Ammonia(NH3)is ubiquitous in the atmosphere,it can affect the formation of secondary aerosols and particulate matter,and cause soil eutrophication through sedimentation.Cur-rently,the use of radioactive primary reagent ion source and the humidity interference on the sensitivity and stability are the two major issues faced by chemical ionization mass spectrometer(CIMS)in the analysis of atmospheric ammonia.In this work,a vacuum ultra-violet(VUV)Kr lamp was used to replace the radioactive source,and acetone was ionized under atmospheric pressure to obtain protonated acetone reagent ions to ionize ammonia.The ionization source is designed as a separated three-zone structure,and even 90 vol.％high-humidity samples can still be directly analyzed with a sensitivity of sub-ppbv.A sig-nal normalization processing method was designed,and with this new method,the quan-titative relative standard deviation(RSD)of the instrument was decreased from 17.5％to 9.1％,and the coefficient of determination was increased from 0.8340 to 0.9856.The humid-ity correction parameters of the instrument were calculated from different humidity,and the ammonia concentrations obtained under different humidity were converted to its con-centration under zero humidity condition with these correction parameters.The analytical time for a single sample is only 60 sec,and the limit of detection(LOD)was 8.59 pptv(signal-to-noise ratio S/N = 3).The ambient measurement made in Qingdao,China,in January 2021 with this newly designed CIMS,showed that the concentration of ammonia ranged from 1 to 130 ppbv.

Fengshuo Dong;Hang Li;Bing Liu;Ruidong Liu;Keyong Hou

Environment Research Institute,Shandong University,Qingdao 266237,China;Key Laboratory of Separation Science for Analytical Chemistry,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,China

环境科学学报（英文版）

[1]Fengshuo Dong;Hang Li;Bing Liu;Ruidong Liu;Keyong Hou-.Protonated acetone ion chemical ionization time-of-flight mass spectrometry for real-time measurement of atmospheric ammonia)[J].环境科学学报（英文版）,2022(04):66-74

Protonated,pptv

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