【作者】 董树清；

【导师】 何品刚； 王清江； 方禹之；

【作者基本信息】 华东师范大学 ， 分析化学， 2009， 博士

【摘要】 毛细管电泳（Capillary Electrophoresis，CE）是离子和荷电粒子以高压电场为驱动力，以毛细管为分离通道，依据样品中各组分之间淌度或／和分配系数的差异而实现高效、快速分离的一类新型液相分离技术。毛细管电泳具有高效、快速、经济、环保等优点，其研究和应用广泛涉及了食品卫生、药物分离、环境分析、生化分析等几乎所有的分析领域。毛细管电泳具有多种联用检测技术，如紫外检测、荧光检测、电化学检测和质谱等。其中，电化学检测中的安培检测技术，相对而言具有较高的灵敏度，且线性范围宽、仪器简单、成本低廉、操作简便，因而毛细管电泳-安培检测法在分析化学领域得到了越来越广泛的研究、应用和发展。本论文基于毛细管电泳-安培检测联用技术高效、快速、灵敏、方便的优势，从化学修饰电极的研制入手，对饮料、氨基酸、菊花、染发剂等食品及日常用品中的有效或有毒成分进行分离检测。不仅扩展了毛细管电泳-安培检测联用技术的应用范围，提高了检测灵敏度，改善了分离效果，而且进一步建立新的实验方法同时分离检测苯二胺类和苯二酚类同分异构体等复杂体系，得到了好的实验结果。论文主要分以下七个部分：第一章简要地综述了毛细管电泳的发展历史、基本原理、分离模式、联用检测技术，应用领域研究进展以及本论文研究的目的和意义。第二章研究制作了同时以聚乙二醇和氧化亚铜为修饰剂的新型双修饰剂碳糊电极（PEG-Cu₂O CPME），并首次将其应用于糖类物质和抗坏血酸的毛细管区带电泳-安培检测。在研究中，通过实验考察各种实验参数对分离检测的影响，最终成功实现了对葡萄糖、蔗糖、果糖和抗坏血酸的同时分离和检测。与未经修饰的纯碳糊电极或只含有一种修饰剂的碳糊电极相比，PEG-Cu₂O碳糊修饰电极在相对较低的检测电位下（+0．30 V vs．SCE）具有较好的催化氧化特性，灵敏度显著提高。在最优化的实验条件下，以此新型碳糊修饰电极为工作电极，上述四种组分在22 min内可以得到完全的分离检测。葡萄糖、蔗糖、果糖和抗坏血酸的线性范围均为1．0×10^-6～5．0×10^-5mol L^-1，检测限最低达到1．0×10^-7mol L^-1数量级（信噪比为3）。实验结果表明，本法具有分离效率高、分析操作简便、检测灵敏度高、结果重现性好等优点，对实际样品的检测得到满意结果。第三章首次利用多壁碳纳米管和氧化亚铜同时做碳糊电极修饰剂测定了19种重要的氨基酸。因氨基酸本身缺乏用于检测的光学性质，如光吸收、光发射和电化学活性，所以常常需要各种衍生技术使其具有光活性或者电化学活性。本文摒弃传统的衍生法，应用多壁碳纳米管和氧化亚铜双修饰剂碳糊电极测定了19种重要的氨基酸。研究发现在此修饰电极上，19种氨基酸的电化学响应与缓冲溶液的pH值有密切的关系，并进一步探索了反应机理。应用该碳糊修饰电极成功地对其中六种电化学响应较高的氨基酸（精氨酸、色氨酸、组氨酸、苏氨酸、丝氨酸、酪氨酸）进行了毛细管区带电泳-安培检测。在最佳实验条件下，六种分析物可在20 min内达到基线分离，其检测限达10^-7～10^-8mol L^-1数量级（信噪比为3），该方法简便易行，灵敏度高，检测结果令人满意。第四章制备了一种新型的聚VB₁₂修饰电极并将其应用于毛细管电泳-安培检测中同时分离检测水果和蔬菜中的抗氧化剂。与普通碳电极相比，此修饰电极对谷胱甘肽、抗坏血酸、香草酸、绿原酸、水杨酸和咖啡酸的电化学催化氧化性质有显著提高。将该修饰电极用于毛细管电泳-安培检测，考察了影响毛细管电泳分离的各种因素：缓冲体系的pH值及溶液的浓度、分离电压、检测电位、进样时间等。在最优化的实验条件下，这六种抗氧化剂能够在pH 8．4的硼砂-磷酸缓冲中15 min内完全分离。并且线性范围较宽2．5×10^-7～1．0×10^-4 mol L^-1，检测限达到10^-7～10^-8mol L^-1数量级（信噪比为3）。结果表明：此法具有操作简便、灵敏度高、重现性好的优点，可以用于实际样品的检测。第五章利用毛细管区带电泳-安培检测技术实现了对染发剂中的邻、间、对苯二胺及邻、间苯二酚的同分异构体的分离检测。考察了缓冲溶液的pH和浓度、分离电压、检测电位、进样时间等实验参数对分离检测的影响。在最优化的实验条件下，以Pt电极作为工作电极，在+0．85 V的检测电位下，这5种分析物在15min内实现基线分离，其线性范围为1．0×10（-6）～1．0×10（-4） mol L^-1，检测限最低可达10^-7mol L^-1数量级（信噪比为3）。实验成功分离检测了8种染发剂样品中的五种同分异构体，回收率为91．0～108．0％，相对标准偏差低于5．0％。结果表明，用铂电极作为工作电极应用于毛细管区带电泳-安培检测法中具有操作简便、灵敏度高、检测限低、重现性好等优点，可被用于实际样品的快速检测。第六章本文针对菊花中的黄酮类物质，通过实验测试了多种缓冲添加剂对毛细管电泳-安培法检测结果的影响，最终确立了合适的缓冲添加剂及其添加位置，实现了对菊花中黄酮类物质的分离检测。并对毛细管电泳实验参数进行优化，在最佳的实验条件下，以碳圆盘电极为工作电极，六种黄酮类物质在20 min内达到基线分离，检测限最低达到10^-8g mL^-1。实验结果表明，使用该经过优化的毛细管区带电泳-安培检测法，分离检测具有较高的灵敏度和较好的重现性，用于对菊花实际样品的检测，结果令人满意。第七章应用交替运行两种不同pH值缓冲溶液的毛细管电泳分离-安培检测法，可以很好的实现同分异构体的分离检测，并且操作简便、灵敏度高、重现性好，为毛细管电泳的方法学研究提供了新的方向。由于邻、间、对苯二胺的pK_a值分别为4．52，5．64，6．04，因而可以在弱酸条件下实现好的分离检测，而邻、间、对苯二酚的pK_a值分别为9．40，9．40和10．04，只在偏碱性的缓冲条件下实现好的分离结果。因此用一个固定pH的缓冲同时全部分离这六个同分异构体是非常困难的（即使在第五章最优化的条件下，也仅能实现其中5种同分异构体的分离检测）。本文设计并应用交替运行两种不同pH值缓冲溶液的毛细管电泳-安培检测法同时分离检测这六种同分异构体，实验结果表明，当很好的控制两种不同pH值缓冲溶液（pH分别为5．8和7．6）的运行时间和顺序，这六种分析物能够在20 min内实现基线分离，检测限达到10^-7mol L^-1数量级（信噪比为3）。为拓宽此方法的应用范围，考察其可行性，我们将此方法应用于其它复杂体系，发现当不同pH值运行缓冲液的运行顺序和时间达到最佳时，可以成功取代缓冲溶液中添加修饰剂分离检测菊花中的黄酮类物质（第六章实验）的方法，省时省力，无有机溶剂污染。更多还原

