Ionic liquid-based air-assisted liquid–liquid microextraction combined with dispersive micro-solid phase extraction for the preconcentration of copper in water samples

Abstract

Ionic liquid-based air-assisted liquid–liquid microextraction (IL-AALLME) combined with dispersive micro-solid phase extraction (D-μ-SPE) was applied for the extraction and preconcentration of Cu prior to analysis by graphite furnace atomic absorption spectrometry. IL [Hmim][PF₆] was used as the extractant, non-ionic surfactant Triton X-100 as the emulsifier and Fe₃O₄ nanoparticles as the sorbent. The emulsion was rapidly formed by pulling in and pushing out the mixture of aqueous sample solution and extraction solvent repeatedly using a 10 mL glass syringe. Then, the extractant phase was mixed with Fe₃O₄ magnetic nanoparticles and separated using a magnet. As a result, the conventional tedious procedure associated with AALLME such as centrifugation was eliminated and the analytical process was accelerated. The experimental parameters affecting the extraction efficiency of Cu such as pH, IL volume, Triton X-100 concentration, Fe₃O₄ amount, number of extraction times and ultrasound time were investigated and optimized. Under the optimal conditions, the calibration curve was linear in the range of 1.5–120 ng mL⁻¹ for Cu with a correlation coefficient (R) of 0.9992. The limit of detection was 0.5 ng mL⁻¹. Finally, the applicability of this newly developed method was investigated for the analysis of Cu in real water samples.