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In this study, a carbon paste electrode modified with TiO2 nanoparticles and ferrocene monocarboxylic acid (FM) was used to prepare a novel electrochemical sensor. The objective of this novel electrode modification was to seek new electrochemical performances for the detection of methyldopa in the presence of folic acid and glycine. The peak potentials recorded in a phosphate buffer solution (PBS) of pH7.0 were 325, 750 and 880mV vs. Ag/AgCl/KCl (3.0M) for methyldopa, folic acid and glycine, respectively. Under the optimum pH of 7.0, the oxidation of methyldopa occurred at a potential about 160mV less positive than that of the unmodified carbon paste electrode (CPE). The response of catalytic current with methyldopa concentration showed a linear relation in the range from 2.0×10−7 to 1.0×10−4 M with a detection limit of 8.0 (±0.2)×10−8 M. [ABSTRACT FROM AUTHOR]

In the present study, a carbon paste electrode chemically modified with gold nanoparticles was used as a sensitive electrochemical sensor for determination of eugenol. The differential pulse voltammetric method was employed to study the behavior of eugenol on this modified electrode. The effect of variables such as percent of gold nanoparticles, pH of solution, accumulation potential and time on voltammogram peak current were optimized. The proposed electrode showed good oxidation response for eugenol in 0.1 mol L − 1 phosphate buffer solution (pH 8) and the peak potential was about + 285 mV (vs. Ag/AgCl). The peak current increased linearly with the eugenol concentration in the range of 5–250 μmol L − 1 . The detection limit was found to be 2.0 μmol L − 1 and the relative standard deviation was 1.2% (n = 7). The effect of interferences on the eugenol peak current was studied. The method has been applied to the determination of eugenol in different real samples, spiked recoveries were in the range of 96%–99%. [ABSTRACT FROM AUTHOR]