Ultrasound-assisted liquid–liquid microextraction based on an ionic liquid for preconcentration and determination of UV filters in environmental water samples

Abstract

In the present study, a dispersive liquid–liquid microextraction with ionic liquids (ILs) as extraction solvents was developed for the preconcentration and determination of four ultraviolet (UV) filters from different environmental water samples. Ultrasound-assisted dispersion of the ILs in the water phase was employed. The UV filters were easily concentrated into the ionic liquid phase. This technique combined the process of extraction and concentration of the analytes into one step and avoided the use of more toxic halogenated solvents. Affecting factors including the type and volume of the ILs and disperser solvents, ultrasonic time, centrifugation time, ionic strength and pH of aqueous samples were optimized. The extracts were directly analyzed by high-performance liquid chromatography coupled with a diode array detector. Under the optimized conditions, the current method provided good repeatability (RSDs < 7.6%, n = 5) and high enrichment factors in the range of 492–834. The limits of detection (LOD) for the UV filters were in the range of 0.06–0.16 ng mL⁻¹. The linearities were between 0.2 and 500 ng mL⁻¹ for 2-hydroxy-4-methoxybenzophenone, 0.5 and 500 ng mL⁻¹ for 2-ethylhexyl 4-(N,N-dimethylamino) benzoate, 0.4 and 500 ng mL⁻¹ for 2-ethylhexyl-4-methoxycinnamate, and 0.5 and 500 ng mL⁻¹ for 2-ethylhexyl salicylate, respectively. The current procedure was successfully applied to simultaneous analyses of four UV filters in environmental water samples. For all analyzed samples, the established method has allowed fast and reliable preconcentration and determination of these UV filters with simple sample pre-treatment requirements.