Quantitative determination of aqueous-phase ozone by chemiluminescence using indigo-5,5'-disulfonate

Indigo-5,5'-disulfonate (IDS) was found to be an efficient reagent for the determination of ozone by chemiluminescence (CL); hence it was applied to the continuous measurements of dissolved ozone (O3(aq]. The optimum reagent composition was determined as 10 mg L-1 IDS plus 2 mM phosphate (pH 7.2). The CL intensity was proportional to the O3(aq) concentration in the range of 0.025-410 ng mL-1. The detection limit was 0.006 ng mL-1, which is 3 orders of magnitude lower than that obtained by spectrophotometry using IDS as reported previously. The reduction of interferences from aldehydes and hydrogen peroxide was attempted. Furthermore, the mechanism of the CL was discussed from CL and fluorescence spectra measured.