This is a working overview of Secondary drying, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-17 and is reviewed periodically as new material appears.
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 removes water from a frozen material by sublimation under reduced pressure. The process begins with freezing, which converts liquid water into ice and fixes the structure of the sample. After freezing, primary drying lowers pressure so ice changes directly to vapor without passing through a liquid phase. Secondary drying then removes bound water that remains after ice sublimation. The result is a dry, porous solid that often retains its original shape.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | Porous cake or plug | Uniform structure suggests the drying cycle preserved the matrix. |
| Reconstitution time | Usually under 2 minutes | Depends on cake porosity, diluent volume, and excipient composition. |
| Water content range | 0.5–3% w/w | Common specification range; exact limits are product-specific. |
| Headspace oxygen | <1% v/v | Inert gas backfill reduces oxidation of sensitive materials. |
| Storage temperature | 2–8 °C or controlled room temperature | Choice depends on accelerated and real-time stability results. |
Storage conditions for dried products usually aim to exclude moisture and oxygen. Vials are sealed under vacuum or with an inert gas, and stoppers must maintain a barrier during transport. Temperature recommendations vary; some materials remain stable at room temperature, while others need refrigeration or frozen storage. Humidity control is critical because dried cakes can absorb water rapidly once a container is opened. Desiccant packs and moisture-barrier bags add further protection during shipping.
Quality control also examines cake structure, color, and reconstitution behavior. A collapsed or shrunken cake can indicate a thermal excursion during drying. Analytical methods such as X-ray diffraction, differential scanning calorimetry, and near-infrared spectroscopy can detect crystallinity or moisture distribution. Regulatory expectations focus on validated assays and lot-to-lot consistency. Questions remain about how well accelerated stability tests predict long-term behavior for every formulation. Visual inspection remains common but is subjective without trained reviewers and reference images.
After lyophilization, a product's quality depends on residual moisture, cake appearance, and reconstitution time. Residual moisture is often measured by Karl Fischer titration or thermogravimetric analysis. A low moisture content can slow chemical degradation, but overly dry cakes may be brittle or slow to dissolve. Stability studies track these attributes over months under defined temperature and humidity conditions. Batch records link these measurements to specific process runs and help identify trends before a product fails specification.
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.
==== Gastrointestinal and colorectal cancer ==== Reviews of preliminary clinical trials on people with colorectal or gastrointestinal cancer suggest that soy isoflavones may have a slight protective effect against such cancers.
Typically, a wide-local excision is performed, in which the tumor is excised including a safety-margin of healthy tissue to ensure its entire removal, which is confirmed by a pathologist. In more advanced disease, a (partial) vulvectomy may need to be performed in order to remove some or all of the vulva. Advanced-stage melanomas can be treated with checkpoint inhibitors.
Australia Army: ASLAV-25 Navy: Armidale-class patrol boats, Hobart-class destroyers, Canberra-class landing helicopter docks Canada Army: Coyote reconnaissance vehicle, LAV VI APC Navy: Harry DeWolf-class offshore patrol vessel Croatia Army: M2 Bradley Georgia Coast Guard: Island-class patrol boat Israel Navy: Super Dvora Mk III-class patrol boat, Shaldag-class fast patrol boat Malaysia Army: ACV-300 IFV New Zealand Army: NZLAV Navy: HMNZS Canterbury multi-role vessel and Protector-class offshore patrol vessels Norway Philippines Army: GKN Simba AIFV, M113 APC Navy: Del Pilar-class offshore patrol vessel, Jacinto-class patrol vessel, Mariano Alvarez-class coastal patrol vessel, and Jose Andrada-class patrol craft Singapore Army: Bionix 25 (replaced by the 30 mm Bushmaster II on the Bionix II), M113A2 Ultra IFV Navy: Endurance-class landing platform dock, Formidable-class frigate Police Coast Guard: New coastal patrol craft (NCPC) Spain Army: VEC-M1 Navy: Meteoro-class offshore patrol vessel Sri Lanka Navy: Hamilton-class cutter, Reliance-class cutter Switzerland Turkey Ukraine Army: Bradley M2A2 ODS & M7 Bradley fire support vehicle,LAV VI Ukrainian Navy: Island-class patrol boat (2019) United States Army: M2/M3 Bradley Navy (Mk. 38 Mod 0, Mk. 38 Mod 2 and Mk.
Sources: en.wikipedia.org
Djalikatou Diallo- former vice-president Guinean Football Federation, former vice-president Nation Assembly, former Minister of National unity and Citizenship. Diaka Sidibé- former Minister of Higher Education, Scientific Research and Innovation, former Minister of Trade, Industry and Small and Medium-sized Enterprises. Kadiatou Émilie Diaby - former Minister of Public Works. Ibrahima Abé Sylla - Minister of Energy, Hydropower and Hydrocarbons, Guinea. Aïssatou Bobo Baldé - former vice president National Assembly. Barry Diawadou – Civil clerk and politician, former member of the French National Assembly and former Minister of Education. Guinea Mamoudou Nagnalen Barry - former minister of Agriculture. Sidibé Fatoumata Kaba (diplomat) - former minister of foreign affairs, former permanent Representative to the African union And The United Nations, former ambassador to Nigeria, Ethiopia. Ambassador to the united states, Guinea. Mama Kanny Diallo - Economist, former Minister of Planning and Economic Development, Guinea. Saifoulaye Diallo –Politician and lawmaker, former member of the French National Assembly, former president of the Territorial Assembly and President of the National Assembly; former Minister of State (foreign affairs, finance, social services). Elhadj Gando Barry - former Minister of Infrastructure and Public Works, CEO Électricité de Guinée. Ibrahima Barry (popularly known as Barry III) – Lawyer and politician, former Minister from Guinea Oumar Diouhé Bah - Minister of Health and public hygiene, Guinea.
