Smartphone-Assisted Detection of Chlorine Concentration in Water Samples Using a Microfluidic Chip

Chlorine is a strong oxidizing agent, aids in killing viruses and bacteria present in the water. The presence of free chlorine in the water eliminates the presence of pathogens and ensures safe drinking water. Meanwhile, residual free chlorine in the water if consumed in excess will lead to various health problems including cancer. World Health Organization has given out suggestions for the safe usage of chlorine in the water treatment. Adequate controlling and monitoring the amount of the chlorine present in the water is crucial for domestic as well as industrial use of water. Various commercial systems are available in the market for chlorine analysis. But these systems are bulky and very expensive. Herein a simple low-cost portable smartphone device is introduced which can be used for the rapid determination of free chlorine content in water. The proposed model relies on the colorimetric action of DPD reagent followed by data processing using the sensing system. The sensing system consists of a smartphone camera as a detector, which captures images and processes data with the help of a smartphone application. The software app is developed to use with the phone for recording and analyzing the RGBA value of the color of the image captured. The portability of the designed system was ensured by using a casing assembly designed using additive manufacturing procedures. The linear range of residual free chlorine estimation is 0–10 ppm with a sensitivity of measurement of 0.02 ppm was confirmed with known chlorine concentration samples as well as blind testing.