Abstract:

An analytical method using QuEChERS extraction and GC-MS/MS (gas chromatography coupled with tandem mass spectrometry)was established for analysis of myclobutanil residues in cowpea and soil of the field, and initial deposition and degradation dynamics of myclobutanil in cowpea and soil of the field was also investigated in a field experiment. Results show that response value of the instrument was in linear relationship with concentration of myclobutanil in the range of 0.001-2 mg·kg^-1, and LOD of the instrument was 8×10^-12 g. Myclobutanilin cowpea and soil samples were extracted with acetonitrile, purified with SPE Bond Elut-Fl columns and determined with GC-MS/MS. When myclobutanil content in the cowpea and soil samples was in the range between 0.05-2 mg·kg^-1, the mean recovery rate reached 86.6%-105.4% with relative standard deviation being 3.0%-7.0%, which means the method satisfies the requirements for detection of myclobutanil residue in cowpea and soil in accuracy, precision and sensitivity. The field experiment shows that the deposition of myclobutanil in cowpea in the initial phase was not significant and differed slightly from that in the soil. The half-life of the substance in cowpea and soil ranged of 3.1-4.3 and 10.5-12.1 d and the growth-dilution effect of cowpea and precipitation are two dominant factors leading to variation of degradation rate of the substance in different regions.

Key words: myclobutanil, cowpea, soil, residue, initial deposition, degradation dynamics