Enhancing NMR of Nonrelaxing Species Using a Controlled Flow Motion and a Miniaturized Circuit.

In this article we show that circulation of the sample in a closed-loop circuit combined to microsized detection can lead to a significant signal NMR enhancement. We present an optimized NMR device based on a mini bubble-pump associated with fluidics and microdetection that can be installed on a commercial NMR spectrometer. In addition to a significant signal enhancement for slowly relaxing nuclei, we show that it enables more precise and frequent monitoring of chemical reactions. An additional modification leads to a stopped-flow system very efficient for instance for 2D NMR experiments with long mixing times.