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Membranes, in dialysis

Just as with osmotic pressure, the membranes in dialysis must be carefully selected to be compatible with the system under study. Specifically, this amounts to impermeability with respect to the colloid(s) involved and permeability with respect to low molecular weight components. [Pg.140]

Dialysis is a membrane barrier separation process in which differential concentration forces one or more sample analytes to transfer from one fluid to another through a membrane. In dialysis, the solution containing the analyte of interest (whose concentration is depleted) is called the feed and the fluid receiving the analyte is called the dialysate. Dialysis is used to remove salts and low-molecular-weight substances from solutions or to remove high-molecular-weight interferences (e.g., proteins) and to allow the measurement of small molecules. [Pg.1408]

Tishchenko G. Neosepta microporous ion-exchange membranes in dialysis desalination of immunoglobulin fraction of mouse ascitic fluids. J Membr Sci 1996 113 237-248. [Pg.323]

Illustration of a dialysis membrane in action. In (a) the sample solution is placed in the dialysis tube and submerged in the solvent, (b) Smaller particles pass through the membrane, but larger particles remain within the dialysis tube. [Pg.206]

Electrodialysis. Electro dialytic membrane process technology is used extensively in Japan to produce granulated—evaporated salt. Filtered seawater is concentrated by membrane electro dialysis and evaporated in multiple-effect evaporators. Seawater can be concentrated to a product brine concentration of 200 g/L at a power consumption of 150 kWh/1 of NaCl (8). Improvements in membrane technology have reduced the power consumption and energy costs so that a high value-added product such as table salt can be produced economically by electro dialysis. However, industrial-grade salt produced in this manner caimot compete economically with the large quantities of low cost solar salt imported into Japan from Austraha and Mexico. [Pg.183]

Reverse Osmosis Membrane Cleaning. Citric acid solutions are used to remove iron, calcium, and other cations that foul ceUulose acetate and other membranes in reverse osmosis and electro dialysis systems. Citric acid solutions can solubilize and remove these cations without damaging the membranes (94—96). [Pg.185]

Fig. 1. General dialysis is a process by which dissolved solutes move through a membrane in response to a difference in concentration and in the absence of differences in pressure, temperature, and electrical potential. The rate of mass transport or solute flux, ( ), is directly proportional to the difference in concentration at the membrane surfaces (eq. 1). Boundary layer effects, the difference between local and wall concentrations, are important in most... Fig. 1. General dialysis is a process by which dissolved solutes move through a membrane in response to a difference in concentration and in the absence of differences in pressure, temperature, and electrical potential. The rate of mass transport or solute flux, ( ), is directly proportional to the difference in concentration at the membrane surfaces (eq. 1). Boundary layer effects, the difference between local and wall concentrations, are important in most...
Fig. 5. Scanning electron micrographs of hoUow fiber dialysis membranes. Membranes in left panels are prepared from regenerated cellulose (Cuprophan) and those on the right from a copolymer of polyacrylonitrile. The ceUulosic materials are hydrogels and the synthetic thermoplastic forms a microreticulated open cell foam with a tight skin on the inner wall. Pictures at top are membrane cross sections those below are of the wall region. Dimensions as indicated. Fig. 5. Scanning electron micrographs of hoUow fiber dialysis membranes. Membranes in left panels are prepared from regenerated cellulose (Cuprophan) and those on the right from a copolymer of polyacrylonitrile. The ceUulosic materials are hydrogels and the synthetic thermoplastic forms a microreticulated open cell foam with a tight skin on the inner wall. Pictures at top are membrane cross sections those below are of the wall region. Dimensions as indicated.
Klein, Ward, and Lacey, Membrane Processes—Dialysis and Electro-Dialysis in Rousseau, Handbook of Sepaiation Piocess Technology, Wiley, 1987. [Pg.554]

Polysiloxane based block copolymers have also been examined with respect to their transport properties, because these copolymers are of special interest as membranes in various biomedical applications 376). The combination of good mechanical, dielectric, permeation and film formation properties of siloxane-carbonate segmented copolymers have led to their use as blood oxygenation, dialysis and microelectrode membranes 392 394. ... [Pg.73]

Membranes. Apart from the role of membranes180 in ISEs, there are at least three important applications of membranes as measurement aids in flow analysis. viz., as diffusion membranes in (1) (partial) dialysis and in (2a) membrane amperometry (MEAM) and (2b) membrane voltammetry (MEVA), and as Donnan membranes in (3) differential ionic chromatography. [Pg.369]

