Determination of the oxidant activity of chlorinated water by chronoamperometry

Abstract

A new version of the chronoamperometric method, adapted to the determination of the oxidative (oxidant) activity of a medium on an example of chlorinated water, was proposed. The supporting solution contained K₄Fe(CN)₆. By its oxidation with oxidants present in the sample, K₃Fe(CN)₆ formed; its reduction current served as an analytical signal. The current of K₃Fe(CN)₆ reduction was recorded at a potential of 0 V, selected from the cyclic voltammogram of the K₃Fe(CN)₆/K₄Fe(CN)₆ system in the range where the oxidized form of the reagent was reduced and the reduced form was stable. A gold electrode was the measuring electrode. The possibility of using a stable solution of K₃Fe(CN)₆ as a component of a standard addition and as a solution for plotting a calibration curve was demonstrated. The limit of detection of the amount of dissolved chlorine and products of its interaction with water is 8 × 10^–6 M. The data obtained by the proposed procedure and by the iodometric methods correlate well with each other (r = 0.93–0.95). The proposed version of the chronoamperometric method can be used to monitor the amount of dissolved chlorine and products of its interaction with water in water supply systems, pools, and disinfecting solutions and to determine other water-soluble oxidants.