Mulugeta Mesay, Megersa Negussie
Department of Chemistry, Addis Ababa University, P.O. Box 1176, Addis Ababa, Ethiopia.
Talanta. 2004 Sep 8;64(1):101-8. doi: 10.1016/j.talanta.2003.11.049.
Supported liquid membrane (SLM) method for preconcentration and enrichment of the two bipyridilium herbicides, namely diquat and paraquat, from environmental water samples has been developed. The permanently charged cationic herbicides were extracted from a flowing aqueous solution to a stagnant acidic acceptor solution across a liquid membrane containing 40% (v/v) di-(2-ethylhexyl) phosphoric acid dissolved in di-n-hexyl ether. The mass transfer of analytes is driven by the counter-coupled transport of hydrogen ions from the acceptor to the donor phase. The efficiency of the extraction process depends on the donor solution pH, the amount of the mobile carrier added to the liquid membrane and the concentration of the counter ion in the acceptor solution. The applicability of the method for extraction of these quaternary ammonium herbicides from environmental waters was also investigated by spiking analyte sample solutions in river water. With 24h sample enrichment concentrations of diquat and paraquat down to ca. 10ng/L could be detected in environmental waters.
已开发出支撑液膜（SLM）法，用于从环境水样中预浓缩和富集两种联吡啶鎓类除草剂，即敌草快和百草枯。将带永久电荷的阳离子除草剂从流动的水溶液中通过含有溶解在二正己醚中的40%（v/v）二（2-乙基己基）磷酸的液膜萃取到停滞的酸性接受液中。分析物的传质是由氢离子从接受相到供体相的反向耦合传输驱动的。萃取过程的效率取决于供体溶液的pH值、添加到液膜中的流动载体的量以及接受液中抗衡离子的浓度。通过在河水中加入分析物样品溶液，还研究了该方法从环境水中萃取这些季铵类除草剂的适用性。经过24小时的样品富集，在环境水中可以检测到低至约10ng/L的敌草快和百草枯浓度。
