Electrodialysis ion transfer as a postcolumn reactor in ion chromatography for enhanced anion detection

This study presents an ion chromatography (IC) system incorporating an electrodialysis ion-transfer device (ITD) as a postcolumn reactor to improve the anion detection sensitivity. The ITD features a donor channel for sample introduction, two ion acceptor channels for ion extraction, and two isolator channels to eliminate electrode-generated gases (H₂ and O₂). In the system, IC-separated analyte anions are introduced to the ITD, where they are extracted to acceptor channels of ultrapure water and detected via conductivity. Compared with conventional IC using a gel-type suppressor (IC-SUP), the IC-ITD showed an 80% reduction in the baseline conductivity for a carbonate/bicarbonate eluent system. Strong-acid-derived anions (Cl^-, Br^-, NO₃^-, and SO₄^2-) were quantitatively transferred at 100 V, whereas weak-acid-derived anions (F^-, NO₂^-, and HPO₄^2-) were incompletely transferred, even at higher voltages. The anion detection sensitivity was substantially enhanced by optimized flow rates, with the acceptor stream running at one-fourth of the donor's flow rate. Compared with conventional IC-SUP, the proposed enrichment strategy increased the conductimetric responses for strong- and weak-acid-derived anions by approximately 7- and 1.8-folds, respectively, because of intensified peaks and the reduced background conductivity level. The IC-ITD enables suppressor-free anion detection via IC, offering a simplified system configuration and enhanced anion detection sensitivity.