<p>A novel analytical system for the determination of amino phenols (AP) in environmental samples is schemed using peroxidase mimetic CoFe₂O₄ nanoparticles with para-phenylenediamine dihydrochloride (PPDD) and hydrogen peroxide. In the presence of catalytically active NPs, the PPDD gets oxidized to 1, 4-diimine, which undergoes electrophilic substitution with AP to form a red chromogenic product, which shows a maximum absorbance at 500&#xa0;nm. CoFe₂O₄ nanoparticles were synthesized by the sol-gel method, followed by characterization with X-ray diffraction (XRD), a Fourier transform infrared spectrophotometer (FTIR), and scanning electron microscopy (SEM). It has a paramount impact on the assay of aminophenols from 0.14 to 19.06 µM. The Michaelis-Menten constant and Vmax of the nanozyme were found to be 1.1 mM and 0.248&#xa0;min^− 1, respectively. Catalytic power and catalytic efficiency of the synthesized nanoparticles were evaluated and found to be 3.26&#xa0;min^− 1 and 0.652 × 10⁶ M^− 1min^− 1, respectively. The molar absorptivity and Sandell’s sensitivity were 1.04 × 10⁴ Lmol^− 1cm^− 1 and 0.0104&#xa0;g^− 1cm², respectively, with a limit of detection of 0.04 µM. The reaction conditions and other analytical parameters were optimized to improve the sensitivity of the methods. The method is simple, sensitive, and rapid, works in a broad range of temperatures and pH, and its applicability has been tested in different water samples.</p>