【Abstract】 Capillary electrophoresis （CE） is a powerful liquid phase separation technique.The separation principle is based on the phenomena that ionized molecules ofdifferent mass and charge will travel with different velocities through a fused silicacapillary under the influence of a high-voltage electric field.Owing to the highseparation efficiency,rapid analysis,minimum consume of samples andenvironmental friendliness,it has been flourishing in wide areas such asenvironmental analysis,pharmaceutical analysis,biochemical analysis,and foodanalysis etc.There are many detection methodologies coupled with CE,such as UV-Visibledetection （UV-Vis）,Laser Induced Fluorescence detection （LIF）,Electrochemicaldetection （ED） and Mass Spectrum （MS）.The major barriers for CE systemintegration with LIF and MS etc.are fluidic interface,sample pretreatment（fluorescence derivatization or labeling）,etc.Since ED,especially amperometricdetection （AD） has many advantages over other widely used techniques in that it ismuch more economical,without complicated pretreatment procedure,and it providesgood selectivity as well as high sensitivity,so it has flourished to various areas.Fromthe standpoint of broadening its application areas,we mainly focus on thedevelopment of new chemically modified electrode （CME） and new method ofCE-AD.This paper begins with a brief introduction of CE,its separation models as well asvarious detection methodologies.Chapter 2 is the determination of three kinds of carbohydrates together withascorbic acid by capillary zone electrophoresis with amperometric detection（CZE-AD） at a carbon paste modified electrode.In this paper,a kind of novel carbonpaste electrode modified with double modifiers-polyethylene glycol （PEG） and Cu₂O（PEG-Cu₂O CPME） in CZE-AD was applied to simultaneously determine glucose,sucrose,fructose and ascorbic acid （AA）.The catalytic electrochemical properties ofPEG-Cu₂O CPME could enhance sensitivity obviously compared with carbon pasteelectrode modified with only PEG or Cu₂O at a relatively lower detection potential（+0.3 V vs.SCE）.The four analytes could be perfectly separated within 22 min,the linear ranges were from 1.0×10^-6 to 5.0×10^-5 mol L^-1 and the detection limits were at10^-7 mol L^-1 magnitude （S/N=3）.The present working electrode was successfullyemployed to analyze beverage samples with recoveries in the range 93～107% andRSDs less than 4%.The results demonstrated that CZE coupled with the PEG-Cu₂Ocarbon paste modified electrode was of convenient preparation,high sensitivity,goodrepeatability and could be used in the rapid determination of practical samples.Chapter 3 states the development of a novel double modifier carbon pasteelectrode-a MWCNT-Cu₂O CPME and its application on several amino acids.Aminoacids are essential building blocks of biological molecules.Though