Optimization of sample pH and temperature for phosphorus-31 nuclear magnetic resonance spectroscopy of poultry manure extracts

Organic phosphorus (P) compounds can be characterized using nuclear magnetic resonance (NMR) spectroscopy provided conditions are suitable for detecting the NMR signal. The objective of the research was to optimize pH and temperature conditions for turkey manure extracts prior to analysis of organic P compounds using NMR. Samples of turkey manure were extracted with 0.25 M NaOH + 0.05 M EDTA. The extracts were lyophilized and resolubilized in distilled H2O before analysis on a General Electric GN500 NMR spectrometer. Initial P-31 NMR experiments were run to determine the optimal instrumental parameters for P-31 studies. Samples were titrated to seventeen pH values ranging from 4.0 to 13.2. Samples adjusted to pH 10.0 had the greatest spectral resolution. A seven-by-three factorial experiment was used to investigate the effect of seven temperatures (5, 10, 20, 30, 40, 50, and 60 degrees C) on three separate samples at pH 6.5, 9.0, or 10.0. Spectra resolution was greatest at pH 10.0 and 20 degrees C.