On-line preconcentration and determination of cadmium, cobalt and nickel in food samples by flame atomic absorption spectrometry using a new functionalized resin

A new chelating sorbent has been developed using Amberlite XAD-2 resin anchored with pyrocatechol through the -CH2- group. This sorbent, characterised by elemental analysis and infrared (IR) spectra, was used as a packing material for a minicolumn in an on-line preconcentration system for cadmium, cobalt and nickel determination. Metal ions were sorbed in the minicolumn, from which it could be eluted directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Metals can be eluted from the minicolumn with 0.50mol L-1 HCl or HNO3. The enrichment factors were 22 (Cd), 23 (Co) and 25 (Ni), for 60s preconcentration time, and 44 (Cd), 40 (Co) and 48 (Ni), if 180s preconcentration time was used. Under the optimum conditions, the procedure allowed the determination of cadmium, cobalt and nickel with detection limits of 0.27, 0.59 and 1.29 mu g L-1, respectively, when preconcentration periods of 180s were used. The accuracy of the procedure was sufficient and evaluated by analysing certified reference materials. The method was applied to the analysis of food samples (black tea and rice flour).