they are soimportant to human beings,it is to some extent very difficult to separate anddetermine amino acids because of their adsorbability to silica capillary andnon-optical and non-electrochemical activity for detection.In this paper,a carbonpaste electrode modified with multiwall carbon nanotubes and copper （I） oxide（MWCNT-Cu₂O CPME） was fabricated and the electrochemical behaviors ofnineteen kinds of natural amino acids at this modified electrode were studied.TheMWCNT-Cu₂O CPME was also successfully applied to the CZE-AD of six kinds ofamino acids.Under the optimal conditions,these amino acids could be perfectlyseparated within 20 min and their detection limits were as low as 10^-7 or 10^-8 mol L^-1magnitude （S/N=3）,which demonstrated that MWCNT-Cu₂O CPME could besuccessfully employed as an electrochemical sensor for amino acids with someadvantages of convenient preparation,high sensitivity and good repeatability.Chapter 4 develops a new kind of vitamin B₁₂ （acquo-cobalamine） chemicallymodified electrode and applies in capillary zone electrophoresis coupled withamperometric detection （CZE-AD） for simultaneous determination of someantioxidants in fruits and vegetables.The catalytic electrochemical properties of thechemically modified electrode could obviously enhance oxidation peak currentsresponses by about five times to glutathione,ascorbic acid,vanillic acid,chlorogenicacid,salicylic acid,and caffeic acid compared with common carbon disk electrode.Furthermore,the effects of working electrode potential,pH and concentration ofrunning buffer,separation voltage and injection time on CZE-AD were investigated.Under the optimum conditions,the six analytes could be completely separated and detected in a borate-phosphate buffer （pH 8.4） within 15 min.Their linear rangeswere from 2.5×10^-7 to 1.0×10^-4 mol L^-1 and the detection limits were as low as 10^-7 or10^-8 mol L^-1 magnitude （S/N=3）.The proposed method has been successfullyemployed to monitor the six analytes in practical samples with recoveries in the range96.0-106.0% and RSDs less than 5.0%.Above results demonstrate that capillary zoneelectrophoresis coupled with electrochemical detection using vitamin B₁₂ modifiedelectrode as detector is of convenient preparation,high sensitivity,good repeatability,and could be used in the rapid determination of practical samples.Chapter 5 states simultaneous determination of three isomers ofphenylenediamines （o-,m-p-phenylenediamine） and two isomers ofdihydroxybenzenes （catechol and resorcinol） in hair dyes was performed by capillaryzone eletrophoresis coupled with amperometric detection （CZE-AD）.The effects ofworking electrode potential,pH and concentration of running buffer,separationvoltage and injection time on CZE-AD were investigated.Under the optimumconditions,the five analytes could be perfectly