A new approach for accurate quantitative determination using fluorine nuclear magnetic resonance spectroscopy
Taichi Yamazaki, Takeshi Saito and Toshihide Ihara
J. Chem. Metrol. (2017), 11:1 ; 16-22
National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8563, Japan
Abstract: A new approach for accurate quantitative determination by fluorine nuclear magnetic resonance ( 19F NMR) spectroscopy is presented and discussed. 19F NMR spectroscopy has similar properties to 1H NMR spectroscopy except for the wide chemical shift dispersion, which is the main difference between the two techniques. The off-resonance effect, which is caused by the chemical shift difference between the excitation pulse offset and the resonance signal position, is expected to be the most important parameter influencing the accuracy of the quantitative analysis by 19F NMR spectroscopy. We propose a new method that reduces the influence of the off-resonance effect in 19F NMR measurement. First, we discussed the areas of signals originating from different functional groups in a molecule. Then, we evaluated the areas of signals originating from two different reference materials (RMs). The accuracy of the ratios of two signal areas in the 19F NMR spectrum of a molecule of Potassium perfluorooctanesulfonate was less than 1 %. We also evaluated the purity of flusulfamide and diflubenzuron as RMs, and found that the method could determine the purity to less than 1 % accuracy relative to the reference values.
Keywords: qNMR; 19F NMR; internal standard method; purity; off resonance effect . © 2017 ACG Publications. All rights reserved.