A novel propylamine sensor featuring a screen-printed Ni electrode was developed. The sensing mechanism was found related not only to the electrochemical reaction on electrode surface but also to the phase transformation of the electrode material itself. The screen-printed Ni electrode needs to be transformed from alpha-Ni(OH)(2) to beta-NiOOH or gamma-NiOOH by voltage cycling before it can oxidize propylamine. The sensing electrode revealed a linear relationship between response current and propylamine concentration in the detection range from 100 to 1000 ppm. The response current test of the sensor showed an average sensitivity of 6.51 mu A/cm(2) ppm with a rapid response time of 7 s. The stability test showed that the sensor maintained a high sensitivity over 16 days. In addition, the selectivity test showed that the sensitivities of the sensor for alkylamines are similar but much higher than those for the biogenic amines. The Ni-electrode sensor is thus suitable for detecting trace alkylamines. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.061205jes] All rights reserved.