This study reports a tetrasulfonated nickel phthalocyanine complex (p-NiTSPc) modified carbon fiber microelectrode (CFME) for the detection of 3-methyl-4-nitrophenol (MNP) at low potentials. The voltammogram of MNP showed a cathodic peak at −0.86 V vs Ag/AgCl corresponding to the reduction of the nitro group. An electrocatalytic activity towards the MNP redox process was observed in the presence of p-NiTSPc. The effects of support electrolyte pH, frequency, scan increment, and pulse amplitude on square wave voltammetry (SWV) peak current were studied and optimized to improve the sensor’s electrochemical response. With these optimized parameters, the calibration curve showed that the peak current increased linearly with MNP concentration, with a limit of detection (LoD) of 0.025 µg/L. Therefore, we report, for the first time, an electrochemical LoD of MNP below 0.1 µg/L, the current regulatory limit for drinkable water.

3-Methyl-4-Nitrophenol, Carbon Fiber Ultramicroelectrode, Nickel Tetrasulfonated Phthalocyanine, Direct Electrochemical Analysis, Square Wave Voltammetry