Ultrasound-assisted emulsification liquid phase microextraction method based on deep eutectic solvent as extraction solvent for determination of five pesticides in traditional Chinese medicine

A kind of green solvents termed deep eutectic solvent (DES) have been considered alternatives to traditional organic solvents. In this study, a method was developed for determination of five pesticide residues including triadimenol, fipronil, tebuconazole, hexaconazole and diniconazole in five different traditional Chinese medicines (TCMs). In the developed method, DES was selected as extraction solvent, ultrasound-assisted emulsification liquid phase microextraction (UA-ELPME) was used for extraction and high performance liquid chromatography (HPLC) equipped with a diode array detector (DAD) was used for quantification. In this method, DES was synthesized with choline chloride and phenol at the molar ratio 1:4 using the heating and stirring method. Meanwhile, several important parameters such as volume of DES (650 μL), volume of tetrahydrofuran (THF, 550 μL) and ultrasonic time (30 min) were optimized by using response surface methodology (RSM) based on a central composite design (CCD). Under the optimized conditions, the limits of detection and quantification of method were in the range of 0.02-0.2 μg mL−1 and 0.05-0.5 μg mL−1, respectively. The correlation coefficients (r) of five calibration curves are greater than 0.9996, relative standard deviation (RSD) of precision for this method of five pesticides were lower than 4.7%, and the mean recoveries were in the range of 81.0–92.1%. The present experiment suggests that DESs are efficiently extract solvents in UA-ELPME method for traditional herbal medicines applications.