Two-phase micro-electromembrane extraction across free liquid membrane for determination of acidic drugs in complex samples.

A dynamic two-phase micro-electromembrane extraction (μ-EME) using electrically induced transfer of charged analytes directly into free liquid membrane (FLM) is proposed as a novel technique for improving enrichment capabilities of μ-EME. The presented set-up employs aqueous sample as donor solution and water immiscible organic solvent (1-octanol) as FLM, which form the two-phase μ-EME system for efficient extraction of model acidic drugs (ibuprofen, ketoprofen, naproxen and diclofenac) from standard solutions, human urine, human serum and wastewater samples. The FLM eliminates migration of matrix components from the complex samples and simultaneously it acts as an acceptor solution for selective trapping and enrichment of the analyte ions. Electrodes are immersed directly into the sample and the FLM and replenishment of analyte ions at the sample/FLM phase interface is accomplished by stirring the sample solution using a conventional laboratory stirrer. At optimized two-phase μ-EME conditions (100 V, 15 min, 1000 rpm) and optimized volume ratio of sample to FLM (480:16 μL), extraction recoveries of 60–97% and enrichment factors up to 29.1 were achieved. Determination of the acidic drugs in resulting FLMs was achieved by capillary electrophoresis with ultraviolet detection with good linearity (r2 ≥ 0.9998) and low limits of detection (4–20 ng/mL).