2011
DOI: 10.5194/amt-4-1471-2011
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A field-deployable, chemical ionization time-of-flight mass spectrometer

Abstract: We constructed a new chemical ionization time-of-flight mass spectrometer (CI-TOFMS) that measures atmospheric trace gases in real time with high sensitivity. We apply the technique to the measurement of formic acid via negative-ion proton transfer, using acetate as the reagent ion. A novel high pressure interface, incorporating two RF-only quadrupoles is used to efficiently focus ions through four stages of differential pumping before analysis with a compact TOFMS. The high ion-duty cycle (>20 %) of the TO… Show more

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Cited by 234 publications
(322 citation statements)
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“…The sensitivity of iodide-based CIMS to a given compound mainly depends on the polarity and hydrogen binding energy of a compound to the I − ion (Lee et al, 2014;Iyer et al, 2016). In the atmospheric pressure ESCIMS, the ion molecule reaction time (a few milliseconds) is set by the electric field, and is up to a factor of 30 or more less than those (30-120 ms) in low-pressure CIMS instruments (Bertram et al, 2011;Lee et al, 2014, Lopez-Hilfiker et al, 2016a. The shorter reaction time should linearly lower sensitivities.…”
Section: Sensitivity To Selected Trace Gasesmentioning
confidence: 99%
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“…The sensitivity of iodide-based CIMS to a given compound mainly depends on the polarity and hydrogen binding energy of a compound to the I − ion (Lee et al, 2014;Iyer et al, 2016). In the atmospheric pressure ESCIMS, the ion molecule reaction time (a few milliseconds) is set by the electric field, and is up to a factor of 30 or more less than those (30-120 ms) in low-pressure CIMS instruments (Bertram et al, 2011;Lee et al, 2014, Lopez-Hilfiker et al, 2016a. The shorter reaction time should linearly lower sensitivities.…”
Section: Sensitivity To Selected Trace Gasesmentioning
confidence: 99%
“…The SS capillary projects 3.5 mm into the IMR and acts as the atmospheric pressure interface between the IMR and the vacuum chamber of a commercial HR-ToF-MS (Tofwerk AG, Thun, Switzerland), effectively dropping the atmospheric pressure to 1.5 Torr in the first quadrupole of the MS, and resulting in a sample flow of ∼ 270 sccm (standard cubic centimeters per minute) into the MS. The HR-ToF-MS and its data acquisition procedures have been described in detail previously (Junninen et al, 2010;Bertram et al, 2011;Lee et al, 2014). The evaporation tube, lens and IMR tube are electrically connected, while the mass spectrometer entrance capillary is electrically isolated from the IMR by a ∼ 1 mm thick jacket of Teflon.…”
Section: Instrument Descriptionmentioning
confidence: 99%
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“…A detailed description of the instrument and principles of operation has been given elsewhere (Bertram et al, 2011;Lee et al, 2014) and in the Supplement. Briefly, the HR-ToF-CIMS used in this study was a differentially pumped time-of-flight mass spectrometer configured to use acetate ion as the reagent ion in the ionization of molecules of interest (Veres et al, 2008;Brophy and Farmer, 2015) via the following reaction:…”
Section: Gaseous Organic Acid Measurementsmentioning
confidence: 99%
“…As pesticides are typically quite large with molecular weights of 200-500 Da, a separation step before analysis of ambient air is often required to eliminate other isobaric molecules that may act as interferences. CIMS is increasingly used to measure trace gas species in the atmosphere because of high sensitivities, resolution, and selectivities of the different reagent ions employed (Bertram et al, 2011;Crounse et al, 2006;Lopez-Hilfiker et al, 2014;Nowak et al, 2007;Brophy and Farmer, 2015;Wentzell et al, 2013). Chemical ionization can be achieved by positive or negative ions, including hydronium, acetate, iodide, and nitrate.…”
Section: T Murschell Et Al: Gas-phase Pesticide Measurementmentioning
confidence: 99%