Spatially Encoded Transfer of 1H Polarization to 13C for Uniform 1 JCH-Response in HSQC

Two dimensional (2D) NMR display better resolution than one-dimensional (1D) 1H NMR. However, 2D NMR does not display a straightforward quantitative aspect due to J-dependent polarization/coherence transfer. 1D 1H NMR is versatile for quantification; however, it displays significant spectral overlap in biological or organic complex mixtures, which forbids quantification of a large number of signals in 1D 1H NMR. The significant variations in 1H13C scalar couplings, T1, T2, and pulse imperfections are the main problems. Although T1, T2 can be suitably chosen to minimize their adverse effect on quantification, the large variations in 1H - 13C couplings lead to variations in cross peak intensity, which is more influenced by the amount of polarization transfer rather than the quantity of metabolites or amount of analytes in a complex mixture. In the present work, we show that spatial encoding of the polarization transfer periods can be executed in 1H13C HSQC using sweep frequency pulses in the presence of a magnetic field gradient. As a result, uniform transfer of polarization from 1H to 13C over a range of 1H - 13C couplings can be performed, subsequently improving the quantitative aspect of HSQC or improve the intensity of cross-peaks, which are mistuned in regular HSQC