Standardization and Practical Application of Quantitative NMR (qNMR)

In Japan, quantitative NMR (qNMR) has already been recognized as a standard method for determining the purity of quantitative samples not only in the Japanese Pharmacopoeia and the Japanese Standards and Specifications for Food Additives but also in the Japanese Industrial Standard (JIS K 0138: 2018). However, since there was no consensus on the establishment of a standard method, the international standardization of qNMR was initiated based on a proposal from Japan. After three years of discussion among experts, International Organization for Standardization/Technical Committee on Food (ISO/TC34) published ISO 24583: 2022" Quantitative nuclear magnetic resonance spectroscopy-Purity determination of organic compounds used for foods and food products-General requirements for H-1-NMR internal standard method." Publication of this standard has resulted in an internationally agreed upon set of requirements for purity determination using qNMR. New technologies emerge from the cycle of basic research, practical use, and standardization, and qNMR is no exception. A novel chromatographic quantification method based on relative molar sensitivity (RMS) is now being put into practical use. The RMS of an analyte with respect to a different reference substance can be determined by using qNMR to accurately determine the molar ratio and then introducing it into the chromatographic system. This method uses the RMS determined by combining qNMR and chromatography instead of the analyte's reference material to determine its content in sample. This method has been adopted in the Japanese Pharmacopoeia, and the development of a general rule in the Japanese Agricultural Standards (JAS) is also under consideration.