A new two-phase hollow fiber-liquid liquid microextraction containing reverse micelle as sensitive and efficient method for the extraction of quercetin in onion and tomato samples was developed for the first time. The extraction is based on the solubilization of analyte in the aqueous core of the reverse micelle of cationic cethyltrimethyl ammonium bromide surfactant, CTAB, which are present in the organic phase and are used as acceptor phase in hollow fiber-liquid phase microextraction. Experimental results show that the electrostatic interaction between the oppositely charged surfactant head group present in the reverse micelles and the analyte molecule has a key role in the extraction [1]. The porous polypropylene membrane acted as a filter to prevent potential interfering materials from being extracted, and no additional cleanup was required. Important parameters that affect the extraction efficiency such as the organic phase, pH, surfactant concentrations, stirring rate, extraction time, temperature and ionic strength were optimized. The optimum condition is obtained when the variables are set to: pH= 7.5, organic solvent= 1-octanol, CTAB concentration= 7 mmol L-1, stirring rate= 900 rpm at room temperature and extraction time= 30 min. Under the mentioned condition, the calibration range was found to be linear over 0.5–1000 ng mL-1 with the limit of detection of 0.1 ng mL-1. The extraction recovery of 97.4%, with relative standard deviation of 3.5%, was obtained via tree replicated measurements on a 15 ng L-1 quercetin standard solution. The proposed preconcentration method provided increased extraction efficiency when compared to the conventional hollow fiber-liquid liquid microextraction method and allowed to analyze lower concentration levels. Finally, the newly developed method was successfully used for the preconcentration and determination of quercetin in onion and tomato samples.
