Quantitative NMR Spectroscopy Using Coaxial Inserts Containing a Reference Standard:  Purity Determinations for Military Nerve Agents

A novel 31P NMR method for the determination of purity for the military nerve agents sarin, soman, and VX has been developed. In contrast to more conventional quantitative NMR methods, stem coaxial inserts are placed into the sample tube to introduce reference material into the analysis without mixing or reaction with the analyte. All sample preparation is eliminated, and the analysis is completed expeditiously in less than 25 min. The method is highly specific and rugged with respect to operator-induced variability, experimental parameters, and all influences from nuclear magnetic relaxation. Nerve agent purity can be determined with a precision and accuracy typically better than 1%, and impurities can be detected at concentrations as low as 25 microg/mL. The limit of quantitation has been estimated at 85 microg/mL. In terms of precision, accuracy and execution time, the method rivals typical chromatographic methods.