Sensitive determination of chlorpyrifos using Ag/Cu alloy nanoparticles and graphene composite paste electrode

• A simple, non-enzymatic and electrocatalytic graphene and Ag/Cu alloy nanoparticles based sensor for chlorpyrifos is fabricated and characterized.
• Highly sensitive and selective differential pulse adsorptive stripping voltammetric method is developed for the determination of chlorpyrifos.
• The method is successfully applied for well water and soil samples and validated with HPLC–UV method.

A novel Ag/Cu alloy nanoparticles and graphene nanocomposite paste electrode was fabricated and its electrochemical activity was investigated using cyclic voltammetry and electrochemical impedance studies. Electrochemical reduction of chlorpyrifos using the nanocomposite produced peak signal based on 2e− reductive cleavage of CCl bond in trichloropyridine moiety. Increase in peak currents and decrease in overpotential for chlorpyrifos was observed for Ag/Cu–graphene nanocomposite compared to Ag–graphene, Cu–graphene, graphene paste and carbon paste electrodes. This could be attributed to the synergistic combination of graphene and Ag/Cu alloy nanoparticles with good adsorption, large surface area, increased active sites leading to fast electron transfer rates and high electrical conductivity of nanocomposite. A differential pulse adsorptive stripping voltammetric method was developed by using the above electrode for highly sensitive determination of chlorpyrifos under optimum instrumental and working conditions. A calibration plot of chlorpyrifos was studied over concentration range, 0.01–100 nM and detection limits of 4 × 10−12 M were achieved. The method was successfully applied to well waters and soil samples and recovery values were in good agreement with HPLC–UV method.