Hodoroaba Vasile-Dan, Rackwitz Vanessa
BAM Federal Institute for Materials Research and Testing , Division 6.8 Surface Analysis and Interfacial Chemistry, 12200 Berlin, Germany.
Anal Chem. 2014 Jul 15;86(14):6858-64. doi: 10.1021/ac5000619. Epub 2014 Jun 30.
The high specificity of the coherent (Rayleigh), as well as incoherent (Compton) X-ray scattering to the mean atomic number of a specimen to be analyzed by X-ray fluorescence (XRF), is exploited to gain more information on the chemical composition. Concretely, the evaluation of the Compton-to-Rayleigh intensity ratio from XRF spectra and its relation to the average atomic number of reference materials via a calibration curve can reveal valuable information on the elemental composition complementary to that obtained from the reference-free XRF analysis. Particularly for matrices of lower mean atomic numbers, the sensitivity of the approach is so high that it can be easily distinguished between specimens of mean atomic numbers differing from each other by 0.1. Hence, the content of light elements which are "invisible" for XRF, particularly hydrogen, or of heavier impurities/additives in light materials can be calculated "by difference" from the scattering calibration curve. The excellent agreement between such an experimental, empirical calibration curve and a synthetically generated one, on the basis of a reliable physical model for the X-ray scattering, is also demonstrated. Thus, the feasibility of the approach for given experimental conditions and particular analytical questions can be tested prior to experiments with reference materials. For the present work a microfocus X-ray source attached on an SEM/EDX (scanning electron microscopy/energy dispersive X-ray spectroscopy) system was used so that the Compton-to-Rayleigh intensity ratio could be acquired with EDX spectral data for improved analysis of the elemental composition.
相干（瑞利）以及非相干（康普顿）X射线散射对通过X射线荧光（XRF）分析的样品平均原子序数具有高特异性，利用这一特性可获取更多关于化学成分的信息。具体而言，通过校准曲线评估XRF光谱中的康普顿与瑞利强度比及其与参考材料平均原子序数的关系，能够揭示与无参考XRF分析所得互补的有关元素组成的有价值信息。特别是对于平均原子序数较低的基体，该方法的灵敏度很高，以至于能够轻松区分平均原子序数相差0.1的样品。因此，可以根据散射校准曲线“通过差值”计算出XRF“不可见”的轻元素（特别是氢）或轻质材料中较重杂质/添加剂的含量。还展示了基于可靠的X射线散射物理模型，这种实验性的经验校准曲线与合成生成的校准曲线之间的出色一致性。因此，在使用参考材料进行实验之前，可以针对给定的实验条件和特定分析问题测试该方法的可行性。在当前工作中，使用了附着在扫描电子显微镜/能量色散X射线光谱仪（SEM/EDX）系统上的微焦点X射线源，以便利用EDX光谱数据获取康普顿与瑞利强度比，从而改进对元素组成的分析。
