Developments in reaction monitoring by NMR

Abstract

NMR is a highly informative non-destructive technique which is why it is so commonly used. However, for the purposes of reaction kinetics there are limitations of the rate at which data can be obtained. There are two main limitations to obtaining NMR kinetic data: the time taken to prepare the sample and begin obtaining data, and the speed at which successive scans can be performed. As each of the two problems are very different there are two themes to this project. The preparation time has been improved using hardware, specifically stopped flow equipment (InsightXpress) that has been developed. This novel stopped flow NMR system allows 95% pre-magnetisation via coils held at close proximity to the bore of the magnet, which can be rapidly injected at speeds up to 2ml/s, for three separate solutions.

Whilst the rate at which successive scans can be obtain is improved via NMR pulse programming, with schemes such as frequency-shifted spatially-selective NMR.1 Another factor limiting the rate at which NMR data can be obtained is sensitivity, this can be significantly improved by pure-shift techniques. A pure-shift method referred to as SHARPER has been developed for reaction monitoring - increasing sensitivity whilst minimising the loss of absolute integration.

Another break-through in NMR spectroscopy is parallel-receiver technology, allowing up to twice the amount of data per time, this has also been developed and employed whilst studying reactions.