Are iodic acid measurements by chemical ionization unambiguous?  

2021 ◽  
Author(s):  
Thomas Lewis ◽  
Juan Carlos Gomez Martin ◽  
Mark Blitz ◽  
Alfonso Saiz-Lopez ◽  
John Plane
Keyword(s):  
Gas Phase ◽  
Chemical Ionization ◽  
Cluster Formation ◽  
Particle Formation ◽  
Molecular Cluster ◽  
Iodic Acid ◽  
Flight Mass Spectrometry ◽  
Ion Molecule Reactions ◽  
Iodine Oxides ◽  
Tof Ms

<p>Field observations of IO<sup>3−</sup> and HIO<sup>3−</sup>-containing cluster anions by chemical ionization–atmospheric pressure interface–time-of-flight mass spectrometry (CI-API-ToF-MS) have been reported1. These observations, which employ nitrate (NO<sup>3−</sup>) reagent ions for reaction with the analytes, have been interpreted as resulting from atmospheric gas-phase iodic acid (HOIO<sub>2</sub>) and molecular cluster formation via HOIO<sub>2 </sub>addition steps. CI-API-ToF-MS chamber measurements with alternative ionization schemes have also reported signals that could be attributed to gas-phase HOIO and HOIO<sub>2</sub>. However, well-established chemical kinetics and thermochemistry do not indicate any straightforward route to gas-phase iodine oxyacids and HOIO2 particle formation in the atmosphere. This does not only hinder the ability of chemical models for linking iodine emissions and particle formation, but also calls into question the interpretation of these CI-API-ToF-MS measurements. It has been proposed that water plays an important role in generating gas phase and HOIO<sub>2</sub>-containing molecular clusters, but recent flow tube experiments have established extremely low upper limits to the rate constants of possible reactions between iodine oxides (IO<sub>x</sub> and I<sub>x</sub>O<sub>y</sub>) and water. In this presentation, we discuss experimental and theoretical kinetics and thermochemistry of proposed routes to gas-phase HOIO and HOIO<sub>2</sub> in the atmosphere as well as potential ion-molecule reactions turning iodine oxides into IO<sup>3-</sup> ions in the CI-API-ToF-MS inlet. We show that there is an important ambiguity in the interpretation of IO<sup>3- </sup>and other signals observed with CI instruments as a result of barrierless reactions between I<sub>x</sub>O<sub>y</sub> and the reagent ions. Experiments for solving this ambiguity and reconciling conflicting results are proposed.</p>

Ion-induced iodic acid nucleation

2021 ◽  
Author(s):  
Xu-Cheng He ◽  
Siddharth Iyer ◽  
Yee Jun Tham ◽  
Mikko Sipilä ◽  
Jasper Kirkby ◽  
...  
Keyword(s):  
Time Evolution ◽  
Marine Boundary Layer ◽  
Cluster Formation ◽  
Particle Formation ◽  
Galactic Cosmic Rays ◽  
Oxidation Products ◽  
Formation Processes ◽  
Iodic Acid ◽  
Nucleation Mechanisms ◽  
Iodine Oxides

<p>Aside from capable of influencing atmospheric oxidation capacity, iodine species are known to contribute to particle formation processes. Iodine particle formation was commonly believed to be important in coastal regions only, e.g. Mace Head, but emerging evidence shows that it also plays an important role in Arctic regions.</p><p> </p><p>Although the nucleation mechanisms have been proposed to involve mainly iodine oxides, recent field observations suggest that HIO<sub>3</sub> plays a key role in the cluster formation processes. Despite these advances, experiments with atmospherically relevant vapor concentrations are lacking and the time evolution of charged cluster formation processes has never been detected at the molecular level to validate the mechanisms observed in the field.</p><p> </p><p>In this study, we carried out iodine particle formation experiments in the CLOUD chamber at CERN. The precursor vapor (I<sub>2</sub>) and oxidation products were carefully controlled at concentrations relevant to those in marine boundary layer conditions. Natural galactic cosmic rays were used to produce ions in the chamber which further initiated ion-induced nucleation processes. An atmospheric pressure interface time-of-flight mass spectrometer was used to trace the time evolution of charged iodine clusters which revealed HIO<sub>3</sub> as the major contributor.</p>

