Suppression of interference from dissolved organic matter using anionic surfactant for electrochemical detection of heavy metals

Dissolved organic matter (DOM) in aqueous environments significantly hampers the electrochemical quantification of heavy metal ions. The mechanism of DOM-induced interference remains elusive, highlighting an urgent need for the development of robust strategies to mitigate such effects and enable precise, sensitive detection of heavy metals. In this study, the interference mechanism of DOM on electrochemical detection were investigated on bismuth-based electrodes, and sodium dodecyl sulfate (SDS) was proposed as a potent agent for countering DOM interference. It reveals that the primary DOM interference originated from the reduction of heavy metal ion diffusion coefficients and hampered electron transfer rates, due to the passivation of the electrode interface. The introduction of SDS leads to micelle formation, which reduce the passivation of the electrode by DOM and enhances the diffusion of heavy metal ions through homogenization of the solution. Furthermore, with the introduction of SDS to water samples spiked with 100 ppb of Pb²⁺, the relative peak currents significantly increased, recovering from 7.0% up to 96.3% for Yujia Lake water, from 6.2% to 72.7% for Tangxun Lake wastewater, and from 1.9% to 30.5% for leachate (10%). This study pioneers a promising strategy to surmount DOM interference using SDS during the electrochemical detection of heavy metals in natural aqueous samples.