Trace Determination of Lead and Cadmium using Graphene/[Ru(NH3)6]3+/Nafion Modi-fied Glassy Carbon Electrodes

Abstract

Graphene/[Ru(NH3)6]3+/nafion modified glassy carbon electrodes were fabricated using the drop coating technique. The fab-ricated electrodes were characterized using scanning electron microscopy (SEM) and cyclic voltammetry (CV). Simultaneous detection of lead (Pb2+) and cadmium (Cd2+) was done via anodic stripping voltammetry (ASV). The effects of varying the amounts of graphene and [Ru(NH3)6]3+ on the transport and sensing properties of the modified electrodes were determined. SEM results showed that the deposited films were smooth and uniform. CV results showed that the peak currents increase monotonically with the amounts of graphene and [Ru(NH3)6]3+. ASV results showed that modification of the GCE with graphene, [Ru(NH3)6]3+ and Nafion greatly enhanced the electrode’s sensitivity in detecting Pb2+ and Cd2+. This can be attributed to the high surface area-to-volume ratio of graphene, the mediation of elec-tron transfer by [Ru(NH3)6]3+ and the antifouling and cationic exchange capabilities of Nafion. The highest peak current for both Pb2+ and Cd2+ were obtained from the electrode modified with 1.5 mg [Ru(NH3)6]3+ and 3.0 mg graphene. A linear relationship between the peak current and metal concentration was obtained in the range of 1.4 ppb to 20 ppb for both Pb2+ and Cd2+ with a detection limit of 1.4 ppb. The modified electrodes were successful in detecting Cd2+ in real water samples. ASV results were verified using atomic absorption spec-troscopy.