The Chemical Ionization/Particle-Induced Ion Source

1986 ◽  
pp. 179-183
Author(s):  
R. B. Freas ◽  
J. E. Campana
Keyword(s):  
Chemical Ionization ◽  
Ion Source

scholarly journals Characterization of the mass-dependent transmission efficiency of a CIMS

2016 ◽  
Vol 9 (4) ◽  
pp. 1449-1460 ◽  
Author(s):  
Martin Heinritzi ◽  
Mario Simon ◽  
Gerhard Steiner ◽  
Andrea C. Wagner ◽  
Andreas Kürten ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Transmission Efficiency ◽  
Ion Source ◽  
Mass Discrimination ◽  
Perfluorinated Acids ◽  
Relative Transmission ◽  
The Absolute ◽  
Primary Ions

Abstract. Knowledge about mass discrimination effects in a chemical ionization mass spectrometer (CIMS) is crucial for quantifying, e.g., the recently discovered extremely low volatile organic compounds (ELVOCs) and other compounds for which no calibration standard exists so far. Here, we present a simple way of estimating mass discrimination effects of a nitrate-based chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer. Characterization of the mass discrimination is achieved by adding different perfluorinated acids to the mass spectrometer in amounts sufficient to deplete the primary ions significantly. The relative transmission efficiency can then be determined by comparing the decrease of signals from the primary ions and the increase of signals from the perfluorinated acids at higher masses. This method is in use already for PTR-MS; however, its application to a CI-APi-TOF brings additional difficulties, namely clustering and fragmentation of the measured compounds, which can be treated with statistical analysis of the measured data, leading to self-consistent results. We also compare this method to a transmission estimation obtained with a setup using an electrospray ion source, a high-resolution differential mobility analyzer and an electrometer, which estimates the transmission of the instrument without the CI source. Both methods give different transmission curves, indicating non-negligible mass discrimination effects of the CI source. The absolute transmission of the instrument without the CI source was estimated with the HR-DMA method to plateau between the m∕z range of 127 and 568 Th at around 1.5 %; however, for the CI source included, the depletion method showed a steady increase in relative transmission efficiency from the m∕z range of the primary ion (mainly at 62 Th) to around 550 Th by a factor of around 5. The main advantages of the depletion method are that the instrument is used in the same operation mode as during standard measurements and no knowledge of the absolute amount of the measured substance is necessary, which results in a simple setup.

Ammonia in the Ion-Source. III. Clustering With N-Oxides, Sulfoxides and Sulfones

1986 ◽  
Vol 39 (12) ◽  
pp. 2161 ◽  
Author(s):  
RG Gillis
Keyword(s):  
Chemical Ionization ◽  
Low Pressure ◽  
Ion Source ◽  
Unimolecular Decomposition ◽  
Positive Ion

Under positive ion chemical ionization conditions, with ammonia as reagent gas at relatively low pressure, N-oxides, sulfoxides and sulfones form clusters with a proton and one or more ammonia molecules; these clusters can be represented as [M+H]+, [M+NH4]+, [M+N2H7]+, [2M+H]+ and [2M+NH4]+. The unimolecular decomposition of the clusters can be followed by the accompanying metastable peaks.

Application of Dual Electron Impact-Chemical Ionization Ion Source to Gaschromatograph-Mass spectrometer

1976 ◽  
Vol 24 (1) ◽  
pp. 139-147
Author(s):  
MASAYA IWANAGA ◽  
KIYOSHI HOSOI ◽  
NORIO KAMESHIMA ◽  
SHOZO ONISHI
Keyword(s):  
Electron Impact ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Ion Source

scholarly journals The airborne mass spectrometer AIMS – Part 2: Measurements of trace gases with stratospheric or tropospheric origin in the UTLS

2015 ◽  
Vol 8 (12) ◽  
pp. 13567-13607 ◽  
Author(s):  
T. Jurkat ◽  
S. Kaufmann ◽  
C. Voigt ◽  
D. Schäuble ◽  
P. Jeßberger ◽  
...  
Keyword(s):  
Nitrogen Oxide ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Trace Gases ◽  
Measurement Techniques ◽  
Ion Source ◽  
Trace Gas ◽  
Ionization Mass ◽  
Custom Made ◽  
Gas Measurements

