Multi residue determination of pesticides in cow milk using deep eutectic solvents-based dispersive liquid–liquid microextraction

Milk and its processed products have an important role in human food chain. They are a well supply of fat, protein, carbohydrate, and minerals which are provide many essential needs of human [1]. However, they can be indirectly contaminated with different pollutants via infected feed, water, and air [2]. Among these compounds pesticides have attracted main concern owning to their extensive application in farming. The presence of pesticide residues in some foods such as milk may be key risk to human health due to their possible toxicity [3]. Therefore many control establishments have advised some arrangements to prevent contamination of milk samples. A dispersive liquid–liquid microextraction method based on deep eutectic solvents has been developed for simultaneous determination of some pesticides including carbaryl, hexythiazox, pretilachlor, iprodione, famoxadone, sethoxydim and fenazaquin from milk samples. In this method, deep eutectic solvents prepared from ethylene glycol: choline chloride and p–chlorophenol: choline chloride are used as dispersive and extraction solvents, respectively. For this purpose, the analytes are extracted from milk samples into ethylene glycol: choline chloride in the presence of sodium chloride and after centrifugation the collected phase is mixed with p–chlorophenol: choline chloride (as the extraction solvent) and injected into deionized water. The cloudy solution is centrifuged and the sedimented phase is injected into gas chromatography–flame ionization detector. Under the optimum extraction conditions, low limits of detection and quantification within the ranges of 0.90–3.9 and 3.1–13 ng mL–1 were achieved, respectively. Precision of the method expressed as relative standard deviation was in the ranges of 4.2–5.3 and 4.8–6.9 for intra– and inter–day (n=5) precision, respectively, at a concentration of 50 ng mL-1 of each analyte. Extraction recoveries and enrichment factors were 64 and 89% and between 320 and 445, respectively. Lastly, several milk samples were successfully analyzed using the proposed method.