| Summary: | 博士 === 國立中興大學 === 化學系所 === 98 === A simple, efficient and novel pretreatment technique termed as ultrasound-assisted emulsification microextraction (USAEME) has been designed and studied for the rapid analysis of organophosphorus pesticides (OPPs) in environmental water and soil samples by gas chromatography-electron capture detector (GC-ECD). A specially designed extraction device was utilized for the facilitated collection of extraction solvent from the extraction unit for the extraction of OPPs in water and soil sample matrixes. A glass syringe as an extraction unit, a microsyringe for extractant addition, and a self-scaled glass capillary tube adopted onto the needle holder of the glass syringe as a means to recover the extractant. A trace amount (few μl) of low-density organic solvent as the extraction solvent was added into the aqueous sample solution followed by the ultrasonic radiations which accelerate the emulsification of μL-level solvent in aqueous solution to enhance the microextraction efficiency of OPPs. The formed emulsion was centrifuged and the amount of separated organic extract was measured in the self-scaled glass capillary tube and then 1 μL of organic extract was directly injected into a GC-ECD for analysis. Parameters affecting the extraction efficiency of OPPs in aqueous samples such as selection of organic extraction solvents, volume of extraction solvent, ultrasound-assisted emulsification time, pH of the sample solution, addition of salt to sample solution were thoroughly investigated. Results showed that the optimum extraction efficiency of OPPs in 5 mL of aqueous sample (pH = 8) by the addition of 20 μL toluene as the extraction solvent, followed by ultrasonication for 30 seconds and then centrifugation for 3 min at 3200 rpm.
An upgraded microwave-assisted extraction (MAE) was coupled with USAEME and applied for the extraction of OPPs in soil samples using water as an extraction medium. Microwave irradiation was utilized to accelerate the extraction of OPPs from soil sample into water medium. Parameters affecting the extraction efficiency of OPPs in soil such as selection of the power and irradiation time of microwave, volume of extraction medium (water) were investigated. Results showed that the optimum extraction efficiency of OPPs in soil matrix was obtained by the microwave irradiation of sample solution at optional pH 8 with the irradiation power of 226 Watt for 2.5 min. MAE coupled with USAEME showed higher extraction efficiency under the extraction time of 8-9 minutes for the extraction of OPPs in soil samples. In order to verify the applicability, the proposed methods were successfully applied for OPPs determination in agricultural water and soil samples. The proposed methods provided a simple, cheap, fast and eco-friendly procedure for the sampling of OPPs from complicated sample matrix.
|
|---|