Cluster Formation by Laser Ablation of Zeolites

1996 ◽  
Vol 457 ◽  
Author(s):  
Hiroshi T. Komiyama ◽  
Azuchi Harano ◽  
Tatsuya Okubo ◽  
Masayoshi Sadakata
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Quartz Glass ◽  
Nd:Yag Laser ◽  
Ultrafine Particles ◽  
Mass Spectra ◽  
Cluster Formation ◽  
Flight Mass Spectrometry ◽  
Positive Ions ◽  
Tof Ms

ABSTRACTSeveral kinds of zeolites, crystal-SiO2 (α-quartz), arnorphous-SiO2 (quartz glass and ultrafine particles) and α-Al2O3, were ablated by an Nd:YAG laser. Generated positive ions from the targets were measured by TOF-MS (time-of-flight mass spectrometry). In the TOF mass spectra of ablated zeolites, TOx (x=0–2, T = tetrahedral atom, e.g., Si, Al), T2Ox (x=1) and T3Ox (x=4,5) were observed up to m/z=170 (m = mass, z = plus charge of clusters). In the spectra due to the oc-quartz, quartz glass and an α-Al2O3 plate, smaller species, T+, TO+ and TO2+, were mainly detected. These results demonstrate that the clusters from zeolites reflect the characters of the mother structure.

scholarly journals Determination of the absorption cross sections of higher-order iodine oxides at 355 and 532 nm

2020 ◽  
Vol 20 (18) ◽  
pp. 10865-10887
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martín ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Particle Formation ◽  
Absorption Cross ◽  
Iodic Acid ◽  
Iodine Oxides ◽  
532 Nm

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layers and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x=2, 3, 5, y=1–12 at λ=355 nm by combining pulsed laser photolysis of I2∕O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross-section determinations are those presenting the strongest signals in the mass spectra, where signals containing four iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355nm,IO= (1.2±0.1) ×10-18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are σ355nm,I2O3<5×10-19 cm2 molec.−1, σ355nm,I2O4= (3.9±1.2)×10-18 cm2 molec.−1, σ355nm,I3O6= (6.1±1.6)×10-18 cm2 molec.−1, σ355nm,I3O7= (5.3±1.4)×10-18 cm2 molec.−1, and σ355nm,I5O12= (9.8±1.0)×10-18 cm2 molec.−1. Photodepletion at λ=532 nm was only observed for OIO, which enabled determination of upper limits for the absorption cross sections of IxOy at 532 nm using OIO as an actinometer. These measurements are supplemented with ab initio calculations of electronic spectra in order to estimate atmospheric photolysis rates J(IxOy). Our results confirm a high J(IxOy) scenario where IxOy is efficiently removed during daytime, implying enhanced iodine-driven ozone depletion and hindering iodine particle formation. Possible I2O3 and I2O4 photolysis products are discussed, including IO3, which may be a precursor to iodic acid (HIO3) in the presence of HO2.

A process model to predict the faith of clusters in CI-APi-TOF mass spectrometers

2020 ◽  
Author(s):  
Ivo Neefjes ◽  
Tommaso Zanca ◽  
Jakub Kubecka ◽  
Evgeni Zapadinsky ◽  
Monica Passananti ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Atmospheric Pressure ◽  
Process Model ◽  
Chemical Ionization ◽  
Binding Energies ◽  
Molecular Formula ◽  
Flight Mass Spectrometry ◽  
Quantum Chemistry Calculations ◽  
Measured Sample ◽  
Tof Ms

&lt;div&gt;Recent technological developments have made it possible to detect the elemental composition of even the smallest airborne clusters at low ambient concentrations through chemical ionization atmospheric pressure interface time-of-flight mass spectrometry (CI-APi-TOF-MS). The charging process and collisions inside the instrument will however affect the molecular composition of the original sample clusters. A process model is therefore needed to connect the mass spectra to the original molecular clusters in the measured sample.&lt;/div&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;&lt;div&gt;Our research has been focused on developing this process model for clusters involving highly oxygenated organic molecules (HOM) with molecular formula C&lt;sub&gt;10&lt;/sub&gt;H&lt;sub&gt;16&lt;/sub&gt;O&lt;sub&gt;8&lt;/sub&gt;. This elemental composition corresponds to one of the most common mass peaks observed in experiments on ozone-initiated autoxidation of &amp;#945;-pinene.&lt;/div&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;&lt;div&gt;For the model, two situations inside the mass spectrometer have to be taken into account: the chemical ionization and collisions with carrier gas inside the atmospheric pressure interface. Recently, a model predicting the fragmentation of clusters as a result of collisions in APi has been developed by Zapadinsky et al. (2018). We used this model to perform numerical simulations of fragmentation in the APi on our selected clusters. The results show that fragmentation is highly unlikely for the considered clusters, provided their bonding energy is large enough to allow formation in the atmosphere in the first place.&lt;/div&gt;&lt;div&gt;&amp;#160;&lt;/div&gt;&lt;div&gt;Current research is focused on developing a model for the charging process inside CI-APi-TOF MS. Configurational sampling is combined with high quality quantum chemistry calculations to derive the binding energies and evaporation rates of the studied clusters. This model should eventually connect the ionized clusters after charging to the original distribution of neutral clusters in the measured sample.&lt;/div&gt;

