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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Autoclave
A chamber for steam sterilization. (TR45)
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Back Pressure
Residual pressure opposing the free flow of liquid or gas at the outlet side of the filter. (TR45) Pressure applied downstream of a filter or other piece of equipment. (TR26)
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Breakthrough Limited
A filtration operation resulting in a significant rise in filtrate turbidity accompanied by a small increase in differential pressure. This occurs when the adsorptive capacity of the filter is reached, resulting in the passage of particles smaller than the pore size of the filter that would normally be removed by adsorption. (TR45)
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Brevundimonas Diminuta (B. diminuta)
Small bacteria (0.3–0.4 &mum in diameter by 0.6–0.1 &mum long) used to challenge a sterilizing grade filter during validation testing. [Formerly Pseudomonas diminuta](TR45)
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Cake
Solids deposited on the upstream side of filter media. (TR15) (TR45) (TR26)
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Chemical Compatibility
The relative stability of filter materials and/or filter assembly components when exposed to process fluids and process parameters. (TR45)
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Clarification
The removal of solid particulates from a liquid through filtration, sedimentation, centrifugation or other means. (TR45)
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Depth Filter
A matrix of randomly distributed fibers creating a tortuous path with pores of undefined size and shape. A filter that removes particles by a combination of adsorption and size exclusion within its porous matrix rather than on its frontal surface. (TR45)
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Differential Pressure
The difference in pressure between the upstream (feed or influent) and downstream (effluent) sides of the filter. (May be modified with the terms: applied, available differential pressure, clean differential pressure, dirty differential pressure, initial differential pressure, or maximum differential pressure). [Synonym: Delta P (Δ P), PSID, Pressure Drop] (TR45) (TR26)
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Diffusion Flow Test
A test to determine the integrity of a filter. The test is based on the measurement of the diffusive (diffusional) flow of a gas through a wetted filter, along with any bulk flow of gas through open (unwetted) pores. Either the gas flow or the downstream liquid, displaced by the gas flow, may be measured. [Synonym: Forward Flow Test] (TR45)
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Downstream Side (of Filter)
The effluent side of the process step (filter). (TR45) The filtrate or outlet side of the filter. (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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Integrity Test
Test to determine the functional performance of a membrane filter or container/closure system. (TR22) A nondestructive test used to predict the functional performance of a filter. (TR45) A nondestructive physical test that can be correlated to the bacterial retention capability of a filter/filter assembly. (TR26)
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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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Media
The part of the filter through which fluid passes that retains particles during filtration. (TR45)
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Pressure Shock
An unanticipated rapid increase in fluid flow. [Synonym: Hydraulic Shock] (TR45)
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Pressure Shock (Backward Pressure Shock)
Rapid backward fluid flow that may result in filter rupture. (TR45)
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Pressure Shock (Forward Pressure Shock)
Rapid increase in forward fluid flow that may dislodge particulates. (TR45)
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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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Rejection
The ability of a filter to exclude solutes or particulate matter from passing through. (TR45)
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Retention Efficiency
The percentage of particles of a specific size that are removed by a filter. (TR45)
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Retention Rating
The means by which a filter manufacturer defines the ability of a filter to retain specific-sized particles. (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
Size-exclusion filtration occurs when a particle is too large to pass through the filter medium and is retained on the surface or within the depth of the filter. (TR45)
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Turbidity
Finely dispersed particles causing cloudiness or haziness in water or other fluid. Turbidity may be measured using a nephelometer. (TR45)
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Void Volume
See Porosity. (TR45)
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Volatile
Evaporates easily; converts easily from a liquid form to gas. (TR45) (TR26)