatic issues, while under-drying affects stability. The endpoint is often judged by pressure rise tests, temperature measurements, or water content analysis. Scale-up depends on matching heat and mass transfer across equipment sizes. Small changes in shelf temperature or pressure can alter cycle length substantially.
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.
Lyophilized solids are often hygroscopic, so handling occurs in controlled low-humidity areas or glove boxes when the material is exposed. Vials remain sealed with elastomeric stoppers and aluminum crimps until use, because airborne moisture can raise residual water and shorten shelf life. The porous cake is fragile and may crack, shrink, or powder during transport. Personnel typically avoid repeated warming and cooling of sealed units, which can draw moisture through closures. These practices aim to preserve the low water content achieved during drying.
In January 2018, Thaçi said that Kosovo would have supported U.S. president Donald Trump's decision to relocate the U.S. embassy from Tel Aviv to Jerusalem, which would have made it the only Muslim-majority nation to do so. Thaçi told Express that if his country was given full United Nations membership, it would vote "all the time" with the U.S., even on the resolution motioned last month to protest Trump's decision. Thaçi met with Trump on the sidelines of the United Nations General Assembly in September 2017 in New York, inviting him to visit Pristina, the capital of Kosovo. According to local media, he said their meeting was "exceptionally friendly, warm." "The Head of State thanked President Trump for his personal support for Kosovo," his office said in a statement, calling the U.S. a "strategic partner" and saying the support of Washington was "crucial to the peace, stability and overall development of Kosovo and the region." Thaçi told Pristina-based broadcaster RTV21, "President Trump, like all other U.S. presidents, has a clear vision for Kosovo. It is unique support to our country. He said that Kosovo is a wonderful country and that we are a wonderful people." On 26 November 2019, an earthquake struck Albania. President Thaçi was part of a presidential delegation that visited the earthquake epicentre and expressed his condolences on behalf of Kosovo. In 2019 he met with Trump's special envoy Grenell, and in February 2020 signed an agreement with Serbia's president Vučić.
Most hematology analyzers provide a five-part differential, enumerating neutrophils, lymphocytes, monocytes, eosinophils and basophils. Some instruments can also count immature granulocytes and nucleated red blood cells. If a six-part differential is provided, the IG or immature granulocyte category consists of promyelocytes, myelocytes and metamyelocytes. Hematology analyzers measure various properties of white blood cells, such as impedance, light scattering parameters, and staining reactions. This data is analyzed and plotted on a scattergram, forming distinct clusters which correspond to white blood cell types. The analyzer counts many more cells than are counted in a manual differential, resulting in improved precision. If abnormal features or cell populations that the analyzer cannot identify are present, the instrument can flag the results for manual blood smear review.
RCH(NHP)CO2H + R'CH(NH2)CO2CH3 → RCH(NHP)C(O)NH(CHR')CO2CH3 + H2O Subsequent to this coupling reaction, the amine protecting group P and the ester are converted to the free amine and carboxylic acid, respectively. For many amino acids, the ancillary functional groups are protected. The condensation of the amine and the carboxylic acid to form the peptide bond generally employs coupling agents to activate the carboxylic acid. The Bergmann azlactone peptide synthesis is a classic organic synthesis for the preparation of dipeptides.
Sources: en.wikipedia.org
In postmarketing studies isolated cases of severe ventricular arrhythmias and renal failure have been seen. Injection site reactions like have also been observed (dermatitis, pain, and discoloration), but are usually mild.
Navigator History of Pharmacy Collection of internet resources related to the history of pharmacy Soderlund Pharmacy Museum Archived 18 July 2019 at the Wayback Machine – Information about the history of the American Drugstore The Lloyd Library Library of botanical, medical, pharmaceutical, and scientific books and periodicals, and works of allied sciences American Institute of the History of Pharmacy American Institute of the History of Pharmacy—resources in the history of pharmacy International Pharmaceutical Federation (FIP) Federation representing national associations of pharmacists and pharmaceutical scientists. Information and resources relating to pharmacy education, practice, science and policy
The fundamental function of platelets is to clump together to stop acute bleeding. This process is complex, as more than 193 proteins and 301 interactions are involved in platelet dynamics. Despite much overlap, platelet function can be modeled in three steps:
Sources: en.wikipedia.org
Women's suffrage was introduced in Denmark and Iceland. Gorlice–Tarnów Offensive — German forces recaptured the Austro-Hungarian fortress Przemyśl from the Russians on the Eastern Front after a three-week siege. Third Battle of Krithia — Ottoman forces counter-attacked after the Allies failed to capture Achi Baba on the Gallipoli peninsula and drive them back to the sea. The attack nearly broke British defenses, but British officer Lieutenant George Moor managed to rally retreating troops and order them to retake a critical lost trench. The action motivated the rest of the force to stand their ground, subsequently Moore was awarded the Victoria Cross for his actions. German submarine SM U-14 was shelled and sunk in the North Sea by Royal Navy ship HMT Oceanic II with the loss of one of her 28 crew. French destroyer Fantassin was accidentally rammed and damaged in the Ionian Sea by Mameluck. She was consequently scuttled by Fauconneau. British submarine HMS E11 slipped past the Dardanelles again and returned to Allied water, after a successful mission that infiltrated Istanbul and the sinking of 11 ships over a three-week period. Submarine commander Martin Dunbar-Nasmith was awarded a Victoria Cross for the mission. The prototype of the Sigrist Bus airplane by the Sopwith Aviation Company was given a test flight and achieved a new altitude record. The model was then used to develop the 1½ Strutter biplane which became available by mid-December.
