The Suppression of J-Modulations in Spin Echo Experiments by Using a J-Refocused Press (JPRESS) Pulse Sequence

Abstract

Analysis of ^1H NMR spectra appears to be difficult due to a large number of metabolite signals present, particularly between 2.0 and 3.0 ppm chemical shift range. The loss of signal intensity due to J modulation can be suppressed by using a homonuclear J-refocused pulse sequence. The suppression of J modulations with the J-refocused PRESS (JPRESS) pulse sequence, theory, in terms of the product operator formalism and experimental results have been presented AX_n systems in some metabolites. The results are in good agreement with the theory. J-coupling modulations in the spectra at different spin echo times (TE) using PRESS and JPRESS pulse sequences have been compared with each other for some metabolites. The refocusing of the J-coupling is perfect for AX system, but incomplete for a multiply coupled system on condition that TE's are less than 1/(4J).