Determination of cobalt, copper and nickel in food samples after pre-concentration on a new pyrocatechol-functionalized polyurethane foam sorbent

Polyurethane foam functionalized with pyrocatechol by covalent coupling through -NC- group, is applied to an on-line pre-concentration system for cobalt, copper and nickel determination in food samples. The preparation of the packing material involved the reaction of 2,3-dihydroxybenzaldehyde with the amino groups of polyurethane foam. Metal ions were sorbed in the minicolumn, from which it could be eluted with acid solutions directly to the nebulizer-burner system of the flame atomic absorption spectrometer (FAAS). Under the optimum conditions, the enrichment factors obtained were 55, 42 and 54, for cobalt, copper and nickel, respectively, if used 180 s pre-concentration time. The detection limits of the proposed procedure were 0.5 (Co), 0.4 (Cu) and 0.6 (Ni) μg L−1. The method was applied to determination of the metals in spinach, rice flour, corn flour and black tea samples. The accuracy of the developed procedure was evaluated by analysis of the certified reference material NIST 1570a Spinach Leaves.