Utilizing Intensity Ratios To Characterize Glass Fragments Via Micro-X-ray Fluorescence

Abstract

Micro-X-ray fluorescence (micro-XRF) is a non-destructive elemental technique which utilizes a focused X-ray source to generate characteristic radiation from the sample. In “bulk” samples, when the X-ray source cannot penetrate through the sample, the count-rates (CPS) for each element is saturated. Weight fractions can then be calculated by employing a Fundamental Parameters calibration model. However, if the sample is not thick enough to absorb the primary X-rays (i.e. “thin” sample), then the count-rates will be influenced by the sample thickness. This effects the calculation of weight fractions, as the Fundamental Parameters model assumes samples are infinitely thick. Figure 1 shows nominal Xray probe depths at various energies and samples matrices. These probe depths are crucial in determining if a sample can be considered “bulk” or “thin” relative to the X-ray energy. In many microXRF applications, comparing and characterizing small fragments (i.e. determining whether they are the same or different) is required. However, the samples may have no consistent thickness or size, and generally must be analyzed “as is”. Therefore, a method is necessary to be able to compare samples while compensating for the influence of sample thickness. This study will look at an alternative intensity-based methodology to characterize samples, using measurements from soda-lime glass fragments to illustrate the improved stability.