scholarly journals A Chemical Ionization Mass Spectrometer for Ground-Based Measurements of Nitric Acid

2006 ◽  
Vol 23 (8) ◽  
pp. 1104-1113 ◽  
Author(s):  
Kazuyuki Kita ◽  
Yu Morino ◽  
Yutaka Kondo ◽  
Yuichi Komazaki ◽  
Nobuyuki Takegawa ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Limit Of Detection ◽  
Field Tests ◽  
Background Level ◽  
Ionization Mass ◽  
Mixing Ratios ◽  
Free Air ◽  
Diffusion Scrubber

Abstract A chemical ionization mass spectrometer (CIMS) instrument has been developed for high-precision measurements of gaseous nitric acid (HNO3) specifically under high- and variable-humidity conditions in the boundary layer. The instrument’s background signals (i.e., signals detected when HNO3-free air is measured), which depend on the humidity and HNO3 concentration of the sample air, are the most important factor affecting the limit of detection (LOD). A new system to provide HNO3-free air without changing both the humidity and the pressure of the sampled air was developed to measure the background level accurately. The detection limit was about 23 parts per trillion by volume (pptv) for 50-s averages. Field tests, including an intercomparison with the diffusion scrubber technique, were carried out at a surface site in Tokyo, Japan, in October 2003 and June 2004. A comparison between the measured concentrations of HNO3 and particulate nitrate indicated that the interference from particulate nitrate was not detectable (i.e., less than about 1%). The intercomparison indicated that the two independent measurements of HNO3 agreed to within the combined uncertainties of these measurements. This result demonstrates that the CIMS instrument developed in this study is capable of measuring HNO3 mixing ratios with the precision, accuracy, and time resolution required for atmospheric science.

scholarly journals A Chemical Ionization Mass Spectrometer for ambient measurements of Ammonia

2010 ◽  
Vol 3 (4) ◽  
pp. 1075-1087 ◽  
Author(s):  
D. R. Benson ◽  
A. Markovich ◽  
M. Al-Refai ◽  
S.-H. Lee
Keyword(s):  
Mass Spectrometer ◽  
Power Plants ◽  
Chemical Ionization ◽  
Background Level ◽  
Fast Response ◽  
Integration Time ◽  
Ionization Mass ◽  
Mixing Ratios ◽  
Optimized Conditions ◽  
Ambient Measurements

Abstract. This study presents a chemical ionization mass spectrometer (CIMS) for fast response, in-situ measurements of gas phase ammonia (NH3). The NH3 background level detected with the CIMS ranged between 0.3–1 ppbv, with an uncertainty of 30 pptv under optimized conditions. The instrument sensitivity varied from 4–25 Hz/pptv for >1 MHz of reagent ion signals (protonated ethanol ions), with a 30% uncertainty estimated based on variability in calibration signals. The CIMS detection limit for NH3 was ~60 pptv at a 1 min integration time (3 sigma). The CIMS time response was <30 s. This new NH3-CIMS has been used for ambient measurements in Kent, Ohio, for several weeks throughout three seasons. The measured NH3 mixing ratios were usually at the sub-ppbv level and higher in spring (200 ± 120 pptv) than in winter (60 ± 75 pptv) and fall (150 ± 80 pptv). High emissions of SO2 from power plants in this region, and thus possible high acidity of aerosol particles, may explain these low NH3 mixing ratios in general.

scholarly journals Airborne observations of formic acid using a chemical ionization mass spectrometer

2012 ◽  
Vol 5 (12) ◽  
pp. 3029-3039 ◽  
Author(s):  
M. Le Breton ◽  
M. R. McGillen ◽  
J. B. A. Muller ◽  
A. Bacak ◽  
D. E. Shallcross ◽  
...  
Keyword(s):  
Formic Acid ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Limit Of Detection ◽  
Standard Addition ◽  
Ionization Mass ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Primary Emissions ◽  
The Uk

