Trace Enrichment of Triazine Herbicides Using the Supported Liquid Membrane Extraction Technique: Applications To The Study of Waters in Ethiopian Lakes
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Date
2000-04
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Addis Ababa Universty
Abstract
Methods for sample preparation of the s-triazine herbicides and their degradation products
in environmental water samples using supported liquid membrane (SLM) has been
developed. The herbicide compounds were selectively extracted from the flowing donor
solution into a porous polytetrafluoroethylene (PTFE) membrane impregnated with 11-
undecane, di-II-hexylether alone or with 25% 6-undecanone and 50% of II-undecane. After
diffusion through the hydrophobic membrane the s-triazine herbicide compounds were
irreversibly trapped into acidic acceptor phase of lower pH. The Effects of different
experimental variables governing the efficiency of the extraction process have been
thoroughly studied and optimized. These include the pH of both the donor and acceptor
solutions, donor flow rate, ionic strengths and the analyte trapping conditions.
FurthelIDore, the conditions for attaining maximum emichment factor fi'om the membrane
extraction have been investigated.
Selectivity of the membrane technique developed was compared with one of the
most frequently used technique for sample preparation of organic pollutants, solid phase
extraction (SPE) in off-line mode. It was observed that the chromatograms obtained using
the SLM methodology were cleaner, indicating the good selectivity of the extraction
method. The liquid membrane serves as a barrier for interfering compounds, and neutral
molecules may not be emiched. The limit of detection for the extracts using SLM
technique was also comparable to that of the SPE. The possibility of determining the
extraction efficiency, and thus the emichment factor, fi'om the donor waste was also
investigated. The results obtained from both the acceptor concenh'ate and the donor waste
agreed well, which in turn indicated efficient permeation through the liquid membrane
thereby giving minimum memory effects.
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Keywords
Triazine Herbicides