Amperometric end-point detection of complexometric titrations with platinum microelectrodes

Abstract

An amperometric method is proposed for end-point detection of complexometric titrations of metal ions in unbuffered solutions with disodium ethylenediaminetetraacetate (Na₂H₂Y). It is based on the use of a platinum disc microelectrode as a sensor for monitoring the hydrogen ions delivered during the titration. Synthetic solutions containing Ca²⁺ and Mg²⁺ ions, each alone or in mixture, are examined. The method is also applied to the determination of the total concentration of Ca²⁺ and Mg²⁺, i.e., the total hardness, in mineral and tap waters. The precision of the method is satisfactory, the relative standard deviation being not greater than 2% for at least three replicates. Comparative measurements performed by the classical procedures using a metallochromic indicator give data agreement within 3.5%.