Cadmium (Cd2+) detection kit utilizing GCE system modified with graphene-doped ZnO/PVA nanocomposite

Access to clean drinking water is a fundamental human need that can be sourced from rivers such as the Citarum River in West Java, Indonesia. However, according to a 2018 World Bank report, the Citarum River is heavily contaminated with cadmium (Cd), with concentrations ranging from 0.03 mg/L to 0.464 mg/L—far exceeding the Indonesian water quality standard of 0.01 mg/L (10 ppb) stipulated in Government Regulation No. 22/2021. To enable the detection of Cd at low concentrations, a portable detection kit based on the Cyclic Voltammetry (CV) method was developed. The system integrates an LMP91000 potentiostat, Arduino UNO microcontroller, ADS1115 analog-to-digital converter, and a Nextion NX8048K050 HMI display. A Glassy Carbon Electrode (GCE) with a graphene-doped ZnO/PVA nanocomposite as the working electrode was employed to enhance sensitivity. The developed kit demonstrated a sensitivity of 4.92 μA/ppb, a linearity (R 2 ) of 0.96, and a limit of detection (LOD) of 4.08 ppb. Measurement errors ranged from 2.26% to 5.02%, confirming that the proposed system can effectively detect Cd concentrations around the regulatory threshold of 10 ppb.