【作者】 姜宪娟；

【导师】 何友昭； 淦五二；

【作者基本信息】 中国科学技术大学 ， 分析化学， 2010， 博士

【摘要】 氢化物／冷蒸气发生法是原子光谱最重要的样品引入方式。化学氢化物／冷蒸气发生法(CHG/CVG)较之常规进样法具有很多的优势,但是通常需要使用价格较贵、性质不稳定的硼氢化钠或者硼氢化钾作还原剂。由于硼氢化物还原能力非常强,可以还原的物质种类多,所以以硼氢化物-酸体系为基础的化学氢化物／冷蒸气发生法容易受到共存的过渡金属离子的干扰,因此对研究者们来说,发展一种新的氢化物发生技术来代替化学法具有很强的吸引力。电化学氢化物／冷蒸气发生法(EC-HG/EC-VG)在某些情况下就可以替代CHG/CVG法。考虑到EC-HG/EC-VG的分析性能与阴极材料的性能和电解池的设计有直接关系,为了提高电化学氢化物发生效率、提高EC-HG/EC-VG原子光谱的灵敏度并拓展其适用的元素范围,本工作主要尝试了选择合适的阴极材料以及改进电化学氢化物发生池的结构以改善电化学法的分析性能。另外通过具体的实验结果和一些物理化学数据,在前人研究的基础上,对电化学氢化物发生机理进行了较为深入的探讨。论文具体工作包括以下几部分：首先采用三维多层网状钨丝电极作为电化学氢化物发生池的阴极,在低温条件下,网状钨丝阴极表面产生的TeH2可以被吹扫气体有效地带出阴极腔,并带入到原子荧光光谱仪中进行定量分析。通过将EC-HG和原子荧光光谱法(AFS)联用,构建了简单、高效的测定实际样品中碲元素含量的分析方法。考虑到导电高聚物聚苯胺(PANI)材料的优良特性,采用线性扫描伏安(LSV)实验研究了Hg(Ⅱ)在PANI修饰电极表面的反应特性,结果发现PANI膜有助于Hg(Ⅱ)的还原,使Hg(Ⅱ)可以在较高的电极电势下还原。本工作中,我们将聚苯胺修饰的石墨电极用作EC-VG系统的阴极材料,通过与AFS法联用,用于Hg(Ⅱ)的测定。由于还原过程中可能包含一个催化过程,该ECVG-AFS法具有灵敏度高、稳定性好、记忆效应低等优点,该方法被成功地用于生物样品中总Hg含量的测定。采用电化学法制备了PANI修饰的Pb电极,并将该PANI/Pb作为电化学氢化物发生池中的阴极材料,建立了电化学氢化物发生-原子荧光光谱系统测定元素Sn的方法。由于PANI膜对Sn(IV)具有较好的还原活性,所以该方法具有较高的灵敏度、良好的稳定性和较低的记忆效应。为了减少氢化物在传输过程中的损失,设计了一种氢化物发生池和气液分离器一体化的整体池。该电化学氢化物发生池以一个小尺寸的石墨管(容积约为180μl)为阴极腔,免除了离子交换膜和专门的阳极电解液的使用。该整体池的无膜结构使电解液能够依次流过阴极腔、气液分离腔和阳极腔,同时起到阴极液和阳极液的作用,具有节约和环境友好等优点；该整体池的密封采用螺帽结构,安装方便,便于清洗。通过将该整体电化学氢化物发生池和AFS联用,建立了一种简单高效的流动注射分析技术,成功地用于生物样品中总砷的测定。更多还原

【Abstract】 The hydride/vapor generation is well-established sample introduction technique in atomic spectrometry when low detection limits are desired. Although the chemical hydride generation technique, which is sample introduction method based on the reaction of sodium tetrahydroborate with the acidic material that has many advantages and is widely used, there are some disadvantages, such as the usage of expensive reagent of sodium tetrahydroborate and its aqueous solutions must be prepared daily because of its unstablility. What’s more, on account of the powerful reducibility of sodium/kalium tetrahydroborate, interferences from concomitant species can be severe. The electrochemical hydride/vapor generation (EC-HG/EC-VG) methods have been developed as alternatives to the chemical methods.Considering the fact that the analytical performances of the EC-HG and ECVG were directly related to the cathode material and the design of the electrolytic cell, efforts were made in this work to develop suitable cathode material for EC-HG or ECVG determination. Besides, systematic researchs, which based on previous work and quantitative data in this work, were also carried out on the mechanism of electrochemical hydride/vapor generation. The details are listed as follows:A three-dimensional reticular W filament electrode was used as the cathode in the EC-HG system. At low temperatures, the TeH2 generated on the reticular W filament cathode surface could be effectively driven out by sweeping gas in the cathode chamber and was determined by atomic fluorescence spectrometry (AFS). A simple and highly accurate method was developed for the detection of Te in soldering tin material by coupling EC-HG with AFS.Considering the excellent characteristics of polyaniline (PANI) material, such as unique stablility and avoids the use of organic solvents, we experimented its performances by Linear sweep voltammetry and found that the PANI film improved the reduction of Hg(Ⅱ), allowing the reduction of Hg(II) at higher potentials. In this work, we developed an ECVG-AFS system with PANI/graphite as cathode for Hg (Ⅱ) determination. Owing to the fact that a catalytic process may be involved in the reduction process, this proposed method had the virtues of higher sensitivity, excellent stability and lower memory effect. This developed method was successfully applied for analyzing trace amounts of mercury in biological samples. In the present work, PANI on Pb electrode was synthesized electrochemically and this PANI/Pb electrode was used as cathode material in the EC-HG-AFS system for the determination of tin. Attributing to the superior reduction activity of the PANI film for Sn (IV), this proposed method had the virtues of higher sensitivity, excellent stability and lower memory effect. This developed method was successfully applied for analyzing total tin in foods.An integrated EC-HG cell was laboratory constructed and a small dimension (180μl) graphite tube used as cathode chamber. This integrated cell was free of ion-exchange membrane and individual anolyte. The non-membrane setup enabled the electrolyte stream to be sequentially pumped through cathode chamber, gas liquid separator (GLS) chamber and anode chamber acted as both catholyte and anolyte. Therefore, it had advantages of low-cost and environmental-friendly. In addition, the screw cap makeup for components seal makes assembling of EC-HG cell be easy, and reduced the time required for cathode replacement or cleaning. A simple and sensitive flow injection method for the detection of As was created by coupling this integrated EC-HG cell with AFS, and this developed method was successfully applied to determine trace amounts of As in biological samples.更多还原