scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (11) ◽  
pp. 3225-3241 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the time-of-flight aerosol chemical speciation monitor (ToF-ACSM), combining precision state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of < 30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~ 8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation and calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (> 10 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps, agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (4) ◽  
pp. 6767-6814 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the economy time-of-flight-aerosol chemical speciation monitor (ToF-ACSM), combining precision of state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of <30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation &amp; calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (>6 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

scholarly journals Improved chloride quantification in quadrupole aerosol chemical speciation monitors (Q-ACSMs)

2020 ◽  
Author(s):  
Anna K. Tobler ◽  
Alicja Skiba ◽  
Dongyu S. Wang ◽  
Philip Croteau ◽  
Katarzyna Styszko ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Anthropogenic Activities ◽  
Chloride Concentration ◽  
Ambient Air ◽  
Aerosol Composition ◽  
Total Chloride ◽  
Ambient Aerosol ◽  
Positive Difference ◽  
The Difference

Abstract. Particulate chloride is an important component of fine particulate matter in marine air masses. Recent field studies also report elevated concentrations of gas-phase reactive chlorine species and particulate chloride related to anthropogenic activities. This work focuses on particulate chloride detection and quantification issues observed for some quadrupole aerosol chemical speciation monitors (Q-ACSM), which are designed for long-term measurement of ambient aerosol composition. The ACSM reports particle concentrations based on the difference between measurements of ambient air (sample mode) and particle-free ambient air (filter mode). For our long-term campaign in Krakow, Poland, the Q-ACSM reports apparent negative total chloride concentration for most of the campaign when analyzed with the default fragmentation table. This is the result of the difference signal from m/z 35 (35Cl+) being negative which dominates over the positive difference signal from m/z 36 (H35Cl+). Highly time-resolved experiments with NH4Cl, NaCl and KCl particles show that the signal response of m/z 35 is non-ideal, where the signal builds up and decreases slowly for all three salts, leading to a negative difference measurement. In contrast, the m/z 36 signal exhibits a near step-change response for NH4Cl during sampling and filter period, resulting in a positive difference signal. The response of m/z 36 for NaCl and KCl is not as prompt as for NH4Cl but still fast enough to have a positive difference signal. Furthermore, it is shown that this behavior is mostly temperature-independent. Based on these observations, this work presents an approach to correct the chloride concentration time series by adapting the standard fragmentation table coupled with a calibration of NH4Cl to obtain a relative ionization efficiency (RIE) based on the signal at m/z 36 (H35Cl+). This correction can be applied for measurements in environments where chloride is dominated by NH4Cl. Caution should be exercised when other chloride salts dominate the ambient aerosol.

scholarly journals High mass resolution MALDI-TOF MS for profiling biomolecules in mixtures

2018 ◽  
Author(s):  
Wenfa Ng
Keyword(s):  
Mass Spectrometry ◽  
Time Of Flight ◽  
High Sensitivity ◽  
Mass Resolution ◽  
High Mass ◽  
Maldi Tof Ms ◽  
Maldi Tof ◽  
Flight Mass Spectrometry ◽  
High Mass Resolution ◽  
Tof Ms

Intact biomolecules carry its identity through its atomic constituents and mass, while fragmented biomolecules require reconstruction for their identity to be retrieved. Hence, for profiling biomolecules in mixtures, the goal would be the gentle ionization of biomolecules by mass spectrometry without inducing fragmentation. Doing so generates an ensemble of ionized intact biomolecules able to be profiled by high sensitivity time-of-flight detector for accurate determination of each biomolecule mass, and thus, identity. Specifically, in time-of-flight detection, high mass resolution determination would require high sensitivity in detecting small differences in time of arrival of biomolecule ions to the detector. While current time-of-flight mass spectrometry provides high mass resolution, greater mass resolution is needed for discriminating different biomolecules in a mixture, where mass differences between biomolecules could be at the sub-Dalton level. With the ability to reliably detect biomolecules with sub-Dalton mass resolution, mass spectrometry with time-of-flight detector such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) could find use in identifying the compendium of biomolecules present in a mixture without tedious and time-consuming separation. The larger question would subsequently be coupling sample preparation needs with the conditions conducive for MALDI-TOF MS analysis. Overall, high mass resolution mass spectrometry techniques for profiling biomolecules would find use as an enabling tool in many areas of analytical science and biological sciences such as proteomics and metabolomics.

