Investigations On Green And Novel Dispersive Liquid-liquid Microextraction In Pesticides Residue Analysis

1. This paper presents a study of the performance of ultrasound-enhanced temperature-controlled (UETC) ionic liquid dispersive liquid-liquid microextraction (IL-DLLME). The use of ultrasonication and heating can enhance the ability of the ionic liquid to extract the analytes. Various parameters that would affect the extraction efficiency, such as the type and volume of the extraction and dispersing solvents, salt concentration, pH value, centrifugation time, effect of temperature on UETC-IL-DLLME, were investigated and optimized. Under the optimal extraction conditions, good enrichment factors (178-197) and recoveries (88.9-98.5%) were obtained. Good linearity was obtained in the range of4-500μg L-1for myclobutanil and in the range of6-500μg L-1for uniconazole, penconazole, tebuconazole and hexaconazole. Based on the optimized conditions, the UETC-IL-DLLME method was applied and combined with high-performance liquid chromatography with diode array detection (HPLC-DAD) to determine the presence of five triazole fungicides. The results showed that the method we proposed could effectively determine the target fungicides in rat blood samples.2. A fast microextraction technique, termed as ultrasound-assisted emulsification magnetic microextraction, was developed for the determination of triazole fungicides (penconazole, tebuconazole and myclobutanil) in fruit juice samples by gas chromatography flame ionization detection. The distinct advantage of the proposed method is taking a low toxic solvent1-octanol as extractant, without a disperser being used. With the help of ultrasound, emulsification can be obtained. The magnetic nanoparticles are applied to retrieve the extractant for replacing centrifugation. Under optimal conditions, good linearity in the range of5μg L-1-500μg L-1, repeatability (RSDs3.5-7.7%), low LODs (1.8-2.3μg L-1) and good recovery (85.4-104.8%) were obtained. Additionally, the intermolecular binding energies were theoretically studied using the density functional theory and the explicit solvent molecule model. A high correlation was found among the extraction efficiency, Kow and the calculated energies, which may guide the application of extractants and the selectivity of the target analytes in analytical methods.3. A new combined assisted dispersive liquid-liquid microextraction was developed in the paper. Four typical pyrethroid insecticides were chosen as the target analytes (fenpropathrin, deltamethrin, ethofenprox and bifenthrin). An ionic liquid synthesised through in-situ metathesis reaction was used as extractant. Without any disperser, ultrasound and vortex assistance were combined during extraction to help emulsification. The eggbeater was applied as a vortex instrument, and the spin bar tied with a Falcon tube containing extraction mixture was immersed in the ultrasonic water bath. Orthogonal experimental design was used to optimize the parameters affected extraction. Under optimal conditions, good linearity in the range of1μg L-1-500μg L-1, repeatability (RSDs6.30-7.50%), low LODs (0.05-0.22μg L-1), good enrichment factors and recovery (102-116,92.3-101.4%) were obtained with high-performance liquid chromatography with diode array detection (HPLC-DAD). Several water samples containing drink water, juices, teas and honeys were chosen as real samples. The proposed method was successfully applied to detect pyrethroid insecticides from these complex matrices.