Thesis (Ph.D.)--Chulalongkorn University, 2013

Simultaneous determination of two pesticides, isoproturon and carbendazim, as the potentially hazardous compounds, by square wave anodic stripping voltammetry using graphene modified screen-printed electrodes was developed. The operational parameters, in terms of the graphene content of the working electrode, type and concentration of supporting electrolyte, applied sample volume, initial scan potential, accumulation potential, accumulation time, and square wave parameters, were optimized using a univariate approach. Under these optimal conditions, isoproturon and carbendazim yields well-defined oxidation peak. It is found that the graphene exhibits obvious activity toward the oxidation of isoproturon and carbendazim since it not only increases the oxidation peak current but also lowers the oxidation potential. The analytical characteristics of the proposed method were then evaluated. A linear detection was obtained in the range of 0.02 - 10.0 mg/L (R² = 0.9991) for isoproturon and 0.50 - 10.0 mg/L for carbendazim (R² = 0.9990), with the limits of detection and quantification being 0.02 and 0.07 mg/L for isoproturon and 0.11 and 0.38 mg/L for carbendazim, respectively. In addition, the relative standard deviations of detection between ten electrodes were 9.2 and 10 % for isoproturon and carbendazim, respectively, whilst satisfactory recoveries were obtained in the analysis of isoproturon and carbendazim in spiked water, soil and vegetable samples (81.4–107%). Consequently, the proposed method showed a great promise as an inexpensive and simple electrode, with additionally a shorter analysis time.