Residues and decline study of etoxazole in apple and soil by gas chromatography-mass spectrometry method

A gas chromatography-mass spectrometry (GS-MS) method was developed for determining etoxazole residues in apple and soil. The soil samples were extracted with acetone and the apple samples were estracted with a mixture of proportionate acetone and ethyl acetate(1 :1,V/V). All the samples were tested by GC-MS without cleanup. Results showed that the ranges of average recoveries and relative standard deviations of the method were 93% to 96% in apple and 91% to 104% in soil, 2.8% to 8.0% in apple and 0.70% to 8.3% in soil respectively, at fortified levels of 0.01 to 1 mg/kg. The limit of detection was estimated to be 0.001 ng, and the limit of quantification was 0.01 mg/kg. International codex alimentarius commission (CAC), China and the United States do not stipulate the MRL of etoxazole in apple but the MRL is 2.0 mg/kg in Japan. Refer to the stipulation, sprayed with high dosage of 30 mg(a.i.)/L for etoxazole 150 g/L EW, the results of residue dynamics indicated that the half-lives of etoxazole in apple and soil were 7.4-14.2 d and 4.2-18.1 d, respectively. Terminal residues in apples were less 1.65 mg/kg after 21 days.