Screen-Printed Electrode Modified by Reduced Graphene Oxide-Acidified Multiwalled Carbon Nanotubes with In Situ Hg-Bi Film for Direct Pb2+ and Cd2+ Detection in Seawater

The increasing heavy metal pollution in marine environments has highlighted the urgent need for rapid, on-site detection methods. In this study, a reduced graphene oxide (rGO) and carboxylated multiwalled carbon nanotube (MWCNTs-COOH)-modified screen-printed electrode (SPE) was coupled with a portable electrochemical workstation for on-site detection of Pb 2+ and Cd 2+ in seawater. The key influencing factors involved in the detection process, such as deposition potential, deposition time, and pH value, have been systematically optimized. The response surface methodology (RSM) was applied to refine the portable electrochemical workstation parameters, including step potential, frequency, and pulse amplitude. The detection capability for heavy metals was significantly enhanced by using square wave stripping voltammetry (SWASV) with in situ Hg-Bi film plating, achieving detection limits of 0.4 μg/L for Pb 2+ and 0.8 μg/L for Cd 2+ . Finally, the portable workstation together with rGO/MWCNTs-COOH/SPE showed recovery rates of 101.33 ± 3.42% ~ 115.85 ± 3.50% for Pb 2+ and 101.32 ± 2.23% ~ 102.00 ± 2.00% for Cd 2+ in real seawater. The results were in good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP-MS), thereby validating the detection accuracy of this platform.