Capability of CI-Orbitrap for Gas-Phase Analysis in Atmospheric Chemistry: A Comparison with the CI-APi-TOF Technique

Abstract

Chemical ionization Orbitrap mass spectrometry (CI-Orbitrap) represents a promising new technique for gas-phase analysis in analytical and atmospheric chemistries mainly due to its very high mass resolving power. In this work, we performed the first side-by-side comparison between a CI-Orbitrap and the widely used atmospheric pressure interface time-of-flight mass spectrometry (CI-APi-TOF) using two different chemical ionization methods, i.e., acetate-ion-based (CH 3 COO -) and aminium-ionbased (n-C 3 H 7 NH 3 + ) schemes. The capability of the CI-Orbitrap at accurately measuring low concentrations of gaseous species formed from the oxidation of α-pinene was explored. Although this study reveals a lack of linearity of the CI-Orbitrap when measuring product ions at very low concentrations (< 1 x 10 6 molecules cm -3 ), very good agreement between both techniques can be achieved by applying a newly developed linearity correction. It is experimentally shown that the correction function is independent of the reagent ion used. Thus, accurate quantification of organic compounds at concentrations as low as 1 x 10 5 molecules cm -3 by the CI-Orbitrap can be achieved.Finally, by means of tandem mass spectrometry, the unique capability of the Orbitrap allows the direct determination of the binding energy of cluster ions between analyte and reagent ions, that is needed for the assessment of a chosen ionization scheme.

Structures and reactivity of peroxy radicals and dimeric products revealed by online tandem mass spectrometry

“…In this study, we report the in-situ structural characterization of gas-phase HOMs, RO 2 radicals, and dimeric products of αpinene and limonene ozonolysis based on online MS/MS using an ultrahigh-resolution Orbitrap mass spectrometer equipped with a NO 3chemical ionization (CI) source 44,45 . Using online MS/MS data, aided by known structure-specific fragmentation patterns from existing offline MS/MS literature, we are able to infer the most plausible isomers of different compounds.…”

Orbitool: A software tool for analyzing online Orbitrap mass spectrometry data

“…However, it is important to mention that the Orbitrap provides non-linear responses when the concentrations of the analytes are very low (i.e., < 1 × 10 6 molecules cm -3 , at a 10-minute integration time). As a result, the calculated isotope abundance may deviate from its true value (Riva et al, 2020).…”

“…Computational approaches, including ion deconvolution procedures, are required to partly resolve this limitation in order to extract the maximum possible information content (Cubison and Jimenez, 2015;Meija and Caruso, 2004;Zhang et al, 2019aZhang et al, , 2019b). To overcome these limitations, we have coupled a high-resolution mass spectrometer (Orbitrap, Eliuk and Makarov 2015) with a CI source (Riva et al, 2019a(Riva et al, , 2020 and an extractive ESI (EESI) inlet (Lee et al, 2020) for online analysis. Similarly, Zuth et al (2018) have combined an atmospheric pressure chemical ionization (APCI) interface to an Orbitrap and have shown that such a technology can achieve much greater mass resolving power at similar detection limit for the real-time measurement of organic aerosols.…”

“…The demand for a new software tool for analyzing Orbitrap data comes along with applying an Orbitrap in long-term continuous online measurements. The commercial software, Xcalibur TM that has been used in our initial studies (Lee et al, 2020;Riva et al, 2019aRiva et al, , 2020, provides an interface for basic data analysis e.g., reading single or averaged scans and exporting the time evolution of selected signal peaks. However, more complicated data analysis is usually needed for investigating the complexity and chemical processes occurring within the atmosphere.…”

Orbitool: a software tool for analyzing online Orbitrap mass spectrometry data

“…Biogenic and anthropogenic sources emit a wide variety of volatile organic compounds (VOCs) into the atmosphere (Hallquist et al, 2009;Shrivastava et al, 2017). Once emitted, VOCs can quickly react with different atmospheric oxidants (OH radicals, O 3 , NO 3 radicals, or Cl atoms) yielding a wide variety of oxidized VOCs (OVOCs) spanning a broad range of chemical formulae and, thus, volatilities (Hallquist et al, 2009;Li et al, 2020;Wennberg et al, 2018).…”