Cobalt based solid state phosphate sensor with submicromolar detection range

Phosphate monitoring is critical in assessing the nutrient pollution in water bodies like lakes and rivers, and in their management. Increase in phosphate concentration can result in algal bloom in the water bodies. Most of the commercial system uses colorimetric methods for phosphate measurements. However, these methods require reagents that may not be suitable for long term field use. Electrochemical methods such as potentiometry offer a good alternative to construct a solid-state sensor. Cobalt is a widely investigated solid-state electrode used for phosphate measurement. But the commercial success of the electrode is limited due to high limit of detection (>10-6M). This study demonstrates a pretreatment protocol to enable cobalt electrodes for phosphate measurements at sub micromolar concentrations (-6M). The two-step current pretreatment enhanced the sensitivity of the sensor from 3.1mV/decade (control) to 15.2mV/decade (with current pretreatment). Except sulphate, no significant interference was observed with common anions (nitrate, chloride, and acetate).