An amperometric method is proposed for end-point detection of complexometri
c titrations of metal ions in unbuffered solutions with disodium ethylenedi
aminetetraacetate (Na2H2Y). It is based on the use of a platinum disc micro
electrode as a sensor for monitoring the hydrogen ions delivered during the
titration. Synthetic solutions containing Ca2+ and Mg2+ ions, each alone o
r 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 re
lative standard deviation being not greater than 2% for at least three repl
icates. Comparative measurements performed by the classical procedures usin
g a metallochromic indicator give data agreement within 3.5%.