Hue Do Thi Kim, Hashimoto Shohei, Nishikawa Haruka, Maeda Yasuaki, Takenaka Norimichi
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University.
Research Organization for University-Community Collaborations, Osaka Prefecture University.
Anal Sci. 2017;33(8):931-938. doi: 10.2116/analsci.33.931.
Direct chemiluminescence emission from the reaction of acidic permanganate and organic compounds was employed for determining the chemical oxygen demand (COD) in water (1-step CL COD). Due to the diversity of organic pollutants in water, there are no standards for COD measurements, and many compounds do not show any chemiluminescence signal in the 1-step CL COD method. As a result, this method shows a low correlation with the conventional COD method. In this study, a new 3-step CL COD method was developed to overcome these drawbacks. The basic principle of the 3-step CL COD method is based on the principle of "back titration" in the COD method: (i) the sample is treated with permanganate under heating, (ii) the excess permanganate is treated with pyrogallol, and (iii) the excess pyrogallol is measured by the chemiluminescence reaction with permanganate. The reagent concentration, sample volume, and heating temperature were optimized, and the 3-step CL COD method successfully obtained the signal from some samples that cannot be detected by 1-step CL COD method. The calibration graph is linear in the range of 0 - 12.86 mg/L with a detection limit of 0.082 mg/L. This method is continuous, sensitive and low cost compared with the conventional method, and is applicable for on-site monitoring. The effect of the chloride ion was investigated, and showed an insignificant effect after two-times dilution of high-salinity samples. The correlation with the COD method for various organic compounds showed a good coefficient of determination, R = 0.9773 (n = 16).
利用酸性高锰酸钾与有机化合物反应产生的直接化学发光来测定水中的化学需氧量（COD）（一步法化学发光COD）。由于水中有机污染物种类繁多，COD测量没有标准，而且许多化合物在一步法化学发光COD方法中不显示任何化学发光信号。因此，该方法与传统COD方法的相关性较低。在本研究中，开发了一种新的三步法化学发光COD方法来克服这些缺点。三步法化学发光COD方法的基本原理基于COD方法中的“返滴定”原理：（i）样品在加热条件下用高锰酸钾处理，（ii）过量的高锰酸钾用连苯三酚处理，（iii）过量的连苯三酚通过与高锰酸钾的化学发光反应进行测量。对试剂浓度、样品体积和加热温度进行了优化，三步法化学发光COD方法成功地从一些一步法化学发光COD方法无法检测到的样品中获得了信号。校准曲线在0 - 12.86 mg/L范围内呈线性，检测限为0.082 mg/L。与传统方法相比，该方法具有连续、灵敏、低成本的特点，适用于现场监测。研究了氯离子的影响，高盐度样品经两次稀释后显示出不显著的影响。与各种有机化合物的COD方法的相关性显示出良好的决定系数，R = 0.9773（n = 16）。
