Ionic Liquid-Magnetic Nanoparticle Microextraction of Safranin T in Food Samples

Abstract

A new two-step microextraction approach combining ionic liquid-dispersive liquid–liquid microextraction with magnetic-dispersive microsolid-phase extraction was developed for the fluorescence determination of safranin T in food samples. In the first step, ionic liquid (1-hexyl-3-methylimidazolium hexafluorophosphate (C6MIM][PF6)) was used to extract safranin T from a sample solution with the assistance of controlled temperature conditions. Fe3O4@SiO2 magnetic nanoparticles were then used to retrieve the ionic liquid, which were collected by application of an external magnetic field. The ionic liquid and safranin T were recovered from the surface of magnetic nanoparticles using ultrasound and an organic solvent. The effective factors in the proposed method, including type and volume of extraction solvent, pH, dispersive temperature and extraction time, type of desorption solvent, amount of Fe3O4@SiO2 magnetic nanoparticles, and ultrasound time were optimized. Under the optimal conditions (extraction solvent, 100 μL of [C6MIM][PF6]; pH 9.0; dispersive temperature, 80 °C; extraction time, 5 min; desorption solvent, acetone; amount of Fe3O4@SiO2 magnetic nanoparticles, 5 mg; ultrasound time, 120 s), the method presented has good linearity (r 2 = 0.9994) in the range of 5–300 ng mL−1. The detection limit was 0.48 ng mL−1, while the relative standard deviation for the analysis of 100 ng mL−1 of the safranin T was 1.47 % (n = 10). The method was successfully applied to the determination of safranin T in tomatoes, tomato sauce, and yuba samples, and good recovery rates (96.71–98.26 %) with relative standard deviation of below 2 % were achieved.