Surfactant-assisted salting-out homogenous liquid-liquid extraction based on deep eutectic solvents using central composite design; application in the extraction of natamycin from fruit juices before its determination by HPLC-UV

In this study, for the first time, surfactant-assisted deep eutectic solvent-based salting-out homogenous liquidliquid extraction performed in a narrow-bore tube has been introduced as a new sample pretreatment approach and used for the isolation of natamycin from fruit juices. In this method, firstly, tween 80 (as a surfactant) and a water-miscible ternary deep eutectic solvent composed of choline chloride: acetic acid: butanol (as an extractant) were added to the sample solution and a homogenous state was formed. This solution was transferred into a narrow-bore tube and in the following, the homogenous solution was broken by addition of sodium chloride (as a phase separation agent). By this action, the analyte was extracted into the produced tiny droplets of extractant. This phase was quantified by high-performance liquid chromatography-ultraviolet detection. Experimental conditions of the developed extraction procedure were investigated and optimized by means of central composite design with variables including surfactant and extraction solvent volume, pH, and sodium chloride amount. Under optimum conditions, low limits of determination and quantification (0.78 and 2.60 ng mL-1, respectively), acceptable repeatability (relative standard deviations of 4.9 and 7.1% for intra- and inter day precisions at a concentration of 25 ng mL-1), and satisfactory extraction recovery (76%) were obtained using the proposed method. At the end, the suggested method was effectively utilized for the analysis of natamycin in different juice samples.