【作者】 马钰华；

【导师】 袁若；

【作者基本信息】 西南大学 ， 分析化学， 2010， 硕士

【摘要】 金属一般以天然浓度广泛存在于自然界中,但随着人类对金属的开采、冶炼、加工及商业制造活动的日益增多,造成大量的金属如铅、汞、铬、钴等进入环境中。金属原本是水生生物及人体生长和发育不可缺少的生命元素,但是当其含量超过一定的界限时就会对生命体产生很强的毒害作用。因此,对环境样品中的金属的浓度进行测定在环境分析中尤为重要。目前,检测金属离子的方法主要有原子吸收光谱法、电感耦合原子发射光谱法、电感耦合等离子体质谱法等,但是这些方法涉及到复杂的样品处理,需要大的基层组织,并且对于大部分的分析实验室太昂贵了。因此,有必要发展一个简单的方法来对金属离子进行测定。离子选择电极由于在分析方面具有独特的优点,如适宜的选择性和灵敏性、宽的线性范围、低的检测限、快的响应时间,特别是容易准备和低的花费等优点而被广泛的应用于化学传感器中来测定各种离子型物种,在过去的几十年中研究出了大量的基于不同中性载体的离子选择电极。如今,对离子选择电极的载体的研究是离子选择性电极研究中比较活跃的一个方向。本论文着重于设计、合成不同的新型中性配体,将其作为载体用于PVC溶剂聚合膜金属离子选择性电极的研究中,采用电化学的方法和手段对这些离子选择性电极的性能进行表征,并将电极初步应用于实物样品分析。本文研究内容如下：1.氮-硫希夫碱配体在镍离子选择性电极中的应用以乙二醛双缩肼基双硫代甲酸苄酯(GBSB)为载体构建了高选择性PVC膜镍离子电极。用电导法研究了载体GBSB对不同金属离子的稳定性和选择性情况,对于Ni2+,摩尔电导在GBSB为1时产生了突变。而对于其它的金属离子,摩尔电导的变化很小。该电极对Ni(II)表现出了很好的电势响应性能,电极响应的线性范围近六个浓度的数量级,检测下限为1.0 x 10-7mol/L。在整个浓度范围内电极的响应时间小于30 s,电极至少能使用三个月,该电极适宜的pH值范围为4.0-7.5。用交流阻抗技术研究了电极膜表面的电化学行为。将该电极初步的运用于电位滴定镍离子时作为指示电极,以及测定牛奶和巧克力样品中的镍离子浓度,并与原子吸收光谱法测定的结果进行了比较。2.新的芳基氨基桥联配体在铬离子选择电极中的应用合成了一种新的芳基氨基桥联配体,2,2’-双{[(2”-苯甲基氨基甲酸基)苯基]甲基}-双-乙醚(BBPMD),以该化合物作为载体制备的聚合物膜电极对Cr3+呈现出高选择性。研究了增塑剂和离子添加剂对该电极的影响,优化了测量条件,得到的最佳电极对Cr3+电位响应的线性范围为2.8×10-6-1.0x10-1mol/L,检测下限8.6×10-7mol/L,响应斜率为19.5±0.2 mV/dec。电极适宜的pH范围为2.5-6.5。在整个浓度范围内电极的响应时间约为10 s。采用紫外-可见光谱滴定法测定了载体BBPMD对不同金属离子的缔合常数和配位数,载体对Cr3+的缔合常数远远大于其他的离子,并且随着溶液中Cr3+含量的增大,吸收峰强度逐渐增大,峰位置发生红移。用交流阻抗技术研究了电极表面的电化学行为。最后,将该电极初步的应用于测定实物样品中的Cr3+浓度以及作为指示电极滴定Cr3+。3.以大环化合物为中性载体的高选择性聚合物膜钡离子电极的研究用4,6-二乙酰基间苯二酚和乙二胺以1：1的比例反应,合成了大环化合物(H4L配体),将其作为载体的PVC膜电极对Ba2+表现出高的选择性,电极响应的线性范围为3.6×10-6-1.0×10-1mol/L,检测限为1.9×10-6mol/L,斜率为29.7±0.2 mV/dec。电极适宜的pH值范围为2.5-7.5。用分别溶液法测定了钡离子电极的选择性系数,除了镍离子外,其他离子的选择性系数都很小。因此,用混合溶液法研究了测定钡离子时,镍离子不干扰钡离子测定的最大浓度。当溶液中镍离子的浓度小于等于5.0x10-5mol/L时,不干扰钡离子的测定。用电导法测定了在DMSO溶液中H4L配体与金属离子络合的稳定常数。同时,用交流阻抗技术和紫外-可见光谱法研究了电极响应的机理。将该电极初步的应用于电位滴定中以及测定实物样品中的钡离子和硫酸根离子的浓度,并运用F-测试法和t-测试法对电极测定的结果与电感耦合原子发射光谱法测定的结果进行了统计比较。4.双穴二氧四胺配体在铝离子选择性电极研究中的应用合成了一种双穴二氧四胺配体,N,N’-双[水杨醛缩(2-氨乙基)]丙二酰胺(NPBS)。以该配体作为载体的电极对Al3+表现出高的选择性。在25℃,pH 3.0硝酸盐溶液中,电极响应的线性范围为7.9×10-7-1.0×10-1mol/L,检测限为4.6×10-7 mol/L,斜率为19.4±0.3 mV/dec.讨论了不同pH值下Al3+的存在状态,电极适宜的pH值范围为2.5-4.0。电极的响应时间约为8 s,该电极连续使用两个月其性能未见明显的下降。采用紫外-可见光谱滴定法测定了载体NPBS对不同金属离子的缔合常数和配位数,载体对Al3+的缔合常数远远大于其他的离子。用交流阻抗技术研究了电极表面的电化学行为,膜本体阻抗随着溶液中Al3+浓度的增加而减少,表明Al3+参与了传输,且载体携带Al3+通过膜相的传输过程为可逆的电极过程,受到扩散控制。该电极被初步的运用于测定实物样品中的铝离子,以及在电位滴定铝离子时作为指示电极。更多还原

【Abstract】 The metal elements usually exist widely in nature with natural concentrations. But as mining, smelting, processing and commercial manufacturing activities increased, lots of metals such as lead, mercury, chromium, cobalt, etc. are discharged into the environment. Metals are the essential life elements of growth and development of aquatic biology and human. However, they will result in strong toxicity to the body when their concentration exceeds a certain limit. Therefore, the determination of metals in environmental samples is very important in the environmental analysis. At present, the main conventional methods for determination are flame and graphite furnace atomic absorption spectrometry, inductive coupled plasma atomic emission spectrometry, inductive coupled plasma mass spectrometry, etc. But these methods involve multiple sample manipulations and costly expenses for most analytical laboratories. Thus, it is necessary to develop a convenient method to determine metal ions. Ion selective electrodes (ISEs) that offer several advantages, such as adequate selectivity, wide linear range, low detection limit, fast