【作者】 韩素平；

【导师】 苏庆德； 淦五二；

【作者基本信息】 中国科学技术大学 ， 分析化学， 2009， 博士

【摘要】 样品前处理,作为整个分析测试过程中最关键的环节,随着现代化学分析技术的飞速发展,其手段也越来越向着快速、准确、自动的方向发展。本论文旨在根据电磁感应加热原理,设计、构建多种在线电磁感应加热系统,并应用于样品的在线消化和在线预富集。本论文第1章首先介绍了流动注射分析技术的原理、发展及常用的联用技术,然后详细介绍了各种样品消化技术和分离富集技术,最后介绍了电磁感应加热基本原理以及磁路设计和电路设计的相关知识。在此基础上设计了各种电磁感应在线加热系统,并对影响系统性能的参数进行优化,通过与不同检测方法联用完成样品的在线预处理和分析检测。方法安全高效、绿色环保、操作简便、成本低廉,符合当今绿色分析化学的发展要求。这些探索性研究为后续进一步的研究工作提供了参考信息。论文具体工作总结如下:第2章使用电磁炉加热消化样品,研制了在线外加热消化还原、氢化物发生原子荧光法分析装置,实现了茶水中As含量的在线测定。对在线消化的温度、酸度、管长,样品的流速,还原剂浓度,载流的种类和浓度等一系列实验条件进行了选择及优化,并对Se⁴⁺、Co²⁺、Cd²⁺、Hg²⁺、Al³⁺、Fe³⁺、Pb²⁺、Cr³⁺等离子对As信号的干扰情况进行了详细研究。在选择的最佳实验条件下,As的检出限为0.063μg L^-1;样品分析精密度（RSD）为2.5%（n=11）,方法准确可靠。在第3章中设计电磁感应加热柱并构建了电磁感应在线内加热体系。处于溶液内部的铁磁性介质在磁场作用下自行发热,由于集肤效应,热量主要集中在铁磁性介质表面。当样品溶液流经电磁感应加热柱时由于热传递快速升温,提高了传热效率和热利用率,从而使加热功率降低。系统地优化了电磁感应加热柱的尺寸和样品在线消化的条件。将实验方法与离线微波快速消解法进行了对比分析,证明实验方法准确可靠。通过与火焰原子吸收光谱法联用成功测定了茶叶样品中的Zn和Mn。在第4章中研制了一种新的低功率电磁感应加热装置,通过改变高频感应加热装置的输出功率进行有效控温,待测样品溶液在较低功率（15 W）时快速升温,可进一步降低电磁感应加热功率。将该装置应用于有机汞的在线氧化,并通过与原子荧光光谱法联用,在线测定了海产品中的无机汞和有机汞。该方法加热速度快,温度容易控制,易实现均匀加热,加热效率高,节能。第5章将电磁感应加热技术应用于固体粉末样品的在线消化。对低功率电磁感应加热系统作进一步改进,通过与流动注射分析技术联用,构建了在线加压电磁感应加热系统。通过优化影响该系统性能的参数以及仪器检测参数确定了最佳的样品在线消化和测定条件,并通过在线消化海藻粉末样品对该系统的性能进行了评价和验证。样品消化时系统内部的压力为0.36 MPa,消化温度可达135℃。温度和压力的提高大大改善了样品的消化效果,可实现固体粉末样品的在线消化,结果令人满意。通过与冷蒸气发生原子荧光法（CVAFS）联用实现了海藻粉末样品中Hg含量的成功测定。此外,该法有效避免了样品消化过程中由于加热导致Hg挥发损失的问题,是一种简便、快捷、价廉、安全的在线消化固体粉末样品的方法。在第6章中,作者进一步拓展电磁感应加热技术的应用领域,将其应用于环境水样化学需氧量（COD）测定时的样品前处理,开辟了一条测定COD的新思路。用电磁感应加热代替传统的回流加热,建立了电磁感应加热氧化水样,分光光度法测定COD的新方法。在加热功率40 W时,以0.004 mol L^-1 K₂Cr₂O₇+5.4 mol L^-1H₂SO₄为氧化剂,在10 min内快速完成水样氧化。以分光光度法在445 nm处测定过量Cr⁶⁺间接计算COD值代替传统的滴定测量。该方法提高了加热效率,减少了能量和试剂消耗,简化了操作程序,并且具有简便、快速、易于操作等优点。第7章研究建立了电磁感应加热技术应用于浊点萃取富集的新方法。构建了在线电磁感应加热—浊点萃取富集系统,通过与火焰原子吸收光谱联用,实现了水样中重金属元素Cr（Ⅵ）、Cd和Cu的在线富集与检测。实验中对影响该系统性能的各个参数进行了选择,并对影响富集倍数的各个条件进行了优化,并从富集倍数、检出限、回收率、相对标准偏差等方面对分析方法进行了验证,证明了本方法的灵敏度和可靠性。更多还原

