Phase correction method in two-dimensional nmr spectroscopy

Abstract

There is disclosed a method of precisely correcting the phase of a two-dimensional NMR spectrum along the two axes. First, a first phase train is applied to a sample. After an evolution period of t.sub.1, a second pulse train is applied. Then, the free induction decay signal emanating from the sample is detected during a detection period of t.sub.2, using a quadrature detection system. This process is repeated with different values of t.sub.1. Thus, a complex NMR spectrum S.sub.1 (t.sub.1, t.sub.2) is obtained. Subsequently, the sample is excited with a pulse sequence which is similar to the first-mentioned pulse sequence except that the second pulse is shifted in phase by 90.degree./n (n is a natural number) with respect to the second pulse of the first-mentioned pulse sequence. The resulting free induction decay signal is detected. This process is repeated with the same number of different values of t.sub.1 as the values of t.sub.1 used in the first set of measurements. Thus, a complex NMR spectrum S.sub.2 (t.sub.1, t.sub.2) is derived. The spectra S.sub.1 (t.sub.1, t.sub. 2) and S.sub.2 (t.sub.1, t.sub.2) are subjected to complex Fourier transformation with respect to the axis t.sub.2. Then, the imaginary part of S.sub.1 (t.sub.1, F.sub.2) and the real part of S.sub.2 (t.sub.1, F.sub.2) are interchanged to give rise to Fourier-transformed spectra S.sub.1 '(t.sub.1, F.sub.2) and S.sub.2 '(t.sub.1, F.sub.2), which are then subjected to complex Fourier transformation with respect to the axis t.sub.1. The phase is corrected along one of the axes. The imaginary part of S.sub.1 '(F.sub.1, F.sub.2) and the real part of S.sub.2 (F.sub.1, F.sub.2) are interchanged. Then, the phase is corrected along the other axis.