摘要
搭建了一套化学电离飞行时间质谱仪用于连续测量大气·OH.该仪器采用了基于63Ni放射源的双管正交式结构大气压化学电离源电离大气中的·OH,最大程度地避免了试剂气体电离及滴定、转化反应间的相互干扰.63Ni放射源首先电离HNO3试剂气体得到试剂离子NO-3,·OH在反应管中与SO2反应最终转化为H2SO4,NO-3与H2SO4发生化学电离反应生成HSO-4离子,进入到质谱仪中进行检测,通过测量NO-3与HSO-4离子的强度,利用化学电离反应方程可直接计算出大气中OH的浓度.所研制仪器用于实验室内·OH的在线检测,在5 s内测得·OH的浓度为1.6×106个·cm-3,实验结果显示该仪器可用于原位连续测量大气中的超痕量自由基.
A home-made chemical ionization time-of-flight mass spectrometer( TOFMS) has been developed for continuous measurements of atmospheric hydroxyl radical. Based on the atmospheric pressure chemical ionization technique,an ionization source with orthogonal dual tube structure was adopted in the instrument,which minimized the interference between the reagent gas ionization and the titration reaction. A63Ni radioactive source was fixed inside one of the orthogonal tubes to generate reactant ion of NO-3from HNO3vapor. Hydroxyl radical was first titrated by excess SO2to form equivalent concentrations of H2SO4in the other orthogonal tube, and then reacted with NO-3ions in the chemical ionization chamber,leading to HSO-4formation. The concentration of atmospheric hydroxyl radical can be directly calculated by measuring the intensities of the HSO-4product ions and the NO-3reactant ions. The analytical capability of the instrument was demonstrated by measuring hydroxyl radical in laboratory air,and the concentration of the hydroxyl radical in the investigated air was calculated to be 1. 6 × 106molecules·cm- 3,based on 5 seconds integration. The results have shown that the instrument is competent for in situ continuous measurements of atmospheric trace radical.
出处
《环境科学》
EI
CAS
CSCD
北大核心
2014年第5期1688-1693,共6页
Environmental Science
关键词
大气压化学电离
飞行时间质谱仪
负离子
·OH
连续测量
atmospheric pressure chemical ionization
time-of-flight mass spectrometer
negative-ion
hydroxyl radical
continuous measurements
