Ultrafiltration properties

Icodextrin (rINN) is a maltodextrin glucose polymer with a mean molecular weight of 20kDa, which is broken down to maltose. It is used as an alternative to glucose as the active osmotic agent for peritoneal dialysis. Icodextrin is similar in structure to dextran, but has improved ultrafiltration properties, because it is less well absorbed than glucose. 

Commercial dynamic ultrafiltration membranes are produced by the Gaston County Dyeing Machine Co. and by CARRE, Inc. The former uses porous carbon tubes and the latter porous metal tubes as the membrane substrate and containment material. The ultrafiltration properties of the CARRE, Inc, ZOSS ultrafilter, hydrous zirconium oxide on porous stainless steel tubes, are provided in Table I as an example of a dynamic ultrafiltration membrane. 

The resulting polymer was obtained in a 68% yield, and it was soluble in water and low molecular weight alcohols. A molecular weight of 100 kD was estimated by the polymer s ultrafiltration properties and by iodine end-group analysis. 

Sulfonated membranes are an excellent base material for bipolar membranes. The deposition of ally-lamine plasma polymer on the surface results in bipolar, amphoteric membranes with improved ultrafiltration properties. 

Ultrafiltration utilizes membrane filters with small pore sizes ranging from O.OlS t to in order to collect small particles, to separate small particle sizes, or to obtain particle-free solutions for a variety of applications. Membrane filters are characterized by a smallness and uniformity of pore size difficult to achieve with cellulosic filters. They are further characterized by thinness, strength, flexibility, low absorption and adsorption, and a flat surface texture. These properties are useful for a variety of analytical procedures. In the analytical laboratory, ultrafiltration is especially useful for gravimetric analysis, optical microscopy, and X-ray fluorescence studies. 

The statistical properties of polymer chains in a quenched random medium have been the subject of intensive investigations during the last decades, both theoretically [79-89] and experimentally [90-96], because diffusion in such media is of great relevance for chromatography, membrane separation, ultrafiltration, etc. 

Influence of U colloidal transport in organic-poor surface waters has been far less studied. Riotte et al. (2003) reported U losses from 0 to 70% during ultrafiltration experiments for surface waters of Mount Cameroon without nearly any DOC. Even in the low concentration waters, U can be significantly fractionated from other soluble elements by the occurrence of a colloidal phase, probably inorganic in origin. However, such fractionations are not systematic because of the occurrence of various colloidal phases, characterised by different physical and chemical properties, and hence different sorption and/or complexation capacities (Section 2.1). 

Traditionally, ultrafilters have been manufactured from cellulose acetate or cellulose nitrate. Several other materials, such as polyvinyl chloride and polycarbonate, are now also used in membrane manufacture. Such plastic-type membranes exhibit enhanced chemical and physical stability when compared with cellulose-based ultrafiltration membranes. An important prerequisite in manufacturing ultrafilters is that the material utilized exhibits low protein adsorptive properties. 

Polysulfone hollow fibers, composite, 76 17 Polysulfone membranes, 75 811 Polysulfones, 70 202-204 properties of, 70 204t Polysulfone ultrafiltration hollow-fiber membrane, 76 4 Polyfsulfonic acid)s, 23 717-725 biomedical applications of, 23 722-723 uses for, 23 717... 

The retention properties of ultrafiltration membranes are expressed as Molecular Weight Cutoff (MWCO). This value refers to the approximate molecular weight (MW) of a dilute globular solute (i.e., a typical protein) which is 90% retained by the membrane. However, a molecule s shape can have a direct effect on its retention by a membrane. For example, linear molecules like DNA may find their way through pores that will retain a globular species of the same molecular weight. 

Terpstra, R. A., B. C. Bonekamp and H. J. Veringa. 1988. Preparation, characterization and some properties of tubular alpha alumina ceramic membranes for microfiltration and as a support for ultrafiltration and gas separation membranes. Desalination 70 395-404. 

---