Supported liquid membrane enrichment using an organophosphorus extractant for analytical trace metal determinations in river waters |
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Authors: | Nii-Kotey Djane Kuria Ndung’u Fredrik Malcus Gillis Johansson L Mathiasson |
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Institution: | (1) University of Lund, Dept. of Analytical Chemistry, P.O. BOX 124, S-221 00 Lund, Sweden, SE |
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Abstract: | Metal ions were preconcentrated from water samples using supported liquid membranes containing 40% w/w di-2-ethylhexyl phosphoric
acid (DEHPA) dissolved in kerosene as the membrane liquid. The driving force for the mass transport of analytes in this system
is the pH gradient across the membrane. The effect of the carrier concentration on the extraction efficiency was studied.
The mechanism for the mass transport in the system was investigated by measuring changes in pH and analyte ion concentration
as well as changes in the concentration of other interfering metal ions present in large excess during the enrichment. The
extraction efficiency was found to be unchanged as long as the pH difference across the membrane was more than 2 pH units.
The long-term stability of the system was investigated at different pHs in the donor solution. Under optimal conditions, the
membrane was stable for at least 200 h with reagent water samples and at least 80 h for river water samples. Enrichment factors
of approximately 15 times could be obtained. The corresponding extraction efficiencies were over 80% for some of the investigated
metal ions. The detection limits of blank samples for Cu2+, Cd2+ and Pb2+ using 120 min processing time were 0.19, 0.024 and 0.09 ng/mL, respectively.
Received: 29 October 1996 / Revised: 17 February 1997 / Accepted: 23 February 1997 |
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