A vast majority of our population does not have access to safe drinking water and this has a significant bearing on their health. In rural areas drinking water is largely obtained from natural sources and these water sources are getting increasingly polluted due to heavy use of fertilizers or excessive drawing of ground-water resulting in high levels of nitrates, fluorides, arsenic or iron. At present, the purity of water can only be tested in laboratories using expensive equipment and highly trained technicians or with chemical test kits of poor reliability. The development of a polysensor aims at providing a low-cost and simple system of testing for impurities in water that can be used by a lay person with a little training.

The system consists of a set of electrochemical sensors and an electronic measuring instrument. The sensors are specific- ion electrodes with potentiometry as the measurement principle. The instrument is battery-operated and portable for field use. The measured contaminant levels are compared with those specified by WHO with a green/red LED lighting up indicating that the sample is potable/non-potable. For a detailed report, there is a 20 char × 4 line LCD display that reads out the measured concentrations. The sensor-cartridge is screen-printed, low-cost and can be easily replaced.

The instrument is currently capable of testing for electrical conductance, total dissolved solids, salinity, pH, chloride and nitrate. Sensors for fluoride, iron and mercury have been developed while sensors for arsenic and microbial contamination are being developed. With some modifications, the system will be suitable for testing for soil condition and adulteration of milk. It is proposed to develop a system for health-care diagnostics based on biosensors that have been created in IIT Bombay labs over the past fifteen years.