This work illustrates a fast, sensitive and selective electroanalytical methodology for simultaneous determination of phenolic derivatives. Optimization of differential pulse voltammetry (DPV) conditions and electrochemical study by cyclic voltammetry (CV) of phenolics are included. Differential pulse voltammetry at screen-printed carbon electrodes (SPCE) was selected for the sensitive detection of m-Cresol and Tert-butylhydroquinone. The introduction of Multi-walled Carbon-Nanotubes with acid groups, MWCNT-COOH, as modifier on working SPCE enhances the performance of electrode surface with a highly catalytic activity on it, allowing a 5-fold higher sensitive analysis than unmodified SPCE, with a limit of detection as low as about 1 mu M. This simple and low-cost methodology has been applied, for first time, to monitoring the electro-Fenton degradation of m-Cresol, giving selective information of the reactant loss and products formation. Aromatic intermediates (monohydroxy, polyhydroxy and quinone phenolic derivatives) have been identified and followed during the electrolysis process. The electro-Fenton with iron on activate carbon is 4-fold faster than with other catalyst. The results are validated by chromatographic (HPLC) technique. The electroanalytical methodology described, in conjunction with the use of small SPCE as sensor transducer, can be implemented for continuous monitoring of end-point of the electro-Fenton reaction at industrial level in wastewater remediation plants, indicating the two main stages of electro-Fenton during the electrolysis. (C) 2015 Elsevier B.V. All rights reserved.