Confocal micro X-ray fluorescence analysis for the non-destructive investigation of structured and inhomogeneous samples

Confocal micro X-ray fluorescence (CMXRF) spectroscopy is a non-destructive, depth-resolved, and element-specific technique that is used to analyze the elemental composition of a sample. For this, a focused beam of mono- or polychromatic X-rays is applied to excite the atoms in the sample, causing them to emit fluorescence radiation which is detected with focusing capillary optics. The confocal design of the instrument allows for depth-resolved analysis, in most cases with a resolution in the lower micrometer dimension after collecting X-rays from a predefined volume within the sample. The element-specific nature of the technique allows information to be obtained about the presence and concentration of specific elements in this volume. This makes CMXRF spectroscopy a valuable tool for a wide range of applications, especially when samples with an inhomogeneous distribution of elements and a relatively light matrix have to be analyzed, which are typical examples in materials science, geology, and biology. The technique is also commonly used in the art and archaeology fields to analyze the elemental composition of historical artifacts and works of art, helping to provide valuable insights into their provenance, composition, and making. Recent technical developments to increase sensitivity and efforts to improve quantification in three-dimensional samples will encourage wider use of this method across a multitude of fields of application in the near future.

Automated summary

Confocal micro X-ray fluorescence (CMXRF) spectroscopy is a valuable non-destructive technique for analyzing the elemental composition of samples. It uses mono- or polychromatic X-rays to excite atoms in the sample, resulting in the emission of fluorescence radiation that is detected with capillary optics. CMXRF has a depth-resolved analysis capability, making it useful for studying samples with inhomogeneous element distribution and a light matrix. It has applications in materials science, geology, biology, art, and archaeology, providing insights into the provenance, composition, and making of artifacts and works of art. Ongoing technical developments aim to increase sensitivity and improve quantification for three-dimensional samples, expanding the method's utility in various fields.