Analysis Of Pesticide Residues In Fruits, Juice And Envirmental Samples By SPME, HF-LPME Coupled With High Performance Liquid Chromatography

This thesis is mainly concerned with the following aspects:(1) A method for the determination of metolcarb and diethofencarb in apples by SPME coupled with HPLC was developed. The experimental conditions of SPME, such as the kind of extraction fiber, extraction time, stirring rate, pH of the extracting solution and desorption conditions were optimized. The SPME was performed on a 60μm PDMS/DVB fiber for 40 min at room temperature with the solution being stirred at 1100 r/min. Separations were carried out on a Baseline C₁₈ column (4.6 i.d.×250 mm, 5.0μm) with acetonitrile/water (55 : 45, V/V) as mobile phase at a flow rate of 1.0 mL/min and photodiode-array detection at 210 nm. The method was linear for both metolcarb and diethofencarb in the range of 0.05～1.0 mg/kg (r＞0.99) with the limit of detection (LOD) of 15 and 5μg/kg, respectively. Excellent recovery and reproducibility values were achieved. The proposed method was shown to be simple, sensitive and organic solvent-free, and is suitable for the determination of the two pesticides in apples.(2) A novel method for the determination of MBC and TBZ in apple juice by SPME coupled with HPLC was developed. The experimental conditions of SPME, such as extraction fiber, extraction time, stirring rate, extraction temperature, desorption mode, desorption time were optimized. The method is linear for MBC and TBZ over the range was 0.05～1.5 mg/L with LOD of 20μg/L and 10μg/L and the correlation coefficients were 0.9985 and 0.9975, respectively. The average recoveries for MBC were 89.0 %～91.0 % and the relative standard deviations (RSDs) were 5.4 %～6.7 %. The average recoveries for TBZ were 88.5 %～96.9 % and the relative standard deviations were 3.5 %～5.2 %. The method is fast, simple, solvent-free and suitable for the determination of carbendazim and thiabendazole in apple juice.(3) A method for the determination of triazine herbicides, named simazine, atrazine and prometryne in soil by FMAE and SPME coupled with HPLC was developed. The experimental conditions of SPME and FMAE were optimized. The herbicides were first extracted from soil in water with the assistance of focused microwave at 100℃for 5 min. Then, an aliquot of the resulting aqueous extract was subjected to SPME with 60μm PDMS/DVB fiber for 40 min at room temperature, with the solution being stirred at 1100r/min. The separation was carried out with acetonitril / water (55/45, V/V) at a flow rate of 1.0 mL/min. The linear quantification range for the three analytes was 25～500μg/kg with linear correlation coefficients of 0.9964, 0.9963 and 0.9997, respectively. The LODs were 10, 8 and 4μg/kg for simazine, atrazine and prometryne, respectively. The method has been successfully utilized for the analysis of soil samples with good reproducibilities (2.7%～6.1%) and good recoveries (83.0%～106.6%). The method is fast, simple, solvent-free and suitable for the determination of simazine, atrazine and prometryne in soil sample.(4) A novel analytical method for the determination of carbamate pesticides (carbofuran, carbaryl, isoprocarb and diethofencarb) in reservoir water by HF-LPME coupled with HPLC was developed. Some main experimental parameters that affect the extraction were optimized. As a result, toluene was selected as both extraction solvent and the impregnation solvent. The extraction was carried out at room temperature in a 5 mL Teflon-lined septum cap vial filled with 4.5 mL sample solution at stirring rate of 720 r/min for 20 min. The toluene extract was dried under nitrogen stream at room temperature. The dried residue was then dissolved in mobile phase for HPLC analysis. The separation was carried out on a Baseline C₁₈ column (4.6 i.d.×250 mm, 5.0μm) with methanol / water (60/40, V/V) as mobile phase at a flow rate of 1.0 mL/min. The diode array detection for carbofuran, carbaryl, isoprocarb and diethofencarb was selected at 200, 223,200 and 208 nm, respectively. The average enrichment factors for the four analytes were greater than 45 folds. The linear quantification range for the four analytes was 10～100μg/L with linear correlation coefficients greater than 0.99. The LODs were 5, 1, 5 and 3μg/L for carbofuran, carbaryl, isoprocarb and diethofencarb, respectively. Good recoveries (82.0 %～102.2 %) and good reproducibilities (2.0 %～6.2 %) were achieved.