Electrochemical Detection of Trace Arsenic(III) by Nanocomposite of Nanorod-Like α-MnO₂ Decorated with ∼5 nm Au Nanoparticles: Considering the Change of Arsenic Speciation

It has been reported that the majority of groundwater shows weak alkaline in which the As(III) species would be present as neutral H₃AsO₃ species and ionized H₂AsO₃^- species. However, as most reported previously, electrochemical detection of As(III) has been operated under acidic conditions and the nonionic As(III) (H₃AsO₃) is the dominant species. Therefore, considering the change of As(III) speciation in different pH conditions, to develop a reliable method for the detection of As(III) in alkaline media might be more meaningful for practical applications. Here, combined the multilayer adsorption of nanorod-like α-MnO₂ with the excellent electrocatalytic ability of ∼5 nm Au nanoparticles (AuNPs), an efficient and ultrahigh anti-interference electrochemical detection of As(III) with AuNPs/α-MnO₂ nanocomposite in alkaline media (nearly real water environment) was developed. Notably, we have provided a thorough electrochemical analytical investigation to confirm the advantage of As(III) detection in alkaline media. The system was evaluated by a series of interference tests, and no obvious interference from commonly coexisting substances (referring to the groundwater, Togtoh region, Inner Mongolia, China) was observed in alkaline media. Furthermore, electrodes robust stability and excellent reproducibility were obtained. Under the optimized conditions, the limit of detection (3σ method) toward As(III) was 0.019 ppb, and the obtained sensitivity was 16.268 ± 0.242 μA ppb^-1 cm^-2. Finally, the proposed method has been successfully employed for detection of As(III) in a real water sample.