Transport of amino acids through organic liquid membranes. II. Aspects of the mechanism

Abstract

This paper discusses the transport of p-aminobenzoic acid (PABA) through a bulk organic liquid membrane. The source phase (SP) is made up of 0.00437 M PABA and 0.075 M NaOH, and the receiving phase (RP) comprises 0.00437 M PABA and 0.075 M NaCl. A chloroform solution containing 1 g of carrier (octanoic acid, lauric acid or decanoic acid) represents the organic phase (OP) or bulk liquid membrane. The obtained data support the hypothesis that, at the SPOP interface, an attack of the carboxylic acid anion upon the amphionic species of PABA, as well as upon Na + ions, takes place. The final result of this attack is a decrease in the amount of PABA in the SP and an increase in the pH value of this phase. At the RPOP interface, the carboxylic acid-PABA complex is decomposed. This phenomenon is determined by the presence of H + ions in the RP phase.