Preparation of a double-step modified carbon paste electrode for the voltammetric determination of propham via bulk modification with fumed silica and drop-casting of maghemite-modified fumed silica nanocomposite

Abstract

In this study, a double-step modified carbon paste electrode (CPE) was prepared for the voltammetric determination of propham (PRO). In the first step, modification of CPE was performed by incorporating 12.5% fumed silica (FS) into paste structure to obtain CPE-12.5FS. In the second step, CPE-12.5FS electrode was modified with drop-casting of maghemite-modified FS (MH@FS) dispersion to prepar CPE-12.5FS/MH@FS. The proposed modification process combined the advantages of both bulk modification and drop-casting techniques and showed synergistic effect on the voltammetric behaviour of the electrode. The electrode was characterized with cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy and X-ray diffraction analysis were used in the characterization of MH@FS. Electrode preparation and measurement conditions were optimized. The highest peak current for the oxidation of PRO was obtained at pH 6. PRO showed an irreversible oxidation on CPE-12.5FS/MH@FS. A linear relationship was obtained between oxidation peak current and PRO concentration in the range of 0.01 mu M and 5.0 mu M. The limit of detection value was calculated to be 4.4 nM. Measurement and fabrication reproducibility of the modified electrode was obtained as 2.95% (N:9) and 4.80% (N:6), respectively. The CPE-12.5FS/MH@FS allowed determining PRO in the presence of the carbamate pesticides of carbofuran and carbaryl. The determination of PRO in real samples such as potato, urine and river water was successfully tested with CPE-12.5FS/MH@FS. The results showed that the electrochemical sensor could be a very promising alternative to other methods of determining PRO