Application Of Novel Liquid Phase Microextraction Techniques In Phthalate Esters Analysis

Phthalate esters (PAEs) are used primarily as plasticizers in polymeric materials, increasing their flexibility only through weak secondary molecular interactions with polymer chains. Being not covalently bound to the vinyl polymer matrix, their migration from plasticized products to contact materials may occur through extraction or evaporation processes. Worldwide production of phthalate esters and their frequent application in different products of everyday use has resulted in their widespread presence in all parts of the environment. Certain phthalate esters, as well as their metabolites and degradation products, can cause adverse effects on human health, in particular on liver, kidney and testicles. Potential endocrine disrupting properties were also reported. Evaluation and monitoring of traces of these compounds from different environmental matrices are imperative for human health protection and environmental control.For the screening of trace phthalate esters in water samples, liquid-liquid extraction (LLE) is the classical method for organic compounds 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.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. 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.Up to now, several different models of LPME have been developed, such as direct LPME, dynamic LPME, hollow fiber membrane LPME, headspace LPME , continuous-flow microextraction (CFME) and dispersive liquid-liquid microextraction (DLLME). When it comes to different sample solutions, different models of LPME can be used. Analytes with high volatilities can be extracted by headspace or direct LPME. For analytes with weak volatilities, direct LPME can be used when the sample solutionhas clean background, otherwise hollow fiber membrane LPME can be used.In this study, new methods based on LPME combined with chromatography have been developed for the determination of phthalate esters. The optimized methods were applied to determine PAEs in lake water, tap water and bottled mineral water to evaluate the application of these methods to real samples.