Speciation of Phosphorus in Pet Foods by Solid-State ³¹P-MAS-NMR Spectroscopy

Solid-state magic angle spinning ³¹P NMR spectroscopy is used to identify and quantify phosphorus-containing species in pet foods. The measurement is challenging due to the long spin-lattice relaxation times (T₁s). Data acquisition times are shortened by acquiring data with a tip angle smaller than 90° and shortening the repetition time. However, the spin-lattice relaxation times (T₁s) of the different ³¹P compounds are quite different, necessitating a separate measurement for each compound in the pet food. Knowledge of T₁ is used to calculate the relative amount of ³¹P in the samples. Samples of known concentration are also measured, enabling the quantitative measurement of total phosphorus content.