Quantitative analysis of nuclear magnetic resonance spectra having solvent peaks

摘要

A method is described for the quantitative analysis of a solution in which the solvent produces a nuclear magnetic resonant (NMR) spectral peak that dominates the system. A first spectrum containing the peak is made by operation of a nuclear magnetic resonant spectrometer at a first gain setting. The NMR apparatus is a pulse-modulated, Fourier-transform type spectrometer. A second spectrum is produced in which a 180 DEG pulse is applied to invert the spectral component magnetization followed after a period of time by a 90 DEG pulse. The period of time is sufficient to allow the solvent or component producing the unwanted peak to relax from the inverted state to a point where there is minimum magnetization along the longitudinal axis. At this point, in many solutions the other components have completely relaxed so that the 90 DEG pulse produces a free induction decay signal which, after undergoing the Fourier-transformation, yields a spectrum that does not include any significant peak due to the solvent. Thereafter, the quantitative analysis is performed by measuring the areas under the respective component peaks and simultaneously solving a series of equations in which the weight of the various components is proportional to the respective areas under the peaks and to the gain settings of the spectrometer.