The use of supercritical fluids as solvents for NMR spectroscopy

Abstract

The goal of this article is to introduce the reader to the use of supercritical fluids as solvents in high-pressure NMR experiments and present some of the interesting research currently being pursued using the technique of high-pressure NMR and the applications of supercritical fluids in this dynamic area. A supercritical fluid can be readily defined for a single component as a solvent above its critical temperature and critical pressure such that no change in pressure can introduce a phase transition in the single fluid phase. While these temperature and pressure conditions are well established for a pure solvent system, for binary and ternary solvents the supercritical conditions and phase behavior are sometimes difficult to determine. Therefore, not only can the physical properties of the solvent be altered with pressure and temperature, but the phase equilibria in supercritical fluid solvents must also be considered. The goal of this article is not to present an in-depth discussion of the different physical states involved in the phase behavior of high-pressure, high-temperature solvents, such as supercritical fluids. There have been numerous reviews of the different properties and behaviors of fluids phases and the interested reader is referred to the excellent recent review by Grunwaldtmore » et al..1 The literature in this article referenced generally covers the time period from 2000 to early 2005.« less