【作者】 乐上旺；

【导师】 李建平；

【作者基本信息】 桂林工学院 ， 分析化学， 2008， 硕士

【摘要】 化学修饰电极是当前电化学、电分析化学方面十分活跃的研究领域,其通过对电极表面的分子剪裁,可按意图给电极预定的功能,以便在电极上有选择地进行所期望的反应,在分子水平上实现了电极功能的设计。目前伏安法测定铬注重对反应体系改进而很少在电极修饰上进行突破,本文制作了银汞合金电极,并在其表面通过自组装修饰上DTPA。利用Cr（III）-DTPA-NO₃^-体系的催化作用测定溶液中的Cr（VI）和无机态Cr（III）。该法无需对样品进行前处理,通过改变扫描前富集方式,分别实现Cr（VI）和无机态Cr（III）的测定,测定的线性范围分别为:5.0×10^-9～5.0×10^-6 mol/L和1.0×10^-8～5.0×10^-6 mol/L,检测限为1.6×10^-10 mol/L和5.1×10^-9 mol/L。该法用于实际水样测定,Cr（VI）和Cr（III）的标准加入回收率为98.5%～105.0%。伏安分析法测定铬需要在一定催化体系或富集时间下才能完成,这样很难保证对被测样品在完整和接近实际生理状态环境下进行实时、连续地测定。然而,电位型离子选择性电极却可以实现,但目前使用的电位型离子选择性电极大部分是PVC膜电极,受制作工艺限制,电极难以微型化。本文报道了以碳为基体电极（Ф200μm）的全固型Cr（III）离子选择性修饰微电极的制作方法,该电极无需内参比和内参比液,比PVC膜电极更易于制作和微型化。该修饰电极在Cr（III）浓度1.0×10^-6～1.0×10^-4 mol/L范围内呈线性关系,能斯特响应工作曲线的斜率为32.5±0.4 mV,检测限为3.6×10^-7 mol/L,响应时间为1.2 s,电极的重现性好,稳定性好,可在2个月内使用。利用该电极,成功地对工业废水中的Cr（III）进行测定,取得了令人满意的结果。生物的生长和适应环境的能力受制于它们对营养物质摄取和代谢废物排放过程的控制能力,植物细胞表面离子流是这种过程的一种具体体现。本文制作了铂微电极（Ф20μm）,通过自组装修饰上DTPA,制备了一种测定Cr（III）的全固型化学修饰选择性微电极,用该电极对铬超积累植物李氏禾根尖的Cr（III）离子流进行微区、在线和连续监测。发现位于根的尖端1.0～1.5 mm处Cr（III）离子浓度较小;对李氏禾根尖表面的Cr（III）电位响应与时间和垂直距离的关系进行测定,发现在根尖表面出现Cr（III）的电位响应从平稳到上升后又略有下降再到平稳的现象;白天根尖端1.2 mm处Cr（III）离子浓度较之夜间要低,而且出现了较大波动性。具有螯合能力的有机酸在超富集植物对外部金属离子排斥（避性）过程中具有重要作用。本文采用电化学沉积法将铱氧化膜修饰在铱丝上,制备了氧化铱膜修饰微电极（Ф20μm）,利用该电极在保持李氏禾样品完整和接近实际生理状态环境下灵敏、直观地测定了铬逆境下李氏禾根尖的有机酸的微量变化。实时、连续地获得李氏禾在逆境胁迫后释放有机酸的生理指标。更多还原

