Simultaneous determination of plasticizer di(2-ethylhexyl)phthalate and its metabolite in human urine by temperature controlled ionic liquid dispersive liquid–liquid microextraction combined with high performance liquid chromatography
Temperature controlled ionic liquid dispersive liquid–liquid microextraction (TC IL-DLLME) combined with high performance liquid chromatography (HPLC) has been developed for the simultaneous determination of di(2-ethylhexyl)phthalate (DEHP) and its metabolite mono(2-ethylhexyl)phthalate (MEHP) in human urine samples. Dibutyl phthalate (DBP) was employed as an internal standard. Some important parameters, such as the type of extraction solvent and dispersive solvent, the volume ratio of extraction to dispersive solvent, volume of a mixture of extraction solvent and dispersive solvent, temperature, sample pH, salt effect, cooling time and centrifugation time, were investigated and optimized to achieve a high extraction efficiency. Under the optimized extraction conditions, the method showed 115- and 164-fold enrichment factors for MEHP and DEHP in urine samples, respectively. It also exhibited high sensitivity with the limits of detection at 0.96 μg L−1 and 3.2 μg L−1 for MEHP and DEHP, respectively. The calibration curves were linear in the concentration range of 20–1920 μg L−1 for MEHP and 60–1920 μg L−1 for DEHP, with the correlation coefficients higher than 0.9990. The proposed method can be expected to monitor the human exposure to the plasticizer agent by determining its metabolites in human urine samples.