Dispersive liquid–liquid microextraction using extraction solvents lighter than water combined with high performance liquid chromatography for determination of synthetic antioxidants in fruit juice samples

A simple, rapid and sensitive sample pretreatment technique, termed dispersive liquid–liquid microextraction (DLLME), was developed as an extraction methodology to determine two synthetic phenolic antioxidants (SPAs), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT), in various fruit juice samples prior to high performance liquid chromatography (HPLC). The extraction method is based on replacing the extraction solvent in the ordinary DLLME, namely the chlorinated organic solvent, with low-density organic solvents such as hexane, ethyl acetate, octanol and 2-ethyl-1-hexanol in the ternary component solvent (aqueous solution:extracting solvent:disperser solvent) system. Several factors affecting the microextraction efficiency, such as type and volume of extraction and dispersive solvents, pH of the sample solution, extraction time, ionic strength and extraction temperature, were investigated. Under the optimum conditions, the method yielded a linear calibration curve ranging from 10 to 2500 μg L−1 for BHA and 2 to 2500 μg L−1 for BHT, with determination coefficients (R2) varying from 0.9993 to 0.9989. Enrichment factors for BHA and BHT were 208 and 203, and limits of detection were 2.5 and 0.9 μg L−1, respectively. The relative standard deviation percent (RSD%) for the extraction and determination at 10 and 100 μg L−1 levels of target antioxidants was less than 4.7% (n = 7). Finally, the designed method was successfully applied for the preconcentration and determination of the studied SPAs in different fruit juice samples, and satisfactory results were obtained.