Sorption of Metals on Pulverized Pumpkin (Cucurbita pepo L.) Peels

The pulverized peel of unmodified and modified pumpkin (Cucurbita pepo L.) was used as sorbent for the determination of Cd, Co, Cr, Fe, Mn, Ni, and Pb by flame atomic absorption spectrometry. The parameters affecting the preconcentration efficiency were investigated. The optimal conditions for preconcentration on unmodified pumpkin peel were identical to those using modified peel: a pH of 8, a preconcentration factor of 10, a flow rate of 3 mL min(-1), and an eluent concentration of 1 mol L-1 for all analytes. The detection limits of the method were 9.2, 8.8, 13.2, 28.7, 6.6, 7.6, and 16.5 mu g L-1, while the quantification limits were 30.6, 29.2, 43.9, 95.5, 22.1, 25.4, and 55.1 mu g L-1 for Cd, Co, Cr, Fe, Mn, Ni, and Pb, respectively. The accuracy of the method was verified with a certified reference material. The relative standard deviation was less than 4% based on 12 measurements. Under the optimum conditions of preconcentration, the recovery values exceeded 94%. The following capacity order was obtained for the analytes (mu mol g(-1)): Ni2+ > Co2+ > Fe3+ > Mn2+ > Cr3+ > Cd2+ > Pb2+.