Eluents for anion exchange

Eluents for Anion-Exchange Chromatography l45 Cation-exchange connector... 

Ion exchange chromatography is based upon the differential affinity of ions for the stationary phase. The rate of migration of the ion through the column is directly dependent upon the type and concentration of ions that constitute the eluent. Ions with low or moderate affinities for the packing generally prove to be the best eluents. Examples are hydroxide and carbonate eluents for anion separations. 

The kind of eluent that is used for anion exchange chromatography depends mainly on the detection system being employed. Since, in many cases, the detection of inorganic and organic anions occurs via conductivity detection, the eluents used are classified into two groups ... 

In contrast to conventional suppressor columns, hollow fiber suppressors are continuously regenerated, and thus do not require an additional pump system. The reactions that occur across the membrane wall are shown in Fig. 3-37. Since fiber suppressors suited for anion exchange chromatography act as cation exchangers, the eluent cations are exchanged with protons in the regenerent solution. The driving force for the diffusion of protons across the membrane is provided by their subsequent reaction with... 

The general requirement for an anion chromatography eluent is that the eluting anion must have useful affinity for anion-exchange resins. Since it is important to minimize the conductivity of the eluent, the preferred anion is one which has a pKa... 

The preferred eluents for anions are dilute carbonate-bicarbonate mixture, sodium hydroxide and, for common alkali metals and simple amines, dilute mineral acids (HCl, HNO3, BaCl2, AgN03, amino acids, alkyl and aryl sulfonic acids). The most common choice is HCl, but in the case of divalent ions, an eluent of much higher affinity for the ion-exchange resin, such as AgN03, must be used. 

The separation of cations is usually carried out on lonPac CS12A with sulfuric acid or methanesulfonic acid as an eluent. For anion analysis, carbonate-selective anion exchangers such as lonPac AS12A, AS14, or AS22 have proved to be suitable. Alternatively, gradient elution on lonPac ASH can be used. As a... 

Fig. 5. Anion-exchange separation of insulin and insulin A- and B-chains, over diethylaminoethyl (DEAF) in a 10.9 x 200 mm column having a volume of 18.7 mL. Sample volume is 0.5 mL and protein concentration ia 16.7 mAf Tris buffer at pH 7.3 is 1 mg/mL for each component ia the presence of EDTA. Eluent (also 16.7 mAf Tris buffer, pH 7.3) flow rate is 1.27 ml,/min, and protein detection is by uv absorbance at 280 nm. The straight line depicts the salt...

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

If a conductivity de tector is used to monitor the effluentj from an ion-exchange column, the signal observed when a solute ion] elutes is proportional to the solute concentration and to the difference in limiting equivalent ion conductances between tbs eluent and solute ions. The detector response for anion-exchangsrj for example, is given by... 

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