Development and Validation of an Electrochemical Sensor for Simultaneous Determination of Cadmium and Lead in River Water Samples from the Anambra River Basin

Simultaneous, rapid, and field-applicable detection of toxic heavy metals in river water is an important analytical chemistry challenge in Nigeria, where laboratory infrastructure constraints limit timely water quality monitoring. This study develops and validates an electrochemical sensor based on a bismuth film-modified glassy carbon electrode for simultaneous determination of cadmium and lead in water samples from the Anambra River Basin, South East Nigeria. The sensor was fabricated by electrodeposition of bismuth film on a glassy carbon electrode surface modified with a reduced graphene oxide and Nafion composite. Electroanalytical performance was characterised by square wave anodic stripping voltammetry. Optimisation of deposition potential, deposition time, bismuth film thickness, acetate buffer concentration, and pH was conducted using response surface methodology. Analytical figures of merit including detection limits, sensitivity, linear dynamic range, selectivity, repeatability, and reproducibility were determined. Interference studies evaluated the impact of common co-existing ions including copper, zinc, iron, and humic substances. River water samples were analysed and results validated against atomic absorption spectrophotometry as a reference method. Detection limits of 0.12 micrograms per litre for cadmium and 0.18 micrograms per litre for lead were achieved, well below WHO guideline values. Recovery values for spiked river water samples ranged from 96 to 104 percent. The developed sensor demonstrates practical utility for decentralised monitoring of cadmium and lead in riverine environments and is suitable for adaptation as a portable field monitoring device. Keywords: electrochemical sensor, cadmium, lead, anodic stripping voltammetry, Anambra River