| Residue of pesticides found in agriculture products, drinking water and environmental exposure has raised much concern from the general public in recent years. In order to protect persons' healthy, the maximum residue levels (MRL) in food were constituted by WHO/FAO-CAC. It is important to exploit simply, fast, efficient pre-treatment technologies for samples and high sensitive, high selective multi-pesticide detections technologies based on pesticide and veterinary drug residues in food and the requirement for international trade on food.The thesis includes three parts:In chapter I , a useful method base on solid-phase extraction (SPE) and micellar electrokinetic capillary chromatography(MEKC) was developed for the simultaneous separate and determination of Imidacloprid; acetamiprid; metsulfuron-methyl; chlorsulfuron; chlorimuron-ethyl; trichlorphon; cardofuran; atrazine; methidathion; metalaxul; triadimefon; chlorfenapyr residues. Selectivity and resolution were studied changing operation voltage, the pH and the concentration of the buffer, the type and concentration of surfactant and the methanol content in the mobile phase. A buffer consisting of 10 mM borate with 54 mM SDS (pH 8.0) gave the best results. The method was simple, rapid and yielded excellent recoveries (70.20%~88.71%), and the limits of detection were between 0.02 and 0.1 mg/kg. The reproducibility and repeatability of the combination of SPE pretreatment and MEKC were good for all the compounds. Micro amount of some pesticides (imidacloprid, metsulfuron-methyl, chlorsulfuron, chlorimuron-ethyl, trichlorphon, atrazine) in plants have been determined by this method with the relative standard deviations (RSDs) ranged from 1.3 to 12.5%.In chapter II, the paper describes the indirect determination of methidathion and its degeneration process by HPLC, HPLC-MS, UV and electrochemical methods. It is shown that the copper(II) catalyzes the hydrolysis reaction of methidathion in a supporting electrolyte of 0.2 mol/L HAc-NaAc (pH=5.2) (100C) . The main hydrolysis product is Bis(2-methoxy-2-l,3,4-thiadiazolin-5-on-4-yl)disulfide (BDF) and 0,0-Dimethyl phosphorothionic acid, then BDF forms complex with copper(II). A sensitive reductionpeak of the complex is determined by linear sweep volmmetry(LSV) with dropping mercury electrode(DME) at -0.866V(vs. saturation calomel electrode ). The mechanism that copper(II) catalyzed degradation reaction of methidathion has been suggested based on the results obtained. The electrochemical characteristics and the mechanism of the electrode reaction have been studied. Based on the reduction of the complex, we propose a LSV method for the indirect determination of methidathion. There is a good linear relationship between peak current and concentration of methidathion in the range 0.1-30 mg/kg with correlation coefficient of 0.9994 and under optimized conditions; detection limit (signal/noise, S/TSN3) was 0.03 mg/kg. The recoveries obtained by LSV method ranged from 82 to 91% and the relative standard deviations (RSDs) ranged from 1.9 to 5.1%. This method is used to determine trace amount methidathion in pear with satisfactory results, compared with results achieved by HPLC.In chapter III, the electrochemical behavior of florfenicol was studied by using cyclic voltammetry, linear scanning voltammetry and bulk electrolysis with coulometry. In a base solution of 0.2mol/L NaOH-NaH2PO4 at pH7.6, florfenicol produced a sensitive reduction peak. The peak potential was -0.886V (vs.SCE) . The linear relation hold between the peak current and the florfenicol concentration in the range from 1.0 X 10-5 mol/L to 7.0 X 10 mol/L(r = 0.9994) with the detection limit of 1.0X10-6 mol/L. The relative standard deviation of 1.0 X 10-4mol/L florfenicol for 10 parallel determinations was 0.25%. The peak also showed adsorptive characteristics. In addition to the number of electrons transferred in the reaction was calculated to 2. Furthermore, a possible mechanism of electrode reduction was discussed.
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