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Term
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Description
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| Absorption |
The taking in or trapping by physical forces of a substance (the sorbate) which penetrates another (the sorbent) |
| Adsorption |
The taking up or trapping of a gas or liquid by attachment to surfaces, for example those of the freeze dryer, the container for the freeze dried product |
| Aerosol |
A particulate suspension in air |
| Air/Gas Bleed |
The continuous or intermittent admission of air, or a selected gas, to a system undergoing continuous evacuation |
| Amorphous |
A solid of non-crystalline and therefore structureless nature |
| Ampoule |
A small glass container for chamber or manifold freeze drying often shaped with a closed bulk and relatively long, sometimes constricted and prescored neck for closure by fusion (heat) sealing. |
| Ampoule Drying |
Freeze drying or other drying of material in ampoules |
| Annealing |
Tempering, conditioning. In freeze drying it is the controlled and generally limited warming of a frozen system with the intent to further development of an ice phase and/or crystallization of one or more other components capable of eutectic behavior. |
| Aqueous |
Containing water |
| Aqueous Solution |
A mixed liquid system in which one or more substances has been dissolved in water |
| ASME |
American Society of Mechanical Engineers |
| ASME Code |
The standard set forth by ASME, that is utilized to ensure a freeze drying system, or other pressure vessel, can withstand internal, and in the case of freeze drying systems, external forces developed as a result of steam sterilization, over a specific temperature range, with a specific material of construction, such as 316L stainless steel. |
| ASME Stamp |
The official label issued by a licensed authority that indicates that a vessel meets ASME standards. The label is visible and permanently affixed to the pressure vessel. |
| Aseptic |
An object or material that is free of viable organisms |
| Atmospheric Pressure |
The pressure exerted at the earth's surface by the atmosphere. For reference purposes a standard atmosphere is defined as 1 Bar or 760 Torr or millimeters of mercury or 760,000 microns of mercury or millitorr |
| Avogadro's Law |
Equal volumes of all gases at the same temperature and pressure contain the same number of molecules. Used for calculating the specific volume of a gas. It is hypothesized that there are 6.06 x 1023 molecules in a gram-molecular weight of any substance |
| Back-Filling Gas |
The gas used to fill product containers after freeze drying is complete and prior to their closure. Typically an inert gas |
| Backstreaming |
A process that occurs in a freeze dryer with very low system pressures where mechanical pump oil vapors can migrate from the oil sealed vacuum pump back into the freeze dryer and can ultimately enter the product. |
| Bar |
The units of pressure equal to the weight of a column of mercury. |
| Barometric Control |
The use of barometric measurement of a temperature to control the freeze-drying process |
| Barometric Measurement |
The inference of the average temperature of all freeze drying fronts at any stage of primary drying by the isolation of the drying chamber from an external condenser and the measurement of a static vapor pressure in the chamber, from which the average product temperature can be determined, by reference to tables |
| Batch Control |
The use of validated in-process sampling and testing methods in such a way that results prove the process has done what it purports to do for the specific batch concerned, assuming control parameters have been appropriately respected. |
| Blank-Off Pressure or Temperature |
The ultimate lower pressure or temperature a system can obtain |
| Boiling |
The change in state from liquid to vapor, accompanied by the generation of bubbles at, and usually below, the liquid surface. This signifies that the vapor pressure equals or exceeds the total pressure at the surface |
| Boiling Point |
The temperature, varying with pressure, at which a liquid boils, usually measured at standard atmospheric pressure |
| Boyle's Law |
For a perfect gas at constant temperature the volume of a given mass is inversely proportional to the pressure acting on it or exerted by it. |
| Breaking Vacuum |
Admitting air or a selected gas into an evacuated chamber, while isolated from a vacuum pump, to raise the pressure towards or up to atmospheric |
| oC |
Temperature measured in degrees Celsius |
| Cake |
The structure of the freeze dried product at the end of drying. |
| Calibration |
Demonstrating that a measuring device produces results within specified limits of those produced by a reference standard device over an appropriate range of measurements. This process results in corrections that are applied for maximum accuracy. |
| Calorie |
