A dopant-assisted iodide-adduct chemical ionization time-of-flight mass spectrometer based on VUV lamp photoionization for atmospheric low-molecular-weight organic acids analysis  

作　　者：Yonglei Zhang Ruidong Liu Mei Li Yingzhe Guo Jichuang Kong Keyong Hou 

机构地区：[1]Environment Research Institute,Shandong University,Qingdao 266237,China

出　　处：《Journal of Environmental Sciences》2025年第3期500-511,共12页环境科学学报(英文版)

基　　金：supported by the National Special Fund for the Development of Major Research Equipment and Instrument(No.2020YFF01014503);the Young Taishan Scholars(No.tsqn201909039);the College 20 Project fromJi Nan Science&Technology Bureau(No.2021GXRC058).

摘　　要：Formic and acetic acids are the most abundant gaseous organic acids and play the key role in the atmospheric chemistry.In iodine-adduct chemical ionizationmass spectrometry(CIMS),the low utilization efficiency of methyl iodide and humidity interference are two major issues of the vacuum ultraviolet(VUV)lamp initiated CIMS for on-line gaseous formic and acetic acids analysis.In this work,we present a new CIMS based on VUV lamp,and the ion-molecular reactor is separated into photoionization and chemical ionization zones by a reducer electrode.Acetone was added to the photoionization zone,and the VUV photoionization acetone provided low-energy electrons for methyl iodide to generate I−,and the addition of acetone reduced the amount of methyl iodide by 2/3.In the chemical ionization zone,a headspace vial containing ultrapure water was added for humidity calibration,and the vial changes the sensitivity as a function of humidity from ambiguity to well linear correlation(R2>0.95).With humidity calibration,the CIMS can quantitatively measure formic and acetic acids in the humidity range of 0%-88%RH.In this mode,limits of detection of 10 and 50 pptv are obtained for formic and acetic acids,respectively.And the relative standard deviation(RSD)of quantitation stability for 6 days were less than 10.5%.This CIMS was successfully used to determine the formic and acetic acids in the underground parking and ambient environment of the Shandong University campus(Qingdao,China).In addition,we developed a simple model based formic acid concentration to assess vehicular emissions.

关 键 词：Formic acid Acetic acid Vacuum ultraviolet(VUV)lamp photoionization(PI) Chemical ionization(CI) Time-of-flight mass spectrometry (TOFMS) Trace gases measurement 

分 类 号：X831[环境科学与工程—环境工程]