Abstract

Amitrole [3-amino- 1,2,4 triazol] is an herbicide wildly used in agricultural practices as a mixed formulation with other pesticides. The Environmental Protection Agency (EPA) prohibited the use of amitrole in food crops due to its proven carcinogenetic effects on animals. Moreover, its good solubility in water may lead to its leaching into the environment, thereby polluting both ground and surface waters. The electrochemical biosensors are used as good tools for pollutants screening and detection as they are fast, simple and cost effective. Here, the main gol was construction of a DNA-biosensor for the detection of amitrol. With fuctionalization of a pencil graphite electrode with salmon sperm ds-DNA, the sensitivity and selectivity of the sensor was increased. The interaction of amitrole and salmon sperm ds-DNA was studied using UV–Vis, electrochemical impedance spectroscopy and differential pulse voltammetry (DPV) at both bare and DNA-modified pencil graphite electrodes. Amitrole showed an oxidation peak around 0.5 V vs. Ag/AgCl (reference electrode) at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV–Vis spectra showed that the absorption intensity of the ds-DNA at 260 nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs–CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025 to 2.4 ng mL^–1 amitrole with a detection limit of 0.017 ng mL^–1. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity.