Simultaneous Determination of Trace Levels of Cd(II) and Pb(II) in Tap Water Samples by Anodic Stripping Voltammetry with 2-mercaptobenzothiazole Modified Electrode

Abstract

Lead and cadmium in tap water can be toxic to human, even at low concentration. The determination of Cd(II) and Pb(II) is very important for environment and health. In this work, in-situ modified Bi-Meso-MBT/GCE on glassy carbon electrode has been developed to determine Cd(II) and Pb(II) in tap water samples. This electrode was less toxic than mercury and mesoporous silica was used as a nanoparticle instead of nafion with the advantage of low cost. The metals were stripped off by square wave anodic stripping voltammetry (SWASV) under the optimized conditions. The optimized conditions were in-situ preparation in acetate buffer pH 6.0, accumulation potential of -1.1 V, deposition time of 300 s and scan rate of 100 mV/s. The linear range of 5-50 ppb for both metals as well as LOD and LOQ of 0.56 ppb, 0.8 ppb and 1.87 ppb, 2.66 ppb for Cd(II) and Pb(II) were obtained respectively. The interaction between bismuth and MBT supports the performance of the modified electrode. The interference caused by cations including Ca(II), Mg(II), Zn(II), Mn(II), Fe(II), Cu(II) and Al(III) were found to provide not more than 5% signal change for both metals. The most interfering ion if present at high concentration is Cu(II) which can be masked by suitable and effective complexing agents. This method was applied to tap water determination which was found within the range of 0.00 to 0.06 x 106 M for Cd(II) and 0.00 to 0.05 × 10-6 M for Pb(II) with standard addition method, lower than the permissible limit in edible portion of water (USEPA 0.015 M for Cd(II) and 0.005 M for Pb(II)) issued by the World Health Organization (WHO). Therefore, the Cd(II) and Pb(II) concentration in tap water samples under the investigation is safe. The results from the proposed method were compared with those by ICP-OES using %recovery whereas standard addition and calibration curve method were compared by t-test. Both revealed to be not significantly different at 95% confident level.