The conductive composite Co@SnO2–PANI was successfully synthesized using hydrothermal/oxidative synthesis. Using differential pulse voltammetry, a glassy carbon electrode modified with a CoSnO2–PANI (polyaniline)-based electrochemical biosensor has been created for the quick detection of two phenolics, hydroquinone (Hq) and catechol (Cat). Differential pulse voltammetry (DPV) measurements revealed two well-resolved, strong peaks for GCE@Co–SnO2–PANI, which corresponded to the oxidation of Hq and Cat at 275.87 mV and +373.76 mV, respectively. The oxidation peaks of Hq and Cat mixtures were defined and separated at a pH of 8.5. High conductivity and remarkable selectivity reproducibility was tested by electrochemical impedance spectroscopy, chronoamperometry, and cyclic voltammetry techniques in standard solution and real water samples. The proposed biosensor displayed a low detection limit of 4.94 nM (Hq) and 1.5786 nM (Cat), as well as a large linear range stretching from 2 × 10−2 M to 2 × 10−1 M. The real-sample testing showed a good recovery for the immediate detection of Hq (96.4% recovery) and Cat (98.8% recovery) using the investigated sensing apparatus. The synthesized biosensor was characterized by XRD, FTIR, energy dispersive spectroscopy and scanning electron microscopy.
