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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- TR 26: Sterilizing Filtration of Liquids (35)
- TR 15: Validation: TFF in Biopharmaceuticals (28)
- TR 45: Depth Filtration (23)
- TR 41: Virus Filtration (15)
- TR 14: Validation: Protein Purification Chromatography (9)
- TR 62: Manual Aseptic Processes (4)
- TR 22: Aseptic Process Simulation (3)
- TR 75: Mycoplasma Filter Rating Method (3)
- TR 50: Alt. Methods Mycoplasma Testing (2)
- TR 66: Single-Use Systems (2)
- TR 69: Bioburden/Biofilm Management (2)
- TR 73: Prefilled Syringe User Requirements for Biotech Applications (2)
- TR 1: Validation: Moist Heat (2)
- TR 28: Process Simulation for Bulk API (2)
- TR 30: Parametric Release (2)
- TR 77: The Manufacture of Sterile Pharmaceutical Products Using Blow-Fill-Seal Technology (2)
- TR 49: Validation: Cleaning Biotech (1)
- TR 51: Biological Indicators (1)
- TR 54-4: QRM: Biotech Drug Substance (1)
- TR 57: Analytical Method Validation (1)
- TR 70: Cleaning/Disinfection Programs (1)
- TR 13: Environmental Monitoring (1)
- TR 85: Enhanced Test Methods - Visible Particle Detection/Enumeration Closures/Containers (1)
- TR 29: Validation: Cleaning (1)
- TR 76: Identification and Classification of Visible Nonconformities in Elastomeric Components and Aluminum Seals for Parenteral Packaging (1)
- TR 43: Glass Defects (1)
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- Biotechnology (52)
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Anaerobic Microorganism
A microorganism that does not utilize oxygen as the final electron acceptor during metabolism; microorganism that will grow only in the absence of oxygen. (TR62)(TR22)
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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)
A means for establishing the capability of an aseptic process as performed using a growth medium. (TR22) (TR62)
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Attachment (Adhesion)
Discrete association of a microorganism with an animate or inanimate surface. (TR69)
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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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Bubble Point
The measured differential gas pressure at which a wetting liquid (e.g., water, alcohol, product) is pushed out of the largest pores of a wetted porous membrane, and a steady stream of gas bubbles or bulk gas flow is detected.(TR15) (TR26) The minimum pressure at which a wetting liquid is pressed out of the pore system of a membrane while forming a steady bubble chain. (TR41)
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Cake
Solids deposited on the upstream side of filter media. (TR15) (TR45) (TR26)
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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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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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Chemical Indicator
Test system that reveals change in one or more predefined process variables based on a chemical or physical change resulting from exposure to a process. (TR01) (TR30)
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Chemical Integrator
A device that is designed to react in a quantitative manner to multiple sterilization variables, (typically, time and temperature and, in some instances, moisture). (TR01) (TR30)
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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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Column Load
The solute that is passed through the column for separation. (TR14)
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Column Packing
Preparation of a column that includes the addition of resin slurry into a column to create a bed suitable for its intended use. Characteristics of a packed column bed include bed height and diameter, backpressure, and number of theoretical plates. (TR14)
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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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Consumables
This refers to items (e.g., SUS, storage bags, tubing, filters, diaphragms, flasks, etc.) that form or are a part of process equipment and are used on a per batch basis. (TR66)
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Cross-Flow Rate
Volumetric rate of fluid flow parallel to the membrane surface. (TR15)
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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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Diavolume (DV)
A volume equal to the retentate volume to which a diafiltration buffer is added. (TR15)
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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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Diffusion Test (or Forward Flow Test)
A test for membrane integrity that involves measuring the rate of gas diffusion through a liquid-wetted membrane.(TR15) An integrity test in which a filter is subjected to differential gas pressures below the bubble point and gas molecule migration through the water-filled pores of a wetted membrane is measured. This behavior follows Fick’s Law of Diffusion (i.e., the gas diffusional flow rate for a filter is proportional to the differential pressure and the total surface area 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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Diffusive/Forward Flow Test
A test to determine the integrity of a filter. [Synonym: diffusive flow test, forward flow test.] (TR26)
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Dimensional Product Quality
The product conforms to the required drawing dimensions. (TR43)(TR76)
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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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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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Effective Filtration Area
The total surface area of the filter available to the process fluid. (TR26)
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Elastomer
Thermoplastic material formulation (that may or may not contain rubber/natural latex) derived from elastic polymer; often used interchangeably with the term “rubber.” (TR73)
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Eluate
Solution (effluent) that flows out of the chromatographic column containing the drug substance. [Synonym: collected product fractions] (TR14)
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Elution
Desorption of a drug substance from a chromatographic column. (TR14)
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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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Feed
The starting solution prior to filtration. (TR15)
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Feed (or Load or Feedstock or Feedstream)
The fluid introduced into a process. (TR41)
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Feed Pressure
The pressure measured at the inlet of the tangential flow filter device. (TR15)
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Filter
A porous medium used for the separation of components in a fluid stream.(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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Filtrate
Fluid that has been passed through a process step (filter). [Synonym: Permeate] (TR15) (TR26)
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Filtration
A process of removing particles from a fluid by passing it through a permeable material, such as a membrane film. (TR41) The process by which particles are removed from a fluid by passing the fluid through a porous material. (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)