Effective extraction and simultaneous determination of Sudan dyes from tomato sauce and chili-containing foods using magnetite/reduced graphene oxide nanoparticles coupled with high-performance liquid chromatography.

A simple, effective, and robust magnetic solid-phase extraction method was developed using magnetite/reduced graphene oxide nanoparticles as the adsorbent for the simultaneous determination of Sudan dyes (I, II, III, and IV) in foodstuffs. The magnetite/reduced graphene oxide nanoparticles were characterized by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The extraction parameters including extraction time, elution solution, and elution time and volume were investigated in detail. Such magnetite/reduced graphene oxide nanoparticles based magnetic solid-phase extraction in combination with high-performance liquid chromatography and variable wavelength detection gave the detection limits of 3-6 μg/kg for Sudan I-IV in chili sauce, tomato sauce, chili powder, and chili flake samples. The recoveries were 79.6-108% at three spiked levels with the intra- and inter-day relative standard deviations of 1.2-8.6 and 4.5-9.6%, respectively. The feasibility was further performed by a comparison with commercial alumina-N. This method is suitable for the routine analysis of Sudan dyes due to its sensitivity, simplicity, and low cost.