Praetz Sebastian, Schlesiger Christopher, Motz Damian Alexander, Klimke Stephen, Jahns Moritz, Gottschalk Christine, Heinrich Lena, Heppke Eva Maria, Malzer Wolfgang, Renz Franz, Vogt Carla, Kanngießer Birgit
Technische Universität Berlin, Institute of Optics and Atomic Physics, Berlin, Germany.
Leibniz University Hannover, Institute of Inorganic Chemistry, Hannover, Germany.
PLoS One. 2025 May 16;20(5):e0323678. doi: 10.1371/journal.pone.0323678. eCollection 2025.
While X-ray diffraction (XRD) is a commonly used method for quantification analysis using Rietveld refinement and quantitative Mössbauer spectroscopy is sporadically used primarily for iron speciation, laboratory X-ray Absorption Fine Structure Spectroscopy (lab-XAFS) is rarely applied for the quantitative determination of sample compositions. With the recent developments of laboratory-based XAFS spectrometers, this method becomes more interesting for many applications as well as for quantification. The goal of this study is to compare quantitative lab-XAFS via Linear Combination Fitting (LCF) of reference spectra with XRD and Mössbauer spectroscopy. Iron species analysis with the focus on the determination of the mass ratio alpha-iron(III) oxide (α-Fe2O3)/iron(II, III) oxide (Fe3O4) was used as an example. The examinations were performed on synthetic α-Fe2O3/Fe3O4 model mixtures and, predominantly, on a natural iron ore sample mainly consisting of the minerals hematite and magnetite, thus, these two iron oxides. For the iron K-edge lab-XAFS measurements an X-ray tube-based spectrometer using the von Hamos geometry with Highly Annealed Pyrolytic Graphite (HAPG) mosaic crystal optic was used. The capabilities and challenges of each method are discussed. The quantitative model mixtures examinations by lab-XAFS show results and accuracies similar to those obtained by XRD and Mössbauer spectroscopy. However, while the quantitative results for the iron ore investigations by lab-XAFS are in good agreement (deviation of 2 percent points) with the XRD results, the composition determined by Mössbauer spectroscopy differs clearly from the lab-XAFS and XRD results. Furthermore, the Mössbauer spectroscopic examinations hint the presence of an additional iron oxide species affecting the quantification. Besides the still common challenges in identification, differentiation and quantification of different iron oxides, the results show that quantitative lab-XAFS can particularly compete with quantitative XRD when determining the species composition of one element. This makes lab-XAFS particularly well-suited for routine analytics.
虽然X射线衍射（XRD）是一种常用的通过Rietveld精修进行定量分析的方法，定量穆斯堡尔谱主要偶尔用于铁的形态分析，但实验室X射线吸收精细结构光谱（lab-XAFS）很少用于样品成分的定量测定。随着基于实验室的XAFS光谱仪的最新发展，这种方法在许多应用以及定量分析中变得更具吸引力。本研究的目的是通过参考光谱的线性组合拟合（LCF）将定量lab-XAFS与XRD和穆斯堡尔谱进行比较。以侧重于测定α-氧化铁（α-Fe2O3）/铁（II,III）氧化物（Fe3O4）质量比的铁物种分析为例。实验在合成的α-Fe2O3/Fe3O4模型混合物上进行，主要是在一个主要由赤铁矿和磁铁矿这两种铁氧化物组成的天然铁矿石样品上进行。对于铁K边lab-XAFS测量，使用了基于X射线管的光谱仪，其采用冯哈莫斯几何结构和高退火热解石墨（HAPG）镶嵌晶体光学元件。讨论了每种方法的能力和挑战。lab-XAFS对定量模型混合物的检测结果和准确度与XRD和穆斯堡尔谱得到的结果相似。然而，虽然lab-XAFS对铁矿石研究的定量结果与XRD结果吻合良好（偏差2个百分点），但穆斯堡尔谱测定的成分与lab-XAFS和XRD结果明显不同。此外，穆斯堡尔谱检测表明存在另一种影响定量的铁氧化物物种。除了在不同铁氧化物的识别、区分和定量方面仍然常见的挑战外，结果表明，在确定一种元素的物种组成时，定量lab-XAFS尤其可以与定量XRD相媲美。这使得lab-XAFS特别适合常规分析。
