γ-FeO magnetic nanoparticle functionalized with carboxylated multi walled carbon nanotube for magnetic solid phase extractions and determinations of Sudan dyes and Para Red in food samples.

Hybrid nanostructures composed of γ-FeO (maghemite) and carboxylated-multi walled carbon nanotube (cMWCNT) were used for the magnetic solid phase extractions and determination of Sudan I, II, III, IV, Para Red, Sudan Black B and Sudan Red 7B in chili products. High performance liquid chromatography (HPLC) was employed for the measurements. Limit of quantification (LOQ) values were found in the range 0.44-2.82ngmL for analytes. The best extraction parameters were determined as pH 8.0, 40mg of magnetic nanoparticle, 4.0min of contact time, 0.3mL desorption by acetonitrile. The samples were dissolved in acetone-dichloromethane-methanol (3:2:1, v/v/v) and diluted with acetonitrile-methanol (v/v; 80:20) before the method was applied. Concentrations of Sudan dyes and Para Red were determined in four samples of chili powder from less than LOQ to 31.21±1.6ngg, two samples of chili tomato sauces (lower than LOQ) and two samples of ketchup (lower than LOQ).