Determination of Rhodamine B in Beverages Using a Polystyrene-Coated Magnetite Nanocomposite for Magnetic Solid Phase Extraction

An efficient magnetic sorbent based on a polystyrene-coated magnetite nanocomposite was prepared for the preconcentration of rhodamine B from beverages. The synthesized nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, and Fourier transform-infrared spectroscopy. Determination of rhodamine B was performed by high-performance liquid chromatography. The optimized adsorption conditions were 70 mg of sorbent, 250 mL of sample, pH 4, 35°C, and 20 min. The optimized elution of analyte was performed using 2.5 mL of methanol at pH 8, 20°C, and 5 min. Under these conditions, the preconcentration factor for rhodamine B was 100, and the calibration curve was linear from 1 to 250 µg/L. The limit of detection was 0.0021 µg/mL, the limit of quantification was 0.0035 µg/mL, and the relative standard deviation was 0.87%. The developed method was used for the determination of rhodamine B in beverages.