A novel planar miniaturized potentiometric sensor for flow injection analysis of nitrates in wastewaters, fertilizers and pharmaceuticals.

A novel all-solid-state miniaturized nitrate sensor is developed, characterized and used for flow injection analysis (FIA) of nitrates in various samples. The sensor incorporates silver bis(bathophenanthroline) nitrate [Ag(bath)(2)NO(3)] as an electroactive material in a plasticized PVC membrane. The sensing membrane (3 mm x 5 mm) is immobilized on a wafer polyimide microchip (size 13.5 mm x 3.5 mm) to offer a planar miniaturized design easily used in a single channel wall-jet flow injection system. Under hydrodynamic mode of operation (FIA) the sensor displays fast response, high sensitivity, long term stability and good selectivity for NO(3)(-) in the presence of many common associated anions. The calibration slope is 55.1+/-0.1 mV decade(-1) over the concentration range 1.0 x 10(-1) to 1.0 x 10(-6) mol L(-1), the lower detection limit is 0.05 microg mL(-1), the working pH is 2-9,and the output is 70-90 samples h(-1). Validation of the assay method reveals good performance characteristics and suggests application for routine determination of NO(3)(-) in industrial wastewaters, fertilizers and pharmaceuticals. The results agree fairly well with data obtained by the standard spectrophotometric methods.