Although Fredrickson claims that her experimental results are still valid, these experimental results have also been questioned due to poor statistical methodology, and Alan Sokal has pointed out that "given [Fredrickson and Losada's] experimental design and method of data analysis, no data whatsoever could possibly give any evidence of any nonlinearity in the relationship between "flourishing" and the positivity ratio — much less evidence for a sharp discontinuity." Another study surveyed a U.S. sample of 3,032 adults, aged 25–74. Results showed 17.2 percent of adults were flourishing, while 56.6 percent were moderately mentally healthy. Some common characteristics of a flourishing adult included: educated, older, married and wealthy. The study findings suggest there is room for adults to improve as less than 20 percent of Americans are living a flourishing life. (Keyes, 2002). Benefits from living a flourishing life emerge from research on the effects of experiencing a high ratio of positive to negative affect. The studied benefits of positive affect are increased responsiveness, "broadened behavioral repertoires", increased instinct, and increased perception and imagination. In addition, the good feelings associated with flourishing result in improvements to immune system functioning, cardiovascular recovery, lessened effects of negative affect, and frontal brain asymmetry.
== Research == Brodbelt's research centers on the development of mass spectrometry-based methods to characterize organic molecules. Brodbelt's early research established methods to use chemical ionization in ion trap mass spectrometers and applied this method to the analysis of petroleum samples. She subsequently worked on gas-phase ion chemistry and photodissociation as methods to break apart organic compounds before they are analyzed by a mass spectrometer. Her work has led to the analysis of compounds including recreational drugs, sunscreen, and pesticides. Her work also includes investigations into proteins and other organic compounds produced by bacteria, such as lipopolysaccharides. In her research, she aimed to develop creative techniques for stimulating ions to produce enlightening fragmentation patterns.
A large group of primarily lichenized fungi (the subclass Ostropomycetidae) apparently lost the ability to form lichens early in its history, reverting to a saprotrophic lifestyle. Later, some descendants regained a photobiont and lichenized again. This finding contradicts older assumptions that once a fungus became obligately lichenized it could never revert. Lineages with complex thalli, especially those bearing cyanobacterial cephalodia, show higher estimated extinction rates: they diversify rapidly but are more prone to die out, perhaps because of ecological specialization. Such large-scale studies now link geological and climatic shifts, for example, the spread of angiosperm forests in the Late Cretaceous–Early Paleogene, to bursts of lichen diversification, revealing a more intricate evolutionary history. In simple terms, this means lichens diversified in bursts when new habitats (like forests with lots of new tree bark) became available. New high-throughput techniques are also solving smaller-scale questions once thought intractable. 'Museomics' now retrieves DNA from old, fragmented specimens. For instance, Leavitt and colleagues (2019) shotgun-sequenced decades-old historical type specimens of the Rhizoplaca melanophthalma group. From three crustose thalli they recovered more than a thousand gene regions, sufficient to position each specimen in a phylogenomic tree and match them with modern material. The data showed one specimen was the distinct species R.
Sources: en.wikipedia.org
Conventional drying uses heat to evaporate water from a material, while lyophilization freezes the material and removes water by sublimation under vacuum. This avoids the liquid phase and reduces thermal damage to sensitive substances. The result is a porous cake that reconstitutes quickly.
A vacuum lowers the pressure below the triple point of water, allowing ice to sublimate directly into vapor without melting. It also removes water vapor from the product chamber and speeds up the drying process. Without vacuum, the ice would melt rather than sublimate.
Not all substances are suitable for lyophilization. Materials must form a stable frozen matrix and tolerate freezing and low pressure. Some small molecules, oils, or volatile compounds may not form a proper cake or may be lost during processing.
Collapse occurs when the product temperature rises above its collapse or eutectic temperature during drying. The frozen matrix loses structure, producing a shrunken or melted appearance. This can slow reconstitution and may affect stability.