Submitted to: Bouyoucos Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/31/2005
Publication Date: 8/21/2005
Citation: He, Z., Honeycutt, C.W., Zhang, T., Bertsch, P.M. 2005. Synthesis and initial characterization of metal-phytate compounds. Bouyoucos Conference Proceedings. Aug 2005; pg 34-35
Technical Abstract: Phytate (inositol hexaphosphoric acid, IP6) has been identified as a major organic P form in soil, animal manure and other environmental samples. In this work, we synthesized seven IP6 metal compounds from NaIP6 and metal chlorides in order to yield spectral information of these solid model compounds which would facilitate characterizing metal-organic P interactions in the environment. The theoretical mole ratio of P:C:metal is 1:1:1 for metal(II)-IP6, and 1:1:0.67 for metal(III)-IP6. Elemental analysis indicated that compounds with Ca, Mg, Cu, Mn, and Al were obtained near stoichiometrically (plus or minus 10%). The two compounds containing Fe(III) were 25-28% higher in metal content, indicating some Fe hydroxide was present. Our data show that the absorption bands from 900 to 1200 cm-1 in FT-IR could be used to classify metal phytate compounds into three groups: (1) light divalent metal (Ca and Mg) phytate compounds with a sharp band and a broad band, (2) heavy divalent metal (Cu and Mn) compounds with splitting broad bands, and (3) trivalent peaks with a shoulder band. The results of enzymatic hydrolysis with 3-phytase demonstrate that nearly all IP6 P in Na (control), Ca, Mg, Mn, and Cu compounds were enzymatically hydrolyzed to soluble inorganic P at pH 5. Enzymatic release of phytate P from Fe and Al compounds was not detected. Taken together, the differential structural and chemical properties of these metal compounds indicate that metal speciation is an important factor, influencing phytate behavior in the environment.