Electrical potential can drive liquid-liquid extraction for sample preparation in chromatography

In this review, we discuss three different approaches to liquid-liquid extraction (LLE) driven by an electrical field (dc):(1)electro extraction, by which ionic analytes are extracted from a stagnant organic solution (immiscible with water) into water;(2)electrochemically-modulated LLE (known as ITIES extraction, where ITIES means “interface between two immiscible electrolyte solutions”), by which ionic analytes are extracted from a flowing aqueous sample and into a stationary organo-gel; and,(3)electro-membrane extraction, by which ionic analytes are extracted from an agitated aqueous sample, through an organic solvent (supported liquid membrane) sustained in the pores in the wall of a porous hollow fiber, and into an aqueous acceptor inside the lumen of the hollow fiber.We review the literature with respect to these techniques, which we compare in terms of performance and working principles, and outline the promising aspects of using electrical fields to enhance and to manipulate LLE.In conclusion, we identify LLE driven by electrical fields as an important field for future development in sample preparation for chromatography and electrophoresis.