Testing Stripping Electroanalytical Techniques using Au/Hg Amalgam Microelectrodes for Quantification and Speciation Studies of Cd(II) and Pb(II)

Abstract

Solid microelectrodes offer several advantages, including the ability to perform localized measurements and resistance to deterioration in complex matrices like sediments and hydrogels. This study explores, for the first time, the application of gold/mercury amalgamated microelectrodes for sensing trace metal ions (Pb(II) and Cd(II)) at nanomolar levels and performing speciation analysis in solutions. This investigation represents a preliminary step toward implementing electrochemical sensors in porous and heterogeneous media. Stripping chronopotentiometry (SCP), which provides in-depth insights into metal speciation analysis, is compared with the classical technique of square wave anodic stripping voltammetry (SWASV). It was found that the complete metal depletion during the reoxidation step in SCP resulted in superior linearity ranges for both calibration and signal variation with deposition times compared to SWASV. While the results for Cd(II) are promising, the SCP signal for Pb(II) displays two discernible peaks, which may complicate speciation studies. SCP at Scanned deposition potential for the Cd/NTA system was successfully used to extract the thermodynamic stability constant. The positive findings for Cd(II) demonstrate the effectiveness of (S)SCP for Au/Hg microelectrode and open new prospects, such as immersing this probe in a hydrogel matrix for a detailed in situ investigation of the Cd status within the material.