Electrically polarized ion-exchange beds in ion chromatography:  ion reflux

All forms of liquid chromatography use eluents that must be prepared and replenished; a widely applied form of ion chromatography (IC) also requires a suppressor and a means for regenerating it. "Ion reflux", as applied to IC, is a new ion-exchange technique where an electrically polarized ion-exchange bed becomes the source of eluent as well as its means of suppression. Using water as the pumped phase, such polarized beds enable the "perpetual" generation and suppression of eluent with little intervention by the user. In one embodiment of ion reflux, continuous eluent generation, ion separation, and continuous suppression are accomplished within a single bed. In another case, where separation is uncoupled from the other two functions, the ion reflux device may be used with existing separators. This paper describes the principles of ion reflux, the advantages and disadvantages of various embodiments, and gives examples of their use in both isocratic and gradient modes of ion separation. These new means for automating eluent generation and suppression should open pathways to new forms of IC instruments and systems.