Study And Application Of Solid-phase Microextraction Coupled To High Performance Liquid Chromatography Method In Analysis Of Environmental Pollutants

With the development of economy,it has become a noteworthy problem forenvironmental pollutants in all over the world.Based on the assessment of the healthhazard and dose response for pollutants,some of pollutants have been included in thepriority pollution list of US Environmental Protection Agency (EPA) and theEuropean Union (EU).The legislation limits of pollutant concentrations also havebeen proposed.These limit values are always low,so it is significant to improve thesensitivity of analytical methods to determine the trace concentration of pollutants andbetter understand the long-term,health effects of chronic exposure to them.Current analytical methods for environmental organic pollutants usuallyaccomplished by gas chromatography (GC) or high performance liquidchromatography (HPLC).However,the chromatographic and detection technique setconstraints on the chemical and physical properties of derivatives,and gaschromatographic analysis imparts the requirement of thermal stability and volatility.Compared with GC method,HPLC method has been more widely applied to analyzeorganic pollutants due to no limit for analytes' thermal stability and volatility.In theseanalytical methods,sample pretreatment can be used as enrichment process toimprove detection limits.Solid-phase microextraction (SPME) is a solvent-free andminiaturizable extraction technique,which has gained widespread acceptance foranalyte matrix separation and preconcentration.In this dissertation,SPME as thesample pretreatment technique to improve sensitivity of analytical methods and solvecomplex sample treatment,the following major innovation works were carried outbased on the previous literatures:(1)Uniform Experimental Design methodology was first used to optimize theSPME conditions.A sensitive method was developed for analysis of bisphenolA (BPA) and 4-nonylphenol (4-NP) in water samples.(2) The matrix effects were investigated in milk for the determination of BPA bySPME-HPLC and how to reduce the matrices interference were studied.Thesensitivity and recoveries have been improved with the proposed method.(3) Oxidized multiwalled carbon nanotubes (MWCNTs-COOH) was used as a novelSPME fiber coating and In-tube SPME medium coupled to HPLC fordetermination of phenols and aromatic amine in environmental water samples.Compared with other methods using UV detection,the sensitivities of proposed methods have been improved greatly.This dissertation consists of six chapters:Chapter 1 A theoretical and practical understanding of microextraction technologieswas described.The recent developments in new coating materials andapplication for various samples were reviewed,including Fiber-SPME,In-tube SPME and stir bar sorptive extraction (SBSE),respectively.Chapter 2 The extraction conditions of SPME were optimized using UniformExperimental Design methodology.Six quantitive optimization factorssuch as temperature,time,volume,salt content,pH and desorption timewere conducted by experimental design methodology.The optimalextraction conditions are determined by mathematical models based on therelationship between parameters and the peak area.The sensitivity of theoptimized method is verified by comparing results with those obtained byprevious methods using same commercial SPME coating.Chapter 3 SPME was used as the sample pretreatment for analysis of BPA in milk.The interaction between protein in milk and BPA was investigated andmatrix effect was validated.Matrix effect was eliminated and satisfactoryrecoveries (milk:93.1-101%;soybean milk:93.9-102%) were achieved.Chapter 4 MWCNTs-COOH as a novel SPME fiber coating coupled HPLC wasapplied for analysis of seven phenols in environmental water samples.Compared with the widely used commercially available SPME fibers,sensitivity of the proposed method was greatly improved usingMWCNTs-COOH coating than other SPME-HPLC-UV methods.Chapter 5 The simultaneous extraction and analysis of aromatic amine fromenvironmental samples was accomplished by automated in-tube SPMEmethod using MWCNTs-COOH as the extraction phase.On the one hand,more materials were used,so it can increase extraction efficiency andimprove the detection limits of analytical method.On the other hand,automated sample-handling procedures provide better accuracy andprecision relative to manual techniques.The proposed method was appliedfor determination of four aromatic amines including 4-nitroaniline,2-nitroanilin,2-chloroaniline and 2,4-dichloroaniline,and the detectionlimit was 0.04,0.07,0.08,0.13 ng mL^-1 (S/N=3),respectively.Chapter 6 The content of formaldehyde in a kind of the antiseptic solution was analyzed by iodine-volume method,acetylacetone spectrophotometricmethod and high-performance liquid chromatography.The conditionstranslated the product to formaldehyde were investigated.The results ofthese experiments showed that the translation became faster under the acidicconditions and higher temperatures.Among the methods studied,theiodine-volume method,under the condition of alkalescence,could use todetermine the content of the dissociated formaldehyde in the samplesolution and detect the release content of formaldehyde in the different storetime for the same sample accurately.