Bonded stationary phases ionic strength

Ion exchange—Ionic mixture components are separated based on the varying strength of ionic bonds formed with sites on the stationary phase. 

Most stationary phases used in bonded-phase chromatography in its reversed-phase mode are based on octadecylsilane functionality (C18 columns). The mobile phases typically used in this context are water, aqueous buffers of a given pH and ionic strength, and mixtures of water and a miscible organic modifier, such as methanol or acetonitrile. 

Gfeller et al.25 1 used a microparticulate chemically bonded diol stationary phase in combination with an exclusively aqueous mobile phase. It allowed post-column ion-pair derivatiza-tion of the separated alkaloids. By changing the pH and the ionic strength of the buffer, the capacity factors of the alkaloids could be varied. 

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