New supported liquid membrane for electromembrane extraction of polar basic endogenous metabolites

Extraction of polar endogenous compounds remains an important issue in bioanalysis although different techniques have been evaluated. Among them, electromembrane extraction (EME) is a relevant approach but supported liquid membranes (SLMs) dedicated to polar molecules are still lacking. In this study 22 organic solvents were evaluated as SLMs on a set of 45 polar basic metabolites (log P from -5.7 to 1.5) from various biochemical families. To investigate a large variety of organic solvents, a parallel electromembrane extraction device was used and a constant current approach was applied to circumvent the heterogeneous conductivities of the different SLMs. Among the tested organic solvents, 2-nitrophenyl pentyl ether (NPPE) appeared the most efficient SLM with the extraction of a large variety of polar cationic metabolites, high extraction yields, and low extraction variabilities. The applied current and the composition of the acceptor and donor solutions were also evaluated and 300 μA per well and acetic acid 1% (v/v), both as acceptor and donor compartments, were the most efficient conditions. The new SLM and the optimized experimental parameters were successfully applied to the extraction of precipitated plasma samples. Although the extraction recovery decreased for most compounds in the biological matrix, process efficiency (PE) up to 90% and low extraction variability (RSD between 2 and 18%) were obtained for several very polar compounds such as choline or acetylcholine, emphasizing the potential of EME for polar compounds.