| Organophosphate pesticides are widely used in the prevention of pests in agricultural products because of their broad-spectrum and high effectiveness on the pests. But excessive use of organophosphate pesticides causes negative results on people and environment, especially influencing the quality and safety of agricultural products. So recently the detection of OPs, especially the detection of OPs in vegetables, becomes the hot problem. The traditional detection methods, such as chromatography, mass spectrometry, etc, have accurate results and high sensitivity, but they take a long time and are very expensive, so they can't meet the requirement of rapid detection on the spot. According to the practical situation of our country, a new kind of rapid detection method is presented in this thesis by using the degradation of microorganism to detect methamidophos, dimethoate and omethoate. From the pretreatment to the detection, the method takes less than 10min, and can meet the requirements of qualitative and semi-quantitative analysis. The main contents and results are as following:1. Research on the rapid detection method of inorganic phosphorus. The optimal conditions of malachite green method for the rapid detection of inorganic phosphorus are as following: 2.5mL 25.56% sulfuric acid, 2.5mL 7.2% ammonium molybdate, 2.5mL 6×10-3mol.L-1 malachite green, 0.4mL 10g.L-1 PVA. PVA as a stable reagent is added after the coloring reaction happened. The standard curve between the concentration of phosphorus and absorbance is determined, the linear range is 00.20mg.L-1, linear regressive equation is: A = 3 .5514c+0.0037, coefficient of determination: R2 =0.0991, sensitivity:ε=1.146×10-3L.mol-1.cm-1, the limit of detection is 0.0052mg.L-1.2. Contrast reactive time, linear relation, detection limit and detection cost, etc. between the methods of malachite green with the improved method of Mo-Sb-Vc. For the method of malachite green, the optimal conditions are as following: the reaction time is 2 min , the sensitivity is 1.146×10-3L.mol-1.cm-1, the detection limit is 0.0052mg.L-1, and the detection cost is 0.1095 yuan. But for the method of Mo-Sb-Vc, the reaction result is that the reaction time is 15min , the sensitivity is 3.103×10-4L.mol-1.cm-1, the detection limit is 0.0117mg.L-1, and the detection cost is 0.0893 yuan. So compared the two methods, we can see that the method of malachite green has the obvious advantage in reactive time, sensitivity and detection limit; these two methods don't have obvious difference in linear relationship and detection cost. Although the cost of malachite green method is higher than the method of Mo-Sb-Vc, the method of malachite green has good result to rapid detection. So the method of is determined as the method for the detection of inorganic phosphorus.3. A kind of microorganism with good degradation effect for methamidophos, dimethoate and omethoate has been found through the inducing and enrichment culture of OPs degradation microorganism in the soil. The microorganism is confirmed as one kind of Aspergillus through preliminary identification, so it is called Aspergillus D in this thesis.4. The lipid culture medium with better synthetical degradation effect is determined by the method of comprehensive balance and orthogonal experimental design. It includes: 0.80% glucose, 0.20% NaNO3,0.05% MgSO4,0.05% KCl,0.008% CaCl2,0.004% MnCl2. The sequence of factors that influent the degradation effect is MgSO4+ KCl>glucose>CaCl2+ MnCl2>NaNO3.5. The synthetical optimal conditions of Aspergillus D are determined by queue measure method and orthogonal experimental design. The conditions are as following: preliminary pH of lipid culture medium is 7.0, culture time is 96h, culture temperature is 30℃, and rotate speed of shaker is 150rpm. The influence of inoculation quantity and passage generation times on microorganism degradation performance is evaluated. The result shows: inoculation quantity has a less influence on degradation performance; two tubes of Aspergillus D are optimal as inoculation quantity; passage generation times have a larger influence on degradation performance, and the first generation Aspergillus D is suitable to be used. 6. The weigh of qJ,qL,qY is determined by entropy-weighing method. The degradation conditions of microorganism are optimized by the efficacy coefficient method, comprehensive grading method and uniform design. The degradation conditions are as following: degradation temp. is 25℃, degradation time is 1min, degradation pH is 6.5, quantity of Aspergillus liquid is 9mL. Under these conditions, the degradation rate on methamidophos, dimethoate and omethoate of 2mg.kg-1 reaches 0.0110,0.0058,0.0238mg.h-1.L-1.NTU-1 respectively.7. Liquid color sensor is used on the detection of inorganic phosphorus, and BP network is used to predict the quantity of inorganic phosphorus in the sample through comparing the forecast effect of the method of BP network, multiple linear regression, and fuzzy pattern recognition. The accuracy of prediction with BP network is 84.1%.8. Contrast labeling recoveries, detection limits and detection time between the method of microorganism degradation and the method of high-handed hydrolysis. The result shows: the range of labeling recoveries for the method of high-handed hydrolysis is from 75% to 98%, and that the range of method of microorganism degradation is only from 9% to 39%, obviously lower than the method of high-handed hydrolysis. Moreover the detection limits of methamidophos, dimethoate and omethoate are 0.2187, 0.1628 and 0.1583mg.kg-1 respectively by using the method of high-handed hydrolysis. The detection limits of methamidophos, dimethoate and omethoate are 0.5285,1.3397 and 1.1356mg.kg-1 respectively by using the method of microorganism degradation, Although the detection limits of the method of microorganism degradation are a little higher than the method of autoclave hydrolysis, but the degradation time is shorter(only 1 min, when the method of high-handed hydrolysis need 30 min), so the method of microorganism degradation can meet the requirement of rapid filtration on the spot and qualitative & semi-quantitative rapid detection for Organophosphate pesticides.9. Research on the pretreatment method of sample based on the Tris-HCl buffer solution was studied. Tris-HCl buffer solution is used to extract OPs in vegetables. The main factors that influence the effect of pretreatment are optimized by the osculating value method and orthogonal experimental design. The optimal conditions of sample pretreatment are as following: pH is 6.5, V:m0 is 1.2, extraction temp. is 20℃, extraction time is 3min. Recoveries of methamidophos, dimethoate and omethoate reach 96.39%,92.46% and 97.64% respectively. The sequence of factors are pH>V:m0>extraction temp.>extraction time。... |
PDF Full Text Request