Deployment of Solid-Supported Natural Deep Eutectic Solvents via Unmanned Aerial Vehicles to Preconcentrate Contaminants from Environmental Water Samples

A simple analytical methodology for extraction and electroanalytical detection of 2-nitrophenol in water is herein presented. The method is based on the preconcentration of the model contaminant on a solid support (sponge) soaked in hydrophobic natural deep eutectic solvents (decanoic acid and menthol) and deployed using an adapted unmanned aerial vehicle. The subsequent analysis was performed electrochemically via square wave voltammetry and boron-doped diamond electrodes. Under optimized conditions, the proposed approach required dipping the sponge impregnated with a hydrophobic NADES in the water sample for only 5 min (well under the autonomy of the drone) and led to a linear range of 0.0250–35.0 μmol L–1 and a limit of detection of 2.8 nmol L–1. Competitive recovery assays (99 ± 5%) as well as intraday (1.62%) and interday (2.60%) were also obtained, supporting the feasibility of the proposed analytical approach. Moreover, the interferent assays were performed using cations and anions commonly found in environmental waters, which showed no significant effects.