An Electrochemical Microfluidic System for On-site Continuous Monitoring of Soil Phosphate

On-site monitoring of phosphate concentration attracted much attention recently for soil fertility management in agricultural product. This study proposes a portable and easy-operate electrochemical microfluidic system with integrated reagent reactions for on-site continuous monitoring of soil phosphate. Polydimethylsiloxane (PDMS) chips with channel layers and PDMS substrates embedded with screen-printed electrodes were prepared using 3D printed molds. Reagents and samples were pumped into the chips at optimal flow rates of 100 μL min ^-1 to automatically react, which were used for cyclic voltammetry (CV) electrochemical detection of analytes via carbon black nanoparticles (CBNPs) modified electrodes. After optimizing experimental conditions including pH value, liquid flow rates, and voltammetry scan rates, the system achieved a linear phosphate concentration range of 5 - 100 μM with a detection limit of 4.2 μM. Moreover, the system exhibited excellent resistance to interference long lifespan and excellent phosphate recovery rate from91.1 to 110.48%. This system has been successfully applied to continuous field phosphate determination in real soil environment. Results elucidated that the system has good practicality and has great potential for fine nutrient management in the field.