Electrochemical determination of paraquat in citric fruit based on electrodeposition of silver particles onto carbon paste electrode

Carbon paste electrodes (CPEs) modified with silver particles present an interesting tool in the determination of paraquat (PQ) using square wave voltammetry. Metallic silver particle deposits have been obtained via electrochemical deposition in acidic media using cyclic voltammetry. Scanning electron microscopy and X-ray diffraction measurements show that the silver particles are deposited onto carbon surfaces in aggregate form. The response of PQ with modified electrode (Ag-CPE) related to Ag/CP loading, preconcentration time, and measuring solution pH was investigated. The result shows that the increase in the two cathodic peak currents (Peak 1 and Peak 2), under optimized conditions, was linear with the increase in PQ concentration in the range 1.0 × 10^-7 mol/L to 1.0 × 10^-3 mol/L. The detection limit and quantification limit were 2.01 × 10^-8 mol/L and 6.073 × 10^-8 mol/L, respectively for Peak 1. The precision expressed as relative standard deviation for the concentration level 1.0 × 10^-5 mol/L (n = 8) was found to be 1.45%. The methodology was satisfactorily applied for the determination of PQ in citric fruit cultures.