Abstract:

The residual dynamics of imidacloprid in tomatoes was investigated and the best solid-phase extraction column was selected for the HPLC-MS analysis of imidacloprid. Meanwhile, a comparative study of commonly used methods for removing residual imidacloprid from tomatoes was performed. A HPLC-MS analytical method based on extraction with acetonitrile and clean-up on a NH2 solid-phase extraction column was developed for the determination of imidacloprid residue in tomatoes. There was a good linear relationship between the peak area and concentration of imidacloprid over the range from 0.01 to 2 mg/L, and the linear equation was Y = 69582.5 X + 68.9, with a correlation coefficient of 0.9999. The mean recoveries of the method varied from 87.5% to 96.5% with a relative standard deviation ranging from 1.7% to 6.7% at four fortification levels in the range from 0.01 to1.0 mg/kg, and the limit of detection was 0.01 mg/kg. This method is characteristic of simplicity, rapidity and accuracy. The degradation dynamics suggested that imidacloprid degraded gradually with prolonged time, that the degradation dynamic curve complied with first-order kinetics equation, and that the half-life of imidacloprid in tomatoes was 3.48 day. Rinsing with tap water, hot water or detergent was employed to remove imidacloprid residue. The results revealed imidacloprid residue reduction could be attained to a certain extent, whereas the effectiveness of rinsing with hot water and detergents was not superior to that of rinsing with tap water.

Key words: imidacloprid, tomato, high-performance liquid chromatography, residual dynamics, removal of pesticide residues