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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Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. The term is commonly used in its shortened form, “phage”. (TR41) (TR 47)
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Bracketing
A demonstration of unit operation performance at two different values of a given parameter (e.g., ionic strength, dwell time or temperature), allowing the use any values of that parameter falling within this range. (TR41)
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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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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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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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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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Feed (or Load or Feedstock or Feedstream)
The fluid introduced into a process. (TR41)
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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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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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Tangential or Cross Flow Filtration (TFF or CFF)
Filtration in which a fluid (feed) stream runs tangential to a membrane. A pressure differential causes some fluid to pass through the membrane. (TR41)