Development of microwave-assisted liquid-liquid extraction combined with lighter than water in syringe dispersive liquid-liquid microextraction using deep eutectic solvents; Application in extraction of some herbicides from wheat

Herbicides are the compounds that are mainly used to stopping and destroying the growth of weeds and unwanted vegetations [1]. The use of herbicides in agricultural and non-agricultural activities is developing to control weeds and in this way different compounds are tested to obtain high efficiency in weeds control [2]. Several forms of herbicides including liquids, granules, and fumigation are used in agriculture. In most cases herbicides are used in liquid formulations and they are added to soil before cultivation stage [3]. Therefore, the herbicide residues have been found in a lot of agriculture products. According to these regulations, the residue of the herbicides should be controlled. In this work, a deep eutectic solvent-based microwave-assisted liquid-liquid microextraction method followed by gas chromatography-mass spectrometry has been reported for the extraction and preconcentration of seven herbicides from wheat samples. The analytes are extracted into a water-miscible deep eutectic solvent under microwave irradiations and then the extractant is used as a dispersive solvent in the following dispersive liquid-liquid microextraction method. In this method, ChCl: phenol and ChCl: butyric acid deep eutectic solvents are used in the first and second steps mentioned above, respectively. After that, the mixture is dispersed into deionized water placed into a syringe with a retracted plunger. By this action, ChCl: butyric acid was dispersed in whole parts of the solution. To break up the cloudy state, acetonitrile is added and the collected organic phase is used in determination system. Low limits of detection and quantification in the ranges of 1.6-12, and 5.5-42 ng kg-1, relative standard deviations ≥ 6.1% (at a concentration of 50 ng kg-1, each analyte) and extraction recoveries and enrichment factors in the ranges of 69-94% and 345-470, were obtained, respectively, under optimal conditions. Lastly, some wheat samples were analyzed and diclofob-methyl was found in two samples.