Residue and dissipation of chlorpyrifos in different tissues of Pyrus bretschneideri Rehd. fruits

To figure out the characteristics of residue and dissipation of chlorpyrifos in different tissues of Ya pear (Pyrus bretschneideri Rehd. cv. Yali) fruits, the selected 20 years old trees of Ya pear were sprayed with 960 mg/L chlorpyrifos on leaves during the period of the fruit development. The fruits were bagged to protect it from the pollution of chlorpyrifos. The patterns of transportation and distribution of chlorpyrifos in the bagged fruits were investigated. Then, the fruits were sprayed with 480 mg/L chlorpyrifos at the maturation stage before harvest. The characteristics of chlorpyrifos distribution in different tissues of the fruits were analyzed. The residue of chlorpyrifos in the fruits was analyzed by using the acetonitrile for extraction and gas chromatograph for detection. The results showed that the chlorpyrifos content in different tissues of the fruits (except the core) tended to increase first and then decrease gradually in 72 h after the spraying under the fruit bagged condition. The highest amount of the contents and the time appeared in the carpopodium, peel, and stalk cavity were 6.66 mg/kg (12 h), 2.42 mg/kg (24 h), and 0.09 mg/kg (12 h), respectively. The results indicated that the chlorpyrifos in bagged fruits derived from the transportation in the branches and leaves, and it went into the fruits via the carpopodium and tended to accumulate in the peel. 24 h and 72 h after the spraying, the chlorpyrifos content in the peel of the no bagged fruits was 12.56 and 7.29 times higher than that the bagged fruits, respectively. The fruits bagging could lower the chlorpyrifos residue in the fruits significantly. When spraying on the fruits at the maturation stage before harvest, the chlorpyrifos residue in the peel was 15.54 mg/kg after 7 days storage. Then, the residue decreased to 13.70 mg/kg and 12.81 mg/kg after 14 d and 25 d storage period, respectively. The chlorpyrifos residue in the peel was 100% of the total in the fruits and the chlorpyrifos residue in the pulp was lower than the limit of quantitation (0.05 mg/kg). The chlorpyrifos residue mainly remained in the peel, which did not tend to diffuse to the pulp during storage.