| Vegetable is a daily necessity whose safety becomes the focus of public attention, as it directly affects human health and safety. The government has imposed limit on pesticide residues in vegetables, so it is very necessary to establish a set of convenient, rapid and accurate methods.This research consists of the following:1. To establish the method of detecting thirty-five pesticide residues in vegetables by using Solid-Phase Extraction-Gas Chromatography;To optimize the experiment terms on the basis of the original experiment method, using simple and convenient sample preparation method; to seek the optimum Chromatographic terms of multiresidues separation and achieve the best separation effect; to validate the accuracy and precision of the method and establish the optimum experimental terms for detecting thirty-five pesticide residues in vegetables by using Solid-Phase Extraction-Gas Chromatography.2. Detection of pesticide residues in the samples with Solid-Phase Extraction-Gas Chromatography was performed on randomly selected vegetables of the city. The obtained data was then statistically analyzed.3. The data gathered from 2003 to 2009 are epidemiologically investigated.The results are as follows:1.The optimum experimental terms for detecting thirty-five pesticide residues in vegetables on using Solid-Phase Extraction-Gas Chromatography: Samples were extracted with acetonitrile,and purified by Solid-Phase Extraction. The optimum Chromatographic term:Mix Reference Material l:pillar:DB-1701; the injector temperature is 170℃; the detector temperature is 260℃; Temperature raise procedure:initially the temperature was set at 80℃for 1 min, ramped to 160℃at a rate of 20℃/min and held for 1 min, ramped to 170℃at a rate of 2℃/min and held for 2 min, ramped to 185℃at a rate of 5℃/min and held for 2 min, ramped to 187℃at a rate of 0.5℃/min and held for 2 min, ramped to 188℃at a rate of 0.1℃/min and held for 2 min, ramped to 189℃at a rate of 0.5℃/min and held for 10 min, ramped to 230℃at a rate of 5℃/min and held for 12 min. Carrier gas:H2 2.5ml/min, air 150ml/min. The split flow ratio:5.0. The makeup flow:30ml/min. Mix Reference Material 2: pillar:spb-1; the injector temperature is 270℃; the detector temperature is 280℃; temperature program:initially the temperature was set at 150℃for 1 min, ramped to 245℃at a rate of 30℃/min; Carrier gas:N2, initially the flow was set at 0.5mVmin for 13.4 min, ramped to 0.8ml/min at a rate of 0.1ml/nin2 and held for 6.1 min, ramped to 1.5mml/min at a rate of 0.1ml/min2 and held for 1 min.2.Thirty-five pesticide residues in vegetables can be detected with Solid-Phase Extraction-Gas Chromatography at the same time. The experiment proves that the method is simple and convenient. It features good separation, high precision, shortened detection time and improved efficiency. The experiment may provide reliable data and basis for the establishment of new national standards.3. The results of sample detection:in the 315 samples,207 samples had detectable residues. The detection rate is 65.7%,24 samples had violation residues. The over-standard rate is 7.6%. In the 35 pesticide residues,23 pesticide residues had been detected,10 of which had no correspondent limits; the detection rate of 4 pesticide residues was more than 10%; the detection rate of dicofol was the highest, reaching 16.8%. In the others the detection rate was less than 10%. Methamidophos can not be detected in the GB, but the data demonstrated that the detection rate of methamidophos is 2.2%.4. The epidemiological investigation result of marketed vegetables during 2003 to 2009:In the 1688 samples,the average detection rate is 39.4%. The average over-standard rate is 11.3%. The multiresidues detection rate is18.7%. The detection rate is 12.9% in 2004, the lowest, while the rate is 91.4% in 2009, the highest; The over-standard rate is 1.9% in 2004, which is the lowest, while the rate is 16.8% in 2007; the multiresidues detection rate is 1.0% in 2004,which is the lowest, while the rate is 67.9% in 2009. The detection rates of leaf vegetable, rootstalk-like vegetable, fruit vegetable and edible fungi are respectively 41.5%,40.0%,34.3% and 39.8%. The detection rate of organophosphorus, carbamates, pyrethroid and organochlorine are respectively 28.6%,4.6%,16.7% and 1.0%.While the detection rate indicates the usage of pesticide, the over-standard rate is the indicator of vegetable safety. The detection and the epidemiological investigation results show that the over standard rate of the marketed vegetables of the city is kept at a safety level.Based on the results above, the article suggests that further efforts should be made:①to reinforce the education and guidance on the rational use of pesticide.②to main monitoring and control over the vegetable with high detection rate.③to regulate the pesticide market, reinforce the supervision over pesticide production and circulation, and ban the use of forbidden pesticide. |