This technique eliminates pharmacokinetic issues with non-equivalent clearance as well as enabling the intravenous dose to be administered with a minimum of toxicology and formulation. The technique was first applied using stable-isotopes such as 13C and mass-spectrometry to distinguish the isotopes by mass difference. More recently, 14C labelled drugs are administered intravenously and accelerator mass spectrometry (AMS) used to measure the isotopically labelled drug along with mass spectrometry for the unlabelled drug. There is no regulatory requirement to define the intravenous pharmacokinetics or absolute bioavailability however regulatory authorities do sometimes ask for absolute bioavailability information of the extravascular route in cases in which the bioavailability is apparently low or variable and there is a proven relationship between the pharmacodynamics and the pharmacokinetics at therapeutic doses. In all such cases, to conduct an absolute bioavailability study requires that the drug be given intravenously. Intravenous administration of a developmental drug can provide valuable information on the fundamental pharmacokinetic parameters of volume of distribution (V) and clearance (CL).
=== SIRSS model - combination of SIR with modelling of social stress === Dynamics of epidemics depend on how people's behavior changes in time. For example, at the beginning of the epidemic, people are ignorant and careless, then, after the outbreak of epidemics and alarm, they begin to comply with the various restrictions and the spreading of epidemics may decline. Over time, some people get tired/frustrated by the restrictions and stop following them (exhaustion), especially if the number of new cases drops down. After resting for some time, they can follow the restrictions again. But during this pause the second wave can come and become even stronger than the first one. Social dynamics should be considered. The social physics models of social stress complement the classical epidemics models.
A fault on a power sub-transmission feeder causes a power shortage in the southern Far North District that affects 23,000 homes and businesses. 7 November – Local authorities in the Clutha District and Southland Region lift local states of emergency caused by the October 2025 New Zealand storms. 8 November – A wildfire breaks out in Tongariro National Park, engulfing 2,500 hectares and leading to the evacuation of campers and the closure of a nearby highway. 9 November: The wildfire in Tongariro National Park engulfs 2,500 hectares, leading to the evacuation of Whakapapa Village. Firefighters manage to contain 20% of the fire. Te Pāti Māori's national council votes overnight to expel MPs Mariameno Kapa-Kingi and Tākuta Ferris following several weeks of internal conflict. The decision is confirmed by the party's leadership the following day. The New Zealand government extends its suspension of NZ$29.8 million worth of funding to the Cook Islands over the next two financial years in response to the Cook Islands government signing several partnership agreements with China in February 2025. 10 November: The wildfire in the Tongariro National Park subsides due to rainfall and the efforts of firefighters to contain the blaze. Residents of Whakapapa Village are allowed to return. An estimated 3,000 hectares have been damaged by the wildfire. The contactless fare payment system Motu Move is launched on public buses and the ferry in Christchurch.
Sources: en.wikipedia.org
Terrestrial radiation is the ubiquitous radiation on Earth caused by radionuclides in the ground that were formed billions of years ago by stellar nucleosynthesis and have not yet decayed due to their long half-lives. Terrestrial radiation is caused by natural radionuclides that occur naturally in the Earth's soil, rocks, hydrosphere, and atmosphere. Natural radionuclides can be divided into cosmogenic and primordial nuclides. Cosmogenic nuclides do not contribute significantly to the terrestrial ambient radiation at the Earth's surface. The sources of terrestrial radiation are the natural radioactive nuclides found in the uppermost layers of the Earth, in the water and in the air. These include in particular
=== Separation of cffDNA === Blood plasma is separated from the maternal blood sample using a laboratory centrifuge. The cffDNA is then isolated and purified. A standardized protocol for doing this was written through an evaluation of the scientific literature. The highest yield in cffDNA extraction was obtained with the "QIAamp DSP Virus Kit". Addition of formaldehyde to maternal blood samples increases the yield of cffDNA. Formaldehyde stabilizes intact cells, and therefore inhibits the further release of maternal DNA. With the addition of formaldehyde, the percentage of cffDNA recovered from a maternal blood sample varies between 0.32 percent and 40 percent with a mean of 7.7 percent. Without the addition of formaldehyde, the mean percentage of cffDNA recovered has been measured at 20.2 percent. However, other figures vary between 5 and 96 percent. Recovery of cffDNA may be related to the length of the DNA fragments. Another way to increase the fetal DNA is based on physical length of DNA fragments. Smaller fragments can represent up to seventy percent of the total cell free DNA in the maternal blood sample.
=== Pregnancy and breastfeeding === The safety of using omeprazole has not been established in pregnant or breastfeeding women. Epidemiological data do not show an increased risk of major birth defects after maternal use of omeprazole during pregnancy.
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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.
It usually appears as a uniform porous plug or cake that fills the container without excessive shrinkage. Color should match the specification, and there should be no meltback or visible foreign matter. Minor cracking may be acceptable if the product still meets moisture and potency limits.
Water content is a key stability parameter because excess water can promote hydrolysis, aggregation, or cake collapse. It also affects reconstitution and product weight. Each product has a target range, and methods such as Karl Fischer titration are used to verify it.
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.