SOME FACTORS AFFECTING RETENTION OF ACIDS IN ION-EXCLUSION CHROMATOGRAPHY

Ion exclusion chromatography (IEC) is one of widely used techniques of high-performance ion chromatography. Invented by Wheaten and Bauman [ 1], it is based on separation of analytes having the same charge as io nic centres of the stationary phase. In IEC ionized solutes are exclud ed from the stationary phase, but their retention is also significantl y influenced by some additional processes such as size exlusion or hyd rophobic adsorption on the stationary phase. In most developed applica tions IEC was employed for separation of weakly dissociated species wi th dissociation constants in the range from 10(-7) to 10(-2). IEC meas urements are usually performed using ion exchange columns of higher ca pacity and usually higher dimensions that those used for conventional high performance ion chromatography. The role of various factors affec ting retention in IEC is currently discussed in the literature [2,3]. In several papers size-exclusion effects [4-6], the role of hydrophobi c absorption [7,8], and also the effect of organic modifiers in the el uent [9,10] have been discussed. This communication provides some new observations concerning the role of solute structure, the role of the ion-exchange strength, and the composition of the mobile phase on rete ntion in IEC. An example of the use of IEC for the separation of stron gly dissociated analytes is also demonstrated.