Simultaneous micro-electromembrane extractions of anions and cations using multiple free liquid membranes and acceptor solutions

Micro-electromembrane extractions (mu-EMEs) across free liquid membranes (FLMs) were applied to simultaneous extractions of anions and cations. A transparent narrow-bore polymeric tubing was filled with adjacent plugs of mu L volumes of aqueous and organic solutions, which formed a stable five-phase mu-EME system. For the simultaneous mu-EMEs of anions and cations, aqueous donor solution was the central phase, which was sandwiched between two organic FLMs and two aqueous acceptor solutions. On application of electric potential, anions and cations in the donor solution migrated across the two FLMs and into the two peripheral acceptor solutions in the direction of anode and cathode, respectively. Visual monitoring of anionic (tartrazine) and cationic (phenosafranine) dye confirmed their simultaneous mu-EMEs and their rapid (in less than 5 min) transfers into anolyte and catholyte, respectively. The concept of simultaneous mu-EMEs was further examined with selected model analytes; KClO4 was used for mu-EMEs of inorganic anions and cations and ibuprofen and procaine for mu-EMEs of acidic and basic drugs. Quantitative analyses of the resulting acceptor solutions were carried out by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D). Good extraction recoveries (91-94%) and repeatability of peak areas (<= 6.3%) were achieved for 5 min mu-EMEs of K+ and ClO4-. Extraction recoveries and repeatability of peak areas for 5 min mu-EMEs of ibuprofen and procaine were also satisfactory and ranged from 35 to 63% and 7.6 to 11.3%, respectively. Suitability of the presented micro-extraction procedure was further demonstrated on simultaneous mu-EMEs with subsequent CE-C4D of ibuprofen and procaine from undiluted human urine samples. (C) 2016 Elsevier B.V. All rights reserved.