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


Patrick Veres, Andy Neuman

Key Publications

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 Science, 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.