Quantitative Analysis of Inorganic Phosphates Using ³¹P NMR Spectroscopy

摘要

Phosphorus-31 nuclear magnetic resonance (31P NMR) is optimized with respect to accuracy, precision, and analysis time for the characterization of inorganic phosphates. Species determinations in commercial sodium tripolyphosphate are routinely achieved with an accuracy and precision (0.1-0.5%) comparable to that obtained by chromatographic methods as determined in interlaboratory analyses. The method has been completely automated using a robotic sample changer and an algorithm for data analysis. In a demonstration of the precision attainable, the hydrolysis kinetics of tripolyphosphate is obtained with a correlation coefficient of 0.998. Extension of 31P NMR to the analysis of higher oligophosphate mixtures (i.e. sodium phosphate glass) has recently been examined using homonuclear 2DJ-resolved spectroscopy to separate the coupling constant and chemical shift information. Semi-quantitative analyses are achieved using curve deconvolution.