DEVELOPMENT OF MINIATURIZED ANALYTICAL SYSTEM FOR RESIDUAL CHLORINE WITH ELECTROCHEMICAL SENSORS

水溶液中的氯用于许多用途，例如消毒和漂白，并且在各种制造过程中也用作强氧化剂。众所周知，氯具有剧毒，而且它还能与环境中的酚类等其他物质发生反应，产生被怀疑是致癌物的氯酚。因此，研制可靠的、连续的痕量余氯测量新方法和新装置是本工作的重点。水中的余氯通常存在于次氯酸（HOCl）或其共轭碱次氯酸离子（ClO-）的纤维蛋白中。本研究证实，在4-8的pH范围内，与铂电极和玻碳电极相比，金电极具有非常大的还原电流和良好的稳定性。本文以金电极电化学传感器为基础，研制了一种用于环境样品中余氯现场监测的便携式微型FIA…More系统。为了达到现场测定的目的，目前的工作是将恒电位器小型化，降低芯片的复杂性，降低功耗，提高动态范围。恒电位器由嵌入式控制器微处理器、A/D转换器、D/A转换器和运算放大器组成。它可以由摄像机（Sony NP-F550, 7.2 V 1500 mA/H）的电池供电。定位器的尺寸为150×100×40毫米，重量仅为350克。电化学测量由笔记本电脑和实验室编写的软件包通过RS-232C接口控制。结果表明，当氯浓度达到5μg/ml时，安培响应随浓度的增大而增大，氯的检出限为0.05 μg/ml。除了大大减小分析系统的尺寸外，这种小型化还实现了速度提高、移动相消耗最小和灵敏度高的优点。该方法已成功地应用于泳池水和自来水中余氯的测定。结果与N，N-二乙基-对苯二胺（DPD）光度法一致。用方波伏安法研究了DPD存在下微量氯在玻碳电极上的电化学行为。在较低的pH值下，观察到一个新的还原波（+0.4 V vs Ag/AgCl），紧接着是DPD的还原波（+0.5 V vs Ag/AgCl）。ca. +0.4 V处的新峰是DPD的氯化产物，与氯浓度成正比。但当氯浓度较低时，该峰与DPD背景严重重叠。本文提出了信号比法与小波变换相结合的方法，用于微弱伏安信号的分离。该方法可以很好地分离重叠的伏安峰，从而在0 ~ 100 μM的线性范围内测定痕量氯，检出限为0.5 μM。该方法的优点是灵敏度高，不受DPD比色法中存在的氧化剂干扰。其机理及在实际样品测定中的应用正在进行中。少

Chlorine in aqueous solutions is used for a number of purposes, such as disinfection and bleaching, and also as a powerful oxidizing agent in various manufacturing processes. It is known that chlorine is highly toxic, and additionally it can further react with other substances, such as phenols, in environment to produce chlorophenols, which are suspected to be carcinogens. Thus, the development of the new methods and devices for the reliable and continuous measurement of residual chlorine at trace levels had been conducted in the present work.Residual chlorine in water is generally present in the fibrin of hypochlorous acid (HOCl), or its conjugated base, the hypochlorite ion (ClO-). It was confirmed in this study that gold electrode exhibited very large reductive currents as well as good stability compared with platinum and glassy carbon electrodes in the pH range of 4-8. Based on the electrochemical sensors with gold electrode, the present study developed a portable miniaturized FIA … More system for on-site monitoring of residual chlorine in environmental samples. As for the purpose of on-site determination, miniaturization of the potentiostat along with a reduction in the complexity of the chip, low power consumption and a high dynamic range was developed in the current work. The potentiostat was built using an embedded controller microprocessor, an A/D converter a D/A converter, and operational amplifiers. It is available operated by a battery for a video camcorder (Sony NP-F550, 7.2 V 1500 mA/H). The size of the potentiostat is 150×100×40 mm and weight is only 350 g. The electrochemical measurements were controlled by a notebook computer and a laboratory-written software package via an RS-232C interface. It was confirmed that the amperometric response increased in proportion to the chlorine concentration up to 5μg/ml, and the detection limit for chlorine was 0.05 μg/ml. Besides a drastic reduction the size of the analytical system, such miniaturization achieved the advantages of increased speed, minimal mobile-phase consumption, and high sensitivity. The proposed method was successfully applied to the determination of residual chlorine in samples of pool water and tap water. The results were well agreed with those obtained by the N,N-diethyl-p-phenylenediamine (DPD) photometric method.The electrochemical behavior of trace chlorine was also studied in the presence of DPD at glassy carbon electrode by square wave voltammetry. In the lower pH value, a new reduction wave (+0.4 V vs Ag/AgCl) was observed, which is closely followed by the reduction of DPD (+0.5 V vs Ag/AgCl). The new peak at ca. +0.4 V was suggested to be generated by chlorinated product of DPD which is in proportion to the concentration of chlorine. But this peak was seriously overlapped by the background of DPD when the concentration of chlorine is low. In this study, signals-ratio method combined with wavelet transform was proposed for the resolution of a weak voltanunteric signal overlapped by other coexisted components. With the proposed method, the overlapped voltammetric peaks can be well separated and thereby the chlorine at trace level could be determined in a linear range of 0 to 100 μM with a detection limit of 0.5 μM. The advantages of proposed method are sensitive and free of some oxidant interthrences which could be a problem in DPD colorimetric method. The mechanism and the application in determination of real samples are now in progress. Less