A novel carbon nanosphere-based sensor used for herbicide detection

Abstract

Bentazon (BTZ) is a post-emergence herbicide widely applied in different cultures. It is characterized by low adsorption and high solubility in water, which facilitates its penetration and contamination of aquatic environments. Human exposure to BTZ is responsible for numerous toxic effects and, therefore, it is of great importance to develop simple and efficient analytical methods capable of accurately detecting the presence of this herbicide in environmental samples. The present paper reports the development and application of a glassy carbon electrode modified with carbon nanosphere-based cross-linked chitosan film for the voltammetric determination of BTZ herbicide. The incorporation of cetyltrimethylammonium bromide surfactant into the supporting electrolyte solution helped enhance the voltammetric signal and the sensor repeatability. The use of chitosan film crosslinked with epicholorohydrin contributed toward improving the properties of the carbon nanospheres, including the electron transfer rate. A set of assays were conducted aiming optimizing the experimental parameters related to the supporting electrolyte composition (pH and surfactant concentration) and the square-wave voltammetry technique. Under optimized conditions and based on the application of the method proposed in the study, a linear concentration range of 1.99 to 65.4 μ mol L −1 was obtained, with limit of detection of 1.4 μ mol L −1 and sensitivity of 6.22 A mol −1 L cm −2 . The modified electrode presented good intra- (2.8%, n = 10 ) and inter-day (1.4%, n = 5 ) repeatability and high selectivity for bentazon. The optimized electroanalytical technique was successfully applied for the quantification of bentazon in environmental water samples (recoveries close to 100%). • Nanostructuring a glassy carbon surface for herbicide sensing purposes is reported. • A robust modified electrode is designed by immobilizing carbon nanospheres within a cross-linked chitosan film. • Adsorptive effects from bentazon oxidation products are reduced by applying cetyltrimethylammonium bromide. • The optimized voltammetric sensor was successfully applied for bentazon determination at environmental water samples.