Partition Coefficients of Some Antibiotics, Peptides and Amino Acids in Liquid-Liquid Partitioning of the Acetonitrile-Water System at Subzero Temperatures

Liquid-liquid equilibrium (LLE) occurs at a subzero temperature for the acetonitrilewater binary system.When the equilibrium temperature is below its LLE critical temperature of 1.32 C, the top phase is acetonitrile-rich and the bottom phase water-rich. It was observed that a human growth hormone analog with 191 amino acids partitioned exclusively into the bottom phase and its bioactivity was retained. This suggests that the liquid-liquid partition system can be used for bioseparations. The new system gives a different selectivity and the low temperature environment offers better stabilities for biomolecules compared to conventional solvent extraction systems. This work presented the partition coefficients of some biomolecules including trypsin, thyroglobulin, transferrin, ribonuclease A; L-phenylalanine, L-tryptophan; val-ala-ala-phe, phe-gly-gly-phe; erythromycin, chloramphenicol, vancomycin, spiramycin, gramicidin D, cycloheximide, fusidic acid, antimycin and tetracycline. Temperature and pH effects, as well as partition mechanisms were probed.