Rationalising spin relaxation during slice-selective refocusing pulses.

Slice-selective refocusing pulses are powerful building blocks in contemporary magnetic resonance experiments, but their use in quantitative applications is complicated by the site-dependent signal loss they introduce. One source of this attenuation is the spin relaxation that occurs during such pulses, which causes losses that depend on the specific longitudinal and transverse relaxation time constants for a given resonance. This dependence is complicated both by any amplitude shaping of the radiofrequency pulse, and by the presence of the spatial encoding pulsed field gradient.

Universally Quantitative Band-Selective Pure Shift NMR Spectroscopy.

NMR spectroscopy is often described as a quantitative analytical technique. Strictly, only the simple pulse-acquire experiment is universally quantitative, but the poor signal resolution of the H NMR pulse-acquie experiment frequently complicates quantitative analysis. Pure shift NMR techniques provide higher resolution, by reducing signal overlap, but they are susceptible to a variety of sources of site-dependent signal loss.

Recovering sensitivity lost through convection in pure shift NMR.

Practical pure shift NMR experiments, especially on instruments equipped with cryoprobes, can sometimes give very disappointing results. Here we show for the first time that this is a consequence of signal loss due to sample convection, and demonstrate a simple adjustment to common pure shift NMR experiments that restores the lost signal.