Past, Present, and Future of X-ray Fluorescence Chemical Imaging

Elemental chemical images reveal how the elements are distributed in a sample. While it may sound useless for a homogeneous solution, it is crucial for understanding properties of heterogeneous systems, such as a rock1, a cereal grain2, or a painting3. In such cases, revealing the chemical composition of parts of the sample might reveal the distribution of minerals, nutrients, or toxic elements. All strategies for measuring the spatial distribution of elements require a probe, whose size will define the lateral resolution of the image, and a detection system. Some techniques are destructive while others preserve the specimen; this latter feature is of special importance for rare and mass-limited samples or in the case of in vivo analysis. Laser ablation coupled to mass spectrometry or optical emission spectrometry, laser induced break down spectrometry, and microprobe X-ray fluorescence spectrometry are some of the most common laboratory techniques employed in chemical imaging.