Determination of Lanthanides By Conductometry Using Some Sequestering Agents

Abstract

The present work envisages establishing conductometry as an analytical technique for the determination of lanthanides by employing the use of different polyaminocarboxylic acids (PACA) as sequestering agents. The technique offers the advantage of eliminating the need of separation or pre-concentration of the sample under study. Five different polyaminocarboxylic acids viz., Ethylenediaminetetracetic acid (EDTA); trans-1,2- Diaminocyclohexane-N,N,Nand#8242;,Nand#8242;-tetraacetic Acid (DCTA); Ethylene glycol-bis(2- aminoethylether)-N,N,Nand#8242;,Nand#8242;-tetraacetic acid (EGTA); N-(2-hydroxyethyl) ethylenediamine- N,Nand#900;,Nand#900;-triacetic acid (EDTA-OH) and 1,3-Diaminopropane-N,N,Nand#8242;,Nand#8242;-tetraacetic acid (TMDTA) have been used as sequestering agents for this work. Effect of different parameters has been studied to establish appropriate conditions for the conductometric study of lanthanideand#8210;PACA complexes which enabled precise lanthanide determinations. For this purpose, firstly, the appropriate cell constant was established by carrying out a number of conductometric titrations at four different cell constant values using two-pole and five ring conductivity cells. The latter was found suitable for the study due to its linearity over a wide concentration range and a quick and stable response. Secondly, the detection limit of the five ring conductivity cell has been determined as 10-5 M by direct as well as conductometric titration methods. Thirdly, the effect of pH on the reaction system has been studied over four different pH ranges. Lastly, the effect of temperature on the reaction system was also studied by carrying out conductometric titrations at four different temperatures. Following the standardization of these parameters all the polyaminocarboxylic acids have been tested for use as potential ligands for the determination of lanthanides in solution containing single lanthanide ion or a mixture of two lanthanide ions. The use of polyaminocarboxylic acid (PACA), and#945;-hydroxyisobutyric acid (HIBA) as a co- ligand has been established for simultaneous.