Abstract. Understanding the role of climate-sensitive trace gas variabilities in the upper troposphere and lower stratosphere region (UTLS) and their impact on its radiative budget requires accurate measurements. The composition of the UTLS is governed by transport and chemistry of stratospheric and tropospheric constituents, such as chlorine, nitrogen oxide and sulphur components. The Airborne chemical Ionization Mass Spectrometer AIMS has been developed to accurately measure a set of these constituents on aircraft by means of chemical ionization. Here we present a setup using chemical ionization with SF5− reagent ions for the simultaneous measurement of trace gas concentrations in the pptv to ppmv (10−12 to 10−6 mol mol−1) range of HCl, HNO3 and SO2 with in-flight and online calibration called AIMS-TG. Part 1 of this paper (Kaufmann et al., 2015) reports on the UTLS water vapour measurements with the AIMS-H2O configuration. The instrument can be flexibly switched between two configurations depending on the scientific objective of the mission. For AIMS-TG, a custom-made gas discharge ion source has been developed generating a characteristic ionization scheme. HNO3 and HCl are routinely calibrated in-flight using permeation devices, SO2 is permanently calibrated during flight adding an isotopically labelled 34SO2 standard. In addition, we report on trace gas measurements of HONO which is sensitive to the reaction with SF5−. The detection limit for the various trace gases is in the low ten pptv range at a 1 s time resolution with an overall uncertainty of the measurement in the order of 20 %. AIMS has been integrated and successfully operated on the DLR research aircraft Falcon and HALO. Exemplarily, measurements conducted during the TACTS/ESMVal mission with HALO in 2012 are presented, focusing on a classification of tropospheric and stratospheric influences in the UTLS region. Comparison of AIMS measurements with other measurement techniques allow to draw a comprehensive picture of the sulphur, chlorine and reactive nitrogen oxide budget in the UTLS. The combination of the trace gases measured with AIMS exhibit the potential to gain a better understanding of the trace gas origin and variability at and near the tropopause.

scholarly journals A Vacuum Ultraviolet Ion Source (VUV-IS) for Iodide-Chemical Ionization Mass Spectrometry: A Substitute for Radioactive Ion Sources

2020 ◽  
Author(s):  
Yi Ji ◽  
L. Gregory Huey ◽  
David J. Tanner ◽  
Young Ro Lee ◽  
Patrick R. Veres ◽  
...  
Keyword(s):  
Formic Acid ◽  
Methyl Iodide ◽  
Chemical Ionization ◽  
Vacuum Ultraviolet ◽  
Ambient Air ◽  
Radioactive Source ◽  
Ion Source ◽  
Ion Sources ◽  
Ionization Mass ◽  
Molecular Chlorine

Abstract. A new ion source (IS) utilizing vacuum ultraviolet (VUV) light is developed and characterized for use with iodide-chemical ionization mass spectrometers (I−-CIMS). The VUV-IS utilizes a compact krypton lamp that emits light in two wavelength bands corresponding to energies of ~10.0 and 10.6 eV. The VUV light photoionizes either methyl iodide (ionization potential, IP = 9.54 ± 0.02 eV) or benzene (IP = 9.24378 ± 0.00007 eV) to form cations and photoelectrons. The electrons react with methyl iodide to form I− which serves as the reagent ion for the CIMS. The VUV-IS is characterized by measuring the sensitivity of a quadrupole CIMS (Q-CIMS) to formic acid, molecular chlorine, and nitryl chloride under a variety of flow and pressure conditions. The sensitivity of the Q-CIMS, with the VUV-IS, reached up to ~700 Hz pptv−1, with detection limits of less than 1 pptv for a one minute integration period. The reliability of the Q-CIMS with a VUV-IS is demonstrated with data from a month long ground-based field campaign. The VUV-IS is further tested by operation on a high resolution time-of-flight CIMS (TOF-CIMS). Sensitivities greater than 25 Hz pptv−1 were obtained for formic acid and molecular chlorine, which were similar to that obtained with a radioactive source. In addition, the mass spectra from sampling ambient air was cleaner with the VUV-IS on the TOF-CIMS compared to measurements using a radioactive source. These results demonstrate that the VUV lamp is a viable substitute for radioactive ion sources on I−-CIMS systems for most applications. In addition, the VUV-IS can likely be extended to other reagent ions, such as SF6− which are formed from high IP electron attachers, by the use of absorbers such as benzene to serve as a source of photoelectrons.

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