Extraction, advantages double solvents

If the compound is present at a low concentration in the presence of many interfering compounds, cleanup and concentration steps become necessary [8]. Solvent extraction procedures are used often for sample preparation for drugs and many other small molecules in the chromatographic technique. Solid-phase methods are very popular because of the wide choice of the packing material. Sample extraction methods have two other main advantages in CE, namely sample concentration and elimination of both sample ions and proteins. Double-solvent extraction is very useful for elec-trokinetic injection, especially for basic compounds. It eliminates variability due to matrix effects in electro-kinetic injection. 

In another example, the advantage of ILs used as solvent phase was clearly demonstrated during the reduction of 4-chloroacetophenone by I. k r. The reaction produced (JJ)-l-(4-chlorophenyl)ethanol in 46.2% yield in aqueous medium and hardly proceeded in aqueous-organic solvent (e.g., decane, tert-butyl methyl ether) biphasic system. However, the addition of 20% [BMIM][Tf2N] doubled the chemical yield of the alcohol product to 92.8% and pushed the product purity to an excellent 99.7% ee. The result was explainable that [BMIM][Tf2N] serves as a substrate reservoir and in situ extracting agent without destructive effects on the cell membranes [57]. 

---