摘要:
循环水及污水中总磷的国家标准方法是用分光光度法测定,当样品中有机磷含量高时,分解易碳化,操作繁琐,分析误差大。本文应用磷钼黄显色示差分光光度技术测定某钢厂循环管道除垢污水中的总磷,通过正交实验确立了采用硝酸-高氯酸消解样品,将样品中聚磷酸盐、有机磷酸盐转化为正磷酸盐,在硝酸溶液中,正磷酸盐与钒钼酸铵作用生成可溶性黄色磷钒钼酸配合物,基于其颜色强度与磷的浓度成正比测定高浓度磷的含量。实验对使用的氧化剂用量、溶解温度、显色条件、测定波长进行优化,结果表明,磷含量在10.0~40.0 mg/L范围符合朗伯-比尔定律,方法精密度(RSD)<1.0%(n=5),加标回收率为98.8%~105.0%。建立的示差光度法比一般光度法相对误差小,准确度更高;与电感耦合等离子体发射光谱法的测定结果基本吻合,且测定成本更低。
Abstract:
The traditional national standard method for determination of total phosphorus in recycling water and sewage by Spectrophotometry has some problems for the samples with high content of organic phosphorus, which is easily carbonized during decomposition with complicated operation and large analytical error. In this pater, Differential Spectrophotometry has been used to measure total phosphorus in recycling water and sewage with the advantages of less relative error and better accuracy and is described in this paper. Based on the orthogonal experiment, HNO3-HClO4 was applied to the after-treated recycling sewage in steelworks. The orthophosphate, polyphosphate and organophosphate were transferred to orthophosphate under digestion conditions. The orthophosphate reacted with vanadium ammonium molybdate in nitric acid to produce yellow dissoluble phosphorus and vanadium molybdate complexes. The color intensity was proportional to phosphorus concentration. The dosage of oxidizing agent, dissolving temperature, chromatogenic condition and measurement wavelength were optimized. The phosphorus content around 10.0-40.0 mg/L allowed the Lambert-Beer law. The recovery was 98.8%-105.0% with RSD less than 1.0% (n=5). The results were consistent with results obtained by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Compared with the routine method of Spectrophotometry, the Differential Spectrophotometry has less relative error and higher accuracy. Compared with ICP-AES, it has a lower testing cost.
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