Comprehensive review of voltammetric techniques for heavy metal detection in water using nanomaterial modified electrodes

Abstract Contamination of heavy metals in environmental matrices such as water and soil poses a severe threat to public health due to the persistence, bioaccumulation, and most major toxic metals that concerns the public safety are lead (Pb), cadmium (Cd), arsenic (As) and mercury (Hg). These toxic chemicals are non-biodegradable and can pollute the food chain, bioaccumulate in biological tissues and cause neurological diseases, renal damage, cardiovascular disease, developmental abnormalities and different malignancies, particularly in sensitive populations such as children and pregnant women. Heavy metals are non-biodegradable and may stay in ecosystems for decades. They constitute considerable concern to the environment and human health even at low concentrations because of long-term exposure. Consequently, monitoring heavy metal contamination has become a global priority in the environmental systems. Regulation agencies like the WHO and EPA require detection at sub-ppb levels, demanding very sensitive and selective analytical techniques. Although the conventional techniques like induced coupled plasma mass spectroscopy (ICP-MS) and atomic absorption spectroscopy (AAS) provide excellent sensitivity, their high cost, complex instruments, and limited portability restrict their usage in the onsite settings. Voltametric electrochemical methods, especially stripping techniques such as anodic stripping voltammetry (ASV), square wave anodic stripping voltammetry (SWASV), and differential pulse voltammetry (DPV), have emerged as powerful, cost-effective, and portable alternatives capable enough to achieve sub-ppb LOD through the preconcentration strategy. Recent progress in electrochemical sensing has been focused on nanomaterial-modified electrodes based on graphene, metal oxides, bismuth films, metal nanoparticles and hybrid nanocomposites which greatly boost the sensitivity, selectivity, conductivity and surface area. Moreover, the integration of electrochemical sensors with flexible electronics, microfluidic systems, wireless communication modules, and smartphone-based platforms has encouraged the development of wearable and portable sensing technologies for environmental monitoring. Emerging wearable sensors, paper-based analytical devices, and handheld electrochemical systems facilitate rapid onsite measurements, real-time data transmission, and decentralized monitoring of heavy metal contamination in drinking water, industrial wastewater, agricultural runoff, and other environmental matrices. This review mainly focuses on the examination of the fundamental principles of voltametric detection, major voltametric stripping techniques, and advanced pulse methods with special emphasis on nanomaterial-modified electrodes incorporating graphene, metal oxides, bismuth films, and hybrid nanocomposites that enhance sensitivity and selectivity significantly. Detection of the particular heavy metals is discussed alongside key analytical performance parameters, interference challenges, and real sample validation in drinking water, and industrial wastewater.