Optimization of ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction for the determination of plasticizers in water by response surface methodology

Abstract

In this work, a simultaneous ionic liquid-based microwave-assisted dispersive liquid–liquid microextraction (IL-based MADLLME) method was developed for the determination of plasticizers in water using high-performance liquid chromatography (HPLC) with ultraviolet detection. Several parameters affecting the extraction efficiency, such as type and volume of ionic liquid and disperser solvent, microwave time and temperature, were investigated by single factor experiments. Then, the microwave irradiation time and temperature, and the volumes of extraction and disperser solvents were optimized using response surface methodology (RSM). The optimal values were determined to be within an extraction volume of 110 μL, a dispersive solvent volume of 0.26 mL, and a microwave irradiation temperature and time of 60 °C and 2 min, respectively. The calibration curves were linear in the range of 23–230 μg L⁻¹ for dimethyl phthalate (DMP), 23.8–238 μg L⁻¹ for diethyl phthalate (DEP), 16.5–165 μg L⁻¹ for benzylbutyl phthalate (BBP), 19.5–195 μg L⁻¹ for dibutyl phthalate (DBP), and 18.6–186 μg L⁻¹ for diethylhexyl phthalate (DEHP). Under the optimum conditions, the limits of detection (LODs) of these plasticizers were in the range of 0.71–1.94 μg L⁻¹. Validation of the methodology was carried out by the method of standard addition at two concentration levels for three water samples. The recoveries of the analytes were in the range of 85.2–103.3%, with the relative standard deviations (RSDs, n = 6) ≤ 5.9%. The results show that IL-based MADLLME is a suitable method for the determination of these five plasticizers in water.