scholarly journals The Mass Resolution of Ca, K Isotopes and CO, N2 and C2H4 Isobars in Isotopes Separator On-Line trap Mass spectrometry

2020 ◽  
pp. 180-185
Author(s):  
Dyavappa B M
Keyword(s):  
Mass Spectrometry ◽  
Penning Trap ◽  
Time Of Flight ◽  
High Accuracy ◽  
Mass Resolution ◽  
Axial Motion ◽  
Calcium Isotopes ◽  
Direct Excitation ◽  
Flight Mass Spectrometry ◽  
On Line

In Isotopes separator on-line trap, ions are trapped, cooled, accumulated, bunched and isotopes or isobars are separated, cyclotron frequencies are determined, which are followed by time of flight mass resolution. The mass resolution of isotopes in Penning trap mass spectrometry is achieved by the direct excitation of axial motion of ions, driven by RF field at the pure cyclotron frequencies of ions. The design and working of Isotopes separator on-line trap which is used for high-accuracy mass spectrometry in the mass resolution of calcium isotopes (40Ca+, 42Ca+, 44Ca+), potassium isotopes (39K+, 41K+) and [28(CO)]+, [(28N2)]+, [28(C2H4)]+ isobars found in mixtures is achieved from time of flight mass spectrometry are presented here.

scholarly journals Improved chloride quantification in quadrupole aerosol chemical speciation monitors (Q-ACSMs)

2020 ◽  
Vol 13 (10) ◽  
pp. 5293-5301
Author(s):  
Anna K. Tobler ◽  
Alicja Skiba ◽  
Dongyu S. Wang ◽  
Philip Croteau ◽  
Katarzyna Styszko ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Anthropogenic Activities ◽  
Fine Particulate Matter ◽  
Chloride Concentration ◽  
Ambient Air ◽  
Aerosol Composition ◽  
Total Chloride ◽  
Positive Difference ◽  
The Difference

Abstract. Particulate chloride is an important component of fine particulate matter in marine air masses. Recent field studies also report elevated concentrations of gas-phase reactive chlorine species and particulate chloride related to anthropogenic activities. This work focuses on particulate chloride detection and quantification issues observed for some quadrupole aerosol chemical speciation monitors (Q-ACSMs) which are designed for the long-term measurement of ambient aerosol composition. The ACSM reports particle concentrations based on the difference between measurements of ambient air (sample mode) and particle-free ambient air (filter mode). For our long-term campaign in Krakow, Poland, the Q-ACSM reports apparent negative total chloride concentration for most of the campaign when analyzed with the default fragmentation table. This is the result of the difference signal from m∕z 35 (35Cl+) being negative, which dominates over the positive difference signal from m∕z 36 (H35Cl+). Highly time-resolved experiments with NH4Cl, NaCl and KCl particles show that the signal response of m∕z 35 is non-ideal when the signal builds up and decreases slowly for all three salts, leading to a negative difference measurement. In contrast, the m∕z 36 signal exhibits a near step-change response for NH4Cl during the sampling and filter period, resulting in a positive difference signal. The response of m∕z 36 for NaCl and KCl is not as prompt as for NH4Cl but still fast enough to have a positive difference signal. Furthermore, it is shown that this behavior is mostly independent of vaporizer temperature. Based on these observations, this work presents an approach to correct the chloride concentration time series by adapting the standard fragmentation table coupled with a calibration of NH4Cl to obtain a relative ionization efficiency (RIE) based on the signal at m∕z 36 (H35Cl+). This correction can be applied to measurements in environments where chloride is dominated by NH4Cl. Caution should be exercised when other chloride salts dominate the ambient particulate chloride.

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