RESUMEN
A simple hydrodynamic chronoamperometric method based on the application of an unmodified carbon paste electrode (CPE) and bulk-modified with different contents of MnO2 was investigated for the determination of H2O2. The optimized method involving the CPE with 5% of MnO2 was applied for the determination of the H2O2 consumption in samples of groundwater from the Central Banat region (Province of Vojvodina, Serbia) treated by the Fenton (Fe(2+) and H2O2) and Fenton-like (Fe(3+) and H2O2) reagents to remove natural organic matter at different initial concentrations of iron species, and of their ratios to the initial concentration of H2O2. Under optimized conditions, with a working potential of 0.40V vs. the saturated calomel electrode and a phosphate buffer solution (pH 7.5) as supporting electrolyte, the method enabled the quantitation of H2O2 in the concentration interval from 1.4 to 65 µg mL(-1) with a relative standard deviation of less than 10%. The results obtained for the H2O2 consumption are in good agreement with those obtained by parallel measurements related to the efficiency of organic matter removal.
Asunto(s)
Restauración y Remediación Ambiental/métodos , Agua Subterránea/química , Sustancias Húmicas/análisis , Peróxido de Hidrógeno/análisis , Hierro/química , Compuestos de Manganeso/análisis , Compuestos de Manganeso/química , Óxidos/análisis , Óxidos/química , Contaminantes Químicos del Agua/química , Carbono/química , Electrodos , Hidrodinámica , Peróxido de Hidrógeno/química , SerbiaRESUMEN
Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE) and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV) mode was applied to determine clothianidin in the concentration range from 2.5 to 23 µg cm⻳ with a relative standard deviation (RSD) not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs), bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 µg cm⻳ with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.