Reaction of o-phenylenediamine and 8-formyl-7-hydroxycoumarin yield a new coumarin salen ligand, (CSB) which was isolated as orange air-stable solid and characterized by melting point, thermogravimetric analysis (TGA), mass spectra, infrared and NMR (1H, 13C) spectroscopy. New CSB was dispersed in nafion and nafion-CSB composite was deposited on a glassy carbon electrode. The modified electrode nafion-CSB/GCE allowed the formation in-situ of mercury film for detection of Pb (II) and Cd(II) by anodic stripping voltammetry (ASV) in buffer phosphate solution pH 3.0 and 4.0. Optimal conditions were studied (mercury concentration: CHg 40.0 mg L-1 ; CSB concentración; CCSB; 20.0 µmol L-1 ; pH 3.0 and pH 4.0; EACC:-1.1 V and tACC: 80).The detection limit (3σ/b) for Pb (II) Cd (II) were of 0.15 µg L–1 for Pb(II) and Cd(II) at pH 3.0. Moreover, 0.071 and 0.080 µg L–1 for Pb(II) and Cd(II), respectively at pH 4.0, The method was validated using ICP multi-element standard solution IX (Merck) containing As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se and Tl 100 mg L-1 . Finally, river, tap and mineral waters were analyzed.