A novel 1,10-phenanthroline-sensitive membrane sensor for potentiometric determination of Hg(II) and Cu(II) cations

Preparation, characterization, and applications of a 1,10-phenanthrolinium cation (phenH(+))-sensitive potentiometric sensor are described. The sensor incorporates a liquid polymeric membrane consisting of phenH-tetraphenylborate, nitrophenyloctyl ether, and poly(vinyl chloride) as ion exchanger, plasticizer, and polymeric support, respectively. The sensor exhibits a fast and Nernstian response to phenH(+) over the concentration range of 6 x 10(-6)-2 x 10(-4) M with a monovalent cationic slope of 58.0+/-0.5 mV/log[phenH(+)] in acetate buffer of pH 4.2. The sensor is successfully applied to the monitoring of the potentiometric titration of Hg(II) and Cu(II) ions with phen solution in the presence of citrate and acetate buffers of pH 4.2, respectively. Sharp inflection breaks (90-180 mV) at 1:1 (metal:phen reaction) are obtained in the presence of chloride and thiocyanate background. This stoichiometry is explained by the formation of insoluble [HgCl(2)(phen)], [Hg(SCN)(2)(phen)], and [Cu(SCN)(2)(phen)] complexes. Optimization of each titration and the effect of foreign ions are evaluated. The method offers the advantages of adequate sensitivity, accuracy, and selectivity for the determination of mercury and copper in pharmaceutical, rock, and tea samples. The results are in good agreement with those obtained using the standard atomic absorption spectrometric and United States Pharmacopeial methods.