An environmental friendly method for the automatic determination of hypochlorite in commercial products using multisyringe flow injection analysis

A multisyringe flow injection analysis system was used for the determination of hypochlorite in cleaning agents, by measurement of the native absorbance of hypochlorite at 292 nm. The methodology was based on the selective decomposition of hypochlorite by a cobalt oxide catalyst giving chloride and oxygen. The difference of the absorbance of the sample before and after its pass through a cobalt oxide column was selected as analytical signal. As no further reagent was required this work can be considered as a contribution to environmental friendly analytical chemistry. The entire analytical procedure, including in-line sample dilution in three steps was automated by first, dilution in a stirred miniature vessel, second by dispersion and third by in-line addition of water using multisyringe flow injection technique. The dynamic concentration range was 0.04-0.78 g L⁻¹ (relative standard deviation lower than 3%), where the extension of the hypochlorite decomposition was of 90 ± 4%. The proposed method was successfully applied to the analysis of commercial cleaning products. The accuracy of the method was established by iodometric titration.