We report the acidbase behavior of OATA, an oligomer synthesized from 3-amino-1,2,4-triazole (ATA). We analyze the UVvis spectroscopy at different media, and we analyze and discuss the acidbase equilibria taking into account tautomeric equilibria at different pH. The low aqueous solubility at neutral pH can be attributed to the neutral form. Indeed, OATA was synthesized in an ordinary filter paper, which can be used as a sensor for ammonia as well as endpoint indication. Using the OATA-containing paper, ammonia concentrations in a solution as low as 5 ppm could be measured. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012