Ti/TiO2ntas/RuO2 Probe for Amperometric Detection of Hypochlorite in Solution

Abstract

Tool to help provide a healthy environment. Disinfection is a process that is designed to kill actively growing and vegetative microbial microorganisms to a certain level. Generally, there are two methods of disinfection: chemical and physical1. The physical agents of disinfection that have been used include ultraviolet light (UV), electron beam, gamma-ray irradiation, sonication, and heat. Considering the chemical methods, there is a great variety of compounds such as chlorine, ozone, the metals copper and silver, phenolic compounds, quaternary ammonium salts, alcohols and hydrogen peroxide among others. Historically, the most widely used chemical disinfection procedure is chlorination because of its low cost, ease of application, and ability to inactivate a wide variety of pathogenic microorganisms.Hypochlorite ion (ClO-) is widely used in daily life applications such as household bleach, disinfection of drinking water and cooling-water treatment among others. Nevertheless, it has been reported that the abnormal production or the excessive intake of ClO- can lead to numerous diseases, including cardiovascular disorders, neuron degeneration, arthritis or even cancer2. Hence, it is of utmost importance to develop rapid and sensitive methods for the determination of ClO-. So far, iodometric titration and colorimetric methods based on the reaction of ClO- with organic reagents have been widely used so as to determine hypochlorite concentration. These methodologies usually require tedious procedures.In the present work, we propose the design of an amperometric sensor for fast hypochlorite analysis. The architecture of the sensor is a RuO2 coating onto a highly ordered titanium dioxide nanotube array (Ti/TiO2NTAs/RuO2). TiO2NTAs were grown by electrochemical anodization of a titanium metal disc in ethylene glycol containing ammonium fluoride (0.3%w/w) and water (2%w/w). The electrochemical synthesis was performed at 30V. Afterwards, RuO2 was deposited layer by layer onto the TiO2NTAs substrate and a final annealing process was performed at 500 oC in order to fix it to the nanostructure.The fundamental analytical parameters (linear range, limit of detection and sensitivity) of the probe were characterized in the presence of hypochlorite. The sensor working potential was also optimized and then fixed at 0.6 V. Finally, the hypochlorite content of different samples was measured using the sensor and compared with the DPD-method value (Standard Methods: 4500-Cl G)3. The proposed amperometric sensor offers an alternative tool to the classical DPD-method, with higher sensitivity, lower limit of quantification and analysis time.