Ionic Liquid Based Microwave-assisted Extraction Of Triazine And Phenylurea Herbicides From Environmental Medium

Triazine and phenylurea herbicides, which are widely used for the controlof many grasses and weeds in agriculture, have been defined as ubiquitousenvironmental pollutants in soil and water in recent years. As they can remainfor an extended period of time in environmental medium, and can therefore betransferred to human by drinking water or agricultural products, thedetermination of triazine and phenylurea herbicides in soil and water is veryimportant.Matrix complexity and the fact that herbicides are usually present at lowconcentrations, lead to higher demands (high sensitivity, selectivity, andresolution power; high speed and efficiency; negligible volume of solvent usedand low experimental cost) on the analytical methods. Common extractionmethods often took long time and used hazardous organic solvents. In thisstudy, novel methods were developed for the analysis of triazine and phenylurea herbicides in soil and water by combining ionic liquids andmicrowave-assisted extraction together.In this thesis, the analysis of triazine and phenylurea herbicides in soil byionic liquid based microwave-assisted extraction (IL-MAE) coupled withhigh-performance liquid chromatography (HPLC) was studied. Theoperational IL-MAE parameters were optimized by univariate method andorthogonal screening. The proposed analytical method was evaluated byconsidering the average spike recoveries (84.0–101%) and relative standarddeviations (2.8–6.0%). The results obtained under the optimized conditionswere compared with methanol-MAE and IL-heating extraction, and it wasdetermined that the IL-MAE method was rapid (4min compared with2h forthe heating extraction), efficient (recoveries were1.6–12.2%higher than theother methods) and environmentally friendly (no volatile organic solventswere used).In this study, microwave was introduced into in situ ionicliquid-dispersive liquid–liquid microextraction method for the first time. Thein situ ionic liquid-based microwave-assisted dispersive liquid–liquidmicroextraction (in situ IL-based MADLLME) was developed for thepreconcentration of four triazine herbicides from water samples, followed bydirect injection of the IL extract into HPLC. The effects of variousexperimental parameters were studied. The proposed method was evaluated bythe linear regression coefficients (R2,0.9992-0.9995), average recoveries(88.4-114%) and relative standard deviations (RSDs,1.6-6.2%). The limits of detections (LODs) for the four triazine herbicides were between0.52and1.3μg L-1. Under the optimized condition, the enrichment factors of four triazineherbicides were between78and125.The established methods are simple, time-saving, efficient andenvironmentally friendly, and may be widely applied in the determination ofother compounds from environmental medium in future.