Residual moisture comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-08-27. Numbers and descriptions here follow the published literature rather than marketing material.
Lyophilization is a dehydration process that removes water from a frozen material by sublimation under low pressure. The material is first frozen so that water becomes ice; then the surrounding pressure is lowered below the vapor pressure of ice. Heat is applied gently so ice changes directly to vapor without passing through a bulk liquid phase. The vapor is collected on a cold condenser, leaving a dry porous matrix. This process differs from simple evaporation because the material remains frozen during the main drying stage.
The process usually has three stages: freezing, primary drying, and secondary drying. Freezing sets the ice crystal structure and can determine pore size in the final cake. Primary drying removes free ice by sublimation at low pressure and low shelf temperature. Secondary drying removes bound water by raising the shelf temperature, although some water may remain as part of the solid. Cycle parameters depend on formulation, fill volume, vial type, and equipment performance.
The physical chemistry of freezing influences whether a formulation forms an amorphous glass or a crystalline solid. Amorphous systems can collapse if product temperature rises above the glass transition temperature of the freeze concentrate. Crystalline systems may show eutectic melting, where ice and solute melt together at a fixed temperature. Formulators add bulking agents, lyoprotectants, and buffers to preserve structure and biological activity. The optimum cycle keeps product temperature below critical thresholds during primary drying while allowing efficient sublimation.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Freeze-drying, lyophilisation | Lyophilisation is the British spelling; the process is not simple evaporation. |
| Primary drying pressure | 0.05–0.3 mbar | Pressure must remain below the vapor pressure of ice at the product temperature. |
| Sublimation temperature | Below 0 °C | Ice changes directly to vapor while the product remains frozen. |
| Typical shelf temperature | −40 to −10 °C | Exact setting depends on formulation critical temperature and equipment. |
| Cycle duration | 12–72 hours | Time varies with fill volume, formulation, and dryer performance. |
In practice, lyophilization is slower and more energy intensive than simple drying. Cycle times can range from hours to several days depending on load, container, and formulation. Amorphous materials may require excipients that help preserve structure during freezing and drying. The method is widely used for biological materials, pharmaceuticals, and foods where heat drying would cause unacceptable change. Open questions remain about scaling cycles between laboratory and production equipment, and this gap affects technology transfer.
Lyophilization removes water by freezing a material and then lowering pressure so ice changes directly to vapor. The process relies on sublimation, the phase transition from solid to gas without an intermediate liquid state. Because the material remains frozen during primary drying, the structure often stays porous. This porous matrix can rehydrate quickly when water is added back. The low pressure also allows vapor to leave the solid matrix without boiling.
A typical cycle begins with freezing, which fixes the material into a solid and determines ice crystal size. Primary drying then raises heat under vacuum so ice sublimes, often near or below the collapse temperature of the formulation. Secondary drying removes bound water that remains after ice is gone, usually by gently warming the product. Each stage balances heat input against pressure to avoid melting or structural damage. Temperature probes and pressure sensors guide the transition between stages.
Stability of a lyophilized product depends on its glass transition temperature, the temperature at which the amorphous cake transitions from a glassy to a rubbery state. Storage below this temperature minimizes molecular mobility and slows chemical degradation. If the storage temperature exceeds the glass transition temperature, the cake may collapse, shrink, or become sticky. Accelerated stability studies at elevated temperatures and humidity help predict shelf life, but they do not always reflect real-time behavior. Residual moisture content also plays a critical role in long-term stability.
Reconstitution involves adding a suitable diluent, often sterile water or a buffer, to the dried cake. Gentle swirling or inversion helps dissolve the material without creating excessive foam. The time required for complete dissolution can range from seconds to several minutes and depends on the cake structure and the diluent. Improper reconstitution, such as vigorous shaking or using the wrong diluent, can cause protein aggregation or loss of activity. After reconstitution, the product may have a limited shelf life and should be used according to its labeling.
S-Methylcysteine sulfoxide is an organosulfur compound with the formula CH3S(O)CH2CH(NH2)CO2H. It is the sulfoxide of S-methylcysteine. It contributes to the flavor of onions (Allium sp.). The compound is usually encountered as one diastereoisomer, the (R)- and (S)-configurations at the carbon and sulfur stereocenters, respectively. The S-methyl part of the name refers to the location of the methyl group on sulfur. Although odorless, S-methylcysteine sulfoxide is acted upon by alliinase and lachrymatory-factor synthase. S-Methylcysteine sulfoxide is produced from glutathione. Related compounds are the unsaturated sulfoxides S-trans-prop-1-enyl cysteine sulfoxide and S-propyl cysteine sulfoxide, both found also in onions, and S-allyl cysteine sulfoxide, typically found in garlic.
