A Novel Liquid-phase Microextraction Method And Its Application To The Analysis Of Environmental Pollutants

In the determination of environmental pollutants, sample preparation is a pivotal process. Liquid-liquid extraction (LLE) is the classical method for its high recovery, stability and low cost, but its disadvantages are also inevitable, such as 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.Efforts have been made on miniaturizing the LLE extraction procedure by greatly reducing the solvent to aqueous phase ratio, which leads to the development of liquid-phase microextraction (LPME). 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. Due to the special interface is needless when it combines with gas chromatography (GC) or high performance liquid chromatography (LPME), LPME has gained increasing attention.Up to now, several different models of LPME have been developed. Because of the simple experimental setup, short analysis time and minimum use of solvent, LPME has been successfully applied to the determination of environmental monitoring, food analysis, biological and medical analysis in recent years. But the disadvantages of the technology are often encountered. (1) The volume of organic microdrop is limited because of the small contact area between microdrop and the tip of microsyringe. (2) The request for operators and environment is strict because of the instability of the microdrop. (3) The precision and sensitivity is relatively low.Considering these disadvantages, in this study, our group developed new sample pretreatment methods based on the conventional LPME, and combined these methods with GC or HPLC to analysis the environmental pollutants in real aqueous samples. In the optimized condition, the new techniques have been applied to the extraction of hydroxybenzene derivatives in Hucheng River in Jingzhou and pond water in our campus, the volatile halohydrocarbons (VHHs) in East Lake and tap water in our laboratory, and phthalate esters (PAEs) in landfill leachates of our campus. In addition, the extraction efficiency of our methods and that of conventional method was compared, the results indicated that the proposed methods are promising sample pretreatment approaches.