Analytical Study of the Lead Ion-selective Ceramic Membrane Electrode

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Abstract
The lead(II) ion-selective ceramic membrane electrode developed by sintering a mixture of lead, silver, and cuprous sulfides showed sensitivity, selectivity, and other response characteristics well suited to analytical utilization. The Nernstian slope was obtained over a concentration range from 10−1 to 10−6m Pb2+ in activity, and the analytical range had a concentration of 10−1–10−7m when the membrane contained less than 30 wt% of cuprous sulfide and more than 1 wt% of lead sulfide. Among the common ions, silver, cupric, mercury(II), ferric, sulfide and iodide ions interfered seriously. About 10 times as many cadmium and bromide ions and more than 1000 times as many alkali metal, alkaline earth metal, zinc, aluminum, nickel, manganese(II), cobalt, and nitrate ions did not interfere with the lead ion, however. The electrode potentials did not change over a pH range from 2 to the pH at which the precipitation of lead hydroxide occurred. The electrode was safely used at temperatures from 0 to 95°C, and the potentials of the membrane satisfied the Nernstian equation within the limits of experimental error. The membrane electrode responded to activity changes very quickly: the rate of those changes was twice that in a lead sulfide-silver sulfide two-component ceramic electrode. A continuous potential measurement for 5 months promised long-term stability and accuracy. The rapid response rate and the long lifetime suggest that the continuous monitoring of some changing systems is feasible.