Collection of low-concentration ammonia and nitric acid gas using a diffusion scrubber and its application to the separation of particulate matter

A diffusion scrubber system equipped with an ion chromatograph (IC) was used for the collection and determination of gaseous NH3 and HNO3 at 100200 ppb levels. Purified water was used as the absorbing solution of the scrubber. The gaseous HNO3 concentration was measured by the impinger trap-IC method and/or the reduction (to NOx)-chemiluminescence method. The gaseous NH3 concentration was measured by the impinger trap (boric acid solution)-IC method. The determined collection efficiencies were more than 97.4% for HNO3 and more than 92.3% for NH3 under a relative humidity of 070%. The relative standard deviations were less than 1.1% (n = 5) for successive collection and analysis. It was confirmed that this system can determine gaseous HNO3 and NH3 correctly even in the presence of ammonium nitrate particles.