总铬全程空白污染来源分析及解决方案

Sources and solution of whole process blank pollution in total chromium monitoring

针对日常工作中发现分光光度法检测总锯的全程空白存在明显的锯检出问题,试验对超纯水、滤纸、硫酸、磷酸的锯本底排查结果显示,锯的主要污染来源为磷酸,3家生产商生产的磷酸均存在明显的辂污染,2家生产商生产硫酸并无明显铭污染。为进一步提高样品测试结果的准确度,需降低全程空白结果,提出只采用(1+1)硫酸消解样品,显色前再加入(1+1)磷酸的优化方案。该方案经高浓度Cr(Ⅲ)标准点样品及实际复杂基体样品验,具有检较好的方法精密度和准确度。

In view of the obvious problem of chromium pollution in the whole process blank of spectrophotometric determination of total chromium in daily work, the chromium background of ultrapure water, filter paper, sulphuric acid and phosphoric acid is investigated. The results show that the main source of chromium pollution is phosphoric acid. There is obvious chromium pollution in phosphoric acid produced by three producers, and there is no obvious chromium pollution in sulphuric acid produced by two producers. In order to further improve the accuracy of the sample results, it is necessary to reduce the blank results of the whole process. An optimum scheme is proposed that only (1 + 1) sulfuric acid is used to digest the sample and (1 + 1) phosphoric acid is added before color development. The scheme has been tested by high concentration trivale nt chromium sta ndard point samples and practical complex matrix samples, and has good precision and accuracy of the method.