TRACE-QUAD: A Multiplexed Electrochemical Platform for Ultrasensitive Detection of Diquat, Paraquat, Glyphosate, and Chlorpyrifos in Drinking Water

Pesticide residues in drinking water pose a global health concern, yet on-site screening remains challenging due to complex matrices and co-occurring contaminants. We present READ 2.0, a portable electrochemical impedance spectroscopy (EIS) platform for multiplexed pesticide detection. The system employs a 16-electrode ZnO/Au array on a PCB, where ZnO enhances surface area and enables Schottky barrier formation for antibody immobilization. Quadrant-based functionalization with DTSSP-antibody conjugates allowed simultaneous nonfaradaic detection of paraquat (PQ), diquat (DQ), glyphosate (Glyp), and chlorpyrifos (Chlp). In spiked drinking water, recoveries ranged from 74-110% (PQ, Chlp), 50-74% (DQ), and 54-68% (Glyp), with <10% CV for DQ, Glyp, and Chlp and 10-20% CV for PQ. Cross-reactivity remained below 10%, and classification aligned with regulatory thresholds (macro precision/recall ∼ 0.82, micro F1 = 0.816). READ 2.0 enables compact, low-volume (10 μL/electrode), supporting its potential for rapid, field-based water safety and environmental monitoring.