【Abstract】 The emergence of chemically modified electrode prompted the development of electrochemistry, which has become an important research direction in the field of modern electroanalytical chemistry. The aim of chemically modified electrodes is to carry out the molecular design on the electrode surface. In other words, some molecule, ion and polymer with excellent properties are immobilized on electrode surface and the electrode with specially chemical and physical properties is obtained.At present voltammetry determination of chromium focus on improving the reaction system and pay no attention to electrode modification. Solid silver-amalgam electrode modified with Diethylenetriaminepentaacetic acid （DTPA） has been fabricated to detect chromium species utilizing the electrode surface DTPA pre-extraction and the catalytic system Cr（III）-DTPA-NO₃^-. By use of this method, the samples need no pretreatment and just change the way of pre-concentration, the Cr（VI） and inorganic Cr（III） has been detected respectively. The peak current linear with the Cr（VI） and inorganic Cr（III） concentrations were, respectively, 5×10^-9～5×10^-6 mol/L and 1×10^-8～5×10^-6 mol/L. The detection limit and the recovery of Cr（VI） and inorganic Cr（III） were, respectively, 1.6×10^-10 mol/L and 5.1×10^-9 mol/L. The results suggested that this modified electrode was effective for the determination of trace amount of Cr（VI） and inorganic Cr（III）.Voltammetry determination of chromium must needs a certain catalyst system or a periode preconcentration time, so this method quite difficulty to real-time and continuous determination of chromium which keeping the sample integrated and approaching to practical situation. Potentiometric method provided a convenient, fast and‘on-line’analytical method. However, these electrodes suffer from the disadvantages of difficulty in fabrication, especially in miniaturization and microfabrication. One of the important aspects of using modified wire ion-selective microelectrodes is that it not only needs a very small volume of sample, but also has other advantages such as the elimination of the inner reference solution, the decrease in the time, lower cost, mechanical flexibility （i.e., the electrode can be used at any angle）, and the possibility of miniaturization and microfabrication, even making intercellular or other in vivo electrochemical measurements possible. A new microelectrode for micro-amount chromium（III） determination was prepared. For this purpose, fuchsin basic was electro polymerized onto a carbon micro disc electrode （Ф200μm）, diethylenetriamminepentaacetic acid （DTPA） was then self-assembled on the electrode surface by the reaction between DTPA and poly（fuchsin basic）. The electrode gave a linear response in Cr³⁺ ions concentration range of 1.0×10^-6～1.0×10^-4 mol/L and has the Nernstian slope of 32.5±0.4 mV per decade. The detection limit is 3.6×10^-7 mol/L. The response time of the electrode is less than 1.2 s, and it can be used for at least 2 months with limited considerable divergences in its potentials. The proposed electrode was applied for monitoring the chromium ion level in wastewater of chromate industries.Growth and adaptation ability of biology were enslaved to their nutrient uptake and emission. Membrane-transport processes was the key link of the nutrient uptake and emission processes, ion flux of the cell surface was the nutrient uptake and emission processes concrete reflection. A new all solid-state selective microelectrode for chromium（III） fluxes determination was prepared. For this purpose, fuchsin basic was electro polymerized onto a Pt micro disc electrode （Ф20μm）, diethylenetriamminepentaacetic acid （DTPA） was then self-assembled on the electrode surface by the reaction between DTPA and poly（fuchsin basic）. Chromium（III） fluxes along the roots of hyper-accumulator plants Leersia hexandra Swartz has been investigated. In the root zones 1.0 to 1.5 mm behind tips the chromium（III） ion influx obviously. At 1.2 mm behind tips, the concentration of the chromium（III） in daytime lower and more oscillatory then at night.The resistance of plants to metals includes avoidance and tolerance, while the organic acids with chelating ability in plants play an important role in the detoxification of metals both externally and internally. Iridium metal wire modified iridium oxide has been developed for detection of the organic acid. The dimensions and response time allowed that use this electrode （Ф20μm） in the measuring H+ fluxes along Leersia hexandra Swartz roots. H+ fluxes showed marked spatial and exhibited an oscillatory pattern. In the external metal detoxification, Leersia hexandra Swartz roots excrete organic acids into rhizosphere, and the metal pollutants are detained outside the roots by the formation of metal-organic acid complex, and their toxicity is reduced.更多还原