PDA Technical Glossary

PDA Technical Glossary

PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.

The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the  PDA Technical Report Portal.

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Anisotropic (Asymmetric) Membrane
A membrane in which the pore size and structure differ from one face to the other. These membranes are usually considered “directional” because of the difference in flow characteristics, depending on which surface of the membrane faces the feed stream. (TR15)
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Aseptic Processing
Handling sterile materials in a controlled environment, in which the air supply, facility, materials, equipment and personnel are regulated to control microbial and particulate contamination to acceptable levels. (TR28) (TR62) (TR69) Handling of sterile product, containers, and/ or devices in a controlled environment in which the air supply, materials, equipment, and personnel are regulated to maintain (product) sterility. (TR13)
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Aseptic Processing Area (APA)
Controlled environment, consisting of several zones, in which the air supply, facility, materials, equipment and personnel are regulated to control microbial and particulate contamination to acceptable levels. (TR22) (TR28) (TR62) (TR70)
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Aseptic Processing Simulation (APS)
Capsule Filter
Compact, self-contained filter assembly. Generally, the whole assembly is disposable. (TR26) (TR41)
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Cartridge Filter
Filter elements encased in a housing. Generally, the filter elements are disposable while the housing units are multi-use. In a few cases, both filter and housings are disposable. (TR26) (TR41)
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Compatibility (Filter)
The ability of a filter to be used with a particular process fluid without a change in the inherent properties of the filter. (TR41)
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Diffusive Flow
The movement of a dissolved gas across a liquidwetted membrane based on the concentration (e.g., gas pressure) differential. (TR26)
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Direct Flow Filtration (DFF) or Normal Flow Filtration (NFF)
In direct flow filtration, all fluid is directed through the membrane in a single pass. (TR41)
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Effective Filtration Area
The total surface area of the filter available to the process fluid. (TR26)
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Fed-Batch Filtration Process
A modification of the batch filtration process in which a separate (typically larger) reservoir feeds a smaller recycle tank. The retentate stream is returned to the recycle tank. (TR15)
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Filter (verb)
To pass a fluid through a porous medium whereby bacteria or other particles are removed from the fluid. (TR26)
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Filter Efficiency
A measurement of how well a filter retains particles. It is usually expressed as the percentage, or ratio, of the retention of particles of a specific size by a filter. (TR26)
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Filterability Test
A test to determine the suitability and sizing of a filter with a given fluid. (TR26)
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Flow Decay Test
An experiment to determine flow rate and throughput of a filter type or combination of filters on a specific liquid, usually by using a small area filter, to determine the sizing of a filter system by extrapolation. (TR45)
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Flow Rate
The volumetric rate of flow of a solution, expressed in units of volume per time (e.g., L/min or gal/day). (TR15) (TR26)
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Flow-through
Effluent that may contain the product that is not retained by chromatography resin during column loading. (TR14)
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HETP (Height Equivalent to the Theoretical Plate)
A measurement of column packing efficiency or integrity, calculated from the column height divided by the number of theoretical plates. (TR14)
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Lenticular Filters
A filter made up of a series of biconvex cells that are stacked on top of one another with rings between them to prevent bypass between the cells. End-caps are then placed at the top and bottom of the assembly and are held in place with a central core. [Synonyms: Lenticular Cartridge, Modules, Filter Elements, Filter Devices] (TR45)
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Log Reduction
Log reduction is defined as the first log being 90%, the second log being 9% and the third log being 0.09% of the original inoculums. (TR70)
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Media
The part of the filter through which fluid passes that retains particles during filtration. (TR45)
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Negative Control
A test article used to assess the performance of an assay in the known absence of a targeted microorganism or nucleic acid. Negative controls are used to minimize a risk of false positive results, which could occur due to non-specific signals. (TR50)
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Nominal Molecular-Weight Cutoff (NMWCO)
A manufacturer’s measure of an ultrafiltration membrane based on a defined solute-retention coefficient. (TR15)
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Nominal Pore Size Rating
A filter rating with an arbitrary value, indicating a particulate size range at which the filter manufacturer claims the filter removes some percentage. Nominal ratings vary from manufacturer to manufacturer and may not be suitable to compare filters among manufacturers. Processing conditions, such as operating pressure and concentration of contaminant may have a significant effect on the retention efficiency of the nominally rated filters. (TR41)
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Nonspecific Model Virus
A virus used for characterization of viral clearance of the process when the purpose is to characterize the capacity of the manufacturing process to remove and/or inactivate viruses in general (i.e., to characterize the general viral clearance capacity of the purification process.) (TR41)
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Recovery
The mass of desired solute in the final product solution (either permeate or retentate, depending on the process), divided by the mass of the desired solute in the initial feed solution, expressed as a percentage. [Synonym: yield] (TR15) (TR45) A measure of the amount of analyte carried through the entire sample preparation and assay procedure and expressed as a percentage of the nominal concentration. (TR57)
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Recovery Study
A laboratory study combining the sampling method and analytical method to determine the quantitative recovery of a specific residue for a defined surface. (TR29) A laboratory study combining the sampling method and analytical method to determine the quantitative recovery of a specific residue for a defined surface. (TR49)
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Rejection
The ability of a filter to exclude solutes or particulate matter from passing through. (TR45)
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Screening Studies
Studies used to select a particular type and grade of filter media. (TR45)
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Sieving Coefficient (S0)
The ratio of the filtrate concentration of component i (Ci,f) to the bulk or feed concentration of component i (Ci,b) as in the following equation: S = Ci,f/Ci,b Where S = 1 for a freely passing solute, typically a low molecular weight solute S = 0 for a solute that is fully retained by the membrane [Synonym: transmission; product transmission] (TR15)
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Stirred-Cell Filtration
A surrogate for tangential flow filtration where shear is achieved by rapidly stirring the solution immediately adjacent to the membrane. Typically the stirring is accomplished by mechanical means, such as through the use of a stir bar or impeller. (TR15)
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Surrogate Fluid
A model process fluid used in a small-scale validation study. The fluid is intended to either match or resemble an actual process fluid as closely as is feasible. (TR41)
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Throughput
The amount of solution that passes through a filter, described as volume per membrane area. [Synonym: capacity.] (TR15) The amount of solution that passes through a filter. It is described as volume through the membrane area. [Synonym: capacity] (TR26)
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Transition Analysis
Mathematical evaluation of the chromatogram tracing as the mobile phase changes from one solution to another. An alternative to HETP and peak asymmetry for evaluating column packing and performance. (TR14)
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Void Volume
See Porosity. (TR45)
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Volumetric Throughput (Vmax)
The maximum volume that can be processed through a filter area. It is the volumetric capacity of the filter for a given process fluid and generally expressed in L/m2. (TR41) (TR47)
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