In this paper, COD tester,heater and micro-reflux tubes produced by American HACH company were used to digest water samples closely, to study the method of determining Chemical Oxygen Demand. The experimental results showed that the accuracy and precision were higher, the relative standard deviations were 0.33% ~ 2.20%, and the coefficients of variations were 0.49% ~ 2.54%. The detection limit was 3mg/L which was lower, when the determination range of reagent were 3 ~150mg/L. The results of standard samples and representative water samples determined by micro -reflux spectrophotometry had no significant differences with the results determined by national standard-reflux method. The relative deviations of the results are all within the confine of quality control request.%采用美国哈希公司生产的COD测定仪和加热器,用微回流管封闭回流消解水样,对水中化学需氧量的测定方法进行研究.实验结果显示,该方法的准确度和精密度较高,测定结果的相对标准偏差在0.33％～ 2.20％之间,变异系数在0.49％～2.54％之间；检出限较低,采用质量浓度测定范围为3～ 150mg/L的试剂测定水样,检出限为3mg/L；对标准样品及具有代表性的水样测定,结果与国标回流法的测定结果相比没有显著性差异,且结果的相对偏差均在质控要求范围内.
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