Recent Trends in Electrochemical Methods for Real-Time Detection of Heavy Metals in Water and Soil: A Review

Heavy trace elements (HTEs), including toxic metals such as Pb, Hg, Cd, and As, present a growing environmental and public health concern due to their persistence and bioaccumulation in water and soil systems. Driven by increased demand for strategic and rare earth metals in emerging technologies, anthropogenic activities such as mining, industrial discharge, and agriculture have intensified environmental contamination. Traditional detection methods such as atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and X-ray fluorescence (XRFS), although highly sensitive, are limited by their cost, complexity, and lack of suitability for continuous measurement (real-time) without taking samples to the laboratory for analysis (in situ and online) applications. This review highlights recent advances in standard electrochemical techniques, particularly voltammetric ones such as square wave voltammetry (SWV), differential pulse voltammetry (DPV), and anodic stripping voltammetry (ASV), in addition to non-voltammetric including electrochemical impedance spectroscopy (EIS) and chronopotentiometry methods enhanced by nanomaterials, including carbon nanomaterials: single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs); metal and metal oxide nanoparticles; polymer and hybrid nanocomposites; and metal organic frameworks. These materials improve sensor sensitivity, selectivity, stability, and portability of standard electrochemical methods, making them ideal for real-time and in situ and online for HTEs. In this review article, current innovations in standard electrochemical techniques with nanomaterials and hybrid nanocomposites improving sensor architecture, functionalization, sensitivity and selectivity are discussed alongside performance metrics and limitations.