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

Abstract

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.