Development and characterization of a clay-graphite-CeO₂ composite electrode for simultaneous detection of heavy metals

A carbon paste electrochemical sensor doped with clay impregnated with cerium oxide (CeO₂), CPE/Clay/CeO₂, was developed and used for the electrochemical sensing of four heavy metals, Cd(II), Pb(II), Cu(II) and Hg(II). The optimum ratio of clay/CeO₂ and sintering temperature were found to be 10 wt.% Clay/CeO₂ and 1000°C respectively. Heavy metals were sensed simultaneously on the 10 wt.% Clay/CeO₂@1000°C sensor using square wave voltammetry (SWV), which was found to yield the highest current density, with optimum parameters: potential increment 0.001 V, amplitude 0.07 V, frequency 15 Hz, preconditioning potential -1.0 V, preconditioning time of 30 s. Linear range calibration curves were obtained in the ranges of 2.0-28 μM, 2.0-25 μM, 2.0-28 μM, 2.0-28 μM for Cd(II), Pb(II), Cu(II) and Hg(II), with respective limit of detection (LOD) and limit of quantitation (LOQ) of 0.42, 1.4 μM for Cd(II), 0.37, 1.2 μM for Pb(II), 0.28, 0.94 μM for Cu(II) and 0.31, 1.0 μM for Hg(II). The prepared CPE/Clay/CeO₂ sensor showed a very high selectivity toward the selected heavy metals.