posted on 2023-01-23, 13:05authored byXin Cai, Rui-Ze Xia, Jia-Jia Ye, Cong-Cong Huang, Yuan-Fan Yang, Long-Ke Zhang, Bo Liang, Meng Yang, Chu-Hong Lin, Pei-Hua Li, Xing-Jiu Huang
Significant
progress has been made in nanomaterial-modified
electrodes
for highly efficient electroanalysis of arsenic(III) (As(III)). However,
the modifiers prepared using some physical methods may easily fall
off, and active sites are not uniform, causing the potential instability
of the modified electrode. This work first reports a promising practical
strategy without any modifiers via utilizing only soluble Fe3+ as a trigger to detect trace-level As(III) in natural water. This
method reaches an actual detection limit of 1 ppb on bare glassy carbon
electrodes and a sensitivity of 0.296 μA ppb–1 with excellent stability. Kinetic simulations and experimental evidence
confirm the codeposition mechanism that Fe3+ is preferentially
deposited as Fe0, which are active sites to adsorb As(III)
and H+ on the electrode surface. This facilitates the formation
of AsH3, which could further react with Fe2+ to produce more As0 and Fe0. Meanwhile, the
produced Fe0 can also accelerate the efficient enrichment
of As0. Remarkably, the proposed sensing mechanism is a
general rule for the electroanalysis of As(III) that is triggered
by iron group ions (Fe2+, Fe3+, Co2+, and Ni2+). The interference analysis of coexisting ions
(Cu2+, Zn2+, Al3+, Hg2+, Cd2+, Pb2+, SO42–, NO3–, Cl–, and F–) indicates that only Cu2+, Pb2+, and F– showed inhibitory effects on As(III) due
to the competition of active sites. Surprisingly, adding iron power
effectively eliminates the interference of Cu2+ in natural
water, achieving a higher sensitivity for 1–15 ppb As(III)
(0.487 μA ppb–1). This study provides effective
solutions to overcome the potential instability of modified electrodes
and offers a practical sensing platform for analyzing other heavy-metal
anions.