Development and Validation of an Amphibious Drone-Based In-Situ SPE System for Environmental Water Monitoring

To improve the efficiency of aquatic environmental monitoring, an in-situ solid-phase extraction (SPE) system using amphibious (waterproof) drones was developed and validated using recovery testing with samples containing known concentrations of systemic insecticides in the laboratory and using real samples from natural water bodies. The system used a water-resistant linear actuator for continuous aspiration at 1–10 mL min−1 through a pre-washed hydrophilic–lipophilic balanced SPE cartridge. The system functioned properly during field sampling using vacuum-mode filtration to avoid overpressure, overcurrent, and contamination through repeated filtration. The recovery tests using 10 ng L−1 of each target analyte in ultra-pure water samples produced satisfactory recovery results of 89–96% (relative standard deviation < 10%). In the real sampling of water bodies, the developed system was able to detect target analytes of 0.9–180 ng L−1. The results are comparable to those obtained using in-situ manual SPE from boat sampling, irrespective of differences in the two aspiration systems. These findings suggest that the application of the developed drone-assisted in situ SPE system can improve the efficiency of real-sample monitoring of natural water bodies.