Microporous filtration

Microporous filtration Pressure gradients Sieving Water and dissolved species Symmetrical porous (100-1000 nm) Bacteria filtration... 

Figure 5. Gelman pleated crossflow filter cartridge. Cartridge components (A) a porous pleated support screen to provide mechanical support under applied pressure (B) the pleated microporous filtration element (C) the pleated spacer which creates the thin flow channel and promotes turbulent flow (D) the impermeable film which creates the flow channel (E) a porous support tube to provide an exit for permeate (F) open-end cap which provides for exit of product flow (G) closed-end cap completely which seals one end of module (H) outer seal ring which creates the seal between the impermeable film in the module and the interior of the housing. The back pressure support tube is not pictured. The ends of the cartridge are potted and sealed. A space between the ends of Film D and the end seals is provided to allow the entrance and exit of the flow-channel fluid.

One investigative study that has raised considerable queries is the report of direct electrical communication between the active site of the enzyme and the conducting polymer when the enzyme is immobilized in polypyrrole microtubules. These microtubules were produced by electropolymerization of the pyrrole monomer inside the pores of a microporous filtration membrane. This configuration is reported to favor direct electron transfer across the polymer structure as well as direct reoxidation of the enzyme at lower potentials than typically used, hence promoting increased selectivity of the resulting amperometric biosensor [178]. Another report investigating the same system claims that it is the underlying platinum metal rather than polypyrrole tubules that is responsible for the observed direct enzyme reoxidation [179]. 

Figure 1.17 Ffltrate flux curves in cross-flow microporous filtration...

Figure 24. Chart showing microporous filtration ranges.

Therefore, while it is safe to say feat a given UF membrane could separate the much smaller lactose from the much larger protein in whey, it is dangerous to assume that selected proteins could be separated from each other without experimental evidence. All microporous filtration (MF, UF and RO) deals with purification, fractionation, concentration or partition. An example of purification is pressure-driven UF removal of particles and high-molecular-wei t species from water subsequendy to be used in hollow-fiber RO desalination. An example of pressure-driven fractionation is separation of protein and lactose from cheese whey for use as food additives (in the... 

Controlling the Morphology of Electronically Conductive Polymers. Convex Kel-F-insulated Pt disk electrodes (A 0.5 cm ) were constructed as described previously (32). The convex electrode surface promoted adhesion between the microporous membrane and the electrode surface (32). These electrodes were pretreated as described previously (32). Nuclepore polycarbonate microporous filtration membranes were used as the template material (32). Membranes with pore diameters of 0.02, 1.0 and 3.0 /im were used. 

Schematic representation of microporous membrane-coated electrode used to synthesize fibrillar/microporous electronically conductive polymer films, a. 7mm glass tube. b. Cu wire. c. Kel-F body. d. Ag/epoxy contact, e. Convex Pt disk electrode, f. Rubber collar, g. Nuclepore microporous filtration membrane. 

PVDF-based microporous filters are in use at wineries, dairies, and electrocoating plants, as well as in water purification, biochemistry, and medical devices. Recently developed nanoselective filtration using PVDF membranes is 10 times more effective than conventional ultrafiltration (UF) for removing vimses from protein products of human or animal cell fermentations (218). PVDF protein-sequencing membranes are suitable for electroblotting procedures in protein research, or for analyzing the phosphoamino content in proteins under acidic and basic conditions or in solvents (219). 

Because membrane filtration is the only currently acceptable method of sterilizing protein pharmaceuticals, the adsorption and inactivation of proteins on membranes is of particular concern during formulation development. Pitt [56] examined nonspecific protein binding of polymeric microporous membranes typically used in sterilization by membrane filtration. Nitrocellulose and nylon membranes had extremely high protein adsorption, followed by polysulfone, cellulose diacetate, and hydrophilic polyvinylidene fluoride membranes. In a subsequent study by Truskey et al. [46], protein conformational changes after filtration were observed by CD spectroscopy, particularly with nylon and polysulfone membrane filters. The conformational changes were related to the tendency of the membrane to adsorb the protein, although the precise mechanism was unclear. 

Jomitz, M.W. and Meltzer, T.H. (2004). Sterilizing filtrations with microporous membranes. Pharmacopeial Forum, 30(5), 1903-1910. 

Inummoglubulms and components of complement stimulate formation of The proteolytic fragment of C5, C53, prepared by gel filtration of serum treated with zymosan, and IgG aggregated by heat both elicited formation of O The ability of IgG to elicit the formation of O by PMN s was also demonstrated when PMNs were exposed to IgG and IgA bound to polystyrene plates or to IgG which was heat-aggregated and bound to micropore filters... 

PORE. I A minute cavity in epidermal tissue as in skin, leaves, or leather, having a capillary channel to the surface that permits transport of water vapor from within outward but not the reverse. 2. A void of interstice between particles of a solid such as sand minerals or powdered metals, that permits passage of liquids or gases through the material in either direction. I11 some structures, such as gaseous diffusion barriers and molecular sieves, the pores ate of molecular dimensions, i.e 4-10 A units. Such microporous structures are useful for filtration and molecular separation purposes in various industrial operations. 3. A cell in a spongy structure made by gas formation (foamed plastic) that absorbs water on immersion but releases it when stressed. 

Membrane chromatography systems include microporous or macroporous membranes that contain functional ligands attached to their inner pore structure, which act as adsorbents. In this sense, membrane chromatography is a hybrid combination of liquid chromatography and membrane filtration. Its most important potential applications include separations of biomolecules, such as proteins, polypeptides, and nucleic acids (85,86). 

It may be possible to do a membrane autopsy to identify the foulant(s) and fouling mechanism. For microporous membranes the blocking law analysis [1], which uses permeate volume (V) vs. time (t) data, can supplement the observations. The generalized relationship at constant pressure and in dead-end filtration mode gives,... 

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