DEVELOPMENT OF MINIATURIZED ANALYTICAL SYSTEM FOR RESIDUAL CHLORINE WITH ELECTROCHEMICAL SENSORS

水溶液中的氯用于许多目的，如消毒和漂白，也在各种制造过程中用作强氧化剂。众所周知，氯具有很高的毒性，此外，它还可以与环境中的其他物质，如酚，进一步反应生成氯酚，这些物质可能是致癌物质。因此，本工作致力于开发可靠、连续测定痕量余氯的新方法和装置。水中的残留氯一般存在于次氯酸的纤维蛋白或其共轭碱次氯酸盐离子(ClO-)中。研究证实，在pH为4~8的范围内，金电极比铂电极和玻碳电极表现出很大的还原电流和良好的稳定性。本研究以金电极电化学传感器为基础，研制了便携式小型化流动注射…。更多现场监测环境样品中余氯的系统。为了达到现场检测的目的，本工作开发了恒电位仪的小型化，同时降低了芯片的复杂性，低功耗和高动态范围。该恒电位仪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构成。它可由视频摄像机(索尼NP-F550，7.2 V 1500 mA/H)的电池操作。该恒电位仪的尺寸为150×100×40 mm，重量仅为350g，由笔记本电脑和实验室编写的软件通过RS-232C接口进行控制。结果表明，当氯浓度达到5μg/ml时，电流响应与氯浓度成正比关系，氯的检出限为0.0 5μg/ml，不仅大大减小了分析系统的体积，而且具有速度快、流动相消耗少、灵敏度高等优点。方法用于池水和自来水中余氯的测定，结果满意。用方波伏安法研究了N，N-二乙基对苯二胺(DPD)存在下，痕量氯在玻碳电极上的电化学行为。在较低的pH值下，出现了一个新的还原峰(+0.4V vs Ag/AgCl)，紧随其后的是DPD的还原(+0.5V vs Ag/AgCl)。DPD的氯化产物在+0.4V处产生新的峰，与氯的浓度成正比。但当氯浓度较低时，这一峰与DPD的背景严重重叠。本文提出了一种信号比法与小波变换相结合的方法来分辨叠加有其他共存分量的微弱伏安信号。该方法能很好地分离重叠的伏安峰，在0~10 0μM范围内线性关系良好，检出限为0.5μM。其机理及其在实际样品测定中的应用正在进行中。较少

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