#Pure point measure distribution free

Flow rate is dependent on the hydrophobicity of the filter material, temperature of the procedure, physical thickness and pore-size distribution of the filter material. The flow rate is determined by using water or alcohol to determine the permeability to flow before any extra pressure drop produced by the filter cake. The standard operating procedure of the filtration step should clearly define the conditions and if possible include the limits of the procedure.

#Pure point measure distribution free

The filters used in ion analysis should be completely free of any ionic impurities. The safest way to use filters for chromatography is to wash them with the same solvent used during filtration and to discard an initial volume of the filtrate. For chromatographic applications the filter material is certified not to add impurities to the process. For many biological applications, the manufacturer certifies the filtration material to be pyrogen-free. Commercial filter manufacturers now certify for specific applications. In some analyses, even a small amount of contaminant is enough to cause problems. Although aggressive solvents or physical conditions may be very compatible with the filter membrane, they may affect the filter-containment system. This housing material is usually plastic, and the manufacturer tests that the plastic used in containing the filter material is not going to leach out impurities under experimental conditions. Sometimes the source of impurities is not from the filtering material but from the housing or support of the filter. The additives and monomers can be entrapped within the body of the filter. This large amount of detergent helps in efficient filtration, lower pressure requirements and permits autoclaving for sterilization. Some contaminants occur in small quantities but some detergents can make up as much as 2–3% of the dry weight of the filter. The source of impurities could be additives, stabilizers, surface modifiers, detergents and monomers in the filter material. The filter devices and materials can be a source of contamination in the filtration process. This also ascertains filter usability as an aqueous barrier. Water is first permeated from the largest pore. The water-breakthrough number is dependent on pre-wetting, temperature and pore size of the filter medium. In this test, the minimum pressure required to permeate water from a filter membrane is measured. It is similar to bubble point as this test also give information about the largest pore of the filter membrane. The water-breakthrough test is used for hydrophobic membranes.

It does not indicate the variability of pore sizes or irregularity of the membrane. This is an indirect measurement of the size of the largest pore on the filter. The gas pressure at this time is the bubble point for the membrane. The bubble starts forming from the largest pore first. The filter membrane is wetted and a gradual increasing gas pressure is applied. Bubble Pointīubble point is a function of pore size, filter medium wettability, surface tension and angle of contact. Some of the most common tests used for this purpose are shown below. The filter material characteristics are covered in this article. Usually the filter manufacturer performs the basic testing to ensure the type, pore size and integrity of the filter. The validation of filtration processes includes all the equipment, physical conditions and material requirements of the process. Sahai, in Encyclopedia of Separation Science, 2000 Filtration Validation