Application Of New Liquid Phase Microextraction Technique In Trace Residual Analysis Of Polychlorinated Biphenyls

Polychlorinated biphenyls(PCBs) are one kind of the most widespread and persistent environmental pollutants since the middle of the last century,and they are mainly used in capacitors,transformers,and plastic and paint industry.Due to their low water solubility,hydrophobic character and resistance to metabolic degradation,PCBs can represent a risk to environmental and human health.Even though the commercial manufacture of PCBs has been banned since the 1980s,the widespread use and environmental release of PCBs through disposal and spillage have resulted in both the contamination of fresh water and the accumulation of these toxicants in aquatic organisms.This raises concerns because exposure to PCBs has been linked to cancer and other adverse health effect,such as reproductive deficiencies,immuno-suppression,and dermatological disorders in humans and other animals。It is very important to investigate the concentration levels of PCBs in environmental samples.PCB residues are often at trace level in the environment,so it is necessary to use a preconcentration step before their analysis.In the determination of environmental pollutans,sample preparation is a pivotal process.Therefore,simple,quick,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, Liquid-phase microextraction(LPME) 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,which is developed as a new solvent-minimized preconcentration technique.In LPME,analytes were extracted from small volume of samples to only microlitre even nano-litre organic solvents.It combines extraction,preconcentration and sample introduction in one step,and is suitable to the development of micromation of modern analytical science.Up to now,several different models of LPME have been developed,such as static liquid-phase microextraction direct LPME,continuous-flow microextraction(CFME), headspace LPME,hollow fiber membrane LPME,dispersive liquid-liquid micro-extraction (DLLME) and ultrasound-assisted emulsification-microextraction(USAEME). LPME has been successfully applied for the application of environmental monitoring, food analysis,biological and medical analysis.There are papers reported the application of LPME technique for the determination of PCBs in environmental samples.However, to our knowledge,little data is available on PCBs analysis in soil and fish samples using the DLLME method.And no data are available on the determination of PCBs in environmental water samples by USAEME.In order to comprehensively evaluate its environmental matrix effects,2,2',5,5'-tetrachlorobiphenyl (PCB 52),2,2',4,5,5'-pentachlorobiphenyl(PCB 101),2,2',3,4,4',5'-hexachlorobiphenyl (PCB 138),2,2',4,4',5,5'-hexachlorobiphenyl(PCB 153),and 2,2',3,4,4',5,5'-heptachlorobiphenyl(PCB 180) were selected as representative congeners of PCBs and studied.High-sensitivity,fast,and cheap methods to determine PCBs compounds in environmental samples by the pretreatment of two modes of LPME (DLLME,USAEME) have been set up.The main researchs are listed as follows:Firstly,DLLME followed with GC-ECD has been presented for the extraction and determination of five polychlorinated biphenyls(PCBs) in soil samples.There are several parameters that affect DLLME performance,including type of extraction solvent used for soil sample,type of extraction and disperser solvent and their volume in DLLME procedure,salt addition and extraction time,which has been optimized to ensure the best extraction conditions.This method has been successfully applied for the trace analysis of PCBs in soil samples,collected from upper,middle and down reaches of Ao River, Wenzhou,China.Secondly,DLLME combined with GC-ECD has been applied to the residual analysis of four polychlorinated biphenyls(PCBs) in fish.There are several parameters that affect DLLME performance,including type of extraction solvent used for fish sample,type of extraction and disperser solvent and their volume in DLLME procedure, extraction time and salt addition,which has been optimized to attain the best extraction conditions.This method has been successfully applied for the determination of PCBs in fish samples,purchased from Wenzhou market,China.Thirdly,USAEME followed by GC-ECD has been applied to the residual analysis of five polychlorinated biphenyls(PCBs) in environmental water samples.To attain high extraction efficiency,parameters such as the kind of extraction solvent,the volume of extraction solvent,extraction time and salt addition have been optimized.This method has been successfully applied for the residual analysis of PCBs in tap,pool,and river water.