Residue Dynamics and Safety Evaluation of Saijunmao in Tobacco Leaves and Soil

To assess the environmental safety of applications of fungicide saijunmao in tobacco,the analytical method and residue dynamics as well as final residues in tobacco and soil were investigated.Tobacco-leaf and soil samples were extracted with methanol/water(70:0,V:V).The extract was partitioned with petroleum ether and dichloromethane successively,and cleaned up on a florisil column with an dichloromethane-methanol mixture(1:1)before its determination by high performance liquid chromatography(HPLC)equipped with an ultraviole(tUV)detector.The average recoveries at spiked levels of 0.01～5.0 mg.kg-1 ranged from 90.50%～93.84% for green tobacco leaf,88.19%～91.90% for dried tobacco leaf and 88.34%～93.04% for soil,with relative standard deviations(RSD)of 1.72%～2.79%,1.83%～ 4.13% and 2.00%～2.71%,respectively.The limit of detection(LOD)was 1.4×10-12 g,while the limit of quantification(LOQ)were determined as 0.01 mg.L-1 for green tobacco leaf,0.01 mg.L-1 for dried tobacco leaf and 0.005 mg.L-1 for soil,respectively.Results of saijunmao degradation dynamics showed that half-life values(T1/2)were 2.85～3.44 d in green tobacco leaves and 2.77～3.26 d in soil,respectively.The final residues of saijunmao in dried tobacco leaves and soil were determined after the third and fourth application at levels of 250 g.a.i..hm-2 and 375 g.a.i..hm-2.The final residues were 1.102～4.230 mg.kg-1 7 days and 0.082～1.813 mg.kg-1 21 days after the last application in dried tobacco leaves.Meanwhile,the residues in soil were not detected.