水质 游离氯和总氯的测定 第2部分:常规控制目的时使用的N,N-二乙基-1,4-苯二胺比色法

[中文适用范围]： 本文件规定了水中游离氯和总氯的测定方法，易于适用于实验室和现场测试。 它基于吸收度测量、光度计中的红色 DPD 颜色复合物或通过将颜色与定期校准的标准进行目视比较来测量颜色强度。 该方法适用于饮用水和其他水，其中额外的卤素（如溴、碘和其他氧化剂）的含量几乎可以忽略不计。 海水以及含有溴化物和碘化物的水属于需要执行特殊程序的一组。 该方法实际上适用于以氯（Cl2）计的总浓度，例如0.0004mmol/l至0.07mmol/l（例如0.03mg/l至5mg/l）氯。 对于更高的浓度，测试部分被稀释。 通常，该方法作为现场方法使用移动光度计和市售即用型试剂（液体试剂、粉末和片剂）。 这些试剂必须符合最低要求，并包含必要的试剂和适合将测量溶液的 pH 值范围调节至 6.2 至 6.5 的缓冲系统。 如果怀疑水样具有不常见的 pH 值和/或缓冲能力，用户必须检查，并在必要时将样品 pH 值调整到所需的范围。 样品的pH值在4～8范围内，必要时在试验前用氢氧化钠溶液或硫酸进行调整。 附录 A 中介绍了区分一氯胺型化合氯、二氯胺型化合氯和三氯化氮形式化合氯的程序。 附录 C 中介绍了测定游离氯和总氯的程序在饮用水和其他低污染水域中，使用介观流体通道泵/比色计用于一次性平面试剂填充比色皿。 [外文原描述]： ISO 7393-2:2017 specifies a method for the determination of free chlorine and total chlorine in water, readily applicable to lab- and field-testing. It is based on measurement of the absorption, the red DPD colour complex in a photometer or the colour intensity by visual comparison of the colour with a scale of standards that is regularly calibrated. This method is appropriate for drinking water and other waters, where additional halogens like bromine, iodine and other oxidizing agents are present in almost negligible amounts. Seawater and waters containing bromides and iodides comprise a group for which special procedures are to be carried out. This method is in practice applicable to concentrations, in terms of chlorine (Cl2), from, for example, 0,000 4 mmol/l to 0,07 mmol/l (e.g. 0,03 mg/l to 5 mg/l) total chlorine. For higher concentrations, the test portion is diluted. Commonly, the method is applied as a field method with mobile photometers and commercially available ready-for-use reagents (liquid reagents, powders and tablets). It is essential that those reagents comply with minimum requirements and contain the essential reagents and a buffer system suitable to adjust the measurement solution to a pH range of typically 6,2 to 6,5. If there is doubt that water samples have uncommon pH values and/or buffer capacities, the user has to check and, if necessary, to adjust the sample pH to the required range. The pH of the sample is within the range of pH 4 and 8. Adjust, if necessary, with sodium hydroxide solution or sulfuric acid before the test. A procedure for the differentiation of combined chlorine of the monochloramine type, combined chlorine of the dichloramine type and combined chlorine in the form of nitrogen trichloride is presented in Annex A. In Annex C, a procedure is presented for the determination of free and total chlorine in drinking and other low polluted waters, for disposable planar reagent-filled cuvettes using a mesofluidic channel pump/colorimeter.