response time, especially easy preparation and low cost, have inevitably been utilized for preparing sensors for several ionic species and the quantity of available electrodes has grown significantly over recent years. Nowdays, studies on the carrier of the ion selective electrode is a very active direction on the studies of the ion selective electrodes. In this thesis, a series of complexes are synthesized and used as carriers of the ion selective electrodes. The performance of the ion selective electrode is characterized by electrochemical methods and the proposed electrodes are applied to the detection of metal ions in real samples.1. Studies on the N-S Schiffbase ligand application on Ni (II) ion selective electrodeNi (II) ion-selective electrode is prepared by incorporating a new N-S Schiff base ligand, glyoxal-bis(S-benzyldithiocarbazate)(GBSB) as neutral carrier into the PVC matrix. The proposed electrode exhibits an excellent near-Nernstian response for Ni2+ion ranging from 2.8×10-7 to 1.0×10-1 mol/L with a detection limit of 1.2×10-7mol/Land a slope of 31.9±0.3 mV/dec in pH 4.0 nitrate solution at 25℃. It has an appropriate response time and suitable reproducibility, and can be used at least three months. The operational pH range of the proposed electrode is 4.0-7.5. In preliminary experiments, the complexation of GBSB with some cations was investigated conductometrically in a DMSO solution in order to obtain a clue about the stability and selectivity of the resulting complexes. The change in conductance of Ni2+ was larger than that for other cations. And the response mechanism is discussed in view of the alternating current (AC) impedance technique. In addition, the electrode is successfully used as an indicator electrode in potentiometric titration of Ni2+ion and in the direct determination of Ni2+ion in milk power and chocolate samples.2. Studies on a new aryl amide bifunctional bridging ligand application on Cr (III) ion selective electrodeA novel Cr(III) ion-selective electrode is constructed by incorporating a new aryl amide bifunctional bridging ligand,2,2’-bis{[(2"-benzylaminoformyl)phenxoyl]methyl}-diethylether (BBPMD) as a neutral carrier into the PVC matrix. The proposed electrode, with optimum membrane composition, exhibits an excellent near-Nernstian response for Cr3+ion ranging from 2.8×10-6 to 1.0×10-1 mol/L with a detection limit of 8.6×10-7mol/Land a slope of 19.5±0.2 mV/dec in pH 3.0 nitrate solution at 25℃. It has an appropriate response time, suitable reproducibility, and good selectivity towards Cr3+ion. The operational pH range of the proposed electrode is 2.5-6.5. The coordination number and association constant of coordination reaction of the carrier towards different metal ions were measured by means of UV-vis spectra titration. The absorbance increases gradually and the peak has a considerable red shift. The A. C. impedance technique was used researching the electrochemical characteristics on the electrode surfance. The excellent analytical features of the proposed electrode could lead to its successful application as an indicator electrode in potentiometric titration of Cr3+ion and in the direct determination of Cr3+ion in tea leaves and coffee samples.3. Studies on macrocyclic tetrabasic ligand application on barium (II) ion selective electrodeIn this study, a novel barium (II) ion-selective polymeric membrane