Kinetic study and analytical applications of the exchange reactions of lanthanides(III) using flow injection techniques

The exchange reactions involving complexes of the light lanthanides (cerium subgroup) and Y(III) with a number of water-soluble complexones and bisazo -dyes have been studied kinetically by using flow-injection (FI) methodolog y and spectrophotometric measurements under the "stopped-flow" conditions. Kinetic data on displacement of the lanthanides (Ln) from their complexes w ith ethylenediamino-N,N,N',N'-tetraacetic acid (EDTA) by copper(II) ions ha ve been exploited to develop a simple and fast FI method for indirect poten tiometric determination of the sum Ln(III) concentration using a copper ion -selective electrode (Cu-ISE). A reliable FI method based on monitoring the ligand substitution reactions between the complexes of Ln(III) with 2,7-bi sazo-derivatives of chromotropic acid and complexones was proposed for spec trophotometric determination of Ln(III) concentration in multicomponent sol utions. The differential kinetic analysis of binary mixtures such as La-Pr (Nm) and Pr (Nm)-Eu was achieved by utilizing the quantitative differences between the rates of ligand substitution reactions of Ln(III)-Chlorophospho nazo III and Ln(III)-Carboxynitrazo complexes with EDTA or triethylentetram ine-N,N,N',N", N"',N"'-hexaacetate (TTGA) in the pH range 3.0-6.5. The new FI methods have been applied to the analysis of artificial samples.