Preparation of epoxidized soybean oil-grafted Fe3O4–SiO2 as a water-dispersible hydrophobic nanocomposite for solid-phase extraction of rhodamine B

•An epoxidized soybean oil-grafted Fe3O4-SiO2 nanocomposite was prepared.•Sorbent features with hydrophobic surface and hydrophilic polar functional groups render it promising for extracting RB in aqueous samples.•The method was applied for the determination of RB in different real samples.

In this study, epoxidized soybean oil-grafted Fe3O4-SiO2 nanocomposite (Fe3O4-SiO2-ESBO) containing a hydrophobic surface and hydrophilic polar functional groups was synthesized. The sorbent showed excellent dispersibility in aqueous solution and was utilized for magnetic solid phase extraction of trace amounts of rhodamine B in aqueous solution prior to its determination using UV–Vis spectroscopy. The sorbent was characterized by Fourier transform infrared spectroscopy, transmission electron microscopy and scanning electron microscopy. The magnetite nanoparticles had spherical shape with their grain size of < 20 nm. The effects of pH, sorbent mass, uptake time on the sorption of rhodamine B on Fe3O4-SiO2-ESBO were investigated using Box–Behnken design. The adsorption capacity of the sorbent was 1355 μg of rhodamine B per gram of sorbent. In optimal experimental conditions, the limit of detection, limit of quantification and enrichment factor of the proposed method were 3.94 μg L− 1, 13.13 μg L− 1 and 26, respectively. The proposed method was successfully applied to the separation and determination of rhodamine B in dish washing liquid, match tips and tap water samples with recoveries in the range 96.40–98.10%.