Development of thermochemically induced fluorescence (TIF) method for the determination of insecticide deltamethrin in Senegalese natural waters

International audience; A simple and sensitive thermochemically induced fluorescence (TIF) method was developed to determine deltamethrin, an insecticide which has toxic effects on human beings and animals. After optimisation at different pH, temperature was increased from 25 to 50°C. TIF method is based on the thermolysis transformation of naturally non-fluorescent pesticides into a fluorescent thermoproduct. The thermolysis kinetics reaction investigated in water at optimal pH 12 and after 4 minutes heating at 40°C made it possible to obtain a low mean half-life time (t1/2 = 1.41 ± 0.06 min), which shows that deltamethrin degrades very rapidly due to heat. The obtained calibration curve gave correlation coefficients close to unity. The limit of detection (LOD = 4.4 ng mL−1) and quantification (LOQ = 15 ng mL−1) values were very low, showing the high sensitivity of the TIF method. TIF method was applied to determination of deltamethrin residues in tap and well waters by standard addition procedure, with satisfactory recovery values between 107.6 and 111.4%. The relative standard deviation (RSD) value of the measured concentrations in spiked water samples was less than 6%, which demonstrated good reproducibility of the TIF method.