Negussie Megersa

Bio: Negussie Megersa is an academic researcher from Addis Ababa University. The author has contributed to research in topics: Extraction (chemistry) & Detection limit. The author has an hindex of 16, co-authored 50 publications receiving 844 citations.

Trace enrichment and sample preparation of alkylthio-s-triazine herbicides in environmental waters using a supported liquid membrane technique in combination with high-performance liquid chromatography

Abstract: Sample pre-treatment and enrichment using the supported liquid membrane (SLM) technique for the determination of alkylthio-s-triazine herbicides in river water samples was investigated. The uncharged herbicide molecules from the flowing aqueous donor solution diffuse through a porous poly(tetrafluoroethylene) membrane, which is immobilized with a water-immiscible organic solvent, and are trapped in a stagnant acidic acceptor phase since they become protonated. Using undecane as a membrane solvent, the SLM methodology was successfully used for the enrichment and separation of seven alkylthio-s-triazine herbicides in environmental waters with extraction efficiencies of 60% or better. The LC results obtained on spiking the pesticides in river water samples further confirmed the selectivity of the method. The influence of the various SLM extraction parameters on the extraction efficiency was studied. In this system, the partition coefficient, Kp, between the donor and the membrane phases is large, and effects due to carry over and membrane memory are very small. Detection limits of about 0.03 µg l–1 were obtained by extraction of 1.0 µg l–1 samples in both reagent and river water at a donor flow rate of 7.0 ml min–1 for about 70 min. Further advantages of the procedure are the reduced analysis time and an increase in the sample accumulation rate in the acceptor phase.

Passive sampling and/or extraction techniques in environmental analysis: a review

Abstract: The current state-of-the-art of passive sampling and/or extraction methods for long-term monitoring of pollutants in different environmental compartments is discussed in this review. Passive dosimeters that have been successfully used to monitor organic and inorganic contaminants in air, water, sediments, and soil are presented. The application of new approaches to the determination of pollutants at the sampling stage is discussed. The main milestones in the development of passive techniques for sampling and/or extraction of analytes, and in biomonitors used in environmental analysis, are summarized in this review. Passive samplers and biomonitors are compared.