Pesticide residues analysis of chlorpyrifos- ethyl, penconazole and imidacloprid on Tomato fruits and their stability under environmental conditions

This study was planned to investigate the following points: 1. Persistence of chlorpyrifos, penconazole and imidacloprid residues on and in tomato fruits. 2. Comparison between big and small tomato fruits for the initial deposit of tested pesticides. 3. Determination of the dissipation rates, half-life values and pre-harvest intervals (PHI) for tested pesticides. 4. Investigating the effect of washing with tap water on the removal of the pesticide residues from tomato fruits. 5. Investigating the impact of some environmental factors i.e., ultra-violet and sun light on the persistence of tested pesticides. The initial deposit of chlorpyrifos on unwashed small fruits was higher than that of big fruits, it was 0.427 and 0.3-83 ppm, respectively. The high initial deposit of chlorpyrifos on small fruits may be due to the higher surface area of small fruits than big fruits per one kilogram, which received the spray solution of chlorpyrifos. The half-life values of chlorpyrifos (RL50) on and in unwashed small and big fruits were 4.95 and 4.33 days, respectively. The initial deposit of penconazole on unwashed small fruits was higher than that of big fruits, it was 0.053 and 0.046 ppm, respectively. The obtained residual half-life values of penconazole (RL50) on and in unwashed small and big fruits were 3.65 and 2.89 days, respectively. The initial deposit of imidacloprid on unwashed small fruits was higher than that of big fruits, it was 0.155 and 0.09 ppm, respectively. The estimated half-life values of imidacloprid (RL50) on and in unwashed small and big fruits were 11.55 and 5.33 days, respectively. Washing removed 21.78 and 16.19% of the initial residues of chlorpyrifos found on unwashed small and big fruits, respectively. While for penconazole, the corresponding values were 43.4 and 52.17% and for imidacloprid the values were 27.10 and 15.56%. The calculated half-life periods were 1.47, 1.07 and 6.3 hours for chlorpyrifos, penconazole and imidacloprid, respectively, when exposed to sunlight. Moreover, the dissipating rate of chlorpyrifos was more rapid than penconazole and imidacloprid when exposed to UV-light. The statistical half-life times for chlorpyrifos, penconazole and imidacloprid were 1.05, 1.44 and 3.47 hours, respectively, after exposure to UV-light.