Tandem dispersive liquid-liquid microextraction as an efficient method for determination of basic drugs in complicated matrices.

A simple and efficient approach is introduced for the improvement of the clean-up and applicability of the dispersive liquid-liquid microextraction (DLLME) method in complicated matrices. For this purpose, two dispersive microextraction methods were combined, and the tandem dispersive liquid-liquid microextraction (TDLLME) method was provided. At first, using the ultrasound-assisted emulsification microextraction (USAEME) method, the tricyclic anti-depressant (TCA) drugs nortriptyline, imipramine, and amitriptyline, as the model compounds, contained in an aqueous sample solution (8.0 mL), were extracted into an organic solvent (35 μL). Then by utilizing the air-agitated liquid-liquid microextraction (AALLME) method, these analytes were simply back-extracted into 50 μL of an aqueous acceptor phase. By performing this convenient extraction method, a high sample clean-up was obtained; the overall extraction time was 7 min. The back-extraction step could be performed in less than 2 min, and very simple tools were required for this purpose. The response surface methodology (RSM) was used for the optimization of the experimental parameters so that the volumes 95 and 50 μL were obtained for the organic solvent and the acceptor phase, respectively, and the pH values of 11.25 and 1.75 were obtained for the donor and acceptor phases, respectively, as the optimal extraction conditions. Under the optimized conditions, TDLLME-HPLC-UV provided a good linearity in the range of 2.5-5000 ng mL(-1), low limits of detection (0.7-1.0 ng mL(-1)), good extraction repeatabilities (relative standard deviations below 6.2%, n=5), and enrichment factors (EFs) of 50-101. Finally, the developed method was successfully used for the determination of the mentioned drugs in the wastewater and human plasma samples.