Extraction, advantages with constant selectivity

Solvent extraction may be accompanied by a chemical reaction. The selectivity and the extraction factor can be greatly improved by carrying out the extraction with a solution of an extractant that chemically converts the solute to a form that is preferentially soluble in the extracting solvent. An additional advantage of this procedure is that the reverse extraction of solute (stripping) can often be carried out by changing the equilibrium constant of the reaction, e.g., by changing the pH or temperature. 

Virus-encoded GTs may actually be more common than believed previously because the list of known viral GTs is far from being complete. Viruses are constantly coevolving with their hosts and many can extract genes, which include those for glycosyltransferases, from the host genome for incorporation into their own. If they can confer a selective advantage to the virus, they could be incorporated permanently into their genomes, which lead to new virally encoded GT variants. 

The advantage of the LMs is integrating extraction and back-extraction of the desired analyte(s) into one step. Using protonation and deprotonation reactions, selected hydrophobic carriers with carboxyl groups have been shown effective in the separation of amino acids, if the carboxyl functionality was ionized [123]. Optimum values of the stability constants of the complexes between particular amino acids and carrier(s) can be found to increase extraction efficiencies. However, the kinetics of mass transfer often has a more pronounced impact on the efficiency of extraction [118]. 

A process which takes advantage of both the solubility characteristics and chemical properties of the amines is One which employs selective absorption in weakly acidic compounds such as cresols. Solubility is in- uenced not only by the solvent, but by the different basicities of the amines, as indicated under dissociation constants in Table 8-19. According to this process, mono- and dimethylamine are separated from trimethylamine by countercurrent extraction of the mixture with cresol saturated with water. The undissolved trimethylamine overhead is the least soluble In various solvents and is more weakly basic than dimethylamine. Prior to extraction, NHj can be removed, under specific conditions, from the three amines by countercurrent extraction with 17 per cent NaOH solution. This operation gives a mixed amine gas overhead and an NaOH solution of NHj. Under another set of conditions employing 10 per cent NaOH lolution in lower volumes, 100 per cent trimethylamine is the overhead gas. 

---