scholarly journals Performance of a corona ion source for measurement of sulfuric acid by chemical ionization mass spectrometry

2010 ◽  
Vol 3 (6) ◽  
pp. 5295-5312
Author(s):  
A. Kürten ◽  
L. Rondo ◽  
S. Ehrhart ◽  
J. Curtius
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Chemical Ionization ◽  
Ion Source ◽  
Ion Sources ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Integration Time ◽  
Ionization Mass ◽  
H2so4 Concentration

Abstract. The performance of an ion source based on corona discharge has been studied. This source is used for the detection of gaseous sulfuric acid by chemical ionization mass spectrometry (CIMS) through the reaction of NO3– ions with H2SO4. The ion source is operated under atmospheric pressure and its design is similar to the one of a radioactive (Americium 241) ion source which has been used previously. Our results show that the detection limit for the corona ion source is sufficiently good for most applications. For an integration time of one minute it is ~6 × 104 molecules of H2SO4 per cm3. In addition, only a small cross-sensitivity to SO2 has been observed for concentrations as high as 1 ppmv in the sample gas. This low sensitivity to SO2 is achieved even without the addition of an OH scavenger. When comparing the new corona ion source with the americium ion source for the same provided H2SO4 concentration, both ion sources yield almost identical values. These features make the corona ion source investigated here favorable over the more commonly used radioactive ion sources for most applications where H2SO4 is measured by CIMS.

scholarly journals Performance of a corona ion source for measurement of sulfuric acid by chemical ionization mass spectrometry

2011 ◽  
Vol 4 (3) ◽  
pp. 437-443 ◽  
Author(s):  
A. Kürten ◽  
L. Rondo ◽  
S. Ehrhart ◽  
J. Curtius
Keyword(s):  
Mass Spectrometry ◽  
Sulfuric Acid ◽  
Chemical Ionization ◽  
Ion Source ◽  
Ion Sources ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Integration Time ◽  
Ionization Mass ◽  
H2so4 Concentration

Abstract. The performance of an ion source based on corona discharge has been studied. This source is used for the detection of gaseous sulfuric acid by chemical ionization mass spectrometry (CIMS) through the reaction of NO3– ions with H2SO4. The ion source is operated under atmospheric pressure and its design is similar to the one of a radioactive (americium-241) ion source which has been used previously. The results show that the detection limit for the corona ion source is sufficiently good for most applications. For an integration time of 1 min it is ~6 × 104 molecule cm−3 of H2SO4. In addition, only a small cross-sensitivity to SO2 has been observed for concentrations as high as 1 ppmv in the sample gas. This low sensitivity to SO2 is achieved even without the addition of an OH scavenger. When comparing the new corona ion source with the americium ion source for the same provided H2SO4 concentration, both ion sources yield almost identical values. These features make the corona ion source investigated here favorable over the more commonly used radioactive ion sources for most applications where H2SO4 is measured by CIMS.

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.

scholarly journals A new technique for the direct detection of HO<sub>2</sub> radicals using bromide chemical ionization mass spectrometry (Br-CIMS): initial characterization

2016 ◽  
Vol 9 (8) ◽  
pp. 3851-3861 ◽  
Author(s):  
Javier Sanchez ◽  
David J. Tanner ◽  
Dexian Chen ◽  
L. Gregory Huey ◽  
Nga L. Ng
Keyword(s):  
Mass Spectrometry ◽  
Chemical Ionization ◽  
Direct Detection ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Integration Time ◽  
Ionization Mass ◽  
Detection Scheme ◽  
Mixing Ratios ◽  
Direct Technique

Abstract. Hydroperoxy radicals (HO2) play an important part in tropospheric photochemistry, yet photochemical models do not capture ambient HO2 mixing ratios consistently. This is likely due to a combination of uncharacterized chemical pathways and measurement limitations. The indirect nature of current HO2 measurements introduces challenges in accurately measuring HO2; therefore a direct technique would help constrain HOx chemistry in the atmosphere. In this work we evaluate the feasibility of using chemical ionization mass spectrometry (CIMS) and propose a direct HO2 detection scheme using bromide as a reagent ion. Ambient observations were made with a high-resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) in Atlanta over the month of June 2015 to demonstrate the capability of this direct measurement technique. Observations displayed expected diurnal profiles, reaching daytime median values of ∼ 5 ppt between 2 and 3 p.m. local time. The HO2 diurnal profile was found to be influenced by morning-time vehicular NOx emissions and shows a slow decrease into the evening, likely from non-photolytic production, among other factors. Measurement sensitivities of approximately 5.1 ± 1.0 cps ppt−1 for a bromide ion (79Br−) count rate of 106 cps were observed. The relatively low instrument background allowed for a 3σ lower detection limit of 0.7 ppt for a 1 min integration time. Mass spectra of ambient measurements showed the 79BrHO2− peak was the major component of the signal at nominal mass-to-charge 112, suggesting high selectivity for HO2 at this mass-to-charge. More importantly, this demonstrates that these measurements can be achieved using instruments with only unit mass resolution capability.

scholarly journals Development of a chemical ionization mass spectrometry system for measurement of atmospheric OH radical

2020 ◽  
Author(s):  
Wei Pu ◽  
Zhouxing Zou ◽  
Weihao Wang ◽  
David Tanner ◽  
Zhe Wang ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Chemical Ionization ◽  
High Reactivity ◽  
Ion Source ◽  
Tropospheric Chemistry ◽  
Ionization Mass Spectrometry ◽  
Chemical Ionization Mass Spectrometry ◽  
Urban Site ◽  
Oh Radicals ◽  
Ionization Mass

Abstract. The hydroxyl radical (OH) is the most important oxidant in the atmosphere and plays a central role in tropospheric chemistry. Ambient OH is extremely difficult to measure because of its low concentration and high reactivity. We have developed and optimized a chemical ionization mass spectrometry (CIMS) system to measure OH based on ion-assisted mass spectrometry. A calibration unit was developed based on chemical actinometry to convert detected signals to OH concentration. Different types of ion sources (210Po and corona source) and scavenger gases (propane, C3F6, and NO2) were compared. Radioactive ion source (210Po foils) was chosen for lower detection limits, and propane was selected for high elimination efficiency and the negligible influence on the signal stability. The sensitivity of the CIMS instrument to OH radicals is influenced by the efficiencies of titration reaction, ion conversion, and ion transmission. Through adjusting their efficiencies by changing the flow rates and voltages, optimal sensitivity was determined. The background noise from OH interferences was reduced by adjusting the flow rate of scavenger gas. The CIMS system achieved a detection limit of ~ 0.15×106 molecules cm−3 (signal/noise = 2). The CIMS was then taken out to measure ambient OH radicals at an urban site in Hong Kong in April 2019. An obvious diurnal pattern of OH radicals was observed, with the highest concentration of ~ 6×106 molecules cm−3 at midday and the lowest concentration of ~ 0.25×106 molecules cm−3 at night, with an overall accuracy of about ±51 %. The results demonstrated the capability of our CIMS for OH measurements on clear days. The tests and results from our study provide a useful reference to other researchers who wish to develop and apply the CIMS technique to measure OH and other chemicals.

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