Many industrial yams have specific surface function requirements. For technical yams the market share for composites or coated fabrics is almost 70%. Furthermore, textile applications also can benefit from a special surface treatment in order to improve the water repellency. Capillary membranes for dialysis, however, have totally different requirements enhanced biocompatibility of the membranes is needed.4-6... [Pg.262]

In vivo microdialysis is based on the principle of dialysis, the process whereby concentration gradients drive the movement of small molecules and water through a semipermeable membrane. In vivo microdialysis involves the insertion of a small semipermeable membrane into a specific region of a living animal, such as the brain. The assembly that contains this semipermeable membrane is called a probe, which is composed of an inlet and an outlet compartment surrounded by a semipermeable membrane (see O Figure 9-1). Using a microinfusion pump set at a low flow rate (0.2-3 /rL/min), an aqueous solution known as the perfusate is pumped into the inlet compartment of the microdialysis probe. Ideally, the... [Pg.222]

Also, discussions of a number of applications of Nafion are not included in this document and are, at most, mentioned within the context of a particular study of fundamental properties. A number of these systems are simply proposed rather than in actual commercial applications. Membranes in fuel cells, electrochemical energy storage systems, chlor-alkali cells, water electrolyzers, Donnan dialysis cells, elec-trochromic devices, and sensors, including ion selective electrodes, and the use of these membranes as a strong acid catalyst can be found in the above-mentioned reviews. [Pg.299]

A process similar to osmosis is dialysis. In dialysis, a dialyzing membrane allows both solvent and minute solute particles of a certain size to pass. The passage of these particles, like osmosis, is from a region of high concentration to a region of low concentration. Our kidneys are a dialysis system responsible for the removal of toxic wastes from the blood. In artificial dialysis, blood is circulated through dialysis tubes made of membranes, which are immersed in a clean solution that lacks the wastes in the blood. The impurities are filtered out of the blood as they move across the walls of the dialyzing tubes. [Pg.133]

Large molecules remain trapped inside a dialysis bag, whereas small molecules diffuse through the membrane in both directions. [Pg.632]

An alternative to the tank transfer system is the semidry transfer system. In this procedure, the gel is stacked horizontally on top of the membrane in the transfer apparatus. Because only a small volume of transfer buffer is used, SDS from the gel is less effectively diluted, which may result in incomplete binding and lower yields, especially with PVDF membranes. For this reason, semidry transfer units are not recommended when reproducible high recoveries of electroblotted proteins are desired (e.g., for subsequent sequence analysis). Some procedures recommend stacking multiple transfer sandwiches to achieve several transfers simultaneously. To prevent unbound protein from migrating through the next gel and onto the membrane in the next transfer stack, sheets of porous cellophane sheets or dialysis membrane are placed between adjacent transfer stacks (see Fig. B3.2.3). Semidry electrotransfer requires shorter transfer times than tank transfer. [Pg.191]

In this case, most ions can pass through the interface but a few are excluded. This situation, which is depicted in Fig. 6.4, is common in dialysis when small ions and low molecular weight substrates can move across the dialysis membrane, but large polyelectrolyte ions, such as proteins, cannot. [Pg.123]

Various fast redox couples such as ferrocene, ferro/ferri cyanide, and ruthenium hexamine have been used as mobile mediators. In order to be electron acceptors their standard potentials must be more positive than that of FADH2/FAD redox couple (E° = 0.05 V, at pH = 7). The requirement of mobility is, however, in conflict with the lifetime of the sensor. Because the mediator is of comparable size to the substrate, it cannot be confined to the electrode proper by, for example, a dialysis membrane. In fact, the only way this type of sensor can operate is in a sample containing a sufficient concentration of the mediator (Cass et al., 1984). Obviously, this requirement makes such sensors suitable only for in vitro applications. [Pg.227]

Campanellae al. [92] Lecithin Soya seed flour, soya seed oil, ground soya seed oil, ground maize germ oil, milk chocolate, soya lecithin in gel capsules, soya lecithin in tablets Phospholipase D and choline oxidase/both immobilised in kappa-carrageenan gel or in dialysis membrane Amperometric gas diffusion electrode for oxygen ... [Pg.280]

The semipermeability behavior of a polymer him can be measured by equipment that permits measurements of the diffusion of a small-molecule dye through the membrane. In the phosphazene systems investigated, the rate of diffusion varied with the polymer side group ratio. A typical polymer with roughly 50% of the side groups as methylamino and 50% as trifluoroethoxy showed a faster transmission of dye molecules in water than did standard cellulose dialysis tubing. [Pg.114]


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See also in sourсe #XX -- [ Pg.30 ]




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