Determination of trace elements in soybean by X-ray fluorescence analysis and its application to identification of their production areas

Trace elemental analysis of soybeans was performed using X-ray fluorescence (XRF) analysis in order to characterise the geographical origins of the beans. By optimising the measurement conditions of an energy-dispersive XRF spectrometer equipped with three-dimensional polarisation optics, determination of trace elements at the sub-μg g−1 level in soybean samples was accomplished. Forty-six samples were analysed. Results showed that there were some differences between the trace element contents, reflecting a difference in their geographical origins. A statistical analysis showed that the concentrations of eight elements (Mg, P, Cl, K, Mn, Cu, Br, and Ba) are good parameters for constructing a discriminant function for geographical origin. In conclusion, we were able to accurately distinguish between domestic and imported soybeans. The present work demonstrates that XRF is useful as a rapid and simple tool for provenance analyses of agricultural products.