Disposable carbon electrodes as an alternative for the direct voltammetric determination of alkyl phenols from water samples

Disposable sensors based on a pencil graphite electrode were described for detection of alkyl phenols. The performances of the disposable bare pencil graphite electrode (PGE) and PGE modified with carbon nanotubes, regarding the cyclic and differential pulse voltammetric determination of 4-nonylphenol, 4-octylphenol, and 4-tert-octylphenol, were compared. Some experimental variables of the electrode surface pretreatment and measurement parameters were optimized. Using a phosphate buffer solution (pH 7.40) as the supporting electrolyte, alkyl phenols gave a well-defined oxidation peak at about 700 mV vs. Ag/AgCl. The detection limits established for each alkyl phenol were: 0.25 μM for 4-octylphenol, 0.42 μM for 4-nonylphenol, and 0.77 μM for 4-tert-octylphenol. This method is suitable for the direct determination of the total content of these pollutants found at micromolar levels in water samples. The results obtained applying this method are in good agreement with those obtained by high-performance liquid chromatography. The developed sensor has shown some advantages such as low cost, sensitivity, and capability to generate reproducible results using a simple and direct electrochemical protocol. By using this type of commonly available disposable working electrode and a portable electrochemical analysis system, the developed method can be applied to the determination of alkyl phenols directly at the sampling point.