Studies on the dynamic variation of pyridaben residues in citrus and soil

To evaluate the residue variation and environment security of using pyridaben in citrus,pyridaben residue in orange and soil samples were extracted with acetone and purified by liquid-liquid distribution and column chromatography,then detected by means of GC/ ECD,with sensitivity of 1×10~(-11)g for ECD and 0.005 mg/ kg for this method,in which the recovery rates of pyridaben standard solutions added in non-sprayed orange and soil were 91.0 % to 105.27 %.Results indicated that the half-life of pyridaben in orange and soil were 11.9 d and 22.3 d in Yunnan,respectively,24.9 d and 22.5 d in Hunan.It is suggested that spraying at recommended 150 mg/ L with interval of 20 d,the final residue could be controlled to lower than 0.136 mg/ kg.Results also showed that the residue mostly existed in peel,seldom in pulp,and varied with varieties in distribution.