Characterization of Membranes

The performance of a membrane is in general characterized by its flux and its selectivity. For practical reasons fluxes for pervaporation membranes are just given in either kg/m h or in mol/m h, either as total flux of all components or separated into the partial fluxes of the different components. For comparison of different membranes very often the so-called pure-component flux at constant temperature (Jo in Eqs. (22) and (23)) is calculated by dividing the actual flux of a component by its concentration in the feed. 

Although this value can be calculated for all components it is most widely used to characterize hydrophilic membranes by their pure water flux . 

The respective pure water flux is then depending on the temperature according to Eq. (15) or Eq. (16). 

The selectivity of a pervaporation membrane is defined in different ways. Most commonly found in Hterature is the so-called a-value. This is calculated as the ratio of the more-permeable component (e.g. water) to the less-permeable component (e.g. organic) in the permeate divided by the respective ratio in the feed. 

Although the a-value looks fairly simple it is not very informative. For most membranes, especially for dehydration membranes the composition of the permeate is constant over a very broad range of feed compositions (e.g. Fig. 3.13). As a consequence the a-value is not a constant but varies considerably with the feed composition, and cannot really be used for the comparison of two membranes. 

---

Hink M. and Visser A. J. W. G. (1999) Characterization of Membrane Mimetic Systems with Fluorescence, in Rettig W. et al. (Eds), Applied Fluorescence in Chemistry, Biology and Medicine, Springer-Verlag,... 

Yada, Y., Higuchi, K., and Imokawa, G., 1995, Purification and biochemical characterization of membrane-bound epidermal ceramidases from guinea pig skin. J. Biot. Chem. 270 12677-12684. 

Characterization of membranes was carried out at 1.0 MPa and 25°C, using pure water and aqueous solution of sodium chloride,(... 

Selected entries from Methods in Enzymology [vol, page(s)] Aspartate transcarbamylase [assembly effects, 259, 624-625 buffer sensitivity, 259, 625 ligation effects, 259, 625 mutation effects, 259, 626] baseline estimation [effect on parameters, 240, 542-543, 548-549 importance of, 240, 540 polynomial interpolation, 240, 540-541,549, 567 proportional method for, 240, 541-542, 547-548, 567] baseline subtraction and partial molar heat capacity, 259, 151 changes in solvent accessible surface areas, 240, 519-520, 528 characterization of membrane phase transition, 250,... 

I. Madar, H. Ravert, B. Nelkin, M. Abro, M. Pomper, R. Dannals, J.J. Frost, Characterization of membrane potential-dependent uptake of the novel PET tracer F-fluorobenzyl triphenylphosphonium cation, Eur. J. Nucl. Med. Mol. Imaging, 2007 Sep 5, [Epub ahead of print],... 

Kitchen, B. J. 1977. Fractionation and characterization of membranes from bovine milk fat globule. J. Dairy Res. 44, 469-482. 

Palmer and Samuelson (1924) were the first to report the isolation and partial characterization of membrane material from milk lipid globules. The methods they used are similar to those used for this isolation today. Brunner (1974), who himself was instrumental in development of isolation methods (Brunner et al. 1953), provided a detailed review of the history of isolation methods. In this section we will summarize the currently used methods and indicate their advantages and disadvantages. 

The two phenomena are furthermore not very suitable for the characterization of membranes, because structural changes may easily occur due to the high pressures which have to be applied. 

Ivnitsky, H., Katz, I., Minz, D., Shimoni, E., Chen, Y Tarchitzky, J., Semiat, R. and Dosoretz, C.G. (2005) Characterization of membrane biofouling in nanofiltration processes of wastewater treatment. Desalination, 185, 255—268. 

Characterization of membrane receptors some general considerations... 

