A novel cyclic voltammetric determination of free chlorine generated by ozone disinfection in seawater aquariums

The amount of free chlorine generated by disinfection is one of core parameters that should be monitored for the seawater aquarium. This article proposes a novel analytical method in which the amount of free chlorine in ozonized seawater can be determined by the conventional cyclic voltammetry (CV) with a bare platinum disk electrode without developing any new sensing material. The amounts of both free chlorine and ozone in ozonized seawater samples were determined by spectrophotometry, which showed that most of ozone was converted to free chlorine. CV experiments with a bare platinum electrode were carried out for the samples and our attention was paid to that the peak current of hydrogen oxidation generated by water electrolysis, which was ignored in the previous studies, depends on the amount of free chlorine in the sample. The CVs exhibited the well–defined oxidation peak for hydrogen molecules and the linear range of free chlorine amounts in the ozonized seawater samples spanned from 0.02 to 0.4 mg L–1 with a correlation coefficient of 0.9982 (n=5), a detection limit of 1.2 × 10–2 mg L–1 at 3σ and a high sensitivity of 4063 μA cm–2 mg–1 L. The repeatability of this technique had a relative standard deviation of 4.41% (n=10).