Properties desirable in resins

It must possess mono-functional exchange groups. There is no difficulty about this with modern resins, but earlier products made from phenol were polyfunctional (OH and COOH groups) and their exchange properties depended on the pH of the solution in which they were immersed. They were not, on this account, suitable for chromatography. 

It must have a controlled degree of cross-linking 4-8% is best for chromatography. 

The range of particle sizes must be as small as possible. 

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