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 (E-pc) of isomers was successfully improved in the presence of 100.0 mu mol 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 mu mol L-1 for p-nitrophenol and 1.14 mu mol L-1 for o-nitrophenol were obtained with linear ranges from 2.0 to 60.0 mu mol L-1 and 3.0 to 60.0 mu mol L-1, respectively. The intraday precision was assessed as relative standard deviation (%) for 20.0 and 40.0 mu mol 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.