QUANTITATIVE-ANALYSIS OF SHORT-CHAIN PHOSPHATES BY P-31 NUCLEAR-MAGNETIC-RESONANCE AND INTERLABORATORY COMPARISON WITH INFRARED AND CHROMATOGRAPHIC METHODS

A method for the analysis of commercial inorganic oligophosphates has been developed based on the use of high-resolution phosphorus-31 Fourier transform nuclear magnetic resonance (NMR). Experimental parameters were selected to optimize accuracy, precision, and analysis time. The accuracy and precision of the NMR method have been demonstrated to be comparable to chromatographic methods and superior to IR and XRD in controlled interlaboratory analyses using commercial sodium tripolyphosphate. This study represents the only thorough and direct comparison of methods for phosphate species analysis. The major source of error in the NMR method is in obtaining reproducible integrations for signals with proximate chemical shifts, but the precision may be greatly improved using a line-shape analysis and curve-fitting routine. Detection limits of 1-10 mg P/L may be attained with phosphorus-31 NMR by scanning overnight.