No abstract

The reactive extraction of 6-aminopenicillanic acid (6-APA) from aqueous buffer solution has been studied using a liquid anion exchanger, tricaprylylmethyl ammonium chloride (Aliquat-336) in n-butyl acetate as the solvent. The extraction equilibrium constant and partition coefficient increase with increase in pH up to a limiting value of pH, beyond which extraction decreases due to coextraction of OH-and buffer anions and hydrolytic decomposition of 6-APA. The experimental data could be predicted from an equilibrium model which takes into account the ideal behaviour of the two liquid phases. The coextraction of the buffer anion under low pH conditions was found to be negligible. The extraction rate measured in a stirred cell of constant interfacial area appears to be dependent on the interfacial mass transfer of the reactive species as well as on the interfacial reaction through its dependence on the concentration of 6-APA in the aqueous and organic phases, respectively.On a etudie I'extraction reactive de I'acide 6-aminopenicillanique d'une solution tampon aqueuse a I'aide d'un echangeur d'anions liquide, le chlorure d'amrnonium tricaprylylmethyl (Aliquat-336) dans du n-butyl acetate coinme solvant. La constante d'equilibre d'extraction et le coefficient de partition augmentent avec le pH jusqu'a une valeur limitante du pH, au-dela de laquelle I'extraction diminue en raison de la coextraction de OH-et des anions tampons ainsi que de la decomposition hydrolytique de 6-APA. Les donnees experimentales peuvent etre exprimees a partir d'un modele d'equilibre qui tient compte du comportement ideal des deux phases liquides. La coextraction de I'anion tampon dans de faibles conditions de pH s'avere negligeable. I1 apparait que la vitesse d'extraction mesuree dan une cellule agitee de surface interfaciale constante depend du transfert de matere interfacial des especes reactives et de la reaction interfaciale par I'entremise de la concentration de 6-APA dans les phases aqueuse et organique respectivement.

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.