分光光度法测量海洋沉积物的碘含量

The Measurement of Iodine in Marine Sediments Using Spectrophotometric Method

摘要: 本文建立了分光光度法测量海洋沉积物碘的方法。对采集自东太平洋、东海、胶州湾，和福建沿海沉积物岩芯的碘进行了研究。处理样品时，将沉积物样品与KOH混合灼烧，之后用水沥取样品中的碘，在酸性条件下，用饱和溴水将I−氧化成IO³⁻，加入淀粉和KI混合溶液显色剂，IO³⁻与显色剂中过量的I−反应生成I₂，最后用紫外可见分光光度计进行测量。研究发现用KOH作为溶剂处理样品，沉积物与KOH的质量比以1:3至1:5为宜，灼烧温度和灼烧时间分别为500℃~800℃和1~4 h为佳。测量时最大光吸收波长为580 nm。对碘含量为2~100 mg/kg的沉积物样品，以2 g样品为例，沥取后定容100 cm³，加入6~12滴20 g/dm³淀粉和10 g/dm³ KI混合溶液显色剂较为合适；上机测量的样品溶液pH值在1.8~2.4之间较为适宜。最后我们对测定得海洋沉积物岩芯中的碘含量水平与文献结果进行了比较。

Abstract: Spectrophotometric method of measuring iodine in marine sediment has been established in this paper. We have studied the iodine in marine sediment cores collected from East Pacific, East China Sea, Jiaozhou Bay, and coastal sea areas of Fujian. For marine sediment sample, iodine was leached with water from sample after it was treated by mixing it with KOH and combusted. Under the acid addition, the iodide in leachant was oxidized into iodate by adding saturated bromine solution. IO³⁻ reacted with I− to form I₂ after starch-KI mixing solution, as the color reagent, was added with excess I−. The measurement was performed by ultraviolet and visible spectrophotometer. It has been shown when igniting sample, the ratio range of 1:3 to 1:5 for sediment to KOH and keeping the combusting temperature at 500˚C - 800˚C for 1 - 4 h are suitable. The most absorbance of light is at wavelength of 580 nm. For the sediment sample of iodine content in the range of 2 - 100 mg/ kg, when the 2 g of sample was treated, 6 - 12 drops of mixing solution of the 20 g/dm³ starch and 10 g/dm³ KI, as the color reagent, would be added when leachant was made up to 100 cm³. The measurement would be conducted at pH of 1.8 - 2.4 for test solution. The comparison of iodine content levels in marine sediment we measured with data of literatures was done.