A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments

Müller, Markus; Piel, Felix; Gutmann, R A; Sulzer, Philipp; Hartungen, Eugen; Wisthaler, Armin

doi:10.1016/j.ijms.2019.116254

Cited by 27 publications

(19 citation statements)

References 19 publications

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“…In these experiments, the relative rate was determined using the following equation: which is similar to eq , except that additional loss processes besides the reaction with OH (e.g., dilution, wall-loss and decomposition) are taken into account using the first-order term k d . Two reference compounds were selected for these experiments, 2-propanol and ethanol, and these, together with the EPB, were monitored continuously using a PTR-ToF-MS 8000 system (Ionicon Analytik) operated in NH 4 + and H 3 O + modes. Both 2-propanol and ethanol have well-defined OH rate coefficients at 291 K, 5.32 and 3.31 × 10 –12 cm 3 molecule –1 s –1 , respectively …”

Section: Experimental Methodsmentioning

confidence: 99%

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Othmani

Ren

Bedjanian

et al. 2021

ACS Earth Space Chem.

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Epoxides have many primary and secondary atmospheric sources. As with other oxygenates, they exhibit a complex temperature-dependent reaction with OH, whose full description is necessary in order to understand their interactions in atmospheric and combustion environments. We measured the kinetics of the title reaction using two complementary absolute methods: pulsed-laser photolysis–laser-induced fluorescence (PLP–LIF) and a discharge-flow mass spectrometric system (DF-MS), both monitoring temporal decays in OH. In addition, two relative methods employing the DF-MS as a function of temperature as well as several simulation chamber experiments at room temperature were performed. A very weak negative temperature dependence was observed at T ≤ 285 K, and only through the combination of precise data and a large temperature range were we able to discern the transition toward positive temperature dependence found at T ≥ 295 K. The non-Arrhenius temperature dependence of OH + 1,2-epoxybutane implies the agency of prereactive complexes in this reaction mechanism, albeit with a smaller effect than that with its acyclic ether analogues. This will have implications for understanding the chemical fate of epoxides within oxidizing environments.

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Section: Experimental Methodsmentioning

confidence: 99%

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Othmani

Ren

Bedjanian

et al. 2021

ACS Earth Space Chem.

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“…In an effort to test the capability of detecting highly oxidized species, we measured SOA generated from limonene ozonolysis with optimized instrumental settings (EVR, Tdrift = 120°C). In addition, we operated the instrument at low reduced electric field strength (E/N = 30 Td; 1 Td = 10 -17 Vcm -2 ) and with NH4 + as the reagent ion (Müller et al, 2020). With these instrumental settings, ionic fragmentation is largely suppressed and highly oxidized organic molecules are detected in their ammonium 185 adduct form (Müller et al, in preparation).…”

Section: Detection Of Highly Oxidized Organic Compoundsmentioning

confidence: 99%

Introducing the Extended Volatility Range Proton-Transfer-Reaction Mass Spectrometer (EVR PTR-MS)

Piel¹,

Müller²,

Winkler³

et al. 2020

Preprint

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Abstract. Proton-transfer-reaction mass spectrometry (PTR-MS) is widely used in atmospheric sciences for measuring volatile organic compounds in real time. In the most widely used type of PTR-MS instruments, air is directly introduced into a chemical ionization reactor via an inlet capillary system. The reactor has a volumetric exchange time of ~ 0.1 s enabling PTR-MS analyzers to measure at a frequency of 10 Hz. The time response does, however, deteriorate if low-volatility analytes interact with surfaces in the inlet or in the instrument. Herein, we present the “Extended Volatility Range” (EVR) PTR-MS instrument which mitigates this issue. In the EVR configuration, inlet capillaries are made of passivated stainless steel and all wetted metal parts in the chemical ionization reactor are surface-passivated with a functionalized hydrogenated amorphous silicon coating. Heating the entire set-up to 120 °C further improves the time-response performance. We carried out time-response performance tests on a set of 29 analytes having saturation mass concentrations C0 in the range between 10−3 and 105 µg m−3. 1/e-signal decay times after instant removal of the analyte from the sampling flow were between 0.2 and 90 s for gaseous analytes. We also tested the EVR PTR-MS instrument in combination with the CHARON particle inlet, and 1/e-signal decay times were in the range between 5 and 35 s for particulate analytes. We show on a set of exemplary compounds that the time-response performance of the EVR PTR-MS instrument is comparable to that of fastest flow tube chemical ionization mass spectrometers that are currently in use. The fast time response can be used for rapid (~ 1 min equilibration time) switching between gas and particle measurements. The CHARON EVR PTR-MS instrument can thus be used for real-time monitoring of both gaseous and particulate organics in the atmosphere. Finally, we show that the CHARON EVR PTR-MS instrument is capable of detecting highly oxygenated species (with up to eight oxygen atoms) in particles formed by limonene ozonolysis.

