Some Pesticide Residues And Nitrate, Nitrite By Capillary Electrophoresis And Electrochemical Analysis

Pesticides residues are commonly found in surface water, ground water, foods, as well as in soil, due to their persistence and water solubility. This creates the need for rapid, simple, and reliable methods for measuring residues. The determination of pesticide residues is an intricate problem because of the large number of chemicals involved.In the first part of this thesis, the progress of the determination method for pesticides was reviewed. Variety of analytical methods, such as high-performance liquid chromatography(HPLC), gas chromatography(GC), thin-layer chromatography (TLC) and immunoassay, have been used for the analysis of pesticides. These analytical techniques have proven to be very reliable for the analysis of pesticides mixtures in samples, but these method, are often time-consuming and expensive due to sample preparation and instrumentation. A relatively new analytical technique that is complementary to GC and HPLC is capillary electrophoresis(CE).The prospects for CE in pesticide analysis are very promising because of its advantages, such as higher separation efficiency, shorter analysis times, and very small consumption of expensive reagents and toxic solvents.In the part Ⅱ, a method for the simultaneous separation and determination of parathion , methyl parathion, carbofuran and isocarbophos by micellar electrokinetic capillary electrophoresis(MEKC) has been developed. The conditions for separation and detection of a mixture of four pesticides have been optimized, and results showed that the investigated compounds could be successfully separated within 9min by using a borate/SDS buffer as the carrier, and 20kV as the applied voltage. The detection limits were in the arrange of 0.8μg/mL-2.0μg/mL. This method was successfully applied to the analysis of pesticides in imitative soil sample. The recoveries of four pesticides were in the range of 97.0%-103.8%.In the part Ⅲ, a MEKC method was developed and applied for determination of the trace chloronicotinyl insecticides by using the sample self-stacking onlinepre-concentration technique. The detection limits are 0.1μg/mL and 0.2μg/mL respectively. In the optimal conditions, this method was successfully applied to the analysis of imidacloprid and acetamiprid in imitative river water and vegetable samples.In the part Ⅳ, a high performance capillary electrophoresis(HPCE) method with UV detection was developed and applied to the determination of nitrate and nitrite in vegetables. The optimal conditions of electrophoresis were studied. The recoveries of nitrate and nitrite were ranged from 95.6% to 104.3% and 94.8% to 101.8% respectively. The relative standard deviations of nitrate and nitrite were 2.7% and 3.5% respectively. The total time for separation and determination was within 6 min.In the part Ⅴ, Some modern electrochemical techniques ,such as LSV, CV and DPV were used for researching the behavior of imidacloprid and acetamiprid. Their electrochemical characteristics at in the surface of glassy carbon electrode have also been studied. A DPV method was developed and used for determination of this two pesticides. The best adsorption conditions were discussed and instrumental conditions were optimized. The method has applied to the direct determination of the pesticide in soil samples.