Journal
of Chemometrics 2002, 16, 111-116.
Alexandre M.
Antunes, Márcia M. C. Ferreira, Pedro L. O. Volpe
The 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.
For more information,
download this article PDF (size: 139K).
For more information
about the Journal of Chemometrics. |
