scholarly journals Chemistry of α-pinene and naphthalene oxidation products generated in a Potential Aerosol Mass (PAM) chamber as measured by acetate chemical ionization mass spectrometry

2014 ◽  
Vol 7 (7) ◽  
pp. 6385-6429 ◽  
Author(s):  
P. S. Chhabra ◽  
A. T. Lambe ◽  
M. R. Canagaratna ◽  
H. Stark ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Acids ◽  
Gas Phase ◽  
Chemical Ionization ◽  
Oxidation Products ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Aerosol Formation ◽  
Ion Chemistry

Abstract. Recent developments in high resolution, time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made possible the direct detection of atmospheric organic compounds in real-time with high sensitivity and with little or no fragmentation, including low volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, for the first time, we examine gas-phase O3 and OH oxidation products of α-pinene and naphthalene formed in the PAM flow reactor with an HR-ToF-CIMS using acetate reagent ion chemistry. Integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec cm−3 s, corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. We present a method that estimates vapor pressures of organic molecules using the measured O/C ratio, H/C ratio, and carbon number for each compound detected by the CIMS. The predicted condensed-phase SOA average acid yields and O/C and H/C ratios agree within uncertainties with previous AMS measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.

scholarly journals Application of high-resolution time-of-flight chemical ionization mass spectrometry measurements to estimate volatility distributions of α-pinene and naphthalene oxidation products

2015 ◽  
Vol 8 (1) ◽  
pp. 1-18 ◽  
Author(s):  
P. S. Chhabra ◽  
A. T. Lambe ◽  
M. R. Canagaratna ◽  
H. Stark ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
High Resolution ◽  
Organic Acids ◽  
Chemical Ionization ◽  
Flow Reactor ◽  
Oxidation Products ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Ion Chemistry

Abstract. Recent developments in high-resolution time-of-flight chemical ionization mass spectrometry (HR-ToF-CIMS) have made it possible to directly detect atmospheric organic compounds in real time with high sensitivity and with little or no fragmentation, including low-volatility, highly oxygenated organic vapors that are precursors to secondary organic aerosol formation. Here, using ions identified by high-resolution spectra from an HR-ToF-CIMS with acetate reagent ion chemistry, we develop an algorithm to estimate the vapor pressures of measured organic acids. The algorithm uses identified ion formulas and calculated double bond equivalencies, information unavailable in quadrupole CIMS technology, as constraints for the number of possible oxygen-containing functional groups. The algorithm is tested with acetate chemical ionization mass spectrometry (acetate-CIMS) spectra of O3 and OH oxidation products of α-pinene and naphthalene formed in a flow reactor with integrated OH exposures ranged from 1.2 × 1011 to 9.7 × 1011 molec s cm−3, corresponding to approximately 1.0 to 7.5 days of equivalent atmospheric oxidation. Measured gas-phase organic acids are similar to those previously observed in environmental chamber studies. For both precursors, we find that acetate-CIMS spectra capture both functionalization (oxygen addition) and fragmentation (carbon loss) as a function of OH exposure. The level of fragmentation is observed to increase with increased oxidation. The predicted condensed-phase secondary organic aerosol (SOA) average acid yields and O/C and H/C ratios agree within uncertainties with previous chamber and flow reactor measurements and ambient CIMS results. While acetate reagent ion chemistry is used to selectively measure organic acids, in principle this method can be applied to additional reagent ion chemistries depending on the application.

scholarly journals Real-time measurements of gas-phase organic acids using SF<sub>6</sub><sup>−</sup> chemical ionization mass spectrometry

2018 ◽  
Vol 11 (9) ◽  
pp. 5087-5104 ◽  
Author(s):  
Theodora Nah ◽  
Yi Ji ◽  
David J. Tanner ◽  
Hongyu Guo ◽  
Amy P. Sullivan ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Organic Acids ◽  
Organic Acid ◽  
Real Time ◽  
Gas Phase ◽  
Chemical Ionization ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Rural Site ◽  
Ionization Mass

Abstract. The sources and atmospheric chemistry of gas-phase organic acids are currently poorly understood, due in part to the limited range of measurement techniques available. In this work, we evaluated the use of SF6- as a sensitive and selective chemical ionization reagent ion for real-time measurements of gas-phase organic acids. Field measurements are made using chemical ionization mass spectrometry (CIMS) at a rural site in Yorkville, Georgia, from September to October 2016 to investigate the capability of this measurement technique. Our measurements demonstrate that SF6- can be used to measure a range of organic acids in the atmosphere. One-hour averaged ambient concentrations of organic acids ranged from a few parts per trillion by volume (ppt) to several parts per billion by volume (ppb). All the organic acids displayed similar strong diurnal behaviors, reaching maximum concentrations between 17:00 and 19:00 EDT. The organic acid concentrations are dependent on ambient temperature, with higher organic acid concentrations being measured during warmer periods.

scholarly journals Chemical ionization mass spectrometry (CIMS) may not measure all gas-phase sulfuric acid if base molecules are present

2010 ◽  
Vol 10 (12) ◽  
pp. 30539-30568
Author(s):  
T. Kurtén ◽  
T. Petäjä ◽  
J. Smith ◽  
I. K. Ortega ◽  
M. Sipilä ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Gas Phase ◽  
Chemical Ionization ◽  
Measurement Data ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
Proton Affinities ◽  
Reaction Thermodynamics

Abstract. The state-of-the art method for measuring atmospheric gas-phase sulfuric acid is chemical ionization mass spectrometry (CIMS) based on nitrate reagent ions. Using computed proton affinities and reaction thermodynamics for the relevant charging reactions, we show that in the presence of strong bases such as amines, which tend to cluster with the sulfuric acid molecules, a significant fraction of the total gas-phase sulfuric acid may not be measured by a CIMS instrument. If this is the case, this effect has to be taken into account in the interpretation of atmospheric sulfuric acid measurement data, as well as in intercomparison of different CIMS instruments, which likely have different susceptibilities to amine-sulfuric acid clustering.

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