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.