Optical sensing of ammonia performed using a 229 nm LED as a far UV-C light source

Ammonia was optically detected using a spectrometer as the light detector and a 229 nm LED as a far UV-C light source, operated at 20 mA at room temperature. The emission wavelength range of the LED, from 218 to 260 nm, included the ammonia absorption range below 230 nm. A difference in emission intensity at 224 nm was observed with and without ammonia, changing linearly with ammonia concentration. The lowest detection limit for ammonia concentration, estimated from the noise level and the linear approximation, was 10–20 ppm.