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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,N′,N′- 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,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.