Extraction equilibria of cephalosporin antibiotics with Aliquat-33

The extraction equilibria of Cephalosporin antibiotics with Aliquat-336 (tricaprylylmethylammonium chloride) in various solvents were studied at pH values above the pK(a2) values of the antibiotics. The reactive extraction, which is essentially an anion-exchange reaction, takes place in a 1:1 stoichiometry. The extraction equilibrium constants (K-P) could be correlated well with the hydrophobicity scale of the antibiotics. The equilibrium constants for coextraction of the buffer ions were found to be lower than those of the cephalosporin antibiotics, indicating the possibility of exploiting the reactive extraction technique for process application. The K-P values obtained for a specific solute were also found to correlate well with the dipole moment of the solvents.