CHELOMETRIC TITRATIONS WITH POLYAMINOCARBOXYLIC ACIDS USING BARIUM AND LEAD PVC-MEMBRANE ION-SELECTIVE ELECTRODES

Barium and lead PVC-membrane ion-selective electrodes have been tested as end-point detectors for the back titration of some metal ions with ethylenediaminetetraacetic acid (EDTA), ethyleneglycolbis (2-aminoeth ylether) tetraacetic acid (EGTA), and 1, 2-diaminocyclohexanetetraacet ic acid (DCTA). Metal ions studied were, Ca2+, Mg2+, Sr2+, Zn2+, CU2+, Cd2+, Co2+, Ni2+, Mn2+, Al3+, and La3+. Titrations have been carried out in the presence of either 10(-3) M NaOH or acetate buffer of pH 5. 5, when using the Ba-ISE or the Pb-ISE respectively as end-point detec tors. Ba2+ or Pb2+ standard solutions were used as the back titrants d epending on the electrode used. Concentrations of the tested metal ion s in the final analyte solutions in all cases were in the range of 5x1 0(-5) to 1x10(-4) M. The two electrodes worked successfully for most m etal ions studied with relative standard deviations of about 1% and me an recoveries of about 100%.