Photochemical–spectrofluorimetric method for the determination of several aromatic insecticides

Abstract

Ultraviolet (UV) photolysis was used to obtain fluorescent photoproducts from four naturally non-fluorescent aromatic insecticides, viz., deltamethrin, diflubenzuron, fenitrothion and fenvalerate. The photochemically-induced fluorescence properties of these insecticides in various solvents (acetonitrile, dimethyl sulfoxide, their mixtures with water, methanol, ethanol and propan-2-ol) are reported. The polarity of the solvent was shown to play an important role in the optimum UV irradiation times (8–48 min) and in the increase in the fluorescence intensity. A photochemically-induced fluorescence method was developed for the determination of the four insecticides under study. Linear dynamic ranges were established over more than two orders of magnitude. The limits of detection ranged from 0.7 to 33 ng ml^–1, according to the compound, with relative standard deviations of less than 2.5%. The applicability of the method to the determination of insecticides in technical formulations was evaluated. The mean recoveries ranged from 90.8 to 100.7%, according to the compound.