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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Velocity
The average linear rate of fluid flow equal to the volumetric flow rate divided by the cross-sectional area of the flow channel. (TR15)
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Transmembrane Pressure (TMP)
The pressure difference equal to the average feed-stream pressure minus the average filtrate-stream pressure. TMP = (Pfeed + Pretentate)/2 - Pfiltrate (TR15)
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Tangential Flow Filtration
Filtration in which the product stream is introduced parallel to the membrane surface and flows in a direction perpendicular to the filtrate flow. (Synonym:cross-flow filtration) (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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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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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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Retention Factor
One minus the ratio of filtrate concentration of component i (Ci,f) to the bulk or feed concentration of component i (Ci,b) as in the following equation:R = 1 - [Ci,f/Ci,b]Where R=0 for a freely passing solute R=1 for a solute that is fully retained by the membrane[Synonym: rejection coefficient, rejection factor] (TR15)
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Retentate
The concentrated feed solution after removal of filtered liquid through the membrane and into the filtrate. [Synonym: concentrate] (TR15)
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Shear Rate
The velocity gradient in a flowing fluid. This value is proportional to the average linear velocity and is inversely proportional to the channel height or diameter when the recirculation is in the laminar flow regime (most TFF applications). (TR15)
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Porosity (Synonym:Void volume)
The percentage of a membrane’s volume that is occupied by pores. (TR15)
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Pore-Size Distribution
The range of pore sizes in a filter used to determine the filter’s average pore size. (TR15)
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Microfiltration (MF)
Pressure-driven, membrane-based separation process in which particles and dissolved macromolecules (typically 0.1 &mum or larger) are retained. (TR15)
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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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Integrity Testing
A method of determining if a membrane or filter is physically intact and free from gross defects. (TR15)
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Fouling (or Clogging)
Adsorption or interaction with components in the feed stream resulting in a decrease in membrane performance. Generally, fouling can be reversed by cleaning the membrane. (TR15) The result of solutes blinding or blocking membrane pores. It is observed as a decrease in the flux (at constant pressure) or an increase in the filtration differential pressure (at constant flux). (TR26)
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Foulant
Solute or suspended solid that interacts with the membrane causing a decrease in performance (see Fouling). (TR15)
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Filtrate
Fluid that has been passed through a process step (filter). [Synonym: Permeate] (TR15) (TR26)
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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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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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Feed
The starting solution prior to filtration. (TR15)
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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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Extractable
A chemical component that is removed from a material by application of an artificial or exaggerated force (e.g., solvent, temperature, time). The term extractable is often erroneously used to describe a leachable. (TR14) (TR15) (TR26) (TR41) (TR45) Chemical substances that can be extracted from components of material process fluid contact surfaces by exertion of an exaggerated force (e.g., organic solvent, extreme elevated temperature, ionic strength, pH, contact time, etc.) Extractables may represent most but not all of the potential leachables that may be seen in process fluids. (TR66) Extractables are organic and inorganic chemical entities that can be released from a pharmaceutical packaging/delivery system, packaging component, or packaging material of construction under laboratory conditions. (TR54-4) Organic or inorganic chemical entity that is forced out of container closure system materials and components under laboratory experimental conditions. (TR73)
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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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Diavolume (DV)
A volume equal to the retentate volume to which a diafiltration buffer is added. (TR15)
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Concentration Factor
The ratio of the initial feed volume to the retentate volume. (TR15)
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Concentration Polarization
A phenomenon in which the concentration of retained solutes increases in the region adjacent to the membrane surface due to limitations in particle transport back into the bulk solution. (TR15)
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Contaminant
Any adventitiously or externally introduced material(s) (e.g., chemical, biochemical, or microbial species) not intended to be part of the process. (TR14) (TR15) (TR70)
An undesired impurity of a chemical or microbiological nature that is introduced into a raw material, intermediate, or API (drug substance) during manufacture. (TR14) (TR15)
Any adventitiously introduced materials (e.g., chemical, biochemical, or microbial species) not intended to be part of the manufacturing process of the drug substance or drug product. (TR69) (TR74)
Any adventitiously introduced material (e.g., chemical, biochemical) or microorganisms including viruses not intended to be included in the manufacturing process of the drug substance or drug product. (TR83)
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Cross-Flow Rate
Volumetric rate of fluid flow parallel to the membrane surface. (TR15)
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Composite Membrane
A membrane consisting of multiple layers. (TR15)
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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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Batch Filtration Process
In a batch filtration process, the entire volume to be filtered is held in a single feed tank. The retentate stream is recycled back to that single feed tank. (TR15)
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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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