The Chromatography of Ionic Solutes

In this scheme, a counter ion Y , attached to the R+ group on the resin, is exchanged for another anion X from solution. To exchange cations, we need a structure with exchange sites that are negatively charged, and associated positive counter ions  

The weak exchangers have a higher capacity than the strong exchangers when fully ionised, but are only fully ionised over a restricted pH range. 

The capacity of an ion-exchanger measures the amount of material that can be exchanged by a given amount of the resin, and is normally expressed in milliequivalents per g of dry resin. 

Classical ion-exchange resins are styrene-divinylbenzene copolymers to which ionisable functional groups are attached. There are several ion-exchange materials that are used for hplc  

The styrene-dvb types have better temperature stability than the other two, but most resins swell in contact with solvents. 

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