Enhanced extraction of phenobarbital from serum with a designed artificial receptor

The primary goal of this work was to determine whether artificial receptors that function on the basis of molecular recognition have analytical capabilities. As an example of such a receptor, we have chosen one directed toward barbiturates. Chloroform enriched with this artificial receptor (1 mM) can extract more than 90% of the phenobarbital from a 20 microM phenobarbital solution in human control serum using a volume ratio (organic/serum) as small as 0.5. In the absence of this receptor, the volume ratio must be greater than 10 to achieve similar extraction efficiencies. In addition to volume ratio, the role of pH, receptor concentration, and solvent type are discussed. The experimental results are found to be in good agreement with predictions based on chemical equilibria. Through the use of this and other similar receptors, the amount of organic solvent used in extractions can be minimized.