Abstract. The first airborne measurements of formic acid mixing ratios over the United Kingdom were measured on the FAAM BAe-146 research aircraft on 16 March 2010 with a chemical ionization mass spectrometer using I− reagent ions. The I− ionization scheme was able to measure formic acid mixing ratios at 1 Hz in the boundary layer. In-flight standard addition calibrations from a formic acid source were used to determine the instrument sensitivity of 35 ± 6 ion counts pptv−1 s−1 and a limit of detection of 25 pptv. Routine measurements were made through a scrubbed inlet to determine the instrumental background. Three plumes of formic acid were observed over the UK, originating from London, Humberside and Tyneside. The London plume had the highest formic acid mixing ratio throughout the flight, peaking at 358 pptv. No significant correlations of formic acid with NOx and ozone were found, but a positive correlation was observed between CO and HCOOH within the two plumes where coincident data were recorded. A trajectory model was employed to determine the sources of the plumes and compare modelled mixing ratios with measured values. The model underestimated formic acid concentrations by up to a factor of 2. This is explained by missing sources in the model, which were considered to be both primary emissions of formic acid of mainly anthropogenic origin and a lack of precursor emissions, such as isoprene, from biogenic sources, whose oxidation in situ would lead to formic acid formation.

scholarly journals Chemical ionization mass spectrometer (CIMS) for ambient measurements of ammonia

2010 ◽  
Vol 3 (2) ◽  
pp. 1133-1162 ◽  
Author(s):  
D. R. Benson ◽  
M. Al-Refai ◽  
S.-H. Lee
Keyword(s):  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Fast Response ◽  
Ionization Mass ◽  
Experimental Conditions ◽  
Molecule Reaction ◽  
Mixing Ratios ◽  
Ambient Nh3 ◽  
Ambient Measurements

Abstract. This study describes a chemical ionization mass spectrometer (CIMS) for fast response, in-situ measurements for gas phase ammonia. Protonated ethanol ions were used as the ion-molecule reaction reagent. The CIMS sensitivity was estimated to be between 4–25 Hz/pptv with 30% uncertainty. The instrument background was below 1 ppbv and at lowest was 300 pptv. The uncertainty associated with the instrumental background was less than 30 pptv under the optimized experimental conditions. The time response was less than 30 s, and the detection limit was approximately 60 pptv. This CIMS was used to measure the ambient NH3 in Kent, Ohio, for several weeks throughout three seasons. The measured ammonia mixing ratios were usually at the sub-ppbv level, and higher during the spring (200±120 pptv) than in the winter (60±75 pptv) and fall (150±80 pptv).

scholarly journals Measurement of ammonia, amines and iodine compounds using protonated water cluster chemical ionization mass spectrometry

2020 ◽  
Vol 13 (5) ◽  
pp. 2501-2522 ◽  
Author(s):  
Joschka Pfeifer ◽  
Mario Simon ◽  
Martin Heinritzi ◽  
Felix Piel ◽  
Lena Weitz ◽  
...  
Keyword(s):  
Detection Limit ◽  
Water Cluster ◽  
Chemical Ionization ◽  
Limit Of Detection ◽  
Trace Gases ◽  
Molecular Structures ◽  
Ionization Mass ◽  
Atmospheric Measurements ◽  
Iodic Acid ◽  
Mixing Ratios

Abstract. Here we describe the design and performance of a new water cluster chemical ionization–atmospheric pressure interface time-of-flight mass spectrometer (CI-APi-TOF). The instrument selectively measures trace gases with high proton affinity such as ammonia and dimethylamine, which are important for atmospheric new particle formation and growth. Following the instrument description and characterization, we demonstrate successful measurements at the CERN CLOUD (Cosmics Leaving OUtdoor Droplets) chamber where very low ammonia background levels of ∼4 pptv were achieved (at 278 K and 80 % RH). The limit of detection of the water cluster CI-APi-TOF is estimated to be ∼0.5 pptv for ammonia. Although no direct calibration was performed for dimethylamine (DMA), we estimate its detection limit is at least 3 times lower. Due to the short ion–molecule reaction time and high reagent ion concentrations, ammonia mixing ratios up to at least 10 ppbv can be measured with the instrument without significant reagent ion depletion. Besides the possibility to measure compounds like ammonia and amines (dimethylamine), we demonstrate that the ionization scheme is also suitable for the measurement of trace gases containing iodine. During CLOUD experiments to investigate the formation of new particles from I2, many different iodine-containing species were identified with the water cluster CI-APi-TOF. The compounds included iodic acid and neutral molecular clusters containing up to four iodine atoms. However, the molecular structures of the iodine-containing clusters are ambiguous due to the presence of an unknown number of water molecules. The quantification of iodic acid (HIO3) mixing ratios is performed from an intercomparison with a nitrate CI-APi-TOF. Using this method the detection limit for HIO3 can be estimated as 0.007 pptv. In addition to presenting our measurements obtained at the CLOUD chamber, we discuss the applicability of the water cluster Ci-APi-TOF for atmospheric measurements.

