The short version of Sublimation 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.
Quality control for lyophilized materials examines appearance, reconstitution time, residual moisture, and mechanical integrity. An acceptable cake is usually uniform and porous, though appearance alone does not prove stability. Karl Fischer titration is a common method for water content, while differential scanning calorimetry can reveal glass transition events. Stability studies track potency, aggregation, and moisture over time under defined temperature and humidity conditions. Specifications are product-specific and may include sterility and endotoxin tests for sterile preparations.
Misconceptions about lyophilization include the idea that dried products are indefinitely stable or that vacuum sealing eliminates all degradation. Chemical reactions can continue in the solid state, and some proteins lose activity even at low moisture. Another misconception is that any freeze-dryer cycle can be scaled by time alone; heat and mass transfer differ with equipment and load. Open questions remain about predicting long-term stability from short accelerated studies, particularly for amorphous formulations. Real-time stability data remain the standard for shelf-life assignment.
After lyophilization, the dried product is often sealed under vacuum or an inert gas to limit moisture and oxygen exposure. Vials, stoppers, and seals must maintain their barrier throughout shelf life. Storage temperature depends on product sensitivity: some cakes tolerate controlled room temperature, while labile biologics require refrigeration. Humidity is a critical variable because dried cakes are hygroscopic and can absorb water when exposed to air. Handling procedures therefore limit open-vial time and use desiccated environments for sampling.
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, uniform cake or powder | Collapsed or shrunken cakes indicate process issues. |
| Reconstitution time | Seconds to several minutes | Depends on cake porosity, excipients, and diluent. |
| Residual moisture | 0.5-3% w/w | Product-specific; measured by Karl Fischer titration. |
| Typical storage temperature | 2-25 °C | Some biologics require 2-8 °C. |
| Container closure | Glass vial with elastomeric stopper | Sealed under vacuum or inert gas. |
Quality assessment of a lyophilized product includes cake appearance, residual moisture, reconstitution time, and container closure integrity. A uniform, porous cake suggests that freezing and drying stayed within the formulation's design space. Cracks, shrinkage, meltback, or a glassy film can indicate thermal abuse or a formulation problem. Analysts also test for subvisible particles and sterility when the product requires those specifications. Visual inspection alone cannot confirm biological activity or chemical stability, so it is combined with analytical methods.
Stability programs monitor lyophilized products under defined temperature and humidity conditions over time. Real-time studies at recommended storage conditions are the reference, while accelerated studies provide early signals of degradation pathways. Because a dry cake can still undergo oxidation, hydrolysis, or aggregation, stability depends on residual moisture, excipients, and container headspace. Open questions include how best to predict long-term stability from short accelerated runs and how vial-to-vial variability affects shelf life. Current guidance treats these predictions as product-specific rather than universally generalizable.
Freeze-dried materials are hygroscopic to varying degrees and can take up moisture after drying. Storage therefore often uses sealed glass vials, rubber stoppers, and crimp seals to limit contact with ambient humidity. A desiccant may be included for moisture-sensitive products, although it is not universal. Controlled room temperature is sufficient for many lyophilizates, while others require refrigeration or freezing. Moisture ingress remains a primary cause of cake collapse, chemical degradation, and loss of reconstitution performance.
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.
Equipment for lyophilization includes a vacuum chamber, temperature-controlled shelves, a condenser, and a vacuum pump. A refrigeration system cools the shelves and condenser below the product's freezing point. Process monitoring often uses Pirani and capacitance manometers, thermocouples, and resistance sensors. Cycle development balances product quality with time and energy use. Some products are annealed during freezing to improve crystallization of bulking agents. Open questions remain about scaling cycles between laboratory, pilot, and production freeze-dryers.
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.
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.
