From pixels to precision: Colorimetric Paraquat detection with a mobile-based green method

Pesticide residues pose a threat to food and environmental safety due to their excessive application in agriculture as a tool for pest management and control, aiming to increase productivity and meet food demand. In this context, paraquat is one of the most commonly used pesticides in agriculture; however, when its residues are present in food, it increases toxicity. Thus, this study aims to propose a new approach for the determination of paraquat in food, employing a colorimetric methodology that is both sensitive and selective using digital images obtained by a smartphone and the Colorgrab® application. The proposed method was applied to fruit and vegetable samples, in which accuracy was evaluated, obtaining recoveries with agreement between 95 and 107 % compared to the conventional method (Spectrophotometry in the UV-vis region). The method demonstrated high analytical performance, with limits of detection (LOD) ranging from 0.127 to 0.164 mg kg^-1 and limits of quantification (LOQ) between 0.423 and 0.547 mg kg^-1, across all tested matrices. To assess the environmental impact concerning the principles of green chemistry, the Green Analytical Procedure Index (GAPI) was evaluated to determine if the methodology aligns with the principles of green chemistry. Therefore, the proposed method proved to be a suitable alternative with analytical capability for the quantification of paraquat. It also promoted the miniaturization of the analytical procedure and can be considered an accessible, easily applicable, and environmentally friendly tool for food quality control.