The isolation of lipids from cells or tissues is not as simple and straightforward as one might desire, but is essentially an important adjunct to characterization of membranes (composition, lipid-to-protein ratio, structure proof, definition, new lipids, etc.). While this is recognized by many investigators in the field, it is difficult for the novice in this area to become aware of some of the potential problems in extraction procedures and the reasons for particular approaches. Thus it seems fitting at this point in time to comment on some of the nuances of the approaches used in isolation, purification, and identification of lipids present in cell membranes. These topics are subdivided into areas which are considered to be of major import to a successful consideration of the extraction procedure. 

Figure 3.15. Schematic representation of the correlation between fuel cell impedance and polarization curve. (Modified from [23], with kind permission from Springer Science+Business Media Journal of Applied Electrochemistry, Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy, 32(8), 2002, 859-63, Wagner N. Figure 4.)...

Wagner N (2002) Characterization of membrane electrode assemblies in polymer electrolyte fuel cells using a.c. impedance spectroscopy. J Appl Electrochem 32(8) 859-63... 

Lear, J.D., Gratkowski, H., DeGrado, W.F. (2001), De novo design, synthesis and characterization of membrane-active peptides, Biochem. Soc. Transact. 29, 559-564. 

Kemner, J., and Zeikus, J. G. 1994. Purification and characterization of membrane-bound hydrogenase from Methanosarcina barkeri MS. Arch. Microbiol. 161, 47-54. 

The ratio of carbon to nitrogen to phosphorus (C N P) has important effects on the rate of biofilm development. It has been reported that membranes which suffered severe biofouling were found to contain a high percentage (typically >60%) of organics. Laboratory characterization of membrane biofilms found that a typical biofilm contains ... 

M. Mulder, Characterization of membranes, in M. Mulder (Ed.), Basic Principles of Membrane Technology. Kluwer Academic Publishers, The Netherlands, 1991, pp. HOIST. 

M. Bjerring. T. Vosegaard. A. Malmendal and N. C. Nielsen, Methodological development of solid-state NMR for characterization of membrane proteins. Concepts Magn. Reson., 2003, ISA, 111-129. 

Bijani S, Fortunato R, de Yuso MVM, Heredia-Guerrero FA, Rodriguez-Castellon E, Coehloso 1, Crespo J, Benavente J (2009) Physical-chemical and electrical characterizations of membranes modified with room temperature ionic liquids age effect. Vacuum 83 1283-1286... 

Industrial applications of perfluorinated ionomer membranes such as the electrolysis of sodium chloride solution to produce chlorine and sodium hydroxide often involve the use of highly concentrated solutions at elevated temperatures. The optimization of these systems depends upon a sound characterization of membrane transport processes under such conditions. Sodium ion is the major current-carrying species through the membrane in a chlor-alkali cell, and... 

While these membranes exhibit sodium ion transport numbers as high as 0.98 mol F-1 (i.e. only 2% of the electrolysis current is carried by hydroxide ion through the membrane) no comprehensive theoretical treatment of this unusually high permselectivity has yet emerged. The variation of permselectivity as a function of various cell parameters is also of interest, not only for practical reasons but also because of the insight that may be gained into the nature of hydroxide ion rejection. This research is directed at the latter problem, that is the characterization of membrane permselectivity... 

Additionally it is also possible to study the interaction between proteins and lipids and this is very important for the structural characterization of membrane proteins (Huster 2005). Last but not least, high resolution P NMR is an established method for the determination of the PL composition of complex mixtures (Schiller and Arnold 2002) that can be very easily quantified by using the integral intensities of the individual resonances. Both aspects of P NMR were recently reviewed (Schiller et al. 2007a). 

Jeon WB, Cheng JJ and Ludden PW (2001) Purification and characterization of membrane-associated CooC protein and its functional role in the insertion of nickel into carbon monoxide dehydrogenase from Rhodospirillum rubrum. J Biol Chem 276 38602-38609. 

Yamakawa, A. Takenawa, T. Purification and characterization of membrane-bound phosphatidylinositol kinase from rat brain. J. Biol. Chem., 263, 17555-17560 (1988)... 

---