scholarly journals Airborne intercomparison of HO<sub>x</sub> measurements using laser-induced fluorescence and chemical ionization mass spectrometry during ARCTAS

2012 ◽  
Vol 5 (2) ◽  
pp. 2529-2565 ◽  
Author(s):  
X. Ren ◽  
J. Mao ◽  
W. H. Brune ◽  
C. A. Cantrell ◽  
R. L. Mauldin III ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Mass Spectrometer ◽  
Atmospheric Chemistry ◽  
Chemical Ionization ◽  
Uv Light ◽  
Laser Induced Fluorescence ◽  
Tropospheric Chemistry ◽  
Ionization Mass ◽  
Data Set ◽  
Mixing Ratios

Abstract. The hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively called HOx, play central roles in tropospheric chemistry. Accurate measurements of OH and HO2 are critical to examine our understanding of atmospheric chemistry. Intercomparisons of different techniques for detecting OH and HO2 are vital to evaluate their measurement capabilities. Three instruments that measured OH and/or HO2 radicals were deployed on the NASA DC-8 aircraft throughout Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS), in the spring and summer of 2008. One instrument was the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) for OH and HO2 measurements based on Laser-Induced Fluorescence (LIF) spectroscopy. A second instrument was the NCAR Selected-Ion Chemical Ionization Mass Spectrometer (SI-CIMS) for OH measurement. A third instrument was the NCAR Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) for HO2 measurement. Formal intercomparison of LIF and CIMS was conducted for the first time on a same aircraft platform. The three instruments were calibrated by quantitative photolysis of water vapor by UV light at 184.9 nm with three different calibration systems. The absolute accuracies were ±32% (2σ) for the LIF instrument, ±65% (2σ) for the SI-CIMS instrument, and ±50% (2σ) for the PeRCIMS instrument. In general, good agreement was obtained between the CIMS and LIF measurements of both OH and HO2 measurements. Linear regression of the entire data set yields [OH]CIMS = 0.89 × [OH]LIF + 2.8 × 105 cm−3 with a correlation coefficient, r2 = 0.72 for OH and [HO2]CIMS = 0.86 × [HO2]LIF + 3.9 parts per trillion by volume (pptv, equivalent to pmol mol−1) with a correlation coefficient, r2 = 0.72 for HO2. In general, the difference between CIMS and LIF instruments for OH and HO2 measurements can be explained by their combined measurement uncertainties. Comparison with box model results shows some similarities for both the CIMS and LIF measurements. First, the observed-to-modeled HO2 ratio increases greatly for higher NO mixing ratios, indicating that the model may not properly account for HOx sources that correlate with NO. Second, the observed-to-modeled OH ratio increases with increasing isoprene mixing ratios, suggesting either incomplete understanding of isoprene chemistry in the model or interferences in the measurements in environments where biogenic emissions dominate ambient volatile organic compounds.

scholarly journals Airborne intercomparison of HO<sub>x</sub> measurements using laser-induced fluorescence and chemical ionization mass spectrometry during ARCTAS

2012 ◽  
Vol 5 (8) ◽  
pp. 2025-2037 ◽  
Author(s):  
X. Ren ◽  
J. Mao ◽  
W. H. Brune ◽  
C. A. Cantrell ◽  
R. L. Mauldin III ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Mass Spectrometer ◽  
Atmospheric Chemistry ◽  
Chemical Ionization ◽  
Uv Light ◽  
Laser Induced Fluorescence ◽  
Tropospheric Chemistry ◽  
Ionization Mass ◽  
Data Set ◽  
Mixing Ratios

