Determination of H2O2 by MnO2 modified screen printed carbon electrode during Fenton and visible light-assisted photo-Fenton based removal of acetamiprid from water.

In this work, the applicability of screen printed carbon electrode bulk modified with MnO 2 as a mediator was investigated for hydrodynamic chronoamperometric determination of the H 2 O 2 content during the Fenton (Fe 2 + , H 2 O 2 ) and the catalytic, visible light-assisted, photo-Fenton (Fe 2 + , H 2 O 2, hν) based removal of the worldwide used neonicotinoid insecticide acetamiprid which has a pyridine ring and a cyano-imine group in its basic skeleton. For the optimisation of the analytical method cyclic voltammetric, differential pulse voltammetric and hydrodynamic chronoamperometric experiments were performed in model solutions containing the phosphate buffer supporting electrolyte pH 7.5, H 2 O 2 , and/or Fe 2 + and acetamiprid. Under optimized conditions at the working potential of 0.40 V vs. saturated calomel electrode in the slightly alkaline supporting electrolyte, electrocatalytic hydrodynamic chronoamperometric determination of H 2 O 2 showed a linear dynamic range from 0.01–1.24 mM, and the relative standard deviation did not exceed 4.2%. In the investigated samples (after appropriate pH adjustment, filtering, and storage of the deep-frozen sample with defrosting immediately before the measurements) the H 2 O 2 contents were determined from the hydrodynamic chronoamperometric curves by the standard addition method. Parallel HPLC-DAD measurements were performed to monitor the concentration/removal of acetamiprid. In the case of the photo-Fenton process (initial concentrations: 0.31; 2.0 and 3.0 mM of acetamiprid, Fe 2 + and H 2 O 2 , respectively) after 10 min of irradiation H 2 O 2 was consumed, while during the Fenton process acetamiprid was removed after 20 min of treatment and around 10% of the initial concentration of the H 2 O 2 remained still unused. [ABSTRACT FROM AUTHOR]