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Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer

DeCarlo, P. F., J. R. Kimmel, A. Trimborn, M. J. Northway, J. T. Jayne, A. C. Aiken, M. Gonin, K. Fuhrer, T. Horvath, K. S. Docherty, D. Worsnop, and J. Jimenez-Palacios (2006), Field-Deployable, High-Resolution, Time-of-Flight Aerosol Mass Spectrometer, Anal. Chem., 78, 8281-8289, doi:10.1021/ac061249n.

The development of a new high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) is reported. The high-resolution capabilities of this instrument allow the direct separation of most ions from inorganic and organic species at the same nominal m/z, the quantification of several types of organic fragments (CxHy, CxHyOz, CxHyNp, CxHyOzNp), and the direct identification of organic nitrogen and organosulfur content. This real-time instrument is field-deployable, and its high time resolution (0.5 Hz has been demonstrated) makes it well-suited for studies in which time resolution is critical, such as aircraft studies. The instrument has two ion optical modes: a single-reflection configuration offers higher sensitivity and lower resolving power (up to ∼2100 at m/z 200), and a two-reflectron configuration yields higher resolving power (up to ∼4300 at m/z 200) with lower sensitivity. The instrument also allows the determination of the size distributions of all ions. One-minute detection limits for submicrometer aerosol are <0.04 µg m-3 for all species in the high-sensitivity mode and <0.4 µg m-3 in the highresolution mode. Examples of ambient aerosol data are presented from the SOAR-1 study in Riverside, CA, in which the spectra of ambient organic species are dominated by CxHy and CxHyOz fragments, and different organic and inorganic fragments at the same nominal m/z show different size distributions. Data are also presented from the MIRAGE C-130 aircraft study near Mexico City, showing high correlation with independent measurements of surrogate aerosol mass concentration.

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Tropospheric Composition Program (TCP)