Simultaneous determination of lead and cadmium by stripping voltammetry using in-situ mercury film glassy carbon electrode coated with nafion-macrocyclic ester

This work report a sensitive and selective anodic stripping method for the simultaneous determination of Pb(II) and Cd(II) using (3,10,18,25-tetraoxapentacyclo [25.3.1.1 ^12,16.0^4,9.0^19,24] dotriaconta1(31),4(9),5,7,12(32),13,15,19,21,23,27,29-dodecaene-2,11,17,26-tetrone) macrocyclic ester (L). Anodic peak currents were increased from 1.16 to 31.48 μA for Pb(II) and 0.22 to 6.68 μA for Cd(II) when the in-situ mercury film electrode was modified with nafion and (L). Moreover, potentials separation values for Cd-Pb shift from 150 to 190 mV. Optimal parameters such as: pH; L concentration (C_L), mercury concentration (C_Hg), accumulation potential (E_ACC) and accumulation time (t_ACC) were pH 4.0 for Pb(II) and 5.0 for Cd(II) using phosphate buffer solution (PBS), CL 12.0 mmol L^-1, C_Hg 28.0 mg L^-1, E_ACC ^-1.0 V and tACC 60. Detection limits (DoL) were 0.085 and 0.80 μg L^-1 for Pb(II) and Cd(II) respectively. The relative standard deviation (RSD) for seven measurements of Pb(II) and Cd(II) 9.0 μg L^-1 were of 2.5 and 2.0% respectively. The method was validated by ICP multi-element standard solution IX (Merck) containing As, Be, Cd, Cr(VI), Hg, Ni, Pb, Se and Tl 100 mg L^-1. Finally, useful of the modified electrode was developed in the analysis of Pb(II) and Cd(II) using tap water samples.