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王大娟, 杨根兰, 向喜琼, 蒋文杰, 朱健. 邻菲啰啉分光光度法测定红层砂岩中Fe(Ⅱ)和全铁的方法探讨[J]. 岩矿测试, 2020, 39(2): 216-224. DOI: 10.15898/j.cnki.11-2131/td.201906200088
引用本文: 王大娟, 杨根兰, 向喜琼, 蒋文杰, 朱健. 邻菲啰啉分光光度法测定红层砂岩中Fe(Ⅱ)和全铁的方法探讨[J]. 岩矿测试, 2020, 39(2): 216-224. DOI: 10.15898/j.cnki.11-2131/td.201906200088
WANG Da-juan, YANG Gen-lan, XIANG Xi-qiong, JIANG Wen-jie, ZHU Jian. Determination of Fe(Ⅱ) and Total Iron in Red Sandstone by o-phenanthroline Spectrophotometry[J]. Rock and Mineral Analysis, 2020, 39(2): 216-224. DOI: 10.15898/j.cnki.11-2131/td.201906200088
Citation: WANG Da-juan, YANG Gen-lan, XIANG Xi-qiong, JIANG Wen-jie, ZHU Jian. Determination of Fe(Ⅱ) and Total Iron in Red Sandstone by o-phenanthroline Spectrophotometry[J]. Rock and Mineral Analysis, 2020, 39(2): 216-224. DOI: 10.15898/j.cnki.11-2131/td.201906200088

邻菲啰啉分光光度法测定红层砂岩中Fe(Ⅱ)和全铁的方法探讨

Determination of Fe(Ⅱ) and Total Iron in Red Sandstone by o-phenanthroline Spectrophotometry

  • 摘要: 红层砂岩是丹霞地貌区的一套陆相或浅水湖相沉积碎屑岩,准确分析红层砂岩中Fe(Ⅱ)和Fe(Ⅲ)在风化过程中的氧化还原关系,可作为该岩块风化程度以及深度的划分依据。在应用邻菲啰啉分光光度法测定铁含量过程中,Fe(Ⅱ)极易被氧化而导致结果偏低,有效防止氧化作用是准确测量Fe(Ⅱ)和Fe(Ⅲ)含量的重点。本文利用Fe(Ⅱ)与邻菲啰啉形成有色络合物的特点,在红层砂岩样品中滴加适量显色剂后用氢氟酸-稀硫酸溶解,取同一溶清液分别经过盐酸羟胺还原、邻菲啰啉显色、乙酸-乙酸铵缓冲液调节pH等步骤后,在分光光度计下测定微量Fe(Ⅱ)和全铁含量。该分析方法测定Fe(Ⅱ)的检出限为0.002%,RSD(n=8)小于2%,加标回收率为92.6%~94.7%。利用该分析方法测定赤水丹霞地貌区红层砂岩中Fe(Ⅱ)含量在0.01%~0.1%,全铁为0.7%~1.5%,差减法计算得Fe(Ⅲ)含量在0.7%~1.5%,测定结果与X射线荧光光谱法、重络酸钾滴定法一致。本方法采用显色剂和氢氟酸-稀硫酸溶解,能有效保存砂岩中原生Fe(Ⅱ),使用同一溶清液既能测定全铁,也能准确测定Fe(Ⅱ),为分析红层砂岩中各类铁含量提供了一种简单、准确的分析方法。

     

    Abstract:
    BACKGROUNDRed bed sandstone is a set of continental or shallow lake clastic rocks in the Danxia landform. Accurate determination of Fe(Ⅱ) and Fe(Ⅲ) in red bed sandstone that indicates the redox relationship during weathering can serve as the dividing basis of weathering degree and depth of the block. During the determination of iron content by phenanthroline spectrophotometry, Fe(Ⅱ) is easily oxidized and the result is a lower value than it should be. Effective prevention of oxidation is the focus of accurate measurement of Fe(Ⅱ) and Fe(Ⅲ) content.
    OBJECTIVESTo explore the preservation method of Fe(Ⅱ) during dissolution and establish a spectrophotometric method for the determination of Fe(Ⅱ) and total iron in red sandstone.
    METHODSColor reagents were added in the samples, and the samples were dissolved by hydrofluoric acid and dilute sulfuric acid, in a constant temperature water bath at 90℃. Hydroxylamine hydrochloride was used as a reducing agent, o-phenanthroline was used as a chromogenic agent, pH was adjusted by acetate-ammonium acetate buffer, and trace Fe(Ⅱ) and total iron were determined by spectrophotometer.
    RESULTSThe detection limit of Fe(Ⅱ) was 0.002%, relative standard deviation (RSD, n=8) was less than 2%, and the standard recovery was between 92.6% and 94.7%. The Fe(Ⅱ) content of red sandstone in the Danxia landform area of Chishui was determined by this analysis method. The content of Fe(Ⅱ) ranged from 0.01% to 0.1%, the total iron content was 0.7%-1.5%, and the content of Fe(Ⅲ) calculated by subtraction was 0.7%-1.5%. The measurement results were consistent with those of X-ray fluorescence spectrometry and potassium complexate titration method.
    CONCLUSIONSThis method uses developer and hydrofluoric acid-dilute sulfuric acid to dissolve the samples, which can effectively preserve the original Fe(Ⅱ) in sandstone. The same solution can be used for the determination of both total iron and Fe(Ⅱ) which provides a simple and accurate analysis method for various types of iron content in red bed sandstone.

     

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