Ion exchange adsorbents

Dismer F. Petzold M. Hubbuch J. Effects of ionic strength and mobile phase pH on the binding orientation of lysozyme on different ion-exchange adsorbents. Journal of Chromatography A, 2008, 1194, 11-21. 

Himmelhoch, S. R. (1971) Chromatography of proteins on ion-exchange adsorbents. Methods Enzym. 22, 273-286. 

The sorbent materials used to construct this type of sensor are widely varied (ion exchangers, adsorbent solids, polymers) and are employed as particles (larger than 30 pm in order to avoid overpressure in the flow system) or films. Most of these sensors are optical and rely on absorption, reflectance or molecular fluorescence measurements. In order to ensure that the sensing microzone is fully compatible with the detector, the sorbent material used must be as transparent as possible (photometry) or give rise to no appreciable light scatter (fluorimetry) so that the baseline (resulting from passage of the carrier) may be as low as possible. 

Recently, several kinds of layered compounds have been proposed for use as catalysts these include silicates, graphite, and acid salts of tetravalent metals. These materials can be expected to provide new applications such as shape selective ion-exchangers, adsorbents, and catalysts [1]. 

Vergnault, H., Mercier-Bonin, M., and Willemont, R.-M. (2004). Physicochemical parameters involved in the interaction of Saccharomyces cereviae cells with ion-exchange adsorbents in expanded bed-chromatography. Biotechnol. Prog. 20,1534-1542. 

This paper describes a procedure for measuring the exposure of personnel to methyl isocyanate (MIC) in air in the occupational environment. The ion exchange adsorbent, together with the high-performance liquid chromatographic procedure as written, is capable of detecting 238 ng of MIC per milliliter. This is equivalent to 0.01 parts per million in a 15-liter air sample volume. 

R. Shiloach (personal communication, 1999) believes that ion-exchange adsorbents are a powerful tool in the purification of proteins. They can be used in the initial steps of the protein recovery process by capturing the proteins, enrichment, or polishing. It is likely that new and improved adsorbents will continue to be introduced. 

S. Afrashtehfar and F F Cantwell, Chromatographic retention mechanism of organic ions on a low-capacity ion exchange adsorbent, Anal. Chem. 54 (1982), 2422-2427. 

Figure 17 shows zinc ions exchange-adsorbed and hydrogen ions released versus final pH for SA calcined at 750°. Inspection of the curves of Fig. 17 reveals that the ratio of hydrogen ion released to zinc ion adsorbed is about 2.5, indicating the formation of the two kinds of chelates shown in Fig. 16. SA calcined at 1000° behaved in a different way, as shown in Fig. 18.

Applezweig, N. Ion Exchange Adsorbents as Laboratory Tools. Annals... 

In SPE, choice of an appropriate solid phase is based on their possible molecular interactions with the targeted compounds. For historical reasons, reversed-phase type adsorbents have been largely utilized to extract compounds from aqueous samples, given the fact that many of them have been developed already for use in reversed-phase chromatography applications and are commercially available. Ion exchange adsorbents have been used to retain counter ions based on electrostatic interactions. Solid phase adsorbents combining hydrophobic and ionic interactions are also present, for example graphitized carbon black (GCB) obtained by... 

Porous solids are of scientific and technological importance because of their ability to interact with atoms, ions, molecules, and supramolecules [1]. The presence of voids of controllable dimensions at the atomic, molecular, and nanometer scales in porous solids endows them with unique interfadal properties [2], As a result, they are widely used as ion-exchangers, adsorbents, catalysts, and catalyst supports. Structurally, they are classified into microporous, mesoporous, and macroporous solids, with pore sizes of less than 2 nm, from 2 to 50 nm, and larger than 50 nm, respectively. Compositionally, they could be inorganic, polymeric, and composite [1-8]. 

The eluent compatibility of a polymeric adsorbent will be dependent upon the chemical structure of the polymer backbone, chemical type of the cross-linking agent, degree of cross-linking, and any subsequent covalent or dynamic modifications carried out. The natural polysaccharide polymers in their native state are hydrophilic and are therefore compatible with aqueous eluents whereas the synthetic polymers can be hydrophobic, as in the case of polystyrene, and hence compatible with organic eluents, or hydrophilic, as in the case of polyacrylamide, and so be compatible with aqueous mobile phases. It is of course possible to modify the eluent compatibility of a polymeric matrix by surface coating or derivatisation. For example, the very hydrophobic maeroporous polystyrene matrices may be coated with a hydrophilic polymer to make ion exchange adsorbents or materials suitable for aqueous size separations [25]. 

---