Analytical Methods for the Measurement of Chlorine Dioxide and Related Oxychlorine Species in Aqueous Solution

The main goal of this research was to seek a better understanding of the analytical measurements 2 24 23 23of the oxychlorine species ClO , Cl O , and Cl O /Cl O .--2The US EPA has developed a new colorimetric method for the measurement of ClO and chlorite ion (Method 327.0).This method is based on the decolorization of the dye Lissamine Green B 22 (LGB) by ClO .Chlorite ion is converted to ClO by Horseradish Peroxidase enzyme and measured withLGB.In the current work, the performance of this method (method detection limit, accuracy, and precision) was evaluated.The interference from dissolved chlorine, chloramine, iron(II), manganese(II), permanganate, and chlorate ions was studied.The underlying chemistry of these reactions is described and used to differentiate between interference and 2 demand.A new method is suggested for the preparation of ClO standards by illuminating a 2 mixture of chlorite ion and a photoacid.By using this method, ClO standards could be prepared reproducibly.Possible future developments for the method are also discussed.2 Chlorite ion interferes with the spectrophotometric measurement of ClO due to the formation of 24 2the Cl O complex.This complex has higher molar absorptivity than ClO at longer wavelengths -2 where the absorbance of concentrated ClO solutions is measured.The formation constant of the complex is 5.0 M as determined in this work.Based on this value, the molar absorptivity of the -1 complex was calculated as a function of wavelength.These values were used to give recommendations to adjust the currently used spectrophotometric measurements.A new mixed disinfectant solution was developed and tested.This disinfectant is created from 2 dissolved chlorine and ClO .It is a potent disinfectant due to the formation of reactive 2 intermediates resulting from the ClO -chlorine reaction.A combination of chemical kinetic and microbiological results was used to estimate the efficacy of the new solutions.It was shown that in this way, fewer microbiological tests are required than using only microbiological results.This leads to shorter development time and lower costs.