Study On The Analytical Methods For Environment And Food Based On Novel Liquid Membrane-Reinforced Hollow-Fiber Liquid-Phase Microextraction Coupled With Capillary Electrophoresis Technology

1.PrefaceCapillary electrophoresis（CE）has been developed into a relatively mature separation and analysis technology,possessing the inherent characteristics of simple device,fast analysis speed,low solvent and sample consumption,and low cost.It can be combined with a variety of detectors.Among them,amperometric detection（AD）is an electrochemical detection technology with good selectivity and high sensitivity,which can directly detect electroactive substances without derivatization.CE-AD system has been widely applied in food,environment,pharmaceutical and other analytical fields.However,pretreatment is an essential first step for sample systems with complex matrices and low target contents.Hollow-fiber liquid-phase microextraction technology（HF-LPME）is a novel green microextraction technology integrating purification and enrichment.This chapter briefly summarized the development history and principle of CE,introduced the application progress of CE-AD system,and emphatically reviewed the development,category and application of liquid-phase microextraction technology and the research progress of HF-LPME modified with different nanomaterials.In this thesis,the relevant research work on the construction and optimization of porous nanomaterials reinforced HF-LPME systems was carried out by CE-AD analytical system,and then the developed methods were tried to be applied for the separation and analysis of trace targets in the environmental and food samples.2.Study on the analytical method of typical phenolic pollutants by Hp ZIF-8@HF-LPME/CE-AD technologyIn this work,HF-LPME co-modified with hierarchical porous ZIF-8（Hp ZIF-8）and double solvents（tributyl phosphate and 2-nitroethyl benzene）was developed for the purification and enrichment of nine typical phenolic pollutants for the first time.This method was based on liquid-liquid-liquid three-phase dynamic HF-LPME model,which integrates extraction and desorption.The obtained enrichment liquid can be directly analyzed by CE-AD without need of derivatization.The main parameters affecting the enrichment efficiency of HF-LPME were optimized by full factor experiment and central composite design.Under the optimum conditions,the maximum enrichment factor reached 1827 times（for bisphenol A）,and the limits of detection were0.060-1.5μg L^-1（S/N=3）in real sample matrixes.This proposed method has been successfully applied to the analyses of different water samples with high ionic strength,including bottled drinking water,tap water,river water and sea water,and the average recoveries were in the range of 80.2-118.0%.This method provides an alternative for the monitoring of typical phenolic pollutants in water samples.3.Study on the analytical method of typical dairy flavor enhancers by ZIF-67@HF-LPME/CE-AD technologyIn this work,porous nanomaterial ZIF-67 and tributyl phosphate were used for the co-modification of supported liquid membrane,and the liquid-liquid-liquid three-phase dynamic HF-LPME mode was utilized for the simultaneous purification and enrichment of five typical dairy flavor enhancers represented by vanillin for the first time.The enrichment solution can be directly sampled by electric injection for CE-AD analysis.The main parameters affecting the enrichment efficiency of the flavor enhancers were discussed based on the univariate method.The results indicated that when the supported liquid membrane was tributyl phosphate containing 0.050 mg m L^-1ZIF-67,donor phase was 10 m L HCl solution（p H=4.00）,acceptor phase was 10μL Na OH solution（200 m M）,stirring rate was 500 rpm,enrichment temperature was 25°C,and enrichment time was 45 min,the highest enrichment factor of the flavor enhancers could reach 890 times（for ethyl vanillin）.This method has been successfully applied to the analysis of milk,milk powder and milk tea samples with the detection limits of0.15-0.30μg L^-1（S/N=3）and the recoveries of 80.1-115.5%.The proposed method is easy to operate and has low solvent and sample consumption,providing a potential green analytical method for the detection of typical flavor enhancers in dairy products.