Vol. 127, No. 1 * Pages 1–142 * January - March 2023

Ammonia is one of the most significant environmental pollutants. Concentration measurements, identifying the sources and studying the transformations in the biosphere are essential, and they are the focus of many investigations. The near-infrared (≈1530 nm) photoacoustic method for simultaneous and selective determination of ¹⁴NH₃/¹⁵NH₃ isotopologues reported here can be suitable for monitoring these phenomena and processes. So far, the photoacoustic method has not been used for this kind of examination. The application of our measurement method makes it possible to eliminate the disadvantages of the previous measurement methods. The detection limit of the PA system is 0.14 ppm and 0.73 ppm for ¹⁴NH₃ and ¹⁵NH₃, respectively, which can be improved by orders of magnitude with further development of sampling and measurement techniques.