Development of Iodide Chemical Ionization TOFMS

Iodide Chemical Ionization TOFMS

An Iodide-Adduct High-Resolution Time-of-Flight Chemical-Ionization Mass Spectrometer: Application to Atmospheric Inorganic and Organic Compounds 

Lee et al.
Environmental Science & Technology, 2014
DOI: 10.1021/es500362a

Online chemical ionization mass spectrometry is uniquely capable of measuring many chemical species and rapid processes relevant to air quality. The development of iodide CI-TOFMS described by Lee et al. in Environmental Science and Technology (2014) significantly advanced the measurement of inorganic gases, oxygenated volatile organic compounds (VOC), and low-volatility VOCs.  

The authors coupled a medium-pressure ion-molecule reactor (IMR) to the API-TOF platform provided by TOFWERK and Aerodyne Research, Inc. Iodide ions were created by flowing methyl iodide source gas through a 210Po ion source, and operational parameters of the IMR were optimized to enhance iodide-molecule adduct formation. Thorough instrument characterization was undertaken, including interpretation of the mass spectrum, response to changing ambient humidity, comparison of ion-molecule binding energies with the measured chemical space, and determination of detection limits and their relationship to functional group.  

The instrument was deployed on a government research aircraft and in chamber experiments, and demonstrated measurement of a number of photochemical oxidation products difficult to measure with conventional analytical techniques.  Iodide chemical ionization mass spectrometry has now been widely adopted, and is used extensively in atmospheric chemistry research.