Metal affinity liquid membrane, Part III: Characterization of transport selectivity

The metal ion affinity concept is used to effect facilitated and selective transport of amino acids through liquid membranes. A palladium organometallic complex, trans-benzyl chloride bis-triphenylphosphinepalladium(II) [BPP-Pd(II)], has been checked for various amino acids, i.e. glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), methionine (Met), histidine (His), phenylalanine (Phe), tyrosine (Tyr), and tryptophan (Trp). The interaction of the different amino acids with the membrane and the carrier has been evaluated in terms of their lipophilicity and polarity. Their liquid-liquid distribution in a solvent containing the palladium organometallic complex correlate with such amino acid properties, except in the case of Phe and Trp which show an interaction exceeding that predicted because of their aromatic structure. The behavior of the amino acids in liquid-liquid distribution can be used to predict their transport through supported liquid membranes (SLM) containing the same carrier. The greater the distribution in the liquid-liquid system, the higher the flux in SLM.