Photochemically-Induced Fluorescence (PIF) and UV-vis Absorption Determination of Diuron and Metalaxyl in Well Water, Kinetic of Photodegradation and Rate of Leach Ability in Soils.

Aromatic pesticides are toxic substances for the environment and humans. In this study, the photodegradation kinetics, the rate of leach ability in soils and the analytical determination of diuron and metalaxyl residues in well water by liquid-liquid extraction procedure have been determined by UV-visible absorption and photochemically-induced fluorescence (PIF). We studied the photodegradation kinetics by UV-visible absorption spectroscopy and a second-order kinetics with lifetime values of 6.0 and 0.5 hours was found in water for metalaxyl and diuron, respectively. Physicochemical parameters affecting the sensitivity of the PIF method, such as solvent, pH and UV irradiation time were investigated. PIF method was then performed in optimal analytical conditions. The limits of detection (LOD) ranging from 3.2 to 14 ng mL⁻¹ were particularly low and the small relative standard deviation (RSD) (< 4 %), indicated a very good analytical sensitivity and a great repeatability of PIF method. Then, an investigation the pesticides leach ability was conducted in agricultural soil. We obtained rates of infiltration of 12.7 mm/min for diuron and 1.6 mm/min for metalaxyl. These results showed that both pesticides have high groundwater pollution potential. Finally, application to the analysis of these pesticides in spiked well water samples yielded satisfactory recovery values (87-108 %). [ABSTRACT FROM AUTHOR]