Magnetic stirring-assisted dispersive liquid–liquid microextraction followed by high performance liquid chromatography for determination of phthalate esters in drinking and environmental water samples

A simple, fast and efficient method for the preconcentration of phthalate esters (PEs) in water samples was developed using magnetic stirring-assisted dispersive liquid–liquid microextraction (MSA-DLLME) followed by high performance liquid chromatography coupled with ultraviolet detection (HPLC–UV). This novel microextraction method is based on the fast injection of extracting solvent into the aqueous solution, which is being stirred by a magnetic stirrer, to form a cloudy binary component solvent (aqueous solution:extracting solvent) system. The extraction parameters such as type and volume of extracting solvent, pH of sample, salt addition, extraction time and stirring rate were optimized. Under the optimal conditions (extracting solvent: 200 μL dodecane; pH of sample: 6.5; extraction time: 5 min; stirring rate: 1000 rpm), linearity was observed in the range of 2–1000 μg L−1 for dimethyl phthalate (DMP) and 1–1000 μg L−1 for diethyl phthalate (DEP), benzyl butyl phthalate (BBP) and di-n-butyl phthalate (DBP) with correlation determination values above 0.99 for them. The limits of detection and quantification were ranged from 0.13 to 0.38 μg mL−1 and 0.43 to 1.27 μg mL−1, respectively. The ranges of intra-day and inter-day precisions (n=5) at 100 μg L−1 of PEs were 1.50–2.65% and 2.31–3.35%, respectively. Finally, the MSA-DLLME method was successfully applied for preconcentration of PEs in drinking and environmental water samples.