A diffusive sampling device for measurement of ammonia in air

作者：Yamada Tomomi; Uchiyama Shigehisa^*; Inaba Yohei; Kunugita Naoki; Nakagome Hideki; Seto Hiroshi

来源：Atmospheric Environment, 2012, 54: 629-633.

DOI：10.1016/j.atmosenv.2012.02.001

• Diffusive sampling device
• Ammonia
• Sampling rate
• Graham%26apos
• s law

A diffusive sampling device, the DSD-NH3, has been developed for measurement of ammonia in air. The DSD-NH3 comprises silica gel impregnated with phosphoric acid as the absorbent, a porous sintered polyethylene tube that acts as a diffusive membrane, and a small polypropylene syringe that is used for the elution of analytes from the absorbent. Silica gel impregnated with phosphoric acid is used as absorbent for the DSD-NH3; basic gases in ambient air, including ammonia, are trapped in the DSD-NH3 device by their reaction with phosphoric acid in the sampler to form their corresponding phosphoric acid salts. After collection, the DSD-NH3 samplers are eluted by water. Cations in the eluate, including ammonium ions, are analyzed by ion chromatography. A side-by-side comparison was made with active samplers, demonstrating good correlation (r(2) = 0.996). The sampling rate (94.5 ml min(-1)) was determined from comparison with an active sampling method and sampling rates. The sampling rate is also calculated from the respective molecular weights according to a rule based on Graham%26apos;s law. The theoretical sampling rate with the DSD-NH3 is 95.4 ml min(-1) and agrees with the experimental value (94.5 ml min(-1)). Little influence of wind velocity on the sampler was observed. The relative standard deviations for ammonia concentrations were 4.7% with face velocity ranging 0-5.0 m/s.

• 出版日期2012-7