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Stefan Zimmermann - One of the best experts on this subject based on the ideXlab platform.
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Formation of positive product ions from substances with low proton affinity in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Rapid Communications in Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Florian Schlottmann, Stefan ZimmermannAbstract:RATIONALE Ion mobility spectrometer are typically equipped with atmospheric pressure chemical ionization (APCI) sources operated at ambient pressure. However, classical APCI ion mobility spectrometers suffer from a limited ionization yield for nonpolar substances with low proton affinity. This is mainly due to ion clustering processes, especially those that involve water molecules, inhibiting the ionization of these substances. METHODS High Kinetic Energy (Hike) Ion Mobility Spectrometers are operated at decreased pressures and High reduced electric field strengths. As most clustering reactions are inhibited under these conditions, the ionization yield for nonpolar substances with low proton affinity in HiKE-ion mobility spectrometry (IMS) should differ from that in classical APCI-IMS. In order to gain first insights into the ionization capabilities and limitation of HiKE-IMS, we investigated the ionization of four model substances with low proton affinity in HiKE-IMS by HiKE-IMS-MS as a function of the reduced electric field strength. RESULTS The four model substances all have proton affinities between those of H2 O and (H2 O)2 but exhibit different ionization energies, dipole moments and polarizabilities. As expected, the results show that the ionization yield for these substances differs considerably at low reduced electric field strengths due to ion cluster formation. In contrast, at High reduced electric field strengths, all substances can be ionized via charge and/or proton transfer in HiKE-IMS. CONCLUSIONS Considering the detection of polar substances with High proton affinity, classical ambient pressure IMS should reach better detection limits than HiKE-IMS. However, considering the detection of nonpolar substances with low proton affinity that are not detected, or only difficult to detect, at ambient pressure, HiKE-IMS would be beneficial.
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Ion Mobility Shift of Isotopologues in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at Elevated Effective Temperatures.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Christoph Schaefer, Maria Allers, Ansgar T. Kirk, Stefan ZimmermannAbstract:Ion mobility spectrometers (IMS) separate ions mainly by ion-neutral collision cross section and to a lesser extent by ion mass and effective temperature. When investigating isotopologues, the diff...
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Field-Dependent Reduced Ion Mobilities of Positive and Negative Ions in Air and Nitrogen in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Stefan ZimmermannAbstract:In High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS), ions are formed in a reaction region and separated in a drift region, which is similar to classical drift tube ion mobility spectrometers (IMS) operated at ambient pressure. However, in contrast to the latter, the HiKE-IMS is operated at a decreased background pressure of 10-40 mbar and achieves High reduced electric field strengths of up to 120 Td in both the reaction and the drift region. Thus, the HiKE-IMS allows insights into the chemical Kinetics of ion-bound water cluster systems at effective ion temperatures exceeding 1000 K, although it is operated at the low absolute temperature of 45 °C. In this work, a HiKE-IMS with a High resolving power of RP = 140 is used to study the dependence of reduced ion mobilities on the drift gas humidity and the effective ion temperature for the positive reactant ions H3O+(H2O)n, O2+(H2O)n, NO+(H2O)n, NO2+(H2O)n, and NH4+(H2O)n, as well as the negative reactant ions O2-(H2O)n, O3-(H2O)n, CO3-(H2O)n, HCO3-(H2O)n, and NO2-(H2O)n. By varying the reduced electric field strength in the drift region, cluster transitions are observed in the ion mobility spectra. This is demonstrated for the cluster systems H3O+(H2O)n and NO+(H2O)n.
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Negative Reactant Ion Formation in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Bennet Timke, Stefan ZimmermannAbstract:Due to the operation at background pressures between 10-40 mbar and High reduced electric field strengths of up to 120 Td, the ion-molecule reactions in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) differ from those in classical ambient pressure IMS. In the positive ion polarity mode, the reactant ions H+(H2O)n, O2+(H2O)n, and NO+(H2O)n are observed in the HiKE-IMS. The relative abundances of these reactant ion species significantly depend on the reduced electric field strength in the reaction region, the operating pressure, and the water concentration in the reaction region. In this work, the formation of negative reactant ions in HiKE-IMS is investigated in detail. On the basis of Kinetic and thermodynamic data from the literature, the processes resulting in the formation of negative reactant ions are Kinetically modeled. To verify the model, we present measurements of the negative reactant ion population in the HiKE-IMS and its dependence on the reduced electric field strength as well as the water and carbon dioxide concentrations in the reaction region. The ion species underlying individual peaks in the ion mobility spectrum are identified by coupling the HiKE-IMS to a time-of-flight mass spectrometer (TOF-MS) using a simple gated interface that enables the transfer of selected peaks of the ion mobility spectrum into the TOF-MS. Both the theoretical model as well as the experimental data suggest the predominant generation of the oxygen-based ions O-, OH-, O2-, and O3- in purified air containing 70 ppmv of water and 30 ppmv of carbon dioxide. Additionally, small amounts of NO2- and CO3- are observed. Their relative abundances Highly depend on the reduced electric field strength as well as the water and carbon dioxide concentration. An increase of the water concentration in the reaction region results in the generation of OH- ions, whereas increasing the carbon dioxide concentration favors the generation of CO3- ions, as expected.
