Determination of heavy metals in root crops using bismuth nanoparticles modified graphene paste electrode
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Electrochemical detection of lead (Pb2+) and cadmium (Cd2+) was accomplished via anodic stripping voltammetry (ASV) using bismuth nanoparticle (BiNP) modified graphene paste electrode (GPE). The electrode was fabricated by mixing bismuth nanoparticles, graphene, and mineral oil and the mixture was packed in a Teflon syringe. The best electrode was determined by varying the amount of BiNP while the amount of graphene and mineral oil were kept constant at 0.21 g and 0.80 μL, respectively. The highest peak currents were obtained using 1.5 mg BiNP modified GPE. The ASV parameters, namely accumulation time, deposition time, and accumulation potential, were optimized. The calibration curve, analytical sensitivity, limit of detection (LOD), and limit of quantitation (LOQ) of the optimized electrode were determined. The correlation values for Pb2+ (R2 = 0.9409) and Cd2+ (R2 = 0.9086) in the calibration curves showed a positive linear relationship between the anodic peak current and heavy metal concentration. The LOD for both Pb2+ and Cd2+ is found to be 100 ppb. The application of the modified electrode on real sample analysis was performed using root crops purchased from local supermarkets. According to ASV and AAS analyses, most of the samples contained Cd2+ while only a few contained Pb2+. Other metals, such as Fe2+ and Cu2+, were also detected via ASV.