Photo-induced fluorescence properties of the propanil herbicide and analytical usefulness

The photo-induced fluorescence (PIF) spectral properties of propanil, a contact anilide herbicide were investigated. In the PIF approach, non-fluorescent propanil was transformed by UV irradiation into strongly fluorescent photo-product(s). The effect of solvents, including water, methanol, methanol-water binary mixtures and cyclohexane, on the propanil PIF properties was studied, and several PIF parameters (irradiation time, excitation and emission wavelengths, medium) were optimized. As a result, the analytical usefulness of a simple, sensitive and precise PIF analytical method was demonstrated for the determination of propanil. The best PIF analytical performances were obtained in an 80/20% v:v methanol/water mixture, with a wide linear dynamic range (LDR) of nearly three orders of magnitude, low limit of detection (LOD) and limit of quantification (LOQ) values of, respectively, 1.3 and 4.7 ng mL −1, and a small relative standard deviation (RSD) of 1.3%. The optimized PIF method was applied to the estimation of propanil residues in various spiked natural water samples, collected in the Senegal River valley, with satisfactory recovery percentage values (97-117%). An interference study of several foreign species, including pesticides and inorganic ions, likely to be present in the Senegal natural waters, was also performed.