Limitations of X-Ray Fluorescence Technology
X-ray fluorescence (XRF) technology exploits the inherent emission properties of materials to interpret their elemental composition. It is one of the primary analytical methods used to determine the chemical content of various samples at the trace and ultra-trace levels. Among the many benefits of X-ray fluorescence technology are its extreme versatility, non-destructiveness, and outstanding levels of accuracy due to the technology’s reliable underlying physics. However, there are drawbacks to this industry-leading method of materials characterization.
In this blog post, XRF Scientific explores the limitations of X-ray fluorescence technology in greater detail. We will also offer a few solutions to the challenges represented by modern elemental analysis.
Outlining X-Ray Fluorescence Technology
Each element in the periodic table exhibits characteristic radiation when excited with short-wavelength energy. In the case of X-ray fluorescence technology, this radiation is on the order of 0.01 – 10 nanometers (nm) and is supplied by a controlled X-ray tube. This ionizes the component atoms of a sample and causes them to eject electrons from their atomic orbitals, emitting secondary X-rays. These are acquired by a high-resolution optical detector and digital signal processor, which converts the energy spectrum into a graphical representation of energy-intensity peaks.
These energy peaks are used to identify and quantify the elements present within a sample with outstanding degrees of accuracy. Similar levels of accuracy can be achieved by optical emission spectrometry (OES) and inductively coupled plasma (ICP) analysis, but X-ray fluorescence technology is the only tool that can reliably be described as completely non-destructive.
However, this simple outline of X-ray fluorescence technology ignores the influences of various interfering factors. In an ideal experiment; peak intensities would represent a linear relationship with the concentration of a given element, but deviations can occur due to strong matrix effects. Primary X-rays may be attenuated or enhanced by material surrounding the sample of interest. This calls the accuracy of direct X-ray fluorescence analysis into question.
Alongside the influence of strong matrix effects, X-ray fluorescence technology is also superficially limited by several other factors, including: the technology’s inability to measure radiation from all elements, and radiation exposure concerns for technology operators. The real-world limitations of these factors is negligible, however.
Overcoming Limitations with Sample Preparation
Direct X-ray fluorescence analysis is often prescribed in cost-competitive, high throughput environments. Portable analyzers are used for in situ measurements of mineral and ore samples in mining applications and earth exploration, but the results offered can be skewed by the complex matrix effects of the surrounding material. There are several essential solutions to this problem.
X-ray fluorescence analyzers must be routinely calibrated using industry-standard reference material to maintain accuracy over repeated use cycles. Yet this can only provide a measure of certainty regarding the integrity of results.
The single most effective method of enhancing the quality of X-ray fluorescence technology results is utilizing robust sample preparation methodologies to remove complex heterogeneities that could cause undesirable attenuation or enhancement of the emission spectrum. Using a eutectic flux, small volumes of sample material can be fused into a glass bead or pellet which eliminates matrix effects while offering an almost perfect homogenous representation of the raw sample material.
Sample Preparation Solutions from XRF Scientific
XRF Scientific is a world leader in X-ray fluorescence technology, offering a portfolio of products and services to assist in the optimization of analytical results in a wide range of markets. If you would like any more information about our essential lab equipment for XRF analysis, simply contact a member of the team today.
