Matrix and Particle Size Effects in Analyses of Light Elements, Zinc through Oxygen, by Soft X-Ray Spectrometry

Abstract

With the development of soft X-ray sources by Henke, it is now possible to extend the range of quantitative analyses by X-ray spectrometry into the very light element range (magnesium through boron). Techniques of specimen preparation, recognized as one of the most critical aspects of quantitative X-ray analysis in the heavier elemental ranges, present new problems, especially with the physically and chemically heterogeneous materials encountered in mineral and rock analysis. This paper presents the results of new tests extended into the light and very light element range. It is shown that most of the problems previously found are intensified as lower atomic number elements are considered; conditions of the specimen surface are critical and require precise control of particle size. In addition, significant absorption by relatively heavier elemental constituents, either in a separate phase or within the same phase, causes poor precision and is difficult to predict. Thus, the combination of matrix absorption within and between discrete phases, combined with the difficulty of grinding different phases to a uniform particle size, suggests that fusion techniques are required for best precision. Without fusion, both scatter and bias are introduced through non-linear calibrations, with each calibration dependent upon specimen composition and particle size. It is concluded that only with nearly uniform specimens, where gross deviations are to be checked (e.g., process control) can ground rock powders be used with success in light element analyses.