Development and use of analytical systems based on mass spectrometry.

1977 ◽  
Vol 23 (1) ◽  
pp. 13-21 ◽  
Author(s):  
E C Horning ◽  
D I Carroll ◽  
I Dzidic ◽  
K D Haegele ◽  
S Lin ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Atmospheric Pressure ◽  
Chemical Ionization ◽  
Negative Ions ◽  
Atmospheric Pressure Ionization ◽  
Gas Chromatograph ◽  
Ion Molecule Reactions ◽  
Ionization Mode ◽  
Effluent Stream

Abstract Contemporary analytical systems based on mass spectrometry include as components a gas chromatograph, a mass spectrometer, and a computer. The form of operation is usually in electron impact ionization mode for identification and structural studies, and in chemical ionization mode for quantitative analyses. Important stages in the development of these systems included the design of "molecule separators" for the concentration of solutes in the gas phase, the use of mass spectrometers as specific ion detectors, the introduction of chemical ionization techniques, and the development of computer-based operation, data acquisition, and data analysis capabilities. A current line of investigation is concerned with the design and use of systems based on atmospheric pressure ionization. Samples are ionized in a small reaction chamber external to the low-pressure region of a quadrupole mass analyzer. The primary source of electrons is a 63Ni foil or a corona discharge. The ionization process leading to positive ions involves a sequence of ion molecule reactions, usually electrons leads to carrier gas ions leads to reagent ions leads to sample component ions. Negative ions may be formed by direct electron attachment, or by ion molecule reactions that include new types of elimination reactions. The source will accept a variety of gases and solvents. The sample may be introduced in the gas phase without solvents, by probe injection, or in the effluent stream from a gas chromatograph. Samples may be introduced in the liquid phase in solvents by injection after the fashion of gas chromatography or in the effluent stream from a high-performance liquid chromatograph. The novel aspects of atmospheric pressure ionization mass spectrometry lie in its versatility and high sensitivity of detection. Few clinical chemistry laboratories now use these systems. Significant future uses are likely to be in analytical work involving therapeutic drug monitoring and studies of drug metabolism, and in analyses for environmental biohazards including pesticides, herbicides, polyhalobiphenyls, dibenzodioxins, and other toxic compounds.

scholarly journals The role of sulphates and organic vapours in new particle formation in a eucalypt forest

2009 ◽  
Vol 9 (4) ◽  
pp. 17793-17815 ◽  
Author(s):  
Z. D. Ristovski ◽  
T. Suni ◽  
M. Kulmala ◽  
M. Boy ◽  
N. K. Meyer ◽  
...  
Keyword(s):  
Gas Phase ◽  
Particle Production ◽  
Cluster Formation ◽  
Particle Formation ◽  
Oxidation Products ◽  
Forest Environment ◽  
Eucalypt Forest ◽  
Hygroscopic Properties ◽  
Simultaneous Growth

Abstract. The influence of biogenic particle formation on climate is a well recognized phenomenon. To understand the mechanisms underlying the biogenic particle formation, determining the chemical composition of the new particles and therefore the species that drive the particle production is of utmost importance. Due to the very small amount of mass involved, indirect approaches are frequently used to infer the composition. We present here the results of such an indirect approach by simultaneously measuring volatile and hygroscopic properties of newly formed particles in a forest environment. We that the particles are composed of both sulphates and organics, with the amount of sulphate component strongly depending on the available gas-phase sulphuric acid, and the organic components being photo-oxidation products of most likely a monoterpene. Our findings confirm a two-step process through nucleation and cluster formation followed by simultaneous growth by condensation of sulphates and organics that take the particles to climatically relevant sizes.

Sign in / Sign up

Export Citation Format

Share Document