【Abstract】 Sample preparation,which is often considered as the bottle-neck of an analytical procedure,is developing to be more rapidly,exactly and automatically.In this thesis, different electromagnetic induction heating（EMIH） systems based on EMIH technique were developed and applied to on-line sample digestion as well as on-line sample preconcentration.In chapter 1,the theory and development of flow injection analysis（FIA） technique as well as the detection methods which were often coupled to FIA were firstly introduced.Then,different sample digestion techniques and sample preconcentration methods were presented in detail.At last,the theory of EMIH was introduced and the relevant knowledge about the magnet design and circuit design was also illustrated.In the following chapters,different EMIH systems were established and the parameters which influence the performance of the proposed system were optimized.In combination with different detection methods,on line sample preparation and detection could be accomplished.The method was safe,high efficient,environmental-friendly,low cost and easy to operate.Additionally,it was in accordance with the requirement of green analytical chemistry.These exploratory studies provided reference information for further studies.In more specific terms,the main work in this thesis was listed as follows:In chapter 2,a simple,rapid method was developed for on-line determination of arsenic in tea.The method employed an electromagnetic induction oven as heating source,followed by pre-reduction of As（Ⅴ） to As（Ⅲ） by means of 25 g L^-1 KI and 25 g L^-1 ascorbic acid and then determined by hydride generation-atomic fluorescence spectrometry（HG-AFS）.The parameters such as the temperature and acidity of on-line sample digestion,the length of the digestion coil,sample flow rate,the concentration of the reductant,the kind and concentration of carrier,etc.were optimized.The interference of coexisting ions such as Se⁴⁺,Co²⁺,Cd²⁺,Hg²⁺,Al³⁺, Fe³⁺,Pb²⁺,Cr³⁺ was studied.Under optimal conditions,the detection limit（3σ） was evaluated to be 0.063μg L^-1,and the relative standard deviation（RSD） for 11 replicate determinations of 5μg L^-1 As was evaluated to be 2.5%.The proposed method was proved to be accurate and reliable.In chapter 3,an electromagnetic induction heating column（EMHC） was designed and another EMIH system was developed to perform on-line sample digestion.In this system,the heat generated inside the sample solution in EMHC and concentrated just in a thin-layer region beneath the heating material,faster heating energy transfer and higher heating efficiency were obtained and the sample solution was quickly digested at a relative lower heating power.The size of EMHC as well as the on-line digestion parameters was investigated systematically.The proposed method was compared with microwave digestion,and the results proved its accuracy and reliability.The developed method was successfully applied to the determination of zinc and manganese in tea leaf by flame atomic absorption spectrometry（FAAS）.In chapter 4,a new low power EMIH device was designed to save heating power and was applied to on-line oxidation of organomercury in seafood.The heating temperature could be easily controlled by adjusting the output of heating power.For total mercury determination,the organomercury in sample solution was quickly oxidized by potassium persulfate in EMHC at a relatively lower heating power（15 W）.Inorganic mercury determination was performed by keeping EMHC at room temperature.In combination with atomic fluorescence spectrometry（AFS）,inorganic mercury and organomercury in seafood could be determined quickly and accurately. In the proposed method,it was easy to control the heating temperature and to accomplish homogeneous heating.Additionally,the heating efficiency was improved and energy consumption was reduced.In chapter 5,the EMIH system was further improved and was employed to perform solid sample decomposition in acid medium.In combination with FIA,an on-line pressurized EMIH digestion system was developed.In the experiment,the parameters which influenced the performance of the proposed system were optimized and the system’s performance was evaluated for on-line digestion of edible seaweeds. The efficiency of acid digestion was improved by a pressure of 0.36 MPa and 135℃reaction temperature.Therefore,the proposed system could be applied for solid sample digestion and the result was satisfactory.By on-line coupling the digestion system to cold vapor generation atomic fluorescence spectrometry（CVAFS）,the developed method could be satisfactorily applied to the determination of mercury in edible seaweeds.The proposed method reduced energy consumption,analysis time and Hg emission.It was a safe,convenient,low-cost method for on-line solid sample digestion.In chapter 6,the EMIH technique was introduced to chemical oxygen demand （COD） determination and opened a new frontier in EMIH application.EMIH was employed instead of conventional reflux heating,and an on-line pressurized oxidation flow injection system for COD evaluation was developed.When samples flowed through the EMHC,they were on-line oxidized by 0.004 mol L^-1 K₂Cr₂O₇+5.4 mol L^-1 H₂SO₄ within 10 min under approximately 145℃reaction temperature and 0.44 MPa manifold pressure,and the corresponding heating power was just 40 W.The reduction in dichromate absorbance due to oxidation of the organic compounds was measured at 445 nm by spectroscopy.The proposed method improved the heating efficiency,reduced energy and reagent consumption,analysis time,hazardous emission,external contamination and tedious operation.EMIH technique was used for on-line sample digestion in the above-mentioned work.In chapter 7,we applied it to cloud point extraction（CPE） for on-line sample preconcentration.A new on-line EMIH-CPE system was designed to preconcentrate Cr（Ⅵ）,Cu and Zn in water samples followed by FAAS detection.In the experiment, the parameters which influenced the performance of the proposed system were optimized.And the method was validated in terms of enrichment factor,limit of detection,recovery and RSD.The results proved the sensitivity and reliability of the proposed method.更多还原