Sensitive Simultaneous Determination of o-Nitrophenol and p-Nitrophenol in Water by Surfactant-Mediated Differential Pulse Voltammetry

Abstract

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 (E_pc) 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 samples.

Keywords:

• Cyclic voltammetry
• differential pulse voltammetry
• glassy carbon electrode
• high-performance liquid chromatography with diode array detection
• nitrophenol isomers
• simultaneous determination
• square wave voltammetry

Additional information

Funding

The authors would like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grant No 481669/2013-2, 305552/2013-9, 307432/2017-3), Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) (Project Pró-Forenses 3353/2014 Grant 23038.007082/2014-03), FAPEMIG, Fundação Araucária do Paraná (163/2014), Instituto Nacional de Ciência e Tecnologia de Bioanalítica (INCT) (FAPESP Grant No 2014/50867-3 and CNPq Grant No 465389/2014-7), Universidade Estadual de Londrina (UEL) for their financial support and fellowships.