Recent Developments in Analytical Science - X-ray Spectroscopy

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Education Article

  • Published: Jul 18, 2016
  • Channels: Ion Chromatography / HPLC / Gas Chromatography / Electrophoresis / Proteomics & Genomics / Proteomics / MRI Spectroscopy / X-ray Spectrometry / Raman / NMR Knowledge Base / Base Peak / Infrared Spectroscopy / Atomic

X-ray Spectroscopy

The term X-ray spectroscopy covers a number of different techniques, one of the most popular being X-ray fluorescence. Its non-destructive nature and ease of use have guaranteed a multitude of applications in contrasting areas, with the common goal of identifying and measuring the elements in a given sample. It has been used in plant studies, archaeology, geochemistry, cosmetics and water.

For handheld, battery-operated XRF analysers, energy dispersive XRF is normally employed as it permits the simultaneous analysis of a number of elements. So, operatives can perform onsite operations such as testing fuel, sorting scrap metal, food testing and forensic analysis. These techniques are designed for bulk analysis but micro-XRF can examine materials on a much smaller scale, to resolution of a few µm. Benchtop versions are also available for this technology. The trend towards portability and simple operation in the field will continue.

So, miniaturisation has been an important development for X-ray systems and this is also true for the long-established X-ray diffraction, for which handheld instruments have been developed. The main application for back-reflection energy dispersive XRD is in the characterisation of ores, which can be analysed with no sample preparation. It should also find application in archaeological and artistic areas. Mineral-specific or phase-specific XRD, which relies on an internal mineral of phase to enhance the signal, is more sensitive than energy dispersive XRD and is suitable for examining one particular component of the sample, typically an ore.

There are interesting developments in X-ray absorption spectroscopy where the extended X-ray absorption fine structure mode of operation allows the local environment of materials to be studied over distances of below 0.05 Angstrom. Typical applications have been in catalyst characterisation. One exciting development is time-resolved XAS which is being facilitated by the introduction of ultrashort laser pulses but more developments in this area are required for better performance to study systems that are not in equilibrium.41

X-ray microscopy, also known as micro-computed tomography, combines elemental analysis and microscopy to allow detailed analysis of solids, liquids, gases and living creatures. They offer better resolution than optical microscopes, due to the shorter wavelength of X-rays than visible light. They can be operated by visualising the whole target at once or scanning over the sample and both 2D and 3D imaging is possible, depending on the system.

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