ADSORPTION-ISOTHERM OF UNDISSOCIATED ELUENT ACID AND ITS RELATION TO THE RETENTION OF SYSTEM PEAKS IN NON-SUPPRESSED ION CHROMATOGRAPHY

The formation of a system peak in non-suppressed ion chromatography is related to the adsorption of undissociated eluent acid onto the funct ionalized resin surface. To clarify the elution behaviour of system pe aks, a new method for determining the isotherms from the capacity fact ors of system peaks using low-pH eluents free from sodium ions was dev eloped. The isotherms for adsorption of undissociated salicylic and ph thalic acids as eluents onto an IC-Anion-PW column, measured by the pr esent method, showed two-site biLangmuir correlations. The capacity fa ctors of system peaks calculated from the equations based on these iso therms were in good agreement with those from actual chromatograms wit h the acidic eluent conditions.