940 SSSAJ: Volume 71: Number 3 • May–June 2007 Trade or manufacturer’s names mentioned in the paper are for information only and do not constitute endorsement, recommendation, or exclusion by the USDA-ARS. Use of the National Synchrotron Light Source, Brookhaven National Lab., was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract no. DE-AC02-98CH10886 Soil Sci. Soc. Am. J. 71:940–943 doi:10.2136/sssaj2006.0175N Received 1 May 2006. *Corresponding author (zhongqi.he@ars.usda.gov).. © Soil Science Society of America 677 S. Segoe Rd. Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Abbreviations: MAS, magic angle spinning; NMR, nuclear magnetic resonance; XANES, x-ray absorption near edge structure. It is expected that the first 50 yr of the 21st century will see rapid agricultural expansion to meet the demands of a wealthier and larger global population (Tilman et al., 2001). With this rapid expansion comes the threat of eutrophication. Simulation models predict that it could take 1000 yr or more to recover from eutrophication caused by agricultural overenrichment of soils (Carpenter, 2005). Increased basic knowledge of P dynamics is needed to minimize these deleteri- ous impacts. More than 35 million Mg of phytic acid (inositol hexaphos- phoric acid), or 51 million Mg of phytate, are formed in crops and fruits each year globally (Lott et al., 2000). Phytate has been found to be a predominant form of organic P in animal manure, soil, and other organic substances (Cosgrove, 1962; He et al., 2006c; Herbes et al., 1975; Turner et al., 2002). Although some information is available on the basic chemistry of phytate (Turner et al., 2002), the interactions and fate of phytate in the environment remain poorly understood. There is an urgent need to better understand the behavior, mobility, and biological availability of phytate in the environment (Turner et al., 2006). Phytate contains a six-C ring with 1 H and 1 phosphate attached to each C. Each of the six phosphate groups is attached in an ester linkage and retains two replaceable Hs. These two non-ester hy- droxyl groups should impart some inorganic P-like (orthophosphate bond) properties to phytate, leading to interactions of phytate with various metal ions in the environment to form various soluble or in- soluble compounds (phytate salts). One of the key issues in P chemis- try is metal speciation of P in the environment, as phosphate can in- teract with metal ions and oxides to affect the solubility and mobility of phosphates. Metal speciation of phosphate and metal–phosphate interactions can be investigated by solid-state 31 P NMR and XANES spectroscopic techniques (Hunger et al., 2004; Peak et al., 2002; Sato et al., 2005; Toor et al., 2005). Whereas these studies have shed light on the metal speciation of inorganic phosphate, it is not possible to resolve these spectral data in detail on specific metal–phytate species due to the lack of reference spectra. To evaluate the feasibility of metal speciation of phytates by solid-state 31 P NMR and XANES spectro- scopic techniques, we determined and analyzed the solid-state spectral characteristics of six metal phytates. These spectra of metal phytates would provide reference spectral characteristics for identifying relevant metal species of phytate as these metals (Na, K, Ca, Mn, Al, and Fe) are abundant in soils (Sato et al., 2005; Shand et al., 1999) and animal manures (He et al., 2003, 2006c; Peak et al., 2002) and phytate is inclined to interact with them (Dao, 2003; He et al., 2006a). MATERIALS AND METHODS The Na and K compounds of phytates and orthophosphates were purchased from Sigma Chemical Co. (St. Louis, MO). The Ca, Mn, Al, and Fe compounds were made in-house (He et al., 2006b). All chemicals were ground to powders in an agate mortar and kept in a desiccator at room temperature until use. Solid-state 31 P NMR spectra were collected on a Varian Inova 500 spectrometer (Varian Inc., Palo Alto, CA) operating at 202.489 MHz using a Doty Scientific 4mm/XC magic angle spinning (MAS) probe (Doty Scientific, Columbia, SC). Bloch decays of 50 ms were collected with a 200 ppm window after 30° excitation pulses. A relaxation delay Solid-state 31 P nuclear magnetic resonance (NMR) and x-ray absorption near edge structure (XANES) spectroscopies have provided knowledge on metal speciation of inorganic P. No effort has been made, however, to accurately assign speciated metal phytates (inositol hexaphosphoric acid salts) using these advanced techniques. Phytate is a predominant form of organic P in animal manure, soil, and other organic substances as each year 51 million Mg of phytate are formed in crops and fruits globally. Currently, the interactions and fate of phytate in the environment are poorly understood. Here we show the solid- state spectral characteristics of six metal phytates. Both spectra were affected by the metal species of the phytates, as significant differences were observed in the shape and position of spectra among the metal phytates. Reference spectra of these pure metal phytate compounds may help in identifying metal species of phytate in environmental samples by these advanced spectroscopic technologies. Distinction of Metal Species of Phytate by Solid-State Spectroscopic Techniques Zhongqi He* C. Wayne Honeycutt USDA-ARS New England Plant, Soil and Water Lab. Orono, ME 04469 Tiequan Zhang Agriculture & Agri-Food Canada Greenhouse & Processing Crops Research Ctr. Harrow, ON, N0R 1G0, Canada Perry J. Pellechia Dep. of Chemistry and Biochemistry Univ. of South Carolina Columbia, SC 29208 Wolfgang A. Caliebe National Synchrotron Light Source Brookhaven National Lab. Upton, NY 11973 SOIL CHEMISTRY NOTE Published online May 16, 2007