ABSTRACT 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 µ g L−1, while the quantification limits were 30.6, 29.2, 43.9, 95.5, 22.1, 25.4, and 55.1 µ 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 (µmol g−1): Ni2+ > Co2+ > Fe3+ > Mn2+ > Cr3+ > Cd2+ > Pb2+.

A procedure for the determination of trace levels of Cd, Co, Cr, Fe, Mn, Ni, and Pb by flame atomic absorption spectrometry using a column preconcentration system is described in which the metals were adsorbed on pulverized banana peel, an economically and environmentally acceptable sorbent. In the optimization procedure, five variables (sample pH, mass of biosorbent, type of eluent, sample flow rate, and volume) were optimized and the capacity of the biosorbent was established. Under the optimized conditions, the detection limits of the method were 2.4, 27.0, 49.4, 31.1, 6.7, 29.6, and 46.2 µg L−1 for Cd, Co, Cr, Fe, Mn, Ni, and Pb, respectively. The precision, expressed as relative standard deviation, was less than 4% based on twelve measurements. The recoveries were 81.1% (Cd), 91.4% (Co), 87.2% (Cr), 90.1% (Fe), 88.0% (Mn), 94.1% (Ni), and 93.2% (Pb) under the optimum conditions (pH; 9, sample flow rate; 3 mL min−1, mass of biosorbent; 200 mg; eluent; 1 mol L−1 nitric acid, preconcentration factor; 10). The sorption capacity of pulverized banana peel was 15.12, 28.85, 32.70, 30.44, 30.94, 28.97, and 8.21 µmol per gram of adsorbent for Cd, Co, Cr, Fe, Mn, Ni, and Pb, respectively.