Tandem air-agitated liquid-liquid microextraction as an efficient method for determination of acidic drugs in complicated matrices

A rapid and simple microextraction method with a high sample clean-up, termed as tandem air-agitated liquid-liquid microextraction (TAALLME), is described. This method is based upon the tandem implementation of the air-agitated liquid-liquid microextraction (AALLME), and this approach improves the applicability of the dispersive liquid-liquid microextraction (DLLME) methods in complicated matrices. With very simple tools, the three non-steroidal anti-inflammatory drugs diclofenac, ibuprofen, and mefenamic acid were efficiently extracted, with an overall extraction time of 7 min. By performing the first AALLME, these acidic analytes, contained in an aqueous sample solution (donor phase, 8.0 mL), were extracted into the organic solvent (1,2-dichloroethane, 37 mu L), and their simple back-extraction into the aqueous acceptor solution (pH, 10.01, 51 mu L) was obtained in 2 min by a second implementation of AALLME. Response surface methodology (RSM) was used for optimization of the experimental parameters. The pH values 2.94 and 10.01 were obtained for the donor and acceptor phases, respectively, and the volumes 99.5 and 51 mu L were obtained for the organic solvent and the acceptor phase, respectively, as the optimal extraction conditions. Under the optimized conditions, tandem AALLME-HPLC-UV provided a good linearity in the range of 0.5-4000 ng mL(-1), limits of detection (0.1-0.3 ng mL(-1)), extraction repeatabilities (relative standard deviations (RSDs) below 7.7%, n = 5), and the enrichment factors (EFs) of 80-104. Finally, the applicability of the proposed method was evaluated by the extraction and determination of the drugs under study in the wastewater and human plasma samples. (C) 2016 Elsevier B.V. All rights reserved.