separated in a 0.04 mol L^-1borate-phosphate buffer （pH 5.8） within 15 min.A 300μm diameter platinumelectrode had good responses at +0.85 V （versus SCE） for the five analytes.Theirlinear ranges were from 1.0×10^-6 to 1.0×10^-4 mol L^-1 and the detection limits were aslow as 10^-7 mol L^-1 magnitude （S/N=3）.The present working electrode wassuccessfully employed to analyse eight kinds of hair dyes samples with recoveries inthe range 91.0-108.0% and RSDs less than 5.0%.Above results demonstrated thatcapillary zone electrophoresis coupled with electrochemical detection using platinumworking electrode as detector was of convenient preparation,high sensitivity,goodrepeatability and could be used in the rapid determination of practical samples.Chapter 6 is about the optimization of CZE for a complicated system.Chrysanthemum is a herbaceous perennial plant possessing antimicrobial,antibacterial,antifungal,antiviral and anti-inflammatory activities,which mostlyowing to it ingredients of flavonoids.Here in this research we focus on the CZEseparation of six kinds of flavonoids in chrysanthemum.With the help of differentadditives into buffer and sample,they could get baseline separation within 20 min andthe LOD could reach 10^-8 g mL^-1 magnitude.The successful practical application on the determination of chrysanthemum samples confirmed the validity and practicabilityof this method.The last chapter is focus on determination of the o-,m-,p-phenylenediamine ando-,m-,p-dihydroxybenzene.Because of the great pKa differences between twogroups of isomers but the similar pKa in each group,it is very difficult to find asuitable pH buffer for the simultaneous separation of the two groups of isomers bycapillary zone electrophoresis （CZE）.In the paper,a novel method based on runningbuffer pH gradients was designed for capillary zone electrophoresis withamperometry detection （CZE-AD） to simultaneously separate two groups ofinteresting positional isomers including o-,m-,p-phenylenediamine and o-,m-,p-dihydroxybenzene.It is found that when the pH gradients running was employedappropriately,the six analytes could be separated in less than 20 min and the detectionlimits were as low as 10^-7 mol L^-1.Furthermore,other factors affecting the CZEseparation,such as working potential,ionic strength of running buffer,separationvoltage and sample injection time were extensively investigated.The feasible of themethod was determinated by using it in the chapter 6 chrysanthemum experiment,theresults showed that the novel method can replace adding modifier in running buffer.Experimental results demonstrated that the method could be successfully employedfor the analytes which could not be separated simultaneously under the immobile plugwith defined pH with some advantages of high sensitivity,good repeatability andsmall sample requirement.更多还原