A chemometric study of amino acid transport through liquid membranes using UV‐vis spectroscopy

Abstract

AbstractThe extraction of amino acids at 298 K through hydrophobic liquid membranes is studied using the bulk liquid membrane (BLM) method. The transport of different mixtures of phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp) in a buffer solution (pH 1.5) was monitored with a diode array spectrometer by recording their UV‐vis spectra at the receiving phase in small time intervals for 30 min. The apparatus used consisted of a Schulmann cell with the buffer solution as the source phase, reverse micelles of Aerosol‐OT (AOT) in chloroform as the liquid membrane, and a buffer solution at pH 9.0 as the receiving phase. The ordinary least squares (OLS) method was applied separately to each mixture, using the experimental spectra of pure compounds. The transport rates, which are given by the slope of the kinetic curves, were found to be very small, of the order of 10−5, 10−6 and 10−7 mol l−1 min−1 for Phe, Trp and Try respectively. The trilinear decomposition (TLD) method was used to estimate the kinetic profiles for each compound in the ternary mixtures and also their transport rates. They are in fair agreement with those obtained by OLS. Tyr basically does not cross the membrane, so two new experiments were carried out using binary mixtures of Phe and Trp. Their transport rates are of the same order of magnitude as those obtained for the ternary mixtures, and in this case the agreement between TLD and OLS results is excellent. Copyright © 2002 John Wiley & Sons, Ltd.