A New, Long-Lived Ca-Selective Electrode

The preparation and performance of a new Ca-selective electrode based on a Nafion(R) membrane modified by means of the new ionic carrier N-ethyl-N-(2-trimethylammoniumethyl)-N'-heptyl-N'-methyl-succinamide are described. This electrode is characterized by a wide linear range extending down to pCa greater than or equal to 5, acceptable selectivity towards alkaline-metal cations, a nearly equal response to Mg2+ ion (which makes it suitable for water hardness determinations) and an extremely long in-service lifetime.