Application Of Liquid Phase Microextraction Novel Techniques In Pesticide Residue Analysis

In the screening of pesticide residues in water samples, liquid-liquid extraction (LLE) is the classical method for pesticide extraction and preconcentration, but it is time-consuming tedious, laborious and requires large amounts of toxic organic solvents, which have a great threaten on human health and environmental protection. Therefore, solvent-free extraction as a promising technique for sample preparation and pretreatment has become one of the most important research areas in modern analytical chemistry and attracted much attention recently. Such extraction techniques as solid phase extraction (SPE), supercritical fluid extraction (SFE) , microwave-assisted extraction (MAE), cloud point extraction (CPE) and solid phase microextraction have been widely applied in various fields.More recently, efforts have been placed on miniaturizing the LLE extraction procedure by greatly reducing the solvent to aqueous phase ratio, leading to the development of liquid-phase microextraction (LPME) methodology. LPME is based on the distribution effect of the analytes between a microdrop of organic solvent at the tip of a microsyringe needle and aqueous sample solution. In LPME, analytes were extracted from small volume of samples to only microlitre even nano-litre organic solvents. This technique belongs to the green analytical technique and is suitable to the development of micromation of modern analytical science. It combines extraction, preconcentration and sample introduction in one step, and proved to be a simple, fast and low-cost sample preparation method. Compared with SPME, LPME has gained increasing attention, due to the special interface is needless when it combines with high performance liquid chromatography(LPME). Since the method was first introduced in 1996, LPME has been successfully applied for the application of environmental monitoring, food analysis, biological and medical analysis. Although the use of LPME in pesticides analysis with gas chromatograph has been described previously, to our knowledge, it has not been used for the analysis of organophosphorous insecticides.Up to now, several different models of LPME have been developed, such as static LPME, dynamic LPME, hollow fiber membrane LPME, headspace LPME and continuous-flow microextraction (CFME). When it comes to different sample solutions, different models of LPME can be used. Analytes with high volatilities can be extracted by headspace or static LPME. For analytes with weak volatilities, static LPME can be used when the sample solution has clean background, otherwise hollow fiber membrane LPME can be used. According to our knowledge, among those several models, dynamic LPME and CFME are relative novel LPME methods, both of which have seldom been reported.In this study, the static LPME, dynamic LPME and CFME techniques have been applied for the extraction of Phoxim, respectively. Parameters relevant to the extraction performance, such as extraction solvent type, solvent drop size, extraction time and salt addition, were studied and optimized. The optimized method was applied to determine phoxim in lake water and tap water to evaluate the application of this method to real samples.