| The flowering Chinese cabbage?Brassica campestris L. ssp. chinensis var. utilis Tsen. et Lee ev Cuilü 80 d? was grown in soil culture.The plants were exposed to different concentrations of Propiconazole(0 mg·kg-1, 50 mg·kg-1, 75mg·kg-1). The final residue,dynamics of digestion and safety evaluation of the propiconazole were studied in flowering Chinese cabbage.The results are as follows:1. The analytical method was using UPLC-MS/MS for the detection of the residues of propiconazole in flowering Chinese cabbage and soil. The samples of Chines cabbage and soil were extracted with ethyl acetate. According to national standards, ‘GBT 20769-2008'choosing the propiconazole precusor ion/product ion transition were m/z 342/159 and m/z342/273 at the model of multi-reaction monitor and m/z 342/159 was used for qualification.In the three levels of 0.05 mg·kg-1, 0.1 mg·kg-1and 0.5 mg·kg-1the average recoveries of this method in the leaves of flowering Chinese cabbage ranged from 85.782% to 91.03%, in the stems of flowering Chinese cabbage ranged from 81.524% to 85.874%,in the soil ranged from 86.738% to 92.04%. The relative standard deviation of this method in the leaves of flowering Chinese cabbage ranged from 5.49% to 8.04%, the relative standard deviation of this method in the stems of flowering Chinese cabbage ranged from 5.12% to7.11%,the relative standard deviation of this method in the soil ranged from 4.46% to7.96%. The sensitivity,accuracy and precision of the method well satisfied the essential rules of pesticide residue determination.2. The results of residual dynamics of propiconazole in the leaves of flowering Chinese cabbage,in the stems of flowering Chinese cabbage and soil showed that:propiconazole dissipateted law was slow after the first fast, the content of it decayed over time, the degradation dynamics of propiconazole accorded with the kinetic equation: C =Coek. The average raw residue of propiconazole in the stems of flowering Chinese cabbage was 0.311 mg·kg-1, the half-life of it was 7.8 d; the average raw residue of propiconazole in the leaves of flowering Chinese cabbage was 0.398 mg·kg-1, the half-life of it was 5.9 d; the average raw residue of propiconazole in the leaves of flowering Chinese cabbage was 0.281mg·kg-1, the half-life of it was 27.9 d. The propiconazole dissipated fast in flowering Chinese cabbage, while it dissipated slowly in soil.3. The results of the final residue of propiconazole in the leaves of flowering Chinese cabbage, in the stems of flowering Chinese cabbage and soil showed that: When the Chineses cabbage was treated by propiconazole(50 mg·kg-1) for one time,on the 3rd day,5th day, 7th day and 10 th day after the last application,the final residue of propiconazole decreased in Chineses cabbage was between 0.191 mg·kg-1 and 0.078 mg·kg-1; when the Chineses cabbage was treated by propiconazole(50 mg·kg-1) for two times,on the 3rd day,5th day, 7th day and 10 th day after the last application, the final residue of propiconazole decreased in Chineses cabbage was between 0.202 mg·kg-1and 0.091 mg·kg-1; when the Chineses cabbage was treated by propiconazole(75 mg·kg-1) for one time, on the 3th day,5th day, 7th day and 10 th day after the last application, the final residue of propiconazole decreased in Chineses cabbage was between 0.236 mg·kg-1 and 0.125 mg·kg-1; when the Chineses cabbage was treated by propiconazole(75 mg·kg-1) for two times, on the 3rd day,5th day, 7th day and 10 th day after the last application, the final residue of propiconazole decreased in Chineses cabbage was between 0.265 mg·kg-1and 0.132 mg·kg-1. These showed that the final residue of propiconazole inereased as the applieation dosage and applieation times increased,or as the harvest interval decreased.4. The results of dietary exposure risk assessment of propiconazole in flowering Chinese cabbage showed that: the RQ?risk quotient? of propiconazole inereased as the applieation dosage and applieation times increased,or as the harvest interval decreased.When the flowering Chinese cabbage was treated by propiconazole(50 mg·kg-1) for one time,on the 3rd day, 5th day, 7th day and 10 th day after the last application,the RQ of propiconazole in flowering Chinese cabbage was between 2.46 and 0.51; when the flowering Chinese cabbage was treated by propiconazole(50 mg·kg-1) for two times,on the3 rd day, 5th day, 7th day and 10 th day after the last application, the RQ of propiconazole in flowering Chinese cabbage was between 2.60 and 0.59; when the flowering Chinese cabbage was treated by propiconazole(75 mg·kg-1) for one time,on the 3rd day, 5th day, 7th day and 10 th day after the last application,the RQ of propiconazole in flowering Chinese cabbage was between 3.03 and 0.81; when the flowering Chinese cabbage was treated by propiconazole(75 mg·kg-1) for two times, on the 3rd day, 5th day, 7th day and 10 th day after the last application,the RQ of propiconazole in flowering Chinese cabbage was between 3.40 and 0.86.In most cases, the average RQ of estimated exposure for Chinese adults by flowering Chinese cabbage was lower than 1 and the potential exposure risk isacceptable; the average RQ of estimated exposure for Chinese minors by flowering Chinese cabbage was higher than 1 and the potential exposure risk is unacceptable.In conclusion, the safety evaluation of the propiconazole results suggested that 20%propiconazole EC be used in flowering Chinese cabbage?Brassica capestris L.ssp.Chinensis var.Utilis Tsen et Lee ev Cuilü 80 d? at most one time at a dose of 50 mg·kg-1 with a safe interval at least 10 days from harvest. The maximum residue limit?MRL? of 20%propiconazole EC in flowering Chinese cabbage was suggested to be 0.07 mg·kg-1. |
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