Solution 31Phosphorus Nuclear Magnetic Resonance Analysis of Acid-Extractable Phosphates in Animal Feces

Characterizing phosphates in animal fecal and manure samples is of interest to environmental-monitoring research efforts. Acid extraction removes relatively mobile phosphates from samples, offering a better indicator of the mobility of phosphates in environment, but acidic extracts impose challenges to the solution phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy, which is commonly used for analyzing phosphates in environmental samples. Acid-extractable metals precipitate phosphates in the alkaline condition under which solution 31P NMR experiment runs, blurring the spectrum for adequate analysis. We found that neutralizing acid extracts with 0.5 M sodium hydroxide (NaOH) plus 50 mM ethylenediaminetetraacetic acid (EDTA) before freeze drying eliminated the chemical interferences otherwise observed. The resulting 31P NMR spectra can be used to quantify acid-soluble phytate and other phosphates in animal fecal and manure samples. The improvement in detection will support efforts to investigat...