Use of Ion Exchange Resins

Ion exchange resins are also useful for demineralising biochemical preparations such as proteins. Removal of metal ions from protein solutions using polystyrene-based resins, however, may lead to protein denaturation. This difficulty may be avoided by using a weakly acidic cation exchanger such as Bio-Rex 70 (which is a carboxylic acid exchange resin based on a polyacrylic lattice). 

Heavy metal contamination of pH buffers can be removed by passage of the solutions through a Chelex X-100 column. For example when a solution of 0.02M HEPES containing 0.2M KCl (IL, pH 7.5) alone or with calmodulin, is passed through a column of Chelex X-100 (60g) in the K form the level of Ca ions falls to less than 2 x 10 M as shown by atomic absorption spectroscopy. Such solutions should be stored in polyethylene containers that have been washed with boiling deionised water (5min) and rinced several times with deionised water. TES and Tris have been similarly decontaminated from metal ions (see reference on atomic absorption analysis on p 62). 

In removing traces of impurities by precipitation it is necessary to include a material to act as a collector of the precipitated substance so as to facilitate its removal by filtration or decantation. The following are a few examples  

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In recent years, the rate of information available on the use of ion-exchange resins as reaction catalysts has increased, and the practical application of ion-exchanger catalysis in the field of chemistry has been widely developed. Ion-exchangers are already used in more than twenty types of different chemical reactions. Some of the significant examples of the applications of ion-exchange catalysis are in hydration [1,2], dehydration [3,4], esterification [5,6], alkylation [7], condensation [8-11], and polymerization, and isomerization reactions [12-14]. Cationic resins in form, also used as catalysts in the hydrolysis reactions, and the literature on hydrolysis itself is quite extensive [15-28], Several types of ion exchange catalysts have been used in the hydrolysis of different compounds. Some of these are given in Table 1. 

There are several apparent advantages to the use of ion-exchange resins as either acid or base catalysts, several of which are as follows ... 

ALKENES via HOFMANN ELIMINATION USE OF ION-EXCHANGE RESIN FOR PREPARATION OF QUATERNARY AMMONIUM HYDROXIDES DIPHENYLMETHYL VINYL ETHER... 

Exudate collection in trap solutions usually requires subsequent concentration steps (vacuum evaporation, lyophilization) due to the low concentration of exudate compounds. Depending on the composition of the trap solution, the reduction of sample volume can lead to high salt concentrations, which may interfere with subsequent analysis or may even cause irreversible precipitation of certain exudate compounds (e.g., Ca-citrate, Ca-oxalate, proteins). Therefore, if possible, removal of interfering salts by use of ion exchange resins prior to sample concentration is recommended. Alternatively, solid-phase extraction techniques may be employed for enrichment of exudate compounds from the diluted trap solution (11,22). High-molecular-weight compounds may be concentrated by precipitation with organic solvents [methanol, ethanol, acetone 80% (v/v) for polysaccharides and proteins] or acidification [trichloroacetic acid 10% (w/v), per-... 

Waksman et al, in 1949, first reported the production of neomycin by fermentation of a culture of S. faUcid-Lcut. (3535). The same organism subsequently formed the basis of an industrial fermentation process for the biosynthesis of neomycin287,288. isolation of the antibiotic from the fermentation media is accomplished by use of ion-exchange resins, such as Amberlite IRC 50 25,250,251. 

The first fractionation of urinary ampholytes in this way was carried out by Boulanger et al. (BIO) in 1952 with the use of ion-exchange resins. They had designed this procedure previously for the fractionation of ampholytes in blood serum (B8). According to this method, deproteinized urine was subjected to a double initial procedure aiming at the separation of low-molecular weight substances from macro-molecular ones. One of the methods consisted of the fractionation of urinary constituents by means of dialysis, the second was based on the selective precipitation of urinary ampholytes with cadmium hydroxide, which, as had previously been demonstrated, permits separation of the bulk of amino acids from polypeptides precipitated under these circumstances. Three fractions, i.e., the undialyzable part of urine, the dialyzed fraction, and the so-called cadmium precipitate were analyzed subsequently. 

It is common to concentrate organic components extracted from soil before analysis is conducted. Concentration of ionic species is not as common. However, the use of ion exchange resins to remove ionic species from soil is a well-established ion removal method. Although this method is not commonly discussed in terms of concentration of ions found in soil, it can lead to increased ion concentration and increased ability of analytical methods to measure trace amounts of ions in soil [26],... 

Inorganic species in soil are generally extracted with either water or an acid solution typically containing hydrochloric acid. Various other components that aid either in the solubilization, extraction, or stabilization of extracted inorganics, such as chelates, are also often added during the extraction process. Basic extractions are not as commonly used as are acid extractions with a few notable exceptions. The use of ion exchange resins to extract ions from soil is well established. 

The separation of small amounts of radioactive material by the use of ion exchange resins is one of the most useful and flexible of separation methods, and one which can be readily adapted to remote control when large amounts of radioactive material are to be handled. The limit of the quantity will be reached when the resin decomposes under the action... 

Glycerine can also be purified by the use of ion-exchange resins to remove sodium chloride salt, followed by evaporation of the water. This process puts additional salts into the wastewater but results in less organic contamination. 

Examples are available from a number of studies. The authors demonstrated that the use of ion-exchange resins as supports for chelators that can be deiivahzed or converted to ions is a versatile technique [22]. Examples involving two different ion-exchange resins help indicate the range of the technique. 

The use of ion-exchange resins for hydrolysis was introduced by Wadman,55 and this method is becoming increasingly popular in the field of glycoproteins. The resin may be used alone,56 in the presence of dilute sulfuric acid,57 or with dilute hydrochloric acid.58,59 The last... 

The use of ion exchange resins and natural or synthetic inorganic exchange materials in the nuclear industry is well documented ( ). In the waste solidification application, the titanates or niobates offer no unique sorption properties. They do, however, provide a relatively high overall sorption capacity for a variety of nuclides in materials which can be converted into a stable ceramic host for the sorbed ions. After the sorption process, the column bed must be consolidated to reduce surface area. The project emphasis was directed toward a stable waste form and a considerable effort was devoted to producing and characterizing a highly dense form with favorable physical, chemical and thermal properties (l ). 

The use of ion-exchange resins tall into live categories I. Transformation of ionic constituents 2. Removal of ionic impurities 2, Concentration of ionic substances 4. fractionation ol tome substances and 5 A variety of other applications. 

The methods of piuification include the use of ion exchange resins, the precipitation of protactinium peroxide and the extraction of aqueous solutions of protactinium salts by various organic solvents. 

In adsorption chromatography the mobile phase is usually a liquid and the stationary phase is a finely-divided solid adsorbent (liquid-solid chromatography). Separation here depends on the selective adsorption of the components of a mixture on the surface of the solid. Separations based on gas-solid chromatographic processes are of limited application to organic mixtures. The use of ion-exchange resins as the solid phase constitutes a special example of liquid-solid chromatography in which electrostatic forces augment the relatively weak adsorption forces. 

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