Paper-Sensors for Point-of-Care Monitoring of Drinking Water Quality

Contamination of water bodies due to the disposal of natural and anthropogenic pollutants is one of the major global concerns in the recent times. Regular on-spot monitoring of water quality has become mandatory wherein diverse classes of materials such as organic, inorganic, heavy metals, or biological wastes are detected employing standard protocols. However, most of the existing laboratory techniques are either costly and/or time consuming owing to the process involving the expert driven sophisticated analysis techniques. Herein, we report the development of three paper based colorimetric sensors for the on-spot quantitative detection of the levels of fluoride (F
^-
), lead (Pb
²⁺
), and pH in drinking water. The variations in the color-intensities of the paper sensors with the variation in the concentration of fluoride (F
^-
), lead (Pb
²⁺
), and pH were converted into electronic signals to enable the development of a point-of-care-testing (POCT) device. For this purpose, initially, the sensors were characterized and calibrated with known concentrations of contaminates before successful validations with real samples. Thereafter, the sensors were illuminated with a light emitting diode from one side while the transmitted rays passing through the sensor was captured by a light dependent resistor (LDR) from the other side. The variation in the color intensity of the paper-sensor with the contaminant loading was found linearly varying with the resistance of the LDR. The sensor was then translated into a specific, stable and user friendly POCT device, which enabled inexpensive spot detection of pollutants in drinking water.