A Preliminary Study On Determination Of Residues And Degradation Dynamical Rhythm Of Organophosphorous Pesticide Extracted From Citrus

Organophosphorous pesticides are very important in agricultural production. So far, they are considered to be the mainly employed insecticides among pesticides in China. Irrational usage of pesticides pollute environment including plants, animals, atmosphere and water bodies. Farm production and processed foods are also in danger of being polluted by pesticide residues. As safe consciousness about foods strengthened by the mass, pesticide residue assay as a practical science is attached more and more attention and criterions of pesticide residuals are optimized gradually.Pesticide residue assay is a technique that determines the trace components in a complex mixture, the process of witch including sample preparation, purification, enrichment, separation, detection and analyses. The technique is required to be high sensitivity, efficient recovery rate, good recurrence and simple and workable operation. The study on pesticide residue detection methods is to optimize the pretreatment techniques and detection techniques. The study on pesticide residue degradation dynamics plays important roles in instructing properly usage of pesticides, high quality farm production and national farm production competitiveness enhancement.In the study we primarily optimized the method of Solid Phase Extraction-High Performance Liquid Chromatography (SPE-HPLC) in organophosphorous pesticides' detection in Citrus, and revealed the degradation dynamical rhythm of chlorpyriphos in Citrus.The method in organophosphorous pesticides' detection by using SPE-HPLC is described as follows: The optimized sample pretreatment techniques included organophosphorous pesticides extraction from Citrus's pericarp and pulp by acetone and ethyl-acetone: optimizing SPE method to purify extractions samples, after eluted with acetone and ethyl-acetone, concentrating the elution solution before determination. Determination was carried out by using HPLC coupled with Photodiode Array Detector. Gradient elution method was employed by starting from 50% acertonitrile and 50% water to 70% acertonitrile and 30% water during 6.5-20mins and back to 50% acertonitrile and 50% waters during 30-35mins. Furthermore, the recoveries, recurrences and the lowest detection limits were determined. The recoveries was between 76.11%-101.82%, RSD 4.31%-8.49%, the lowest limit of the three organophosphorous pesticides was 0.012mg/kg, 0.015mg/kg, 0.021mg/kg respectively, witch meet with the requirements of determine many pesticide residues in a single run.The degradation dynamics rhythm of chlorpyriphos in Citrus was also studied. The results showed that more pesticide residue and faster were found in pericarp of Citrus than in the pulp, the half life of the pesticide was found no significant difference in different part of Citrus treated with by different pesticide concentrations.