A unit of heat equal to that required to raise the temperature of one gram of water from 14.5 to 15.5C. A calorie is equal to 4.1868 joules. 1 Kcal equals 1,000 calories which equals 3.96 BTU |
| Capacitance Gauge/Manometer |
A form of vacuum gauge in which movement of a sensitive membrane is interpreted in terms of a variation in electrical resistance. Currently considered the most accurate method of pressure measurement for use in freeze dryers |
| Certification |
Documented testimony by qualified authorities that a system qualification, calibration, validation or revalidation has been performed appropriately and that the results are acceptable. |
| Circulation Pump |
A pump for conveying the heat transfer fluid through shelves in a freeze dryer |
| Cold Junction |
Point of connection between thermocouple metals and the electronic instrument |
| Cold Junction Compensation |
Electronic means to compensate for the effective temperature at the cold junction |
| Collapse |
During freeze drying the irregular shrinkage of, or loss of, an internal structure in the cake, sometimes accompanied by bubbling as the structure support of the ice crystals is withdrawn during sublimation. Collapse is associated with non eutectic or amorphous freezing. It takes place in the freeze drying front and continues until stopped by desorption. It can be stopped if the freeze drying front is cooled below the threshold collapse temperature. |
| Conax Connection |
A device to pass thermocouples or other wires through the wall of a vacuum tight vessel. |
| Qualification Process Validation |
Establishing documented evidence that a process does what it purports to do based on information generated during actual implementation of the process |
| Collapse Temperature |
(Tc). Typically measured by freeze dry microscopy. It is when the addition of energy to the product leads to a melting at the freeze dry - ice interface, sometimes resulting in cake shrinkage. |
| Condenser (cold trap) |
In terms of the lyophilization process, this is the vessel that collects the moisture on a cold surface and holds it there as ice. The condenser protects the vacuum pump oil from contamination and in trapping out moisture helps with vacuum maintenance. |
| Condenser Chamber |
A vessel connected to a freeze drying chamber and containing the condenser |
| Condenser/Receiver |
In terms of refrigeration this unit condenses the hot refrigerant gas into a liquid and stores it under pressure to be reused by the system |
| Contamination |
In the vacuum system, the introduction of water vapor into the oil in the vacuum pump, which then causes the pump to lose its ability to attain its ultimate pressure |
| Control Parameters |
Thos operating variables that can be assigned values that are used as control levels |
| Convection |
Heat transfer by actual movement in a gas or liquid promoted by differences in density at different temperatures |
| Critical Temperature |
The temperature above which a gas cannot be liquefied by compression |
| Cryobiology |
The branch of science dealing with the behavior of biological systems below ambient or physiological temperature, most especially at sub freezing temperatures |
| Cryoprotectant |
A compound capable of preventing or reducing the damage to a formulated preparation during freezing, frozen storage, and thawing |
| Crystal |
A solid substance in which the atoms or molecules are arranged in an orderly geometric pattern in each of three dimensions |
| D Value |
The decimal reduction value refers to the time in minutes required under specified lethal conditions for a one-log or 90% reduction of a microbial population |
| Defrosting |
The removal of the ice from a condenser by melting or by mechanical means |
| Degree of Crystallization |
The volume or weight fraction of material converted to crystalline states, which for a eutectic solution or pure water is 1.0 |
| Degree of Supercooling |
The number of degrees through which a system has been cooled below the equilibrium freezing point and remains liquid |
| Dehydration |
The removal of water from any substance |
| Denature |
Of soluble protein, to render it irreversibly insoluble |
| Density |
The mass per unit volume |
| Derivative |
Anticipatory action that calculates the rate of change of the process and compensates to minimize overshoot and undershoot. |
| Desiccant |
A drying agent |
| Desorbing |
The act of desorption |
| Desorption |
The release of liquids or gases trapped by sorption |
| Diffusion |
The motion of atoms and ions, or molecules on with respect to the another, in gases , liquids or solids |
| DIN |
Deutsche Industrial Norms, a widely recognized German standard for engineering units |
| Dry |
Devoid of water |
| Dry Cake |
Dry layer. The partially or wholly dry porous mass of solute residue exposed as ice sublimes during freeze drying |
| Dry Weight |
The weight of an absolutely dry substance |
| Drying |
The removal of moisture by any known means |
| Duty Cycle |
Percentage of "load on time" relative to total cycle time |