== Protactinium-233 == Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233 (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect 233Pa from further neutron capture producing 234Pa and 234U, which are not useful as fuel.
Raines (born 1958), chemical biologist and expert on the chemistry and biology of proteins Mark SaFranko, writer, playwright and actor Kenneth B. Smith (1931–2008), President of the Board of Education of the Chicago Public Schools who also served as President of the Chicago Theological Seminary Leo Sternbach (1908–2005), chemist, invented precursor to Valium Bruce Wands (1949–2022), educator, author, artist, and musician, with a specific interest in digital art Edward Weston (1850–1936), electrical engineer and inventor whose Weston Electrical Instrument Company won the contract to illuminate the Brooklyn Bridge
Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to air. Strontium has physical and chemical properties similar to those of its two vertical neighbors in the periodic table, calcium and barium. It occurs naturally mainly in the minerals celestine and strontianite, and is mostly mined from these. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was discovered in 1790 by Adair Crawford and William Cruickshank. It was identified as a new element the next year from its crimson-red flame test color. Strontium was first isolated as a metal in 1808 by Humphry Davy using the then newly discovered process of electrolysis. During the 19th century, strontium was mostly used in the production of sugar from sugar beets (see strontian process). At the peak of production of television cathode-ray tubes, as much as 75% of strontium consumption in the United States was used for the faceplate glass. With the replacement of cathode-ray tubes with other display methods, consumption of strontium has dramatically declined. While natural strontium (which is mostly the isotope strontium-88) is stable, the synthetic strontium-90 is radioactive and is one of the most dangerous components of nuclear fallout, as strontium is absorbed by the body in a similar manner to calcium. Natural stable strontium is not hazardous to health at low levels.
Sources: en.wikipedia.org
Anders Ericsson of Florida State University did not believe that sufficient evidence existed to suggest that the skills of Price and another documented case, Brad Williams, needed additional explanation: "Our work has pretty much concluded that differences in memory don't seem to be the result of innate differences, but more the kinds of skills that are developed." As the condition has become better known, more people claiming to have hyperthymestic abilities have emerged. In the aftermath of the 2006 Neurocase publication alone, more than 200 people contacted McGaugh; however, only a handful of cases were determined to be actual cases of hyperthymesia. The second verified case was Brad Williams, the third was Rick Baron, and in 2009, Bob Petrella became the fourth person diagnosed with hyperthymestic syndrome. The U.S. television program 60 Minutes featured actress Marilu Henner in 2010 for her superior autobiographical memory ability. Henner claimed to remember almost every day of her life since age 11. The show was initially pitched as a story featuring hyperthymestic violinist Louise Owen, but the reporter Lesley Stahl volunteered her friend Henner as having a similar ability. In 2012, reports emerged of H.K. Derryberry, a blind 20-year-old man who could clearly recall every day of the last nine years of his life. Derryberry had been born at 27 weeks, weighing just over 2 pounds (0.91 kg) and was in neonatal intensive care for 96 days. A brain hemorrhage was the likely cause of cerebral palsy, and his premature birth brought congenital blindness.
Fracture mechanics was developed during World War I by English aeronautical engineer A. A. Griffith – thus the term Griffith crack – to explain the failure of brittle materials. Griffith's work was motivated by two contradictory facts:
==== Anti-seizure medication ==== The anti-convulsant medications gabapentin and pregabalin may be used to reduce pain. There is tentative evidence that gabapentin may be of benefit for pain in about 18% of people with fibromyalgia. It is not possible to predict who will benefit, and a short trial may be recommended to test the effectiveness of this type of medication. Approximately 6/10 people who take gabapentin to treat pain related to fibromyalgia experience unpleasant side effects such as dizziness, abnormal walking, or swelling from fluid accumulation. Pregabalin demonstrates a benefit in about 9% of people, it may also enhance sleep quality. Pregabalin reduced time off work by 0.2 days per week. A 2025 review found that, for enhancing sleep quality in FM, pregabalin might be beneficial but had potential risks.
