Epoxy matrix membrane potentiometric sensor based on zirconium titanium phosphate ion exchanger for flow injection analysis of nitrite

Preparation, characterization, origin of response and applications of a potentiometric sensor based on the use of a zirconium titanium phosphate (ZTP)-epoxy membrane are described. Zirconium titanium phosphate (ZTP) cationic exchanger embedded in an epoxy matrix is converted into a hydrated zirconium oxide anion exchanger which responds to many anionic species. A sensor based on this exchanger exhibits near-Nernstian response for nitrite and other anions over the concentration range 10(-1)-10(-5) M. Under optimized conditions, the gas dialyzer/flow-injection system provides a throughput of ca. 60 samples per hour with a high selectivity for nitrite ion over most common anions and acidic gas releasing species. Determination of nitrite at levels as low as 5 x 10(-4) M or less in the presence of sulfite and sulfide ions is performed by using a modified carrier buffer stream (10(-2) M MES, pH 5.5 containing formaldehyde and Pb2+). Significant advantages are offered by the ZTP-epoxy membrane based sensor including a long lifetime ( >2 years), excellent stability and reproducibility (ca. 1 mV), fast response time ( < 30 s), wide pH working range (pH 4.5-8), low detection limit (4 x 10(-5) M) and high thermal stability(up to 80 <degrees>C).