Dynamics and residues of chlorpyrifos and dichlorvos in cucumber grown in greenhouse

The dynamics and residue contents of chlorpyrifos and dichlorvos in cucumber grown in greenhouse were investigated. The pesticides were applied at cucumber with different doses and spraying times. Analysis was carried out by liquid chromatography-tandem mass spectrometry. The degradations of chlorpyrifos and dichlorvos applied at 1.5 times recommended dose and 1 spraying times in cucumber coincided with Ct = 0.0753e−0.433t, Ct = 0.235e−0.199t, respectively. The half-lives obtained were 1.60 days for chlorpyrifos and 3.48 days for dichlorvos. When the cucumber treated with pesticides at the recommended doses and spraying times, the residues of chlorpyrifos was 0.036 mg kg−1 with 1 days interval which below the MRL established by EU, UK and Japan, dichlorvos was 0.008 mg kg−1 with 5 days interval which below the MRL established by EU and UK. When cucumber treated with pesticides at 1.5 times recommended dose or/and one more recommended spraying times, the residues of chlorpyrifos and dichlorvos were below MRLs with 5 or more days interval. Compared with 1.5 times recommended dose, the residue contents of chlorpyrifos and dichlorvos influenced more by one more recommended spraying times.

► The behaviors of chlorpyrifos and dichlorvos in greenhouse cucumber were studied. ► The half-lives were 1.60 and 3.48 days for chlorpyrifos and dichlorvos respectively. ► Cucumbers with pesticides used at normal case should be harvest with 5 days interval. ► The residues and harvest interval are closely related to spraying times and dose.