Modelling of ion-exclusion chromatography and vacancy ion-exclusion chromatography of selected aromatic acids on strongly acidic resin in the H + form

Ion-exclusion chromatography (IEC), a chromatographic technique based on exclusion of dissociated sample molecules, finds many applications in a variety of analytical separations of weak acids. Vacancy ion-exclusion chromatography (v-IEC) is an alternative technique in which the column is equilibrated with the sample solution flowing as mobile phase through the system, and pure water is injected as the sample. In this technique, characteristic negative ‘vacant’ peaks are obtained. The objective of the work described in this paper was to describe the mechanisms of retention in IEC and v-IEC for selected aromatic acids, under analytical and concentration-overload conditions, with pure water, dilute sulphuric acid solution, and dilute sulphuric acid containing a small amount of heptanol as the three mobile phases. The retention times and peak shapes predicted by use of the model were in good mutual agreement for a wide range of concentrations for all the analytes investigated.