in present study preconcentration followed by solid phase extraction of heavy metal ions, Cu(II), Co(B), Ni(II) and Pb(II) using a multiwalled carbon nanotubes (MWNTs) and complexing reagent o-cresolphthalein complexone were investigated. The effects of parameters, including pH of the solutions, amounts of complexing reagent, eluent type, sample volume, flow rates of solution, and matrix ions, were examined for the optimum recoveries of the analyte ions. The preconcentration factor was 40. Detection limit (3s) obtained for the investigated metals in the optimal conditions were observed in the range of 1.64-5.68 mu g l(-1). The validation of the presented method was obtained by the analysis of certified reference material HR 1 (Humber river sediment), the obtained results were agreed with certified values. The optimum experimental conditions that ensure the efficiency of the procedure have been investigated and have been successfully applied to the determination of trace elements in environmental samples with satisfactory results. (C) 2009 Elsevier B.V. All rights reserved.