An interdigitated microelectrode array (IME) that was coated with a film of a vanadium oxide xerogel served as a solid-state cell in which an anodic process in the presence of ammonia was promoted. The platinum indicator electrode array was modified with a film of mixed-valent ruthenium oxide with cyano cross-links, and the xerogel was loaded with KCl prior to use. Ammonia samples were quantified by injection of vapors into a gas cell that contained the modified and coated IME. Measurements under potentiostatic conditions yield linear calibration curves over the range of 2 to 27 mu mol/ml.