Tuning solvents

The possibility of fine-tuning solvent properties by varying temperature and pressure. 

Binary solvent mixtures provide a simple means of controlling solvent strength but limited opportunities for controlling solvent selectivity. With ternary and quaternary solvent mixtures, it is possible to fine-tune solvent selectivity while maintaining a constant solvent strength [105-107]. In addition, there are only a small number of organic modifiers that can be used as binary mixtures with water. 

As is seen from the presented data, ILs are true designer solvents. The modification of their constituents gives solvents with very different properties, namely, efficiency and selectivity of extraction of various solutes. In the near future, it should have important implications, as more and more finely tuned solvents are likely to appear for a variety of tasks. 

This makes it possible to tune solvent properties to optimize chromatographic separations. Because of the lower viscosity and higher diffusivity of supercritical fluids compared to common solvents, a higher mobile phase velocity can be used in the column, leading to a higher process throughput than that of liquid chromatography. 

If solute a values change by too much (leading to mixing of other bands) when solvent C is substituted for B (as in Fig. 22), fine-tune solvent selectivity by using ternary-solvent mixtures C/B/A (Fig. 22). 

The ability to fine tune solvent properties of SCFs through changes in operating conditions can be exploited in a wide range of applications, such as extraction, fractionation, and reaction processes, where flexibility in process implementation offers the researcher/processor a gamut of possibilities. 

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