NITRITE-SELECTIVE OPTICAL SENSORS BASED ON ORGANOPALLADIUM IONOPHORES

Development of nitrite-selective bulk optode membranes, based on novel organopalladium ionophores, is described herein. These nitrite-selective optodes are composed of a plasticized poly(vinyl chloride) impregnated with the organopalladium ionophore, a proton-selective chromoionophore, and in some cases lipophilic additives. Two novel organopalladium ionophores (NI-I and NI-II) and different proton chromoionophores (ETH-7075, ETH-5294 and ETH-2439) were evaluated for the development of nitrite-selective bulk optode membranes. The developed nitrite optodes were found to be more selective for nitrite over other anions including the more lipophilic anions such as perchlorate, nitrate, iodide, and bromide. For instance, the optical selectivity coefficients, log Knitrite, anionopt, for NI-I, ETH7075 optode are as follow: ClO4-, -1.2; NO3-, -3.4; I-, -1.5; Br-, -2.1. Further, the nitrite optical selectivity obtained using the present optode systems is greatly enhanced 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 membranes are discussed as well.