Trace Enrichment of Triazine Herbicides using the Supported Liquid Membrane Extraction Technique: Applications to the Study of Waters in Ethiopian Lakes
| dc.contributor.advisor | Solomon, Prof. Theodros | |
| dc.contributor.author | Negussie Megersa | |
| dc.date.accessioned | 2021-12-17T09:05:48Z | |
| dc.date.accessioned | 2023-11-09T16:19:15Z | |
| dc.date.available | 2021-12-17T09:05:48Z | |
| dc.date.available | 2023-11-09T16:19:15Z | |
| dc.date.issued | 2000-04 | |
| dc.description.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 nundecane, di-n-hexylether alone or with 25% 6-undecanone and 50% of n-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. Furthermore, the conditions for attaining maximum enrichment factor from 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 enriched. 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 enrichment factor, from the donor waste was also investigated. The results obtained from both the acceptor concentrate and the donor waste agreed well, which in turn indicated efficient penneation through the liquid membrane thereby giving minimum memory effects. XVI The applicability of the method for extraction of th e compounds of s-tri azine herbicides from water samples containing complex matrices was studi ed by spi king analyte sample solutions both in reagent water and ri ver water. The resulting chromatograms were not differing much, which also refl ects the selectivity of the membrane extraction developed. Water samples collected from Southern Ethiopian lakes were pre-treated and extracted in the same manner. There are a number of agricultural fi elds in this region where herbicides are periodically applied. Thus, the lake waters certainly contain considerable quantities of these residues and degradation products. The water samples, in which the phosphate buffer was dissolved to obtain neutral pH, were extracted at high donor flow rate, 5.0 mLimin, for 10 h. Low quantities of atrazine and terbutryn were identified in Awassa Lake, while only atrazine could be seen in the extracts from Chamo Lake. In both cases the concentration range of these compounds were estimated to vary from 0.02 to 0.05 Ilg/L. None of these herbicides or other s-triazine compounds could be detected in the extracts of the water samples collected from Abbaya lake. A mixture of the parent compounds and the degradation products of the s-triazine herbicides were also successfully extracted in the liquid membrane system containing carriers, e.g., trioctyl phosphine oxide (TOPO). Low detection limits were obtained for the aqueous samples spiked in river water, water containing humic acid and also in urine. Effects of the flowing donor channel, while the acceptor concentrate collected, on analyte permeation was studied in detail and better analyte results were obtained than the stagnant donor system particularly for the more polar compounds. | en_US |
| dc.identifier.uri | http://etd.aau.edu.et/handle/12345678/29345 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Applications to the Study of Waters in Ethiopian Lakes | en_US |
| dc.title | Trace Enrichment of Triazine Herbicides using the Supported Liquid Membrane Extraction Technique: Applications to the Study of Waters in Ethiopian Lakes | en_US |
| dc.type | Thesis | en_US |