Sensitive voltammetric determination of cadmium and copper in jasmine rice using a boron-doped reduced graphene...

Heavy metal contamination in food crops remains a critical environmental and public health issue, particularly for cadmium (Cd²⁺) and copper (Cu²⁺), which can accumulate through soil, water, and agricultural inputs. Reduced graphene oxide (rGO) was prepared via boric acid-assisted thermal reduction of graphene oxide followed by acid washing. A boron-doped reduced graphene oxide modified graphite electrode (rGO/GE) was then fabricated and applied for the sensitive voltammetric determination of Cd²⁺ and Cu²⁺ in jasmine rice using differential pulse anodic stripping voltammetry (DPASV) coupled with a standard addition technique. DPASV analysis included immersion of the rGO/GE and the deposition of target metal ions (Cd²⁺ and Cu²⁺) and bismuth onto the electrode surface. The synthesized GO and rGO were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), UV-vis spectroscopy, and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDS). Results confirmed the complete reduction of GO to rGO using boric acid as the reducing agent. The method showed excellent reproducibility and sensitivity, with limits of detection (LODs) of 30 µg/L for Cd²⁺ and 0.05 µg/L for Cu²⁺. Electrochemical analysis results show that the actual concentrations of Cd²⁺ and Cu²⁺ in Royal Umbrella brand jasmine rice were 0.46 ± 0.01 mg/kg and 1.16 ± 0.06 mg/kg, respectively. The results were validated using atomic absorption spectroscopy (AAS), which provided relative differences of 0.00% for Cd²⁺ and 8.7% for Cu²⁺. These findings demonstrate that the rGO/GE sensor provides a reliable and cost-effective tool for trace heavy metal assessment in food matrices, offering significant potential for routine environmental and food safety monitoring. HIGHLIGHTS: An rGO/GE electrode was developed for sensitive detection of Cd²⁺ and Cu²⁺ in rice. Results of the method showed excellent agreement with AAS, with low relative differences (0.00% and 8.7%). The proposed electrochemical sensor offers a rapid, precise, and low-cost alternative for heavy metal monitoring in food samples.