Electrochemically etched gold wire microelectrode for the determination of inorganic arsenic

An electrochemical method for direct determination of inorganic arsenic [As(III), As(V), and total inorganic arsenic] was developed using an electrochemically etched gold wire microelectrode (Au-ME) by square wave anodic stripping voltammetry. Bromide was adopted to facilitate the electrochemical etching of gold through its complexation with gold ions, and controllably etched gold wire microelectrode can be obtained by adjusting the linear sweep voltammetry recycling numbers. Although the diameter of Au-ME decreases from 25.67 to 15.41 μm, for the determination of As(III) in 0.5 M H2SO4, the sensitivity increases 1.5-fold to 6.8 μA cm−2 ppb−1 and the limit of detection (LOD) decreases 2.8-fold to 2.6 ppb; for determination of As(V) in 0.25 M HCl, the sensitivity increases 1.6-fold to 2.6 μA cm−2 ppb−1 and LOD decreases 2.5-fold to 3.9 ppb. The As(V) deposition mechanism is put forward: first, chemically reduce to As(III) associated with active chlorine, and then electrochemically reduce to As(0), which experience two reduction step. Given that the LODs for both As(III) and As(V) are lower than the arsenic guideline value of 10 ppb, Au-ME shows efficiency in determining trace arsenic when applied to real environmental samples.