If you have been reading about residual moisture and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-05-11. Numbers and descriptions here follow the published literature rather than marketing material.
A typical cycle begins with freezing, sometimes including an annealing step to control ice crystal size. Freezing conditions influence the pore network that later allows vapor escape. During primary drying, shelf temperature and chamber pressure are set so heat enters the product while its temperature stays below the collapse or eutectic point. Secondary drying then raises the shelf temperature to desorb bound water and lower residual moisture. Cycle design depends on formulation, fill volume, container type, and equipment capability.
The physics of lyophilization couples heat transfer, mass transfer, and phase behavior. Sublimation requires a vapor pressure difference between the ice front and the chamber, and the dried layer adds resistance to vapor flow. Amorphous formulations are characterized by a glass transition temperature of the maximally freeze-concentrated solute, often denoted Tg'. Crystalline bulking agents can provide structure, while amorphous excipients stabilize labile components. Open questions remain about spatial heterogeneity, edge effects, and how laboratory cycles scale to production.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Physical state | Solid, porous cake or powder | Depends on formulation and container |
| Typical storage temperature | 2–25 °C, protected from moisture | Some materials require colder conditions |
| Solubility class | Usually readily soluble after reconstitution | Not an intrinsic chemical property |
| Common analytical method | Karl Fischer titration | Used for residual moisture |
| Common synonyms | Freeze-drying; lyophilisation | Lyophilisation is a spelling variant |
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.
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.
1933 beschrieben I. Abelin und A. Florin, dass Schilddrüsenhormone den Grundumsatz stark erhöhen, einen Glykogen- und Fettschwund veranlassen sowie Herz- und Atemfrequenz beschleunigen. Die künstliche Herstellung des Thyroxins wurde erstmals 1927 von Charles Robert Harington in London durchgeführt. 1912 beschrieb Hakaru Hashimoto als erster die Struma lymphomatosa und gilt seitdem als Entdecker der Hashimoto-Thyreoiditis. 1965 meldete Beverley E. P. Murphy sein Patent zur direkten Messung von Thyroxin in Körperflüssigkeiten an, das am 3. Dezember 1968 von der Patentbehörde angenommen wurde. Bis zu diesem Zeitpunkt waren nur indirekte Schilddrüsenfunktionstestungen, wie etwa die Messung des absoluten Iodgehaltes oder des proteingebundenen Iodes im Blut, durchgeführt worden.
== Literatur == Alfred Benninghoff, Detlev Drenckhahn (Hrsg.): Anatomie. Makroskopische Anatomie, Histologie, Embryologie, Zellbiologie. 16. Auflage. Band 2, Urban & Fischer bei Elsevier, München 2004, ISBN 3-437-42350-9, S. 197–203. Hugo Čzerný, Uwe Gille: Endokrine Drüsen, Glandulae endocrinae. In: F.-V. Salomon, H. Geyer, U. Gille: Anatomie für die Tiermedizin. Enke-Verlag, Stuttgart 2004, ISBN 3-8304-1007-7, S. 622–632. Christian Hessler: Schilddrüse. In: Franz Xaver Sailer, Friedrich Wilhelm Gierhake (Hrsg.): Chirurgie historisch gesehen: Anfang – Entwicklung – Differenzierung. Dustri-Verlag, Deisenhofen bei München 1973, ISBN 3-87185-021-7, S. 200–203. Rudolf Hörmann: Schilddrüsenkrankheiten. Leitfaden für Klinik und Praxis. 4. Auflage. Abw Wissenschaftsverlag, Berlin 2005, ISBN 3-936072-27-2. Lewis E. Braverman, David S. Copper, Peter A. Copp (Hrsg.): Werner & Ingbar’s The Thyroid: A Fundamental and Clinical Text. 11. Auflage. Wolters Kluwer Health, Philadelphia 2020, ISBN 978-1975112967. Wieland Meng, mit Beiträgen von Chr. Reiners: Schilddrüsenerkrankungen. 4. Auflage. Urban & Fischer, München/Jena 2002, ISBN 978-3-437-22950-3.
Octreotid ist ein synthetisches Analogon des Peptidhormons Somatostatin, das als Arzneistoff eingesetzt wird. Octreotid besteht aus acht Aminosäuren (D-Phe-cyclo[Cys-Phe-D-Trp-Lys-Thr-Cys]-Thr(ol)). In Deutschland ist Octreotid u. a. zur Behandlung der Akromegalie und bestimmter Magen-Darm-Tumoren (GEP-NET, z. B. Karzinoide) zugelassen. Über DOTA an 111Indium oder 68Gallium gekoppelt (Edotreotid, DOTATOC) wird es in der Somatostatin-Rezeptor-Szintigrafie, beziehungsweise in der Positronen-Emissions-Tomographie (PET), zum Nachweis (Diagnostik) dieser Tumoren verwendet. Für therapeutische Zwecke (Radionuklidtherapie) können Betastrahler, wie beispielsweise 90Yttrium oder 177Lutetium, verwendet werden. Octreotid kann zur Behandlung von Cluster-Kopfschmerzattacken und bei sekretorischem Durchfall verwendet werden, wenn andere Arzneistoffe ineffektiv oder kontraindiziert sind.
Melanozyten-stimulierende Hormone (MSH), auch Melanotropine, sind eine Gruppe von Peptidhormonen, die in Hypothalamus und Hypophysenzwischenlappen gebildet werden und die gleiche Gruppe von Melanocortinrezeptoren (MC1R, MC2R, MC3R, MC4R und MC5R) aktivieren. Sie regulieren in den pigmentbildenden Melanozyten die Melaninsynthese sowie die Melanozytenexpansion und die Pigmentdispersion. Sie begrenzen die Fieberreaktion. Weiterhin sind sie an der Regulierung von Hunger (appetitmindernde Wirkung von α-MSH durch Bindung an MC3R und MC4R im Hypothalamus) und sexueller Erregung beteiligt.
Sources: de.wikipedia.org
Freezing only converts liquid to solid. Lyophilization adds vacuum and controlled warming so frozen solvent sublimes, leaving a dry porous solid. The two steps are related but not interchangeable.
Reduced pressure keeps the solvent below its triple point, allowing ice to become vapor without melting. Vacuum also helps remove water vapor from the product chamber. The exact pressure is chosen with the formulation and equipment.
Residual moisture is water that remains in the dried solid after secondary drying. It is often measured by Karl Fischer titration, near-infrared spectroscopy, or thermogravimetry. Acceptable levels depend on the material and its stability profile.
Conventional drying uses heat to evaporate liquid water, often at temperatures that can degrade sensitive materials. Lyophilization freezes the material first and then removes water by sublimation under vacuum. This avoids prolonged exposure to liquid water and high heat.