A New Liquid-phase Microextraction Method And Its Application To The Determination Of Environmental Pollutants

In the determination of environmental pollutants in water samples, liquid-liquid extraction (LLE) is the classical method for sample preparation 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 (HPLC). Since the method was first introduced, LPME has been successfully applied for the application of environmental monitoring, food analysis, biological and medical analysis.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). The technique has attracted increasing attention in recent years because of the simple experimental setup, short analysis time and minimum use of solvent. But the disadvantages of the technology such as instability of microdrop, relative low precision and sensitivity are often encountered.In order to conquer these disadvantages, new sample pretreatment techniques have been developed, and applied for the extraction of chlorophenols and nitrophenols in water samples. The optimized methods were applied to determine chlorophenols and nitrophenols in lake and tap water. In addition, the extraction efficiency of our method and the conventional headspace liquid-phase microextraction was compared, and the result indicates that the proposed method is a promising sample pretreatment approach.