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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Addis Ababa Universty


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.



Triazine Herbicides