In the BG system the pound is a basic unit from which the unit of mass (the slug) is defined by Newton's second law, whereas in the EE system the units of force and mass (the pound-force and pound-mass respectively) are defined independently through the second law using the proportionality constant gc. Kinematic viscosity has units of square feet per second (ft2/s) in both the BG and EE systems. Nonstandard units include the reyn (lbf·s/in2), a British unit of dynamic viscosity. In the automotive industry the viscosity index is used to describe the change of viscosity with temperature. The reciprocal of viscosity is fluidity, usually symbolized by
Caffeine (1,3,7-trimethylxanthine) is the alkaloid most present in green and roasted coffee beans. The content of caffeine is between 1.0% and 2.5% by weight of dry green coffee beans. The content of caffeine does not change during maturation of green coffee beans, but higher caffeine content is found in plants grown at higher altitudes. The solubility of caffeine in water increases with temperature and with the addition of chlorogenic acids, citric acid, or tartaric acid, all of which are present in green coffee beans. For example, 1 g (0.035 oz) of caffeine dissolves in 46 mL (1.6 US fl oz) of water at room temperature, and 5.5 mL (0.19 US fl oz) at 80 °C (176 °F). Trigonelline (N-methyl-nicotinate) is a derivcular-weight peptides and amino acids. Mature coffee contains free amino acids (4.0 mg amino acid/g robusta coffee and up to 4.5 mg amino acid/g arabica coffee). In Coffea arabica, alanine is the amino acid with the highest concentration, i.e., 1.2 mg/g, followed by asparagine of 0.66 mg/g, whereas in C. robusta, alanine is present at a concentration of 0.8 mg/g and asparagine at 0.36 mg/g. Roasted coffee beans do not contain any free amino acids; the amino acids in green coffee beans are degraded under roasting temperature to Maillard products (reaction products between the aldehyde group of sugar and the alpha-amino group of the amino acids). Further, diketopiperazines, e.g. cyclo(proline-proline), cyclo(proline-leucine), and cyclo(proline-isoleucine), are generated from the corresponding amino acids, and are the major source of the bitter taste of roasted coffee.
Sources: en.wikipedia.org
The receiver has a directional antenna (typically a small Yagi) which is rotated until the received signal is strongest; at this point the antenna is pointing in the direction of the animal. Sophisticated systems used in recent years use satellites to track the animal, or geolocation tags with GPS receivers which record and transmit a log of the animal's location.
restriction map A diagram of known restriction sites within a known DNA sequence, such as a plasmid vector, obtained by systematically exposing the sequence to various restriction enzymes and then comparing the lengths of the resulting fragments, a technique known as restriction mapping. See also gene map.
== Ownership == The British pharmaceutical firm Beecham was the longtime owner of Brylcreem. Sara Lee acquired the personal care unit of SmithKline Beecham in June 1993. In January 2012, the global rights to the Brylcreem brand were sold by Sara Lee Corporation to Unilever. Brylcreem is marketed in the United States by Combe Incorporated, in Europe by Unilever and in India by Hindustan Unilever Limited. Before Godrej acquired a 51% stake of Sara Lee, in their joint venture Godrej Sara Lee in May 2010, the brand was distributed by Godrej in India.
March 12: Law expanding the civil capacity of professional unions; married women may join and participate (including in administration and leadership) without their husband's permission. July 31: Law criminalizing incitement to abortion and anti-contraceptive propaganda. August 12: Decree enacting the Peace Treaty of November 27, 1919, which created the League of Nations (SDN) and established principles such as the prohibition of child labor, restrictions on youth labor for both sexes, and "equal pay for equal work"; women may be technical advisors within the SDN on certain topics. 1921
Sources: en.wikipedia.org
The main change is sublimation, in which ice becomes water vapor without melting into liquid water. This occurs when the chamber pressure is held below the vapor pressure of ice while mild heat is supplied. The result is a dry, porous solid that retains much of its original shape.
Freezing determines ice crystal size, solute distribution, and the pore network left after drying. A slow or fast freezing rate can produce different cake structures and affect reconstitution. It also sets whether the formulation follows an amorphous or crystalline drying path.
It removes most free water during primary drying and part of the bound water during secondary drying. A small residual moisture content often remains and is specified for each product. Complete removal is generally neither practical nor desirable for stability.
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.