Study On Residue Dynamics And Photodegradition Of Chlorpyrifos And Chlorothalonil In Pepper Of Greenhouse And Field

Residues analytical methods of chlorpyrifos and chlorothalonil in pepper were established. Dissipation residues of chlorpyrifos and chlorothalonil on plastic shed and field pepper, as well as photochemical degradation of chlorpyrifos and chlorothalonil under pepper with high-pressure mercury lamp and sunlight were studied t in this paperResidues of chlorpyrifos and chlorothalonil were extracted from pepper with acetonitrile, cleaned up with florsil and determined by GC-ECD. The limit of detection of chlorpyrifos (LOD) was 0.01ng and the method detection limit (MDL)of chlorpyrifos in the samples of pepper was 0.002mg/kg.The average recoveries and coefficient of variations of the method were 84%-90%,2.84-4.53%. The limit of detection of chlorothalonil (LOD) was 0.1ng and the method detection limit (MDL)of chlorpyrifos in the samples of pepper was 0.01mg/kg.The average recoveries and coefficient of variations of the method were 83%-98%,2.45-3.42%. Residues of chlorpyrifos and chlorothalonil were extracted on pepper surface with acetonitrile and determined by GC-ECD. The average recoveries and coefficient of variations of the method were 84%-94%,2.38-4.25%. The average recoveries and coefficient of variations of the method were 96%-102%,2.49-3.3%.These results showed that both the methods accorded with demands of residue analysis of pesticides.With the mentioned method, dissipation dynamics of chlorpyrifos and chlorothalonil on plastic shed and field pepper had been studied in Anhui during summer and winter in 2009. The results showed that the dissipation half-life of chlorpyrifos on plastic shed pepper was 1.4d in summer and 5.3d in winter; the dissipation half-life of chlorpyrifos on field pepper in summer was 0.8d and 3.1d in winter. The dissipation half-life of chlorothalonil on plastic shed pepper was 2.2d in summer and 3.1d in winter; the dissipation half-life of chlorpyrifos on field pepper in summer was 1.7d and 2.2d in winter. The photolytic rate of chlorpyrifos and chlorothalonil on plastic shed was quicker than that of on field pepper; And the photolytic rate of chlorpyrifos and chlorothalonil in summer was quicker than that of in winter.With the certain quantitative chlorpyrifos and chlorothalonil on pepper surface, including different initial concn, different lamp, different color pepper, and different thick film were research. The results indicated that: The decrease of the thick of film could speed up the photodegradition of chlorothalonil and chlorpyrifos;In the experimental range of initial concn,the photolysis reaction of chlorpyrifos and chlorothalonil accorded with first order reaction kinetics and its photolytic rate was negatively correlated with its initial concn;The photolytic rate of chlorpyrifos and chlorothalonil under high-pressure mercury lamp was quicker than that of under sunlight; The half-life of chlorpyrifos was 2.1 hour under high-pressure mercury lamp and 1.7day under sunlight; the half-life of chlorothalonil was 1.8 hour under high-pressure mercury lamp and 1.8day under sunlight. The color of pepper also had a significant effect, with a decreasing degradation on rate of chlorpyrifos and chlorothalonil in the sequence of red pepper > yellow pepper > green pepper .The degradation of chlorothalonil and chlorpyrifos alone was faster than mixed in all kinds color.