THEORETICAL-MODELS FOR ELECTRODIALYTIC SAMPLE TREATMENT IN TRACE ANALYSIS BY LIQUID-CHROMATOGRAPHY

Basic considerations for analyte enrichment and recovery obtainable by electrodialysis as a sample treatment method are given. Equations are derived which describe the dependence of the concentration profiles o f ionic compounds on the electric field strength in a set-up with stag nant donor and acceptor solutions. It is shown that analyte recovery i ncreases when less ion-selective membranes are used in the electrodial ysis cell. Computer models are used to estimate the analyte enrichment for a flowing donor (sample) and a stagnant acceptor phase. About 10- fold enrichment can be obtained in an electrodialytic sample treatment system within 20 min under maximum current conditions. A compromise h as to be found between analyte recovery and the donor (sample) flow ra te.