Trace level determination of cadmium and lead in coffee (Coffea) using gold nanoparticles modified graphene paste electrode

S. Palisoc¹², J. Leoncini¹ and M. Natividad¹²*

¹De La Salle University, Condensed Matter Research Laboratory, Physics Department, 2401 Taft Avenue, PH922 Manila, Philippines
²De La Salle University, Condensed Matter Research Unit, CENSER, 2401 Taft Avenue, PH922 Manila, Philippines
*Correspondence: michelle.natividad@dlsu.edu.ph

Abstract:

Gold nanoparticles (AuNP) modified graphene paste electrodes (GPE) were fabricated using graphene powder, gold nanoparticles, and mineral oil. The fabricated electrodes were used as working electrode in anodic stripping voltammetry (ASV) for the determination of trace concentrations of cadmium (Cd²⁺) and lead (Pb²⁺). The modified GPE was characterized using scanning electron microscopy and cyclic voltammetry. Optimization of the electrode’s AuNP content and the ASV parameters was performed. It was determined that the GPE modified with 0.5 mg AuNP obtained the highest anodic current peaks for both Cd²⁺ and Pb²⁺. The calibration curves obtained using the said electrode showed a linear relationship between heavy metal concentration and peak current and the detection limits were found to be 256 ppb for lead and 267 ppb cadmium. The modified electrode was successful in determining traces of Cd²⁺ and Pb²⁺ in coffee samples. The presence of the heavy metals in the samples were verified using atomic absorption spectroscopy.

Key words:

Determination of heavy metals in root crops using bismuth nanoparticles modified graphene paste electrode

S. Palisoc¹², Y.A. Malabuyo¹, R.C. Pereja¹ and M. Natividad¹²*

¹De La Salle University, Condensed Matter Research Laboratory, Physics Department, 2401 Taft Avenue, PH 922 Manila, Philippines
²De La Salle University, Condensed Matter Research Unit, CENSER, 2401 Taft Avenue, PH 922 Manila, Philippines
*Correspondence: michelle.natividad@dlsu.edu.ph

Abstract:

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.

Key words:

bismuth nanoparticles, graphene, heavy metals, root crops, voltammetry