SUMMARY
The electrochemical behaviour of potassium hydrogenperoxomonosulfate (KHSO5) in the presence of sodium dodecylbenzenesulfonate (SDBS) has been studied using cathodic voltammetry at the carbositall electrode as indicating in the potential range of +1.0…–1.2 V (the reference electrode Ag, AgCl/K?l(sat)) (Ep = +0.3 V). It has been experimentally proven that the height of KHSO5 reduction peak decreases and the potential of the reduction peak is shifted toward more electronegative values with increasing of the background electrolyte pH from 0.80 to 7.17. The maximum peak (Ip) occurs at a pH of approximately 0.8 and at a pH around 5 the analytical signal almost disappears. The effect of pH on the peak potential (Ep) shows the following: when the pH value increases in the interval from 0.8 to 2, Ep remains almost constant, but Ep decreases sharply to the negative value with pH increasing over 2. It has been experimentally proven that SDBS leads to increase of the current peak and the peak potential shifts to the more electropositive side (+0.25? +0.3V). The influence of the present SDBS has been examined. The current peak increases with the concentration of the surfactant up to 1.2×10–3 mol L–1 and then stays almost constant with the increase in the concentration of SDBS above 3.0×10–3 mol L–1. The linear relationship was observed in the KHSO5 concentration range of (1.8–9.0)×10–5 mol L–1, the calibration curve equation was I? = (4.3±1.1)×104 ? (r = 0.998). When determining KHSO5 in the test solution of “Ecocid S” disinfectant with the concentrations of 4.65×10–5, 6.20×10–5 and 7.75×10–5 mol L–1) the RSDs were 0.025, 0.023 and 0.021, respectively (d = –0.64 ... +0.16%); LOD = 6.50×10–6 mol L–1, LOQ = 2.17×10–5 mol L–1.