Selective-Excitation-Based Method for Measurement of Nmr Relaxation Time

Abstract

Relaxation time provides invaluable insights into the molecular structure, interactions, and dynamics in nuclear magnetic resonance spectroscopy. However, conventional relaxation-time measurement techniques produce inaccurate relaxation times when the spectral peaks overlap because of the narrow chemical-shift range and J-coupled splitting. This study proposes a method that combines selective excitation with a conventional relaxation-time measurement method to accurately measure the longitudinal and transverse relaxation times in complex samples. This method eliminates the interference caused by overlapping peaks in proton relaxation-time measurement and preserves the crucial coupling information of the sample. The feasibility and effectiveness of the method were demonstrated through experiments using three types of samples: a simple sample, a mixture with overlapping peaks, and a complex compound with overlapping peaks. This method selectively excites the spin of interest in a single scan without additional accumulation, demonstrating a minor loss of spectral sensitivity and facilitating the measurement of low-concentration samples, making it widely applicable to chemical analyses.

Keywords: nuclear magnetic resonance, relaxation-time measurement, selective excitation, overlapping peaks