Electromembrane extraction—looking into the future

Abstract

Analytical microextraction techniques, including solid-phase microextraction (SPME) Arthur & Pawliszyn (Anal Chem 62:2145–2148, 1990), stir bar sorptive extraction (SBSE), Baltussen et al. (J Microcol 11:737–747, 1999), single-drop microextraction (SDME) Jeannot & Cantwell (Anal Chem 68:2236–2240, 1996), hollow-fiber liquid-phase microextraction (HF-LPME) Pedersen-Bjergaard & Rasmussen (Anal Chem 71:2650–2656, 1999), dispersive liquid-liquid microextraction (DLLME) Berijani et al (J Chromatogr A. 1123:1–9, 2006), and electromembrane extraction (EME) Pedersen-Bjergaard & Rasmussen (J Chromatogr A 1109:183–190, 2006) have gained considerable interest in recent years. The latter technique, EME, differs from the others by the fact that mass transfer and extraction is facilitated by electrokinetic migration. Thus, basic or acidic analytes are extracted in their ionized form from aqueous sample, through an organic supported liquid membrane (SLM) and into an aqueous acceptor solution under the influence of an electrical potential. EME provides pre-concentration and sample clean-up, and can be performed in 96-well format using only a few microliter organic solvent per sample (green chemistry). Extraction selectivity is controlled by the direction and magnitude of the electrical field, by the chemical composition of the SLM, and by pH in the acceptor solution and sample. This trends article discusses briefly the principle, performance, and current status of EME, and from this future directions and perspectives are identified. Unlike traditional extraction methods, EME involves electrokinetic transfer of charged analyte molecules across an organic phase (SLM) immiscible with water. This process is still not fully characterized from a fundamental point of view, and more research in this area is expected in the near future. From author's point of view, such research at the interface between electrophoresis and partition will be highly important for future implementation of EME.

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