Square wave voltammetric detection by direct electroreduction of paranitrophenol (PNP) using an organosmectite film-modified glassy carbon electrode

• Cethyltrimethylammonium ions were used to modify a smectite-type clay.
• The organoclays were fully characterised and exploited as sensing material for the electroanalysis of PNP.
• The developed sensor was optimized and allowed the determination of PNP with a detection limit of 3.75×10−8 M.

This work describes the development of a low-cost and reliable adsorptive stripping voltammetric method for the detection of PNP in water. Organoclays were prepared by intercalation in various loading amounts of cetyltrimethylammonium ions (CTA+) in the interlayer space of a smectite-type clay mineral. Their structural characterization was achieved using several techniques including X-ray diffraction (XRD), N2 adsorption–desorption (BET method) and Fourier Transform Infrared spectroscopy (FTIR) that confirmed the intercalation process and the presence of the surfactant ions within the clay mineral layers. Using [Fe(CN)6]3− and [Ru(NH3)6]3+ as redox probes, the surface charge and the permeability of the starting clay mineral and its modified counterparts were assessed by multisweep cyclic voltammetry, when these materials were coated on the surface of a glassy carbon electrode (GCE). In comparison with the bare GCE, the organoclay modified electrodes exhibited more sensitive response towards the reduction of paranitrophenol (PNP). Under optimized conditions, a calibration curve was obtained in the concentration range from 0.2 to 5.2 µmol L−1; leading to a detection limit of 3.75×10−8 mol L−1 (S/N=3). After the study of some interfering species on the electrochemical response of PNP, the developed sensor was successfully applied to the electroanalytical quantification of the same pollutant in spring water.

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