Magnetic graphene oxide nanocomposites as the adsorbent for extraction and pre-concentration of azo dyes in different food samples followed by high-performance liquid chromatography analysis.

This work presents a method of magnetic solid-phase extraction (MSPE) combined with high-performance liquid chromatography (HPLC) to analyse five synthetic azo dyes (tartrazine, amaranth, carmine, sunset yellow, allura red) in different food samples. The magnetic graphene oxide nanocomposite (GO@Fe3O4) was prepared by a one-step solvothermal method and used as the sorbent for extraction and pre-concentration of azo dyes in food samples. The as-prepared GO@Fe3O4 nanocomposite was characterised by transmission electron microscope, Fourier transform-infrared spectroscopy, X-ray diffraction, vibrating sample magnetometer, and Brunuer-Emmett-Teller analysis. The extraction and desorption parameters were investigated, including the material amount, extraction time, pH of the solution, desorption temperature, and desorption solvents. Under the optimised conditions, the limits of detection (LODs) were 1.14-2.23, 0.36-0.77 and 0.68-1.26 ng/g for candy, jelly, and plum candy, respectively. The limits of quantification (LOQs) were 4.02-7.73, 1.21-2.50 and 2.31-4.20 ng/g for candy, jelly, and plum candy, respectively. For the analysis of spiked jelly, recoveries were between 73.2% and 107.7%, with RSDs lower than 1.34 %. The developed method was successfully applied to the analysis of real samples including jelly, candy and plum candy.