Residue Dynamics of Myclobutanil in Onion

[Aims] myclobutanil is regarded as a fungicide against onion rust with good application prospect.The method for the determination and residue dynamics of myclobutanil in onion has not been reported.The aim is to establish a method for the determination and residue dynamics of myclobutanil in onion.[Methods] gas chromatography-mass spectrum(gc-ms) was used for the determination of the residue dynamics and final residues of myclobutanil in onion in spring.onion samples were extracted with acetonitrile and the extracts were cleaned up by sPe column filled with sax tandem psa,followed by determination using gas chromatography-mass spectrum with selected ion monitor(gc/ms/sim).[Results] The fortified recovery at level of 0.01-0.10 mg/kg ranged from 93.0-107.9%,with relative standard deviation of 2.1-5.6%,and the limit of quantification for myclobutanil in onion was 0.002 mg/kg.The field residue dynamics study showed that the half-lives of myclobutanil in onion was 3.4 d.When the onion was sprayed two to three times with myclobutanil 12.5% ce 62.5 mg a.i./kg and 125.0 mg a.i./kg,at the 7th and 14th day after the last application,the final residues of myclobutanil in onion were 0.003-0.017 mg/kg.[Conclusions] This gas chromatography method was accurate and reliable.The last redisue of myclobutanill in onion in harvest was below the mrl in Japan and met the requirement of export.