The dissipation rates of myclobutanil and residue analysis in wheat and soil using gas chromatography-ion trap mass spectrometry

Abstract

The dissipation of myclobutanil (triazole fungicide) in wheat plant, grain and soil under the local weather and soil conditions was studied and fungicide residues were determined by GC-ITMS. Myclobutanil (25% EC) was applied at two dosages, 60 g a.i. ha−1 (recommended) and 120 g a.i. ha−1 (2 times of the recommended dosage) in the experimental fields in Shandong, Beijing and Henan provinces (experimental localities). The detection limit (LOD) and the limit of quantification (LOQ) of myclobutanil were 0.6 µg kg−1 and 2 µg kg−1 respectively, and they were much below the maximum residue limit (MRL 0.02 mg kg−1) in the EU. The average recoveries were 76.4–97.7, 82.6–92.6 and 75.0–94.4% with relative standard deviation (RSD) of 6.3–15.9, 3.8–17.3 and 3.0–19.7% in wheat plant at four spiking levels (0.01, 0.1, 0.5, 10 mg kg−1), wheat grain at four spiking levels (0.005, 0.01, 0.1, 10 mg kg−1) and soil at five spiking levels (0.002, 0.01, 0.1, 0.5, 10 mg kg−1), respectively. The results showed that the half-lives of myclobutanil in wheat plant and soil from Shandong, Beijing and Henan were 3.5–4.5 and 11.0–11.7 days, respectively. At harvest, wheat grain samples were found to contain myclobutanil well below the MRL following the recommended dosage and the interval of 20 days after last application.