Mercuracarborand "anti-crown ether"-based chloride sensitive liquid/polymeric membrane electrodes

Highly sensitive and selective chloride liquid/polymeric membrane electrode s are described that employ [9]mercuracarborand-3 (MC3), a neutral preorgan ized macrocyclic Lewis acid, as the anion carrier, MC3-based chloride-sensi tive membrane electrodes, doped with different mole percentages of cationic additives (5, 10, and 60 mol % tridodecylmethylammonium chloride) relative to the amount of the. carrier, exhibit enhanced potentiometric selectivity for chloride over other anions, including more lipophilic anions such as p erchlorate, nitrate, and thiocyanate, In addition, the selectivity coeffici ents obtained are shown to meet the requirement for clinical applications. The obtained selectivity pattern is shown to correlate very well with Hg-19 9 NMR titrations of MC3 with various anions, performed in organic solvents. Optimized membrane electrodes show a near-Nernstian response toward chlori de over a wide concentration range and have micromolar detection limits. MC S-based chloride sensors show a fast response time (in the order of few sec onds), as well as short recovery time. The developed mercuracarborand-based sensors do not practically respond to pH changes over the pH range of 2.5- 7.0, Response characteristics (e.g., detection limit, linear range, respons e slope, and selectivity) of the [9]mercuracarborand-3 based chloride senso rs remain essentially the same over a period of similar to 2 months, reflec ting remarkable stability and well-defined chemistry of the macrocyclic Lew is acid ionophore.