Highly sensitive and simultaneous electrochemical determination of lead and cadmium ions by poly(thionine)/MWCNTs-modified glassy carbon electrode in the presence of bismuth ions

A novel low-cost method for simultaneous measurement of Cd2+ and Pb2+ is proposed. In this method, the surface of the glassy carbon electrode (GCE) was modified with multi-walled carbon nanotubes (MWCNTs) and poly(thionine) (PTH), afterward, Pb2+ and Cd2+ were measured simultaneously in the presence of bismuth ions in-situ, using square wave anodic stripping voltammetry (SWASV). Scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to characterize the proposed electrode. Operational parameters affecting the measurement of metal ions were investigated, such as buffer pH and electrochemical parameters. In the optimal conditions, the linear responses were acquired in the concentration range 2.0-400.0 nM for both the analytes. The limit of detection (at S/N = 3) was found to be 0.6 nM for Pb2+ and 0.4 nM for Cd2+. The reproducibility, expressed as the relative standard deviation (RSD), was obtained as 4.5% for Cd2+ and 14.7% for Pb2+, (each 5 nM level; for n = 5). The fabricated sensor was employed for the simultaneous determination of the target analytes in real samples with satisfactory results. [GRAPHICS] .