Low cost, portable voltammetric sensors for rapid detection of nitrate in soil

The excessive use of nitrate fertilizer in agriculture has been a serious problem causing giant economic loss and environment pollution. Therefore, nitrate sensing in soil is very important for environment and agriculture. In this work, we develop a rapid sensing platform for on-site nitrate detection, which is composed of an easily conducted extraction filter (ECEF) and a sensing element based on cadmium sulfide nanorods (CdS NRs) modified screen printed electrode (CdS NRs-SPE). Nitrate extraction from soil can be easily conducted by ECEF in 3 min using a syringe coupled with a filter. The extracted solution is subsequently injected onto the CdS NRs-SPE, which can directly detect nitrate in neutral media within 10 min. The detection limit of nitrate is 2.3 μM (S/N = 3) and a linear range from 0.05 to 5 mM. Moreover, the CdS NRs-SPEs are portable, low cost (3 dollars), and can be reused for over one month without significant loss of the performance, implying its promising application for intelligent nitrogen-management and developing precise fertilization in modern agriculture.