Pure shift NMR - Broad band homodecoupled HSQC

In most 2D NMR spectra the position of the peaks, the chemical shift, is the most important piece of information. If splitting of the peaks by scalar coupling is observed, it is usually ignored. In fact, in many cases scalar coupling in 2D experiments can be detrimental. The splitting increases the chance of overlap and makes it harder to determine accurately the chemical shift. Pure shift experiments, in which the scalar coupling is removed, do not have these problems and are also more sensitive because the peaks are narrower and taller. Heteronuclear 2D experiments, such as HSQC, can be converted to pure shift experiments without loss of sensitivity by applying broad band homo decoupling during acquisition.

Pure Shift NMR - PSYCHE

Pure shift NMR spectra are spectra in which the scalar coupling has been removed so that all signals appear as singlets, as in 1D ¹³C spectra. For ¹³C spectra the coupling is removed by applying ¹H composite pulse decoupling during acquisition. Acquiring a pure shift ¹H spectrum, however, is not so easy because applying ¹H decoupling during acquisition would saturate the ¹H signals and prevent them from being detected. To acquire pure shift ¹H NMR spectra two ingenious modifications have been developed to enable removal of the coupling in a 1D ¹H spectrum. This technique is known as PSYCHE (Pure Shift Yielded by CHirp Excitation)¹.