Abstract. The hydroxyl (OH) and hydroperoxyl (HO2) radicals, collectively called HOx, play central roles in tropospheric chemistry. Accurate measurements of OH and HO2 are critical to examine our understanding of atmospheric chemistry. Intercomparisons of different techniques for detecting OH and HO2 are vital to evaluate their measurement capabilities. Three instruments that measured OH and/or HO2 radicals were deployed on the NASA DC-8 aircraft throughout Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) in the spring and summer of 2008. One instrument was the Penn State Airborne Tropospheric Hydrogen Oxides Sensor (ATHOS) for OH and HO2 measurements based on Laser-Induced Fluorescence (LIF) spectroscopy. A second instrument was the NCAR Selected-Ion Chemical Ionization Mass Spectrometer (SI-CIMS) for OH measurement. A third instrument was the NCAR Peroxy Radical Chemical Ionization Mass Spectrometer (PeRCIMS) for HO2 measurement. Formal intercomparison of LIF and CIMS was conducted for the first time on a same aircraft platform. The three instruments were calibrated by quantitative photolysis of water vapor by ultraviolet (UV) light at 184.9 nm with three different calibration systems. The absolute accuracies were ±32% (2σ) for the LIF instrument, ±65% (2σ) for the SI-CIMS instrument, and ±50% (2σ) for the PeRCIMS instrument. In general, good agreement was obtained between the CIMS and LIF measurements of both OH and HO2 measurements. Linear regression of the entire data set yields [OH]CIMS = 0.89 × [OH]LIF + 2.8 × 104 cm−3 with a correlation coefficient r2 = 0.72 for OH, and [HO2]CIMS = 0.86 × [HO2]LIF + 3.9 parts per trillion by volume (pptv, equivalent to pmol mol−1) with a correlation coefficient r2 = 0.72 for HO2. In general, the difference between CIMS and LIF instruments for OH and HO2 measurements can be explained by their combined measurement uncertainties. Comparison with box model results shows some similarities for both the CIMS and LIF measurements. First, the observed-to-modeled HO2 ratio increases greatly for higher NO mixing ratios, indicating that the model may not properly account for HOx sources that correlate with NO. Second, the observed-to-modeled OH ratio increases with increasing isoprene mixing ratios, suggesting either incomplete understanding of isoprene chemistry in the model or interferences in the measurements in environments where biogenic emissions dominate ambient volatile organic compounds.

scholarly journals Measurements of hydroperoxy radicals (HO<sub>2</sub>) at atmospheric concentrations using bromide chemical ionization mass spectrometry

2018 ◽  
Author(s):  
Sascha R. Albrecht ◽  
Anna Novelli ◽  
Andreas Hofzumahaus ◽  
Sungah Kang ◽  
Yare Baker ◽  
...  
Keyword(s):  
Water Vapor ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Limit Of Detection ◽  
Ion Source ◽  
Detection Sensitivity ◽  
Detection Methods ◽  
Ionization Mass ◽  
Key Species ◽  
Atmospheric Concentrations

Abstract. Hydroxyl and hydroperoxy radicals are key species for the understanding of atmospheric oxidation processes. Their measurement is challenging due to their high reactivity, therefore very sensitive detection methods are needed. Within this study, the measurement of hydroperoxy radicals (HO2) using chemical ionization combined with an high resolution time of flight mass spectrometer (Aerodyne Research Inc.) employing bromide as primary ion is presented. The 1σ limit of detection of 4.5 × 107 molecules cm−3 for a 60 s measurement is below typical HO2 concentrations found in the atmosphere. The detection sensitivity of the instrument is affected by the presence of water vapor. Therefore, a water vapor dependent calibration factor that decreases approximately by a factor of 2 if the water vapor mixing ratio increases from 0.1 to 1.0 % needs to be applied. An instrumental background most likely generated by the ion source that is equivalent to a HO2 concentration of 1.5 ± 0.2 × 108 molecules cm−3 is subtracted to derive atmospheric HO2 concentrations. This background can be determined by overflowing the inlet with zero air. Several experiments were performed in the atmospheric simulation chamber SAPHIR at the Forschungszentrum Jülich to test the instrument performance by comparison to the well-established laser-induced fluorescence (LIF) technique for measurements of HO2. A high linear correlation coefficient of R2 = 0.87 is achieved. The slope of the linear regression of 1.07 demonstrates the good absolute agreement of both measurements. Chemical conditions during 15 experiments allowed testing the instrument’s behavior in the presence of atmospheric concentrations of H2O, NOx and O3. No significant interferences from these species were observed. All these facts are demonstrating a reliable measurement of HO2 by the chemical ionization mass spectrometer presented.

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