Method for the determination of Pb, Cd, Zn, Mn and Fe in rice samples using carbon nanotubes and cationic complexes of batophenanthroline

Among cereals, rice is the second most cultivated staple crop in the world. It may be contaminated by toxic heavy metals present in water or soil. Therefore, monitoring the presence of heavy metals in rice and its products is a matter of a great importance from the nutritional and toxicological view. In this paper, a simple and effective analytical procedure based on dispersive micro solid-phase extraction with the use of oxidized multiwalled carbon nanotubes and batophenanthroline was developed for the determination of lead, cadmium, zinc, manganese and iron in white and wild rice samples. Due to the high preconcentration factor of 200, the optimized procedure allows obtaining detection limits between 0.13 and 0.35 ng mL(-1) using flame atomic absorption spectrometry (FAAS). Novel preconcentration method can successfully be applied in food analysis with accuracy better than 7% rel. and repeatability lower than 3%.