Studies of selectivity in the amaranth method for chlorine dioxide

Studies were designed to evaluate the amaranth method for measuring chlorine dioxide in water. Specifically, the effects of pH and temperature are examined for the amaranth method. The results of interference studies are reported for free available chlorine species, chlorite ion, chlorate ion, iron (III) ion, oxidized manganese, and monochloramine. Additional research focused on selectivity enhancement for chlorine dioxide over free available chlorine using ammonia/ammonium chloride buffer and gas diffusion-flow injection analysis. The results of method detection limit and accuracy and precision studies are reported for measuring chlorine dioxide in the presence of free available chlorine.