Determination of heavy metals in mussel and oyster samples with tris (2,2′-bipyridyl) ruthenium (II)/graphene/Nafion® modified glassy carbon electrodes

Tris (2,2'-bipyridyl) ruthenium(II)/graphene/Nafion (R) modified glassy carbon electrodes (GCEs) were fabricated using the drop coating method. The modified electrode was used as the working electrode in differential pulse voltammetry (DPV) for the determination of lead, cadmium, and copper in mussel and oyster samples. The concentration of Tris (2,2'-bipyridyl) ruthenium (II) and graphene were varied while those of Nafion (R), methanol, and ethanol were held constant in the coating solution. The morphology and elemental composition of the fabricated electrodes were analyzed by scanning electron microscopy and energy-dispersive x-ray spectroscopy. Cyclic voltammetry (CV) was done to investigate the reversibility and stability of the modified electrodes. The modified electrode with the best figures of merit was utilized for the detection of copper (Cu2+), lead (Pb2+) and cadmium (Cd2+) via DPV. This was the electrode modified with 4 mg [Ru (bpy)3](2+) and 3 mg graphene. The anodic current and metal concentration showed linear relationship in the range of 48 ppb-745 ppb for Pb2+, 49 ppb-613 ppb for Cd2+, and 28 ppb-472 ppb for Cu2+. The limits of detection for lead, cadmium, and copper were 48 ppb, 49 ppb, and 28 ppb, respectively. Results from atomic absorption spectrometry (AAS) were compared with those measured with DPV. Lead, cadmium, and copper were in mussels, oysters, and sea water. In addition, DPV was able to detect other metals such as zinc, iron, tin and mercury in sea water samples and some samples of oysters.