Tropospheric Chemistry: Instruments

Iodide Ion ToF (Time-of-Flight) CIMS (Chemical Ionization Mass Spectrometer)

I- ToF CIMS instrument
I- ToF CIMS instrument installed for airborne sampling

Principle of the Measurement

Chemical ionization mass spectrometric detection of gas phase organic and inorganic analytes via I- adduct formation

Species Measured

Reactive nitrogen species: HONO (nitrous acid), N2O5 (dinitrogen pentoxide), HNCO (isocyanic acid)
Halogen species: BrO, BrCl, BrCN, ClNO2, Cl2
Sulphur species: HPMTF (Hydroperoxy methyl thioformate)
Organic species: HCOOH (formic acid) and other low to intermediate volatility organics

Time Response

Instrumental response <1 sec, Field response is limited by inlet surface affinity for each compound

Detection Limit

Precision on 1s data various by species


(15% + 0.03 pptv) for N2O5
(15% + 0.05 pptv) for ClNO2
(30% + 15 pptv) for HONO
(20% + 5 pptv) for HNCO
(15% + 100 pptv) for HCOOH
(25% + 0.2 pptv) for halogenated species


TOFWERK/Aerodyne Research Inc. (modified)

Field Projects

Key Publications

Robinson, M.A., J.A. Neuman, L.G. Huey, J.M. Roberts, S.S. Brown, and P.R. Veres, Temperature-dependent sensitivity of iodide chemical ionization mass spectrometers, Atmospheric Measurement Techniques, doi:10.5194/amt-15-4295-2022, 2022.

Veres, P.R., J.A. Neuman, T.H. Bertram, E. Assaf, G.M. Wolfe, C.J. Williamson, B. Weinzierl, S. Tilmes, C. Thompson, A.B. Thames, J.C. Schroder, A. Saiz-Lopez, A.W. Rollins, J.M. Roberts, D. Price, J. Peischl, B.A. Nault, K.H. Møller, D.O. Miller, S. Meinardi, Q. Li, J.-F. Lamarque, A. Kupc, H.G. Kjaergaard, D. Kinnison, J.L. Jimenez, C.M. Jernigan, R.S. Hornbrook, A. Hills, M. Dollner, D.A. Day, C.A. Cuevas, P. Campuzano-Jost, J. Burkholder, T.P. Bui, W.H. Brune, S.S. Brown, C.A. Brock, I. Bourgeois, D.R. Blake, E.C. Apel, and T.B. Ryerson, Global airborne sampling reveals a previously unobserved dimethyl sulfide oxidation mechanism in the marine atmosphere, Proceedings of the National Academy of Sciences, doi:10.1073/pnas.1919344117, 2020.

Veres, P. R., Roberts, J. M., Wild, R. J., Edwards, P. M., Brown, S. S., Bates, T. S., Quinn, P. K., Johnson, J. E., Zamora, R. J., and de Gouw, J., Peroxynitric acid (HO2NO2) measurements during the UBWOS 2013 and 2014 studies using iodide ion chemical ionization mass spectrometry, Atmos. Chem. Phys., doi:10.5194/acp-15-8101-2015, 2015.

Neuman, J. A., J. B. Nowak, L. G. Huey, J . B. Burkholder, J. E. Dibb, J. S. Holloway, J. Liao, J. Peischl, J. M. Roberts, T. B. Ryerson, E. Scheuer, H. Stark, R. E. Stickel, D. J. Tanner, and A. Weinheimer, Bromine measurements in ozone depleted air over the Arctic Ocean, Atmos. Chem. Phys., doi:10.5194/acp-10-6503-2010, 2010.

Neuman, J. A., T. B. Ryerson, L. G. Huey, R. Jakoubek, J. B. Nowak, C. Simons, and F. C. Fehsenfeld, Calibration and evaluation of nitric acid and ammonia permeation tubes by UV optical absorption, Environ. Sci. Technol., doi:10.1021/ES06422L, 2003.

Neuman, J. A., L. G. Huey, R. W. Dissly, F. C. Fehsenfeld, F. Flocke, J. C. Holecek, J. S. Holloway, G. Hübler, R. Jakoubek, D. K. Nicks Jr., D. D. Parrish, T.B. Ryerson, D. T. Sueper, and A. J. Weinheimer, Fast-response airborne in situ measurements of HNO3 during the Texas 2000 Air Quality Study, J. Geophys. Res., doi:10.1029/2001JD001437, 2002.