Membrane-free electroextraction using an aqueous two-phase system

In this paper we report a method of continuous electroextraction of amino acids as model samples using a caseinate-poly(ethylene-glycol) - PEG - two phase system in a microchip able to separate compounds based on their differences in electrophoretic mobility and solvent affinity. Fundamentally, the phase boundary replaces a physical membrane, suppressing the diffusion. When external potential is applied, the molecules selectively cross this barrier. The selectivity of the amino acids extraction is the result of their electrochemical properties and applied voltage. We applied this method to amino acids extraction and the results suggest the possibility of high levels of purification by controlling the electric field strength across the liquid barrier. It is a promising method for complex sample separation as well as for the purification of individual compounds.