Pure Shift

Pure shift refers to a 1H spectrum that has collapsed all the J coupling multiplets into singlets.   That is, it is a homo-decoupled 1H spectrum.   This overcomes a main limitation to the resolution in proton spectra, which is the overlap caused by broad multiplets.   Often, one can combine this pure-shift experiment with additional approaches to improve resolution such as Non-Uniform Sampling (NUS) and covariance processing to yield very-high resolution 2D spectra.  We have only two pure-shift experiments implemented at Columbia: 1D proton, and HSQC.

Shown below is a pure-shift 1D  1H spectrum of sucrose, and below it is a standard spectrum.  A recent improved 1D sequence, PSYCHE-TSE[1], gives artifact free spectra.  The primary disadvantage of 1D pure shift is the lower sensitivity compared to standard 1D. For the PSYCHE technique, it is at least 50 times less.


[1] Foroozandeh, Chem. Commun., 2015, 51, 15410.

Pure-shift 1D NMR

The improved resolution of pure-shift HSQC relative to the standard HSQC is shown below. The pure-shift peaks, shown below in blue, are much smaller and thus display higher resolution in the F2 proton dimension. The sensitivity for pure-shift HSQC is similar to standard HSQC.  Diastereotopic germinal protons will retain their coupling to each other.   

HSQC pure shift spectrum