Differential electrolytic potentiometry with ion-selective electrodes for end-point detection in compleximetric titrations of mercury(II), copper(II), nickel(II) and bismuth(III)

Abstract

Electrodes prepared by activating hydrophobized spectrographic graphite rods with various mercury(II) chalcogenides, alone or mixed with silver(I) chalcogenides or mercury itself, were used successfully in differential electrolytic potentiometry (d.e.p.) to locate end-point in compleximetric titrations of mercury(II) solutions with EDTA. Several materials gave useful d.e.p. peaks at the expected end-point, showing that these electrodes can replace the commoner mercury and amalgamated gold electrodes. To demonstrate the usefulness of the sensors in EDTA titrations of metal ions other than mercury(II), titrations of copper(II) were performed. The electrode response takes place via reaction of the ion with sulphide of selenide in the electroactive layer. Electrodes activated by copper(II), bismuth(III), nickel(II) chalcogenides were also studied; those sensors that produced good ion-selective electrodes were also useful in d.e.p. titrations.