Highly Sensitive Detection of Arsenite Based on Its Affinity toward Ruthenium Nanoparticles Decorated on Glassy Carbon Electrode

Abstract

Metallic ruthenium nanoparticles (Ru NPs) are formed on the glassy carbon electrode (GC) at electrodeposition potential of -0.75 V, as observed from X-ray photoelectron spectroscopy. Thus formed Ru NPs have the arsenite selective surface and conducting core that is ideally suited for designing a highly sensitive and reproducible response generating matrix for the arsenite detection at an ultratrace concentration in aqueous matrices. Contrary to this, arsenate ions sorb via chemical interactions on the ruthenium oxide (RuO2 and RuO3) NPs formed at -0.25 V, but not on the Ru NPs. For exploring a possibility of the quantification of arsenite in the ultratrace concentration range, the Ru NPs have been deposited on the GC by a potentiostatic pulse method of electrodeposition at optimized -0.75 V for 1000 s. Arsenite preconcentrates onto the Ru surface just by dipping the RuNPs/GC into the arsenite solution as it interacts chemically with Ru NPs. Electrochemical impedance spectroscopy of As(III) loaded RuNPs/GC shows a linear increase in the charge transfer resistance with an increase in As(III) conc. Using a differential pulse voltammetric technique, arsenite is oxidized to arsenate leading to its quantitative determination without any interference of Cu(2+) ions that are normally encountered in the water systems. Thus, the use of RuNPs/GC eliminates the need for a preconcentration step in stripping voltammetry, which requires optimization of the parameters like preconcentration potential, time, stirring, inferences, and so on. The RuNPs/GC based differential pulse voltammetric (DPV) technique can determine the concentration of arsenite in a few min with a detection limit of 0.1 ppb and 5.4% reproducibility. The sensitivity of 2.38 nA ppb(-1) obtained in the present work for As(III) quantification is considerably better than that reported in the literature, with a similar detection limit and mild conditions (pH = 2). The RuNPs/GC based DPV has been evaluated for its analytical performance using the lake water, ground water, and seawater samples spiked with known amounts of As(III).