XANES Spectra of Metal Phytate Compounds.

Metal speciation of phosphate and metal-phosphate interactions can be investigated by molecular-scale X-ray absorption near edge structure (XANES) spectroscopic analysis. Much of the effort, however, has been focused on inorganic P speciation (i. e. metal-orthophosphate interactions). Phytate (inositol hexaphosphoric acid, IP6) is a predominant form of organic phosphorus in plant seeds, animal diets and manure, and soil. Whereas many studies have investigated the wet chemistry of IP6, there is little information on the characterization of solid metal IP6 compounds. This information is essential for further understanding and assessing the chemical behavior of IP6 in diverse soil-plant-water ecosystems. To advance the application of XANES for evaluating metal speciation of IP6 in the environment, we investigated the P K-edge XANES spectral features of mono-, di-, and tri-metal IP6 compounds. The intensity, position, and width of spectra at approximately 2153eV were analyzed and compared among the metal IP6 compounds and their inorganic counterparts. These results provide information for properly selecting model compounds for XANES reference spectra in studies of metal-IP6 interactions in the environment.