== Biosimilars == In December 2020, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Kixelle, intended for the treatment of diabetes. The applicant for this medicinal product is Mylan IRE Healthcare Limited. Kixelle was approved for medical use in the European Union in February 2021. Kixelle was renamed to Kirsty. Trurapi was approved for medical use in Canada in October 2020. Truvelog and Truvelog Solostar were approved for medical use in Australia in October 2020. In October 2021, Kirsty was approved for medical use in Canada. In February 2022, the CHMP adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product Truvelog Mix 30, intended for the treatment of diabetes. The applicant for this medicinal product is sanofi-aventis groupe. It was approved for medical use in the European Union in April 2022. In January 2024, the European Commission withdrew the marketing authorization for Truvelog Mix 30 (insulin aspart) in the European Union. The withdrawal was at the request of the marketing authorization holder, Sanofi Winthrop Industrie, which notified the European Commission of its decision to permanently discontinue the marketing of the product for commercial reasons. In February 2025, insulin aspart-szjj, sold under the brand names Merilog and Merilog Solostar, is a biosimilar to Novolog that was approved for medical use in the United States in February 2025.
The commission noted that such incidents in July and August 2008 "could no longer be countered by the JPKF" and "reactivating the peacekeeping mechanism was not an alternative means of redress available for Georgia." It also noted that Georgian attack on Tskhinvali on 7 August was a response, albeit not proportionate, to South Ossetian attacks in the following paragraphs:
A curriculum revision effort involving more clinical instruction in the first two years of medical school was unveiled for the entering class of 2011. In conjunction with the University of Cincinnati Medical Center, the college also sponsors 56 accredited residency and fellowship training programs through the Office of Graduate Medical Education.
Sources: en.wikipedia.org
Alan Hutchinson Fairlamb, CBE, FRSE, FLS, FMedSci, FRSB (born 30 April 1947, Newcastle upon Tyne, England) is a Wellcome Trust Principal Research Fellow and Professor of Biochemistry in the Division of Biological Chemistry and Drug Discovery at the School of Life Sciences, University of Dundee, Scotland. From 2006-2011 he was a member of the Scientific and Technical Advisory Committee of the Special Programme for Research and Training in Tropical Diseases (TDR) -- an independent global programme of scientific collaboration co-sponsored by UNICEF, UNDP, the World Bank and WHO. Currently he is a member of the governing board of the Tres Cantos Open Lab Foundation, whose aim is to accelerate the discovery and development of medicines to tackle diseases of the developing world in an open collaborative manner. Fairlamb and his team have studied the protozoan parasites causing three different diseases - sleeping sickness, Chagas disease and leishmaniasis. He was one of the 250 scientists involved in the genome sequencing of these parasites. In 1985, Fairlamb discovered a unique thiol compound present in these parasites, and named it trypanothione. This thiol metabolite is quite different from its human equivalent, glutathione. Trypanothione allows the parasites to fend off free radicals and other toxic oxidants produced by the immune system of the infected patient, and was shown to be vital for parasite survival and virulence. For instance, antimonials neutralize the Leishmania parasite's antioxidant defence system, allowing the patient to clear the infection.
== Other rhEGFs == Several other products containing recombinant human EGF have been marketed. The potencies of these products can differ by the expression system used, despite all intending to match the structure of human EGF. Instead of measuring by mass, the international unit system from the World Health Organization provides a way to describe the potency-adjusted amount of rhEGF. However, the WHO does not prescribe a specific way of measuring the potency. rhEGF bioassay remains a field in active development.
Abdul Haleem's accomplice, Muhammad Ridzuan bin Md Ali, on the other hand, was sentenced to death for drug trafficking and later hanged on 19 May 2017. After the changes to the law, the first executions to take place were those of drug traffickers Tang Hai Liang and Foong Chee Peng on 18 July 2014, after their sentences were finalized and their refusal to further appeal against their sentences.
In multiple electrode aggregometry, anticoagulated whole blood is mixed with saline and a platelet agonist in a single-use cuvette with two pairs of electrodes. The increase in impedance between the electrodes as platelets aggregate onto them, is measured and visualized as a curve.
Sources: en.wikipedia.org
No. Freeze-drying removes water but does not reliably kill microorganisms. Sterile lyophilized products are typically prepared aseptically before freezing or are sterilized by a validated method. Microbial control depends on the entire manufacturing process.
Storage temperature is set by the least stable component in the formulation. Proteins, vaccines, and some small molecules can degrade faster at higher temperatures. Refrigeration slows these changes but does not stop them completely.
Collapse occurs when the product exceeds its collapse or glass transition temperature during drying. The ice structure then loses support, and the cake may shrink, melt back, or become dense. Formulation and cycle adjustments are used to keep the product below that threshold.
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.