Electroanalytical Determination of Arsenic(III) and Total Arsenic in 1 mol L⁻¹ HCl Using a Carbonaceous Electrode Without a Reducing Agent

Abstract

Arsenic(V) [As(V)] was reduced to As(0) at pH 0.0 and As(III) at pH 4.5 on a carbon-paste electrode modified with hematite, which allowed their selective determination. Arsenic(V) suffered interference from copper (Cu) and bismuth (Bi). Arsenic(III) was almost free of them. Humic acid did not affect the signal of As(V) but increased the signal of As(III). Arsenic was preconcentrated at −0.8 V for 100 s. The response was linear up to 70 µg L⁻¹ for As(V) and 50 µg L⁻¹ for As(III). The limits of detection were 2 µg L⁻¹ and 5 µg L⁻¹ respectively. This method was applied to drinking water and compost lixiviate.

Keywords:

• Arsenic
• As(V) direct reduction
• chemically modified electrode
• selectivity

This work has been supported by the Secretaría General para la Prevención de la Contamìnación y el Cambio Climático (SGPCCC) of the Spanish Environmental Ministry.

Notes

Notes. pH 2.0, 0.01 mol L⁻¹ HCl + 0.10 mol L⁻¹ KNO₃ supporting electrolyte, pretreatment −0.800 V for 100 s. SQW parameters: step height of 0.008 V, amplitude of 0.040 V, and frequency of 150 Hz. Np: no peaks.

Notes. Deposition step: −0.800 V for 100 s. SQW parameters: step height of 0.008 V, amplitude of 0.040 V, and frequency of 150 Hz.