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High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) at 40 mbar.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Florian Schlottmann, Maria Allers, Ansgar T. Kirk, Alexander Bohnhorst, Stefan ZimmermannAbstract:High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at an absolute pressure of 20 mbar reaching High reduced electric field strengths of up to 125 Td for controlled reaction Kinetics. This significantly increases the linear range and limits chemical cross sensitivities. Furthermore, HiKE-IMS enables the ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to new reaction pathways and the inhibition of clustering reactions. In addition, HiKE-IMS allows the observation of additional orthogonal parameters related to an increased ion temperature such as fragmentation and field-dependent ion mobility, which may help to separate compounds that have similar ion mobility under low field conditions. Aiming for a hand-held HiKE-IMS to carry its benefits into field applications, reducing size and power consumption of the vacuum system is necessary. In this work, we present a novel HiKE-IMS design entirely manufactured from standard printed circuit boards (PCB) and experimentally investigate the analytical performance in dependence of the operating pressure between 20 mbar and 40 mbar. Hereby, the limit of detection (LoD) for benzene in purified, dry air (1.4 ppmV water) improved from 7 ppbV at 20 mbar down to 1.8 ppbV at 40 mbar. Furthermore, adding 0.9 ppmV toluene, the signal of the benzene B+ peak decreased by only 2% at 40 mbar. Even in the presence of High relative humidity in the sample gas above 90% or toluene concentrations of up to 20 ppmV, the LoD for benzene just increased to 9 ppbV at 40 mbar.
Ansgar T. Kirk - One of the best experts on this subject based on the ideXlab platform.
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Formation of positive product ions from substances with low proton affinity in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Rapid Communications in Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Florian Schlottmann, Stefan ZimmermannAbstract:RATIONALE Ion mobility spectrometer are typically equipped with atmospheric pressure chemical ionization (APCI) sources operated at ambient pressure. However, classical APCI ion mobility spectrometers suffer from a limited ionization yield for nonpolar substances with low proton affinity. This is mainly due to ion clustering processes, especially those that involve water molecules, inhibiting the ionization of these substances. METHODS High Kinetic Energy (Hike) Ion Mobility Spectrometers are operated at decreased pressures and High reduced electric field strengths. As most clustering reactions are inhibited under these conditions, the ionization yield for nonpolar substances with low proton affinity in HiKE-ion mobility spectrometry (IMS) should differ from that in classical APCI-IMS. In order to gain first insights into the ionization capabilities and limitation of HiKE-IMS, we investigated the ionization of four model substances with low proton affinity in HiKE-IMS by HiKE-IMS-MS as a function of the reduced electric field strength. RESULTS The four model substances all have proton affinities between those of H2 O and (H2 O)2 but exhibit different ionization energies, dipole moments and polarizabilities. As expected, the results show that the ionization yield for these substances differs considerably at low reduced electric field strengths due to ion cluster formation. In contrast, at High reduced electric field strengths, all substances can be ionized via charge and/or proton transfer in HiKE-IMS. CONCLUSIONS Considering the detection of polar substances with High proton affinity, classical ambient pressure IMS should reach better detection limits than HiKE-IMS. However, considering the detection of nonpolar substances with low proton affinity that are not detected, or only difficult to detect, at ambient pressure, HiKE-IMS would be beneficial.
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Ion Mobility Shift of Isotopologues in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at Elevated Effective Temperatures.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Christoph Schaefer, Maria Allers, Ansgar T. Kirk, Stefan ZimmermannAbstract:Ion mobility spectrometers (IMS) separate ions mainly by ion-neutral collision cross section and to a lesser extent by ion mass and effective temperature. When investigating isotopologues, the diff...
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Field-Dependent Reduced Ion Mobilities of Positive and Negative Ions in Air and Nitrogen in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Stefan ZimmermannAbstract:In High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS), ions are formed in a reaction region and separated in a drift region, which is similar to classical drift tube ion mobility spectrometers (IMS) operated at ambient pressure. However, in contrast to the latter, the HiKE-IMS is operated at a decreased background pressure of 10-40 mbar and achieves High reduced electric field strengths of up to 120 Td in both the reaction and the drift region. Thus, the HiKE-IMS allows insights into the chemical Kinetics of ion-bound water cluster systems at effective ion temperatures exceeding 1000 K, although it is operated at the low absolute temperature of 45 °C. In this work, a HiKE-IMS with a High resolving power of RP = 140