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Extraction of 7-aminocephalosporanic acid (7-ACA) has been investigated using secondary and tertiary amines and a quaternary ammonium salt (Aliquat-336) as the carriers. The values of the distribution coefficients have been reported in a range of aqueous-phase pH values and concentrations of 7-ACA using different carriers in n-butyl acetate as the diluent. As expected, ion-pair extraction with secondary and tertiary amines exhibits lowerings of the distribution coefficient with increase of pH, whereas the ion exchange extraction with quaternary ammonium chloride (Aliquat-366) exhibits an opposite but more pronounced pH dependence, providing at the same time higher values of distribution coefficient at high values of pH. Both the extraction principles can be exploited to achieve extraction and reextraction of 7-ACA in the pH range of 5 to 8 in which it is relatively stable.

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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.

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