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“…One such reagent ion is NH 4 + , which has been used in various forms of chemical ionisation mass spectrometry (CI-MS), [9][10][11][12][13][14][15][16] including proton transfer reaction mass spectrometry (PTR-MS) [17][18][19][20][21][22] and recently in PTR3 instruments. 23 NH 4 + reagent ions are also used in ion mobility spectrometry (IMS) 24 and high kinetic energy ion mobility spectrometry (HiKE-IMS) 25 techniques.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of reactions of NH₄⁺ with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry

Swift

Smith

Dryahina

et al. 2022

Rapid Comm Mass Spectrometry

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Rationale To assess the suitability of NH4+ as a reagent ion for trace gas analysis by selected ion flow tube mass spectrometry, SIFT‐MS, its ion chemistry must be understood. Thus, rate coefficients and product ions for its reactions with typical biogenic molecules and monoterpenes need to be experimentally determined in both helium, He, and nitrogen, N2, carrier gases. Methods NH4+ and H3O+ were generated in a microwave gas discharge through an NH3 and H2O vapour mixture and, after m/z selection, injected into He and N2 carrier gas. Using the conventional SIFT method, NH4+ reactions were then studied with M, the biogenic molecules acetone, 1‐propanol, 2‐butenal, trans‐2‐heptenal, heptanal, 2‐heptanone, 2,3‐heptanedione and 15 monoterpene isomers to obtain rate coefficients, k, and product ion branching ratios. Polarisabilities and dipole moments of the reactant molecules and the enthalpy changes in proton transfer reactions were calculated using density functional theory. Results The k values for the reactions of the biogenic molecules were invariably faster in N2 than in He but similar in both bath gases for the monoterpenes. Adducts NH4+M were the dominant product ions in He and N2 for the biogenic molecules, whereas both MH+ and NH4+M product ions were observed in the monoterpene reactions; the monoterpene ratio correlating (R2 = 0.7) with the proton affinity, PA, of the monoterpene molecule as calculated. The data indicate that this adduct ion formation is the result of bimolecular rather than termolecular association. Conclusions NH4+ can be a useful reagent ion for SIFT‐MS analyses of molecules with PA(M) < PA(NH3) when the dominant single product ion is the adduct NH4+M. For molecules with PA(M) > PA(NH3), such as monoterpenes, both MH+ and NH4+M ions are likely products, which must be determined along with k by experiment.

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A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments

Cited by 27 publications

References 19 publications

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Introducing the Extended Volatility Range Proton-Transfer-Reaction Mass Spectrometer (EVR PTR-MS)

Kinetics of reactions of NH₄⁺ with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry

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A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments

Cited by 27 publications

References 19 publications

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Gas-Phase Rate Coefficient of OH + 1,2-Epoxybutane Determined between 220 and 950 K

Introducing the Extended Volatility Range Proton-Transfer-Reaction Mass Spectrometer (EVR PTR-MS)

Kinetics of reactions of NH4+ with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry

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Kinetics of reactions of NH₄⁺ with some biogenic organic molecules and monoterpenes in helium and nitrogen carrier gases: A potential reagent ion for selected ion flow tube mass spectrometry