Catalytic determination of chloride in water using a lab-on-valve flow system

The application of flow-based systems in chemical analysis proved to be advantageous, namely due to the reduction of sample and reagent consumption as well as waste production. Moreover, the ease of automation contributes to the increase in efficiency, minimizing potential sample contamination as well as the contact between the analyst and toxic reagents. Water is a fundamental part of Earth's ecosystem and monitoring its parameters is essential. Chloride is present in aquatic environments, and the chloride concentration is a key parameter to be monitored for assessing water quality. A high chloride concentration can have aesthetic effects on drinking water and potential toxicity resulting from the water treatment process’s by-products. In natural waters, chloride is present in a wide range, from 10 to 19000 mg/L [1]. In this context, this research focused on developing an efficient method with a lab-on-valve flow system enabling the routine monitoring of chloride concentration. The proposed method uses chloride as a catalyst for the oxidation reaction between 3,3′,5,5′-tetramethylbenzidine and H2O2. The instrumental conditions were studied to attain the best operation conditions. The linearity range and the limit of quantification allowed us to monitor chloride in diverse water bodies.