X-ray fluorescence spectrometry (XRF) is a powerful tool for elemental analysis in various field samples. XRF has great advantages of nondestructive and rapid elemental analysis without the complicated and time-consuming chemical pretreatment such as acid digestion or alkaline fusion in comparison with other elemental analysis such as inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and atomic absorption spectrometry (AAS).

A hot topic of XRF analysis was the elemental analysis of samples of asteroid 162173 Ryugu retrieved by the Hayabusa2 spacecraft [1]. The collected samples delivered from the Ryugu to Earth on 2020 December 6 were analyzed nondestructively by wavelength dispersive XRF (WDX), energy dispersive XRF (EDX), and synchrotron radiation XRF (SR-XRF). As the result, the Ryuguu was found to be composed of carbonaceous meteorites, especially Ivna-type carbonaceous meteorites called CI chondrites.

Recently, a micro-XRF analysis has become a most important tool for observing the elemental distribution in the local area of samples. Nishiwaki et al. [2, 3] analyzed elemental distribution of K, Ca, Mn, Fe, Cu, and Zn in the Chinese chive (Allium tuberosum) leave using SR-micro-XRF by Kirkpatrick-Baez (KB) mirror. The authors concluded that XRF intensity ratios of Ca/K, Fe/Mn, and Zn/Cu can be used in the early detection of withered leaves and to predict the factors causing withering. Huang et al. [4] studied the accumulation and transport mechanisms of chromium in medicinal plant in China (Coptis chinensis Franch) by analyzing SR-micro-XRF in combination with laser ablation ICP-MS (LA-ICP-MS), X-ray absorption near-edge spectroscopy (XANES), ICP-MS to detect Cr subcellular concentration.

A polycapillary X-ray lens, which is convenient X-ray focusing optics for micro-XRF analysis, can produce a high brilliant micro-X-ray beam from 10 to 100 μm using laboratory X-ray source. Sanyal and Dhara [5] improved the detection limits of major and trace elements (Si, P, S, V, Cr, Mn, Co, Ni, Cu, and Mo) in stainless steel by optimizing the geometry of the micro-XRF instrument. Nakano et al. [6] enables improvement of the detection limit for the particle samples through a confocal micro-XRF configuration that allows elemental information to be obtained only at the “confocal point” by mounting two polycapillary X-ray lenses and adjusting the excitation and detection focus points to the same position. While confocal micro-XRF is typically used for depth elemental analysis and 3D elemental analysis, the authors applied it to reduce the background noise caused by scattered X-rays.

For analysis of geochemical samples, a use of transportable or handheld EDX spectrometer is adequate to the on-site elemental analysis. However, successful elemental analysis of soil samples by XRF requires appropriate sample preparation and matrix correction for various factors of analytical error (matrix effect, mineral effect, particle size effect, and moisture  effect). Kanrar et al. [7] proposed the sample preparation method for accurate determination of sulfur in uranium ores by preparing a very thin and uniform sample specimens containing S on thin Mylar film. Nakano et al. [8] developed a new correction method for soil moisture effect using a combination of Compton scattering X-rays and moisture content in on-site XRF analysis of six hazardous metals (Cr, As, Se, Cd, Hg, Pb) in contaminated soil.

Total reflection X-ray fluorescence (TXRF) analysis was primarily used before 2000 to determine surface ultra-trace metal concentrations on flat sample surfaces . Recently, TXRF technique has been applied to the field of environmental sample, human health, and forensic science. Sengoku et al. [9] analyzed single synthetic fibers obtained from several textile products by portable TXRF spectrometer for application in crime scene investigation. Matsuyama et al. [10] proposed the analytical method of trace elements in scalp hair for TXRF analysis to evaluate human health and environmental contamination. The proposed preparation method for TXRF was directly digesting the human hair on specific sample holder.

XRF technique is well establish method as an elemental analysis. On the other hand, a new X-ray generator [11] and X-ray detector [12] have been developed in recent years. Therefore, novel application of XRF analysis is considered to increase in the future.

figure a