Nitrite-selective optical sensors based on organopalladium ionophores

Development of nitrite-selective bulk optode membranes, based on novel orga nopalladium ionophores, is described herein. These nitrite-selective optode s are composed of a plasticized poly(vinyl chloride) impregnated with the o rganopalladium ionophore, a proton-selective chromoionophore, and in some c ases lipophilic additives. Two novel organopalladium ionophores (NI-I and N I-II) and different proton chromoionophores (ETH-7075, ETH-5294 and ETH-243 9) were evaluated for the development of nitrite-selective bulk optode memb ranes. The developed nitrite optodes were found to be more selective for ni trite over other anions including the more lipophilic anions such as perchl orate, nitrate, iodide, and bromide. For instance, the optical selectivity coefficients, log K-nitrite,anion(opt), for NI-I, ETH-7075 optode are as fo llow: ClO4-, -1.2; NO3-, -3.4; I-, -1.5; Br-, -2.1. Further, the nitrite op tical selectivity obtained using the present optode systems is greatly enha nced in comparison with that obtained using an anion-exchanger based optode membrane. Response characteristics such as, dynamic range, detection limit , response time and signal reproducibility of the prepared nitrite optode m embranes are discussed as well.