QUANTITATIVE ANALYSIS OF NUCLEAR MAGNETIC RESONANCE SPECTRA HAVING SOLVENT PEAKS

摘要

QUANTITATIVE ANALYSIS OF NUCLEARMAGNETIC RESONANCE SPECTRA HAVINGSOLVENT PEAKSAbstract of the DisclosureA method is described for the quantitative analysisof a solution in which the solvent produces a nuclearmagnetic resonant (NMR) spectral peak that dominatesthe system. A first spectrum containing the peak ismade by operation of a nuclear magnetic resonantspectrometer at a first gain setting. The NMR apparatusis a pulse-modulated, Fourier-transform type spectrometer.A second spectrum is produced in which a 180° pulse isapplied to invert the spectral component magnetizationfollowed after a period of time by a 90° pulse. The periodof time is sufficient to allow the solvent or componentproducing the unwanted peak to relax from the invertedstate to a point where there is minimum magnetization alongthe longitudinal axis. At this point, in many solutionsthe other components have completely relaxed so thatthe 90° pulse produces a free induction decay signalwhich, after undergoing the Fourier-transformation,yields a spectrum that does not include any significantpeak due to the solvent. Thereafter, the quantitativeanalysis is performed by measuring the areas under therespective component peaks and simultaneously solving aseries of equations in which the weight of the variouscomponents is proportional to the respective areas underthe peaks and to gain settings of the spectrometer.