Microscale continuous ion exchanger

A microscale continuous ion exchanger based on two liquid streams flowing in parallel is presented. The ion exchange reaction occurs through diffusional transfer of molecules between the ion exchanger phase and the eluent phase and is applied for conductivity suppression. Two approaches are demonstrated. In the first approach, a liquid ion exchanger (i.e. a strongly basic compound, e.g., tetraoctylammonium hydroxide, or a secondary amine, e.g., Amberlite IA-2) is dissolved in an organic solvent immiscible with the aqueous eluent. The system allows for sensitive suppressed conductivity detection of various inorganic cations. When the weakly basic secondary amine is used, conductometric detection of heavy metals is possible. In the second approach, a suspension of finely ground ion-exchange resin is used as the ion exchanger phase. In this case, the suspension need not involve an organic solvent. Theoretical models and computations are presented along with experimental results. The potential of such a system as a chip-scale post-separation suppressor/reactor is evident.