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 (similar to 20 nm), used as signal enhancers corn 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 (R-ct) and capacitance of double layer (C-dl) were elucidated using Randles model for the equivalent circuit of the electrochemical cell. R-ct 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. (c) 2012 Elsevier B.V. All rights reserved.