A voltammetric sensor was designed to analyze thiosulfate (TS), 4-chlorophenol (4-CP) and nitrite (NT), which are water pollutants, in mixed samples by combining the high conductive properties of NiO nanoparticle (NiO/NPs) and the excellent mediator properties of novel catechol derivative (2,4-dime thyl-N'-11-(2,3-dihydroxyphenyl)methylidenelaniline). 2,4-Dimethyl-N'-[1-(2,3-dihydroxyphenyl)meth ylidene]aniline was synthesized for the first time and proposed as a high-quality modifier for electrocatalytic analysis of TS and its simultaneous analysis in the presence of 4-CP and NT. At a pH = 6.0 as an optimum condition in electrochemical analysis, we seen the synergic effect for the simultaneous determination of TS, 4-CP and NT in the range of 0.05-400.0 mu M,1.0-600.0 mu M, and 10.0-700.0 mu M, with a limit of detection of 0.01 mu M for TS, of 0.7 mu M for 4-CP, and of 5.0 mu M for NT respectively. (C) 2017 Elsevier Inc. All rights reserved.