Development of Sensor for Free Available Chlorine Estimation in Surface Water

Abstract

The development of portable sensors that can be used outside the lab is an active area of research in the electro analytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy carbon, platinum or gold electrodes, are costly and require time-consuming preparation. In this work an alternatives have been proposed, where pencil graphite electrodes (PGEs) has been used as sensing platform. Surface of pencil has been used to make it suitable for estimating free chlorine in water sample. Chlorine is a common disinfectant in the water industry, and the residual free chlorine concentration in water distributed to the consumers must be lower than the value set by the regulatory bodies. The pencil graphite-electrode shows high selectivity, low detection limit and linear response to free chlorine in the relevant concentration range at the applied potential of 1.5V and no response to commonly interfering ions such as NO3 -, SO4 2-, CO3 2-, Cl-, HCO3 - has been observed. Further investigation has been conducted on the storage stability and response time on FAC sensing. The sensitivity of free chlorine has been found to be 50μAmM-1cm-2. The pencil graphite electrodes were also used for detection of chlorine with a relatively wide concentrations ranging up to 8 mM, with a limit of detection of 46 μM. It exposes that the stability of PGEs 97.93% after 14 days of its initial activity. This sensor is being proposed as a low cost device for determining free chlorine in water samples with short response time of t90 less than 5 sec.