electrode based on macrocyclic tetrabasic ligand (H4L) that derived from the reaction of 4,6-diacetylresorcinol and ethylenediamine in the molar ratio 1:1 as a neutral carrier was described. The electrode containing 2.04 wt% ionophore,66.40 wt% o-NPOE,31.23 wt% PVC and 0.33 wt% HTAB displayed excellent potential response characteristics to Ba2+ion ranging from 3.6×10-6 to 1.0×10-1 mol/L, with a detection limit of 1.9×10"6 mol/L and a slope of 29.7±0.2 mV/dec in pH 4.0 nitrate solution at 25℃. The response time was about 10 s for Ba2+ion over the entire concentration range and the potentials stayed constant for more than 2 min. And the proposed electrode could be used two months and didn’t show visible loss of response characteristics. The potential remains constant at pH range 2.5-7.5. The selectivity coefficients of Ba2+ion selective electrode were determined by the separate solution method (SSM). The electrode is selective towards Ba2+ion over a number of other cations except for Ni2+ion, as the selectivity coefficient value is slightly higher. To know the exact concentration of Ni2+ion that can be tolerated in the determination of Ba2+ion, some mixed run studies were carried out and the proposed electrode could tolerate Ni2+ion at the concentration≤5.0x10-5mol/L. The complexation of H4L with some metal ions was investigated conductometrically in a DMSO solution in order to obtain a clue about the stability and selectivity of the resulting complexes. Then, the response mechanism was discussed in view of UV-visible spectroscopy and the A.C. impedance technique. Finally, the proposed electrode was successfully applied to the detection of Ba2+ions in real samples as well as sulphate (Ⅱ) ions in water. The statistical comparison for the results of the proposed method and the reference one was carried out with regard to precision and accuracy by using F-test and t-test.4. Studies on the double-cavity dioxotetraamine ligand application on Al(III) ion selective electrodeThis work describes the fabrication of a selective polymeric membrane potentiometric sensor for Al3+ion based on N, N’-propanediamide bis (2-salicylideneimine) (NPBS) as a neutral carrier. The proposed sensor, with optimum membrane composition, exhibited an excellent near-Nernstian response for Al3+ion ranging from 7.9×10-7 to 1.0×10’1 mol/L with a detection limit of 4.6×10-7 mol/Land a slope of 19.4±0.3 mV/dec in pH 3.0 nitrate solution at 25℃. It showed a relatively fast response time (8 s), suitable reproducibility and stability, and good selectivity towards Al3+ion. The operational pH range of the proposed sensor was 2.5-4.0. The excellent selective response of the proposed electrode towards Al3+ions mainly resulted from the coordinate interaction between the carriers and Al3+ions. To confirm the interaction between the carriers and Al3+ions, the UV-visible spectroscopic experiments were carried out. The coordination number and association constant of coordination reaction of the carrier towards different metal ions were measured by means of UV-visible spectra titration. And the alternating current (A. C.) impedance technique was used researching the electrochemical characteristics on the electrode surfance. In addition, the proposed sensor was successfully used as an indicator electrode in potentiometric titration of Al3+ ion and in the direct determination of Al3+ion in real samples.更多还原