Dopant assisted photoionization ion mobility spectrometry for on-site specific and sensitive determination of atmospheric ammonia

Ammonia (NH3) is a critical hazard gas in both outdoor and indoor environments, which tends to cause problems on the environment and public health. This work is to propose a dopant assisted ion mobility spectrometry (DAPI-IMS) for on-site specific and sensitive determination of the atmospheric NH3. Using 2-butanone as dopant, preliminary reactant ions (C4H8O)(2)H+ other than (H2O)(n)H+ were generated in the DAPI source. That provided a molecular substitution reaction channel for efficient ionization of NH3 and ensured better resolution of NH3 peak. Further, by introducing the NH3 sample gas along with dopant into the IMS drift tube of unidirectional gas flow mode, the DAPI-IMS was enabled to specifically and sensitively detect the NH3 in a background of high humidity and complex matrix. The DAPI-IMS exhibited a linear response range of 20-800 ppb(v) to NH3 with a sensitivity of 0.20 fC/ppb(v) and a limit of detection as low as 4.0 ppb(v). The potential of the DAPI-IMS for direct atmospheric NH3 measurement was also demonstrated via on-site monitoring the day to day emission profiles of NH3 in toilet.

Automated summary

The DAPI-IMS technique utilizes a dopant and NH3 sample gas to achieve specific and sensitive detection of NH3 in high humidity and complex matrix background, with a linear response range of 20-800 ppb(v) and a sensitivity of 0.20 fC/ppb(v).