Express standardization of sulfide solutions using voltammetric titration on two points

Abstract

A new method called voltammetric titration on two points for express (≤5 min) standardization of unstable sulfide solutions has been developed. The method can be used as an alternative to the classical K₃[Fe(CN)₆] titration. The same redox reaction underlies the new method: 2[Fe(CN)₆]³⁻ + S²⁻ → 2[Fe(CN)₆]⁴⁻ + S⁰. The analytical signal, current of ferricyanide reduction, is used for immediate calculation of the sulfide concentration. Two analytical signals of electrochemically active K₃[Fe(CN)₆] before (I₀) and after (I₁) its quantitative interaction with the analyzable sample is enough to get an accurate concentration. The method accuracy has been confirmed by comparison of experimental (Δ_exp) and calculated (Δ_calc) data, and with recovery study.