吡虫啉、苯醚甲环唑和百菌清在甘蓝中的消解及残留分布

Dissipation and residues distribution of imidacloprid,difenoconazole and chlorothalonil in cabbage

为明确吡虫啉、苯醚甲环唑和百菌清在露地甘蓝中的消解动态及残留分布规律,在田间施用农药后,采用液相色谱-质谱联用仪和气相色谱仪,对不同时间甘蓝样品及甘蓝不同部位的农药残留量进行了分析。结果表明:3种农药在甘蓝中的消解动态均符合一级反应动力学模型,其中,吡虫啉消解最快,苯醚甲环唑次之,百菌清最慢,半衰期分别为1.35、2.28和2.47 d。最终残留试验结果显示:施药后7和14 d,吡虫啉、百菌清在甘蓝中的残留量均符合食品中农药残留限量要求,而苯醚甲环唑在施药后14 d的残留量仍高于最大残留限量值(MRL)。3种农药在甘蓝不同部位中的残留量差异显著(P<0.05),其中甘蓝内球叶中未检出或残留量较低,外球叶中初始残留量较低,1至5 d可降至MRL值以下,外叶中的残留量显著高于其他部位。该结果表明,采后处理甘蓝时若去除其外叶,可有效降低甘蓝中的农药残留量,提高质量安全水平。

The dissipation dynamics and residue distribution of imidacloprid,difenoconazole and chlorothalonil in cabbage grown in open field were investigated.The field experiments were carried out and liquid chromatography-mass spectrometry and gas chromatograph were used to determine the pesticide residues of cabbage samples at different time intervals after pesticide application.The results showed that the dissipation dynamics of three pesticides were accorded with the first-order kinetics model,and the half-lives were 1.35,2.28 and 2.47 days,respectively.The dissipation rate of imidacloprid was the fastest,followed by difenoconazole and chlorothalonil.The residues of imidacloprid and chlorothalonil were lower than the maximum residue limits(MRLs)in cabbages on 7 days and 14 days after application,however,the residue of difenoconazole was slightly higher than the MRL on 14 days after application.The residues of three pesticides in different parts of cabbage showed significant differences(P<0.05).The pesticide residues in cabbage inner bulb were not detected or very low in cabbage inner bulbar leaves.The initial residue in cabbage outer bulbar leaves was low either,and it was reduced below MRL from 1 to 5 d.However,the pesticide residues in cabbage outer leaves were significantly higher than those in other parts.It can be concluded that removing the outer leaves of cabbage could reduce the pesticide residues and improve the safety and quality of cabbage effectively.