Abstract: Broccoli is a typical vegetable for both domestic consumption and exportation. Chlorpyrifos, phoxim, and indoxacarb are 3 pesticides used widely in plant protection. Field experiments were conducted to study the residues and dissipation dynamics of these pesticides in broccoli flowers and leaves, with 1 time and 1.5 times the recommended use dosage, under greenhouse and open field conditions. The samples were treated by the QuEChERS method and the liquid chromatography-tandem mass spectrometry (LC-MS/MS) detection. The method validation results showed that, with the concentrations of 0.02, 0.2, and 1 mg/kg, the recovery rates of chlorpyrifos, phoxim, and indoxacarb were 85.8%-101.0%,90.8%-105.3%, and 86.1%-107.5%, respectively. The limit of detection (LOD) and limit of quantification (LOQ) were 0.006 and 0.01 mg/kg, respectively. The results showed that the method meets the detection requirement. The dissipation results showed that, in broccoli flowers, the half-lives were 5.53-7.20 d for chlorpyrifos, 3.55-3.92 d for phoxim, and 6.11-7.73 d for indoxacarb. While, in broccoli leaves, the half-lives were 4.33-6.93 d for chlorpyrifos, 3.85-5.77 d for phoxim, and 3.85-5.33 d for indoxacarb. In soil, the half-lives were 23.1-34.6 d for chlorpyrifos, 23.1-34.6 d for phoxim, and 17.3-23.1 d for indoxacarb. The final residues showed that, for these 3 pesticides, the residues in broccoli leaves were higher than these in broccoli flowers. With the trial application dosage, the final residues of chlorpyrifos and indoxacarb were lower than the MRLs in EU, Japan, and CAC. While for phoxim, the final residues with higher application dosage exceeded the MRLs.

Key words: chlorpyrifos, phoxim, indoxacarb, broccoli, dissipation dynamics