Chelating agents Complexes with lanthanides

The lanthanides form many compounds with organic ligands. Some of these compounds ate water-soluble, others oil-soluble. Water-soluble compounds have been used extensively for rare-earth separation by ion exchange (qv), for example, complexes form with citric acid, ethylenediaminetetraacetic acid (EDTA), and hydroxyethylethylenediaminetriacetic acid (HEEDTA) (see Chelating agents). The complex formation is pH-dependent. Oil-soluble compounds ate used extensively in the industrial separation of rate earths by tiquid—tiquid extraction. The preferred extractants ate catboxyhc acids, otganophosphoms acids and esters, and tetraaLkylammonium salts. 

In addition to these techniques, applications of capillary electrophoresis for lantharride analysis have appeared recently (Corr and Arracleto 1996, Vogt and Comadi 1994). Capillary electrophoretic separations rely on differences in the electrophoretic mobility of analyte species in an electrolyte buffer while tmder the influence of an applied electric field. For lanthanide analysis, the mobilities of the solvated cations are not adequately differentiated for an effective mutual separation, though separation from trarrsition metals or alkali/alkaline-earth metals should be readily accomplished. Introduction of chelating agents that form complexes with the ions leads to improved separation efficiency through... 

Lanthanide complexes with water-soluble chelating agents... 

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