Incomplete Trapping in Supported Liquid Membrane Extraction with a Stagnant Acceptor for Weak Bases
journal contributionposted on 14.08.1998, 00:00 by Luke Chimuka, Negussie Megersa, Jan Norberg, Lennart Mathiasson, Jan Åke Jönsson
Supported liquid membrane extraction is a powerful analytical methodology for continuous extraction and enrichment of ionizable organic pollutants from aqueous environmental samples. Sample workup with this technique can be hampered by low enrichment factors due to incomplete trapping in the stagnant acceptor solution for weak basic compounds. The different parameters, such as acceptor pH and ionic strength of both the donor and acceptor solutions, related to this problem were studied theoretically and experimentally. A simple equation for the maximum enrichment factor was developed. Results showed that the ionic strengths of the two aqueous phases in the system have an effect on the maximum enrichment factor, which can be increased by increasing the ionic strength of the donor phase. For chloro-s-triazines, a satisfactory agreement was obtained between the experimental measurements and theoretical estimations. This study defines the practical analytical applications and limitations of the system where the analytes are partially ionized in the acceptor solution.