Study of Cu, Cu-Ni and Rh-modified Cu porous layers as electrode materials for the electroanalysis of nitrate and nitrite ions

Three porous materials (Cu, a Cu-Ni alloy with 70 at.% Cu and Rh-modified Cu) have been tested as electrodes for the electroanalysis of nitrate and nitrite ions, in either neutral or basic media, using mainly a flow injection technique. Porous Cu and Cu-Ni were prepared by electrodeposition at high current density, exploiting the transient template action of hydrogen bubbles. Rh-modified Cu electrodes were obtained from porous Cu, through a galvanic displacement reaction. All materials had a linear response for both nitrates and nitrites, at concentrations up to 10^-3 M, at least. Sensitivities, detection limits and stability were determined. Compared with Cu, used as a benchmark, (i) Rh-modified Cu had higher sensitivity for nitrates, comparable sensitivity for nitrites, lower or comparable detection limits and overall better stability; (ii) Cu-Ni had lower sensitivity, but exhibited lower detection limits and more stable performance for most analyte/medium combinations.