Impedimetric label-free immunodetection of phenylurea class of herbicides

We report label-free detection of phenylurea herbicides by impedance spectroscopy using class specific anti-diuron antibodies. Gold nanoparticles (∼20 nm), used as signal enhancers cum immobilization matrix, were electrodeposited on carbon screen-printed electrodes (SPE) and functionalized with specific anti-diuron antibodies for the development of bio-interface. Faradic impedance spectroscopy was performed and changes in electrical parameters such as resistance to charge transfer (Rct) and capacitance of double layer (Cdl) were elucidated using Randles model for the equivalent circuit of the electrochemical cell. Rct parameter was used to draw the analytical inference and also for calculating the percentage cross reactivity of diuron antibody with various common analogues. The cross-reactivity was 397% with monuron, 64.2% with linuron and the least (22.9%) with fenuron. The diuron was detected in a label-free manner with a limit of detection equal to 5.46 ng mL−1. The observed response was linear in the useful analytic range of 1–1000 ng mL−1 for the standard diuron detection in water. The obtained results showed good promise for routine label-free monitoring of herbicides in environmental samples.