| Water is the origin of human life, and the security of water environment is also a concerned issue. China is a large agricultural country, and the use of pesticides promotes the development of agricultural production. In recent years, pesticides have been widely used in agriculture, and its residues cause environmental pollution. Therefore, it is necessary to analysis and detection of pesticide residues existed in environmental water.Chlorinated phenoxyacid herbicides are widely used in agriculture. This kind of herbicides has high boiling point, big polarity, is not easy to volatilize, and easy to dissolve in the water and ethanol with stable chemical nature. Meanwhile, it is difficult to be biodegradable and is generally easy to remain in the soil, water environment, crop stalks and fruit. The herbicides has medium toxic, and its derivatives and metabolites have a strong biological activity on the plant, thus it has endocrine interference effects on human and livestock, especially stimulation to the eyes, skin, gastrointestinal mucous and respiratory.Therefore, it is important to strengthen the control and research of chlorinated phenoxyacid herbicides pollution.The domestic and foreign have played high attention on chlorinated phenoxyacid herbicides residual contamination situation. And a large number of related standards and methods have been developed for analysis. The sample former process is necessary step before analysis of chlorinated phenoxyacid herbicides. Liquid-liquid extraction and solid phase extraction are two common techniques. In the work, we studied the optimum conditions of solid phase extraction(SPE) former process, choosing PFBBr which has higher derived efficiency, low toxicity, strong feasibility for derivation, then used gas chromatograph-mass spectrometer(GC-MS) as a detector method. Moreover, we used the establishing determine method for analysis seven kinds of chlorinated phenoxyacid herbicides(Dicamba, MCPA, Dichlorprop, 2,4-D, 2,4,5-TP, 2,4,5-T, 2,4-DB) in the environment water. The main contents and results are as follows:(1) We established gas chromatography-mass spectrometric method for seven chlorinated phenoxyacid herbicides in the water. The temperature of column box was120 °C and the inlet temperature was 230 °C. Aliquots of 1 ?L of the sample extract wereinjected into the gas chromatograph. The colum of DB-5MS capillary column(methyl phenyl siloxane, 30 m × 0.25 mm × 0.25 ?m) was used. The oven temperature programme was as follows: starting temperature 120 °C, increased at 10 °C/min to 290 °C and held for2 min. The helium(purity ? 99.999%) was used as a carrier gas. The mass spectrometry was performed in electron ionisation(EI) mode with an ionising energy of 70 e V. The ion source temperature was set at 230 °C, GC-MS interface temperature was 280 °C and the solvent delays 6 min. The analysis was performed in selected ion monitoring(SIM) mode. Under the optimum conditions, seven kinds of herbicides can be separated. The linearity of both qualitative and quantitative were good, which 6 kinds of linearity in the range from 0.05 to100 mg/L, the linearity range of 2,4-DB from 0.02 to 100 mg/L. The correlation coefficients(r2) between 0.9991 and 0.9995.(2) We researched the effects of derivatives dosage and derivative conditions on chlorinated phenoxyacid herbicides derivation efficiency. And we also modified the purification conditions. The experiment finally chooses PFBBr as derivatizing agent and was used 300 ?L(30 g/L), the amount of catalyst K2CO3 was 25 ?L(100 g/L). We choosed water bath temperature 40 °C for 2 hours. The experiment compared the purifying effect of silica gel decontaminating column and florisil decontaminating column, and the result shows that silica gel decontaminating column could obtain better purification effect. So we selected a total amount of 4 m L toluene: n-hexane(1:6) solvent to drip washing for removed the derived by-products, then finally used 8 m L toluene: n-hexane(9:1) to elute the target.The experimental comparison indicates that eluting four times could wash the target off completely, and ultimately achieved the purpose of purification.(3) We modified the solid phase extraction conditions. Compared with four solid phase extraction columns which used different fillers and had different specifications. Finally we found MEGA BE-C18(1 GK 6 m L) had better returns-ratio for seven kinds of targets than the other three, which were able to reach 80% to 120%, so chooses MEGA BE-C18(1 GK 6m L). Compared different elution solvent's elution efficiency to seven chlorinated phenoxyacid herbicides, and ultimately selects dichloromethane whith the recovery ranged between 83.92 and 90.68%. Comparison of the p H and the effect of Na Cl on extraction efficiency. The p H was choosen to use 2 and without Na Cl..(4) Using well-established method for the detection of seven chlorinated phenoxyacid herbicides in the water samples carried on LOD, LOQ, returns-ratio increasing and accuracy experiments. The sensitivity of the method was good, LOD was 0.88 ng/L-1.68 ng/L, LOQ was 2.94 ng/L-5.61 ng/L. Recoveries were evaluated in water matrices with the spikedconcentrations of 1 mg/L, 1 mg/L and 10 mg/L in all cases. The results showed that the recovery of seven chlorinated phenoxyacid herbicides ranged between 79% and 100%, and the relative standard deviation was less than 10.0%. Based on the results presented above,the methodology meets the requirements for multiple pesticide determination in water matrices and will have broad applications in aqueous. |
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