| Pesticide residues is a general term referring to the trace pesticide and its toxic degradation products remained in vegetables, fruits, soil, atmosphere and water because of the incomplete decomposition of pesticides after which are used for a period of time. Presently, the problem of pesticide residues has had a serious impact on human life. Residues of pesticides can enter into and do severe harm to human body through vegetables, fruits, water and atmosphere directly, and the environment and human food chain indirectly. According to a preliminary statistics of the World Health Organization, at least 115,000 people worldwide die of pesticide poisoning each year and more than 85% of the cancer cases are associated with pesticide residues. Therefore, it’s very urgent to find a fast, sensitive, selective and easy to operate method to detect pesticide residues, which will be significant in solving environmental pollution caused by pesticide residues, improving ecological environment and protecting human health.This dissertation mainly studied copper fungicides and several conventional insecticides. Firstly, using fluorescein as chromophores, an ion colorimetric probe which could recognize the metal ions Cu2+ was designed and a lot of corresponding research has been done to its spectral characteristics and identification performance. This method is very important to detect copper fungicides. Then, a new method for the detection of conventional pesticides by MALDI-TOFMS was established. This method is simple and rapid, and has high sensitivity and simple pretreatment procedures. Moreover, through the study of beta-cypermethrin pesticides’ impact on digestive enzymes in cabbage moth larvae, it provided a theoretical basis for the rational use of pesticides, reduction of a series of adverse effects on environment and agricultural production caused by pesticides. The followings are the specific contents of the study:1、The existing problems of irrational use of pesticides by farmers were analyzed, the current situation of pesticides residues and its harm to human body were elaborated, and the research progress of the current methods for the detection of pesticides residues was summarized in detail.2-The fluorescein is a kind of important material for the construction of fluorescent probe. The change of colors can be shown obviously through the interaction between the spiro structures and open-cycle structures. And the changes can be identified easily by naked eye. Using fluorescein and 3-bromo-5-methyl salicylaldehyde as raw material, the author of this paper designed and constructed a fluorescein based ion probe-BMSFH, which had a good selectivity to Cu2+ and could identify Cu2+ specially in the physiology system of pH 7.4. Its recognition performance, spectrum characteristics and sensing mechanism were studied and the results showed that BMSFH at 502nm had new absorption peak accompanied by obvious color change because of the presence of Cu2+. However, other common alkali-, alkaline earth-, transition-and rare earth metal ions induced no or minimal spectral change. This change in spectral signal and color was due to the form of BMSFH opened via coordination with Cu2+in a 1:1 stoichiometry and their association constant was determined as 1.4×104 L·mol-1. Experimental results indicated that the BMSFH could provide a rapid, selective and sensitive response to Cu2+ with a linear dynamic range 3.3-330 μmol·L-1.3、Matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOFMS) is an indispensable tool for the analysis of large biological molecules. Because of the interference of traditional matrix ions fragments for the detection of small molecules, MALDI-TOFMS makes the characterization and detection of small molecules obscured and difficult. To overcome this problem, considerable efforts have been made to develop various methodologies in recent years. Various sample-supporting materials were applied in MALDI-TOFMS for the analysis of small molecules. With excellent optical and electrical properties, graphene is considered as a prominent material in energy absorption, storage and transfer. Furthermore, it has a relatively high tolerance for interferences and almost does not produce effective interference fragments because of its special structure. Thus graphene is an excellent matrix to use. There has been some research on small molecule including peptides, amino acids, fatty acids, as well as nucleosides and nucleotides by using grapheme as matrix. But almost no research has been reported on the detection of pesticide residues by using the method of MALDI-TOFMS which uses graphene as matrix. In this study, the residues of Propoxur, promecarb, imidacloprid, dimethoate, Thiamethoxam and beta-cypermethrin were successfully detected respectively in positive and negative ion mode using MALDI-TOFMS method which used the simply synthesized graphene derivative as matrix, and a good detection feature mappinghas been obtained which made it possible to qualitatively and quantitatively detect the six pesticides. This experiment not only provided a reliable method for rapid detection of pesticides but also offers a new idea for the detection of other trace organic pollutants.4、In recent years, gas chromatography-mass spectrometry (GC-MS) technology has been widely applied in the detection of pesticide residues. In the research, five pesticides such as propoxur, promecarb, dimethoate, thiamethoxam and beta-cypermethrin were detected by GC-MS. A clear quantitative linear relation about the five pesticides has been established and their addition recovery rates and relative standard deviations in cabbage were measured. Its limits of detection (LODs) for each pesticide were determined and they were 0.032,0.01439,0.0126,0.083,0.018 ppm accordingly, the addition recovery rates of the five pesticides in cabbage were above 82% and relative standard deviations were less than 15%. The results showed that this method could meet the requirements of pesticide residue analysis in the detection limit, recovery rate and relative standard deviation.5、To further understand the effect of beta-cypermethrin pesticides on digestive enzyme of insects and provide a theoretical basis for rational use of pesticides to reduce their harmful effects brought to environment and agricultural production, this research studied the influence of beta-cypermethrin on the digestive enzymes of 4rd,5rd and 6rd instars cabbage moth larvae. The results showed that the influence of beta-cypermethrin on the activity of the four kinds of digestive enzymes of cabbage moth larvae including intestinal protease, amylase, sucrase, and trehalose increased with the increase of dosage, the activity of the four kinds of enzymes decreased obviously with the extension of processing time and the effect weakened gradually with the increase of age. After 3-hour and 6-hour treatment of 6rd instars cabbage moth larvae, its amylase activity was 1.17 and 1.04 times as high as that of the controlled. This influence had an enhanced process to amylase activity which decreased gradually with the constant infiltration of beta-cypermethrin and was lower than the comparison after 9-hour treatment. Beta-cypermethrin showed an obvious inhibition to the rest of three kinds of digestive enzyme activity and this inhibition to the activity of protease was more serious than that of sucrose and trehalase. Therefore, when using pesticides, the younger the easier to be controlled. Beta-cypermethrin should be applied on cabbage moth larvae before they are four years old. Thus the population can be completely controlled at low doses and its residues can be reduced at the same time. |
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