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Preparation and FT–IR Characterization of Metal Phytate Compounds
Author(s) -
He Zhongqi,
Honeycutt C. Wayne,
Zhang Tiequan,
Bertsch Paul M.
Publication year - 2006
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2006.0008
Subject(s) - phytic acid , metal , chemistry , phosphate , infrared spectroscopy , metal ions in aqueous solution , zinc , fourier transform infrared spectroscopy , hydrolysis , inorganic chemistry , characterization (materials science) , divalent , nuclear chemistry , materials science , organic chemistry , chemical engineering , nanotechnology , biochemistry , engineering
Phytic acid (inositol hexaphosphoric acid, IP6) has long been recognized as the predominant organic P form in soil and animal manure. 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. As the first step in full characterization, we synthesized eight metal phytate compounds and investigated their structural features using Fourier transform infrared spectroscopy (FT–IR). The absorption features from 900 to 1200 cm −1 in FT–IR could be used to identify these phytates as: (i) light divalent metal (Ca and Mg) compounds with a sharp band and a broad band, (ii) heavy divalent metal (Cu and Mn) compounds with splitting broad bands, and (iii) trivalent metal (Al and Fe) compounds with a broad band and a shoulder band. Three different types of chemical structures of metal–phytate compounds were presented based on the FT–IR information. We further demonstrated that metal orthophosphates possessed different FT–IR spectral characteristics from their IP6 counterparts. The unique spectral features of metal phytates from 1000 to 700 cm −1 could be used to distinguish phytate compounds from metal phosphate compounds. Thus, FT–IR analysis after fine tuning could provide an analytical tool to investigate the basic metal phytate chemistry in molecular levels, such as the competitive interactions between phosphate and phytate with a specific metal ion, and the conversion (or hydrolysis) of metal phytate to metal phosphate under various conditions.