POTENTIOMETRIC ANION SELECTIVITY OF POLYMER MEMBRANES DOPED WITH PALLADIUM ORGANOPHOSPHINE COMPLEX

The potentiometric anion selectivity of polymer membrane-based electro des formulated with a palladium organophosphine complex (benzylbis (tr iphenylphosphine)palladium(II) chloride) as the membrane active compon ent is examined. The electrode is shown to exhibit a non-Hofmeister se lectivity pattern with a significantly enhanced response toward nitrit e over the concentration range of 10 mu M-10 mM (log-linear range) and a detection limit 5.0 mu M. The effect of lipophilic anionic (tetraph enylborate derivatives) and cationic (tetraalkylammonium) site additiv es within the membrane on the anion selectivity is examined in detail. Addition of both cationic and anionic sites is shown to improve poten tiometric anion selectivity, suggesting that the palladium complex may operate simultaneously as a neutral and charged carrier-type ionophor e within the polymer membrane phase. Using optimal membrane formulatio ns (with added 20-30 mol % cationic sites), the sensors prepared with the palladium complex do not exhibit proton/hydroxide response in the range of pH 3.5-12, a potential advantage over previously reported nit rite electrodes prepared with Co(III) corrins and porphyrin complexes.