Evaluating the Effects of Iron and Aluminum Ions On Phytate Quantification In Animal Manure Using Hpic.

Phosphorous has been recognized as a major contributor to eutrophication of inland bodies of water in the United States.  Efforts to decrease phosphorous loads have been implemented nationally in the last 15 years.  One of the keys to this effort is the accurate identification and quantification of different phosphorous forms, especially in manures.  Of the organic phosphorous forms found in manures, myo-inositol hexakisphosphate (phytate), is frequently the most abundant.  It, however, is also extremely recalcitrant, traditionally necessitating the use of expensive and time consuming spectroscopic techniques for accurate quantification.  A method, proposed by Ray et al. (2012), allows for rapid, sensitive, robust, and relatively low cost analysis of phytate using high performance ion chromatography (HPIC). However, questions have been raised over interference from cations such as iron and aluminum that can interact with phytate. To gauge the robustness of this technique we conducted two tests.  In the first test, we spiked two dairy manure samples and one chicken litter sample with five different concentrations of ferric and aluminum chloride.  We also spiked the two dairy manure samples with an additional 1000 mg/l phytate, with and without the five rates of ferric and aluminum chloride.  We then used the extraction, cleanup, and HPIC analysis to quantify the amount of phytate in the manure samples.  In the second test, we used the HPIC method to analyze phytate in runoff from manure amended soils.  We used one dairy manure sample, spiked with phytate, and one chicken litter sample to assess the HPIC method’s ability to enumerate phytate movement or retention in topsoil.  We will present the results of both studies and discuss how the HPIC method may be an accurate, robust, and rapid technique for measuring phytate in manure and runoff samples.