Ammonia is an inorganic agent found both in nature and in the human body, which is of great interest for modern sensory applications. Here we use GaP, GaN and GaAs epitaxial nanowires as sensitive elements of the ammonia sensors fabricated via a simple protocol on the platform with golden interdigital contacts. Impedancemetry is used to study change of the device properties with addition of ammonia to the reference medium (water). GaP and GaNbased devices exhibit sufficient response to the ammonia presence with the detection limit lower than 10ppm. This work is aimed at fabrication and study of precise, technological and relatively cheap ammonia sensors compatible with a liquid medium, and motivated by the possibility of using this type of adsorption sensors in medical, environmental equipment and biological purposes.