Sensitive simultaneous determination of o-nitrophenol and p-nitrophenol in water by surfactant-mediated differential pulse voltammetry

A simple, low-cost and sensitive electroanalytical method was developed for the simultaneous determination of p-nitrophenol and o-nitrophenol isomers in water samples at a glassy carbon electrode (CGE) in the presence of cationic surfactant. The electrochemical behavior of p-nitrophenol and o-nitrophenol was studied by cyclic voltammetry (CV) in 0.1 mol L−1 acetate/acetic acid buffer (pH 3.70) in the presence and absence of cetylpyridinium bromide. The resolution of overlapped cathodic peaks potentials (Epc) of isomers was successfully improved in the presence of 100.0 µmol L−1 cetylpyridinium bromide, thus making this approach ideal for the simultaneous determination of isomers. Under the optimized conditions in 0.05 mol L−1 HEPES buffer at pH 7.0 using differential pulse voltammetry (DPV) at a scan rate of 45 mV s−1, pulse amplitude of 220 mV and modulation time of 10 ms, limits of detection 0.59 µmol L−1 for p-nitrophenol and 1.14 µmol L−1 for o-nitrophenol were obtained with linear ranges from 2.0 to 60.0 µmol L−1 and 3.0 to 60.0 µmol L−1, respectively. The intraday precision was assessed as relative standard deviation (%) for 20.0 and 40.0 µmol L−1 concentrations were 4.30% and 2.41% for p-nitrophenol and 4.87% and 2.20% for o-nitrophenol, respectively. The developed method was applied for the determination of the isomers in lake water samples. The accuracy was attested by comparison with high-performance liquid chromatography with diode array detection (HPLC-DAD) as a reference analytical technique. Recovery values ranging from 90.3% to 111.8% also attested to the accuracy of method for analysis of real samples52914621476CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE MINAS GERAIS - FAPEMIG481669/2013-2; 305552/2013-9; 307432/2017-3; 465389/2014-73353/2014; 23038.007082/2014-03163/201