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) methodology and spectrophotometric measurements under the “stopped-flow” conditions. Kinetic data on displacement of the lanthanides (Ln) from their complexes with ethylenediamino-N,N,Nʹ,Nʹ- tetraacetic acid (EDTA) by copper (II) ions have been exploited to develop a simple and fast FI method for indirect potentiometric 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-bisazoderivatives of chromotropic acid and complexones was proposed for spectrophotometric determination of Ln(III) concentration in multicomponent solutions. 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)-Chlorophosphonazo III and Ln (III)-Carboxynitrazo complexes with EDTA or triethylentetramine-N,N,Nʹ,N?,Nʹ,N?,Nʹ?hexaacetate (TTGA) in the pH range 3.0-6.5. The new FI methods have been applied to the analysis of artificial samples.