Analytical method for the determination of meptyldinocap as the 2,4-dinitro-octylphenol metabolite in cucumber and soil using LC-MS/MS and a study of the residues in a Chinese cucumber field ecosystem

Background: Meptyldinocap (2,4-DNOPC) is a novel powdery mildew (Erysiphe necator) fungicide which shows protectant and post-infective activities. However, there is no reliable validated LC-MS/MS method for measuring trace levels of meptyldinocap in cucumber. A method for the determination of 2,4-DNOPC using LC-MS/MS in cucumber and soil was developed. Additionally, the mode of degradation and the residue levels in cucumbers and soils were investigated.

Results: Recoveries of meptyldinocap from cucumber and soil samples were found to be 81.4-95.1%. The limits of quantification were found to be 0.01 mg kg(-1) in cucumber and soil. The half-lives of metpyldinocap in cucumbers and soils were in the ranges of 1.6 to 2.2 days and 3.1 to 4.4 days. The harvest residue levels of meptyldinocap in cucumbers and soils were in the ranges of below 0.01 mg kg(-1) to 0.92 mg kg(-1) , and below 0.01 mg kg(-1) to 0.53 mg kg(-1) . 5 days after application; the harvest residue levels of meptyldinocap in cucumbers in all treatments were below 0.1 mg kg(-1) .

Conclusion: Compared with the MRL for meptyldinocap in cucumber (0.1 mg kg(-1) ), set by the EU, it is suggested that there should be a pre-harvest interval of 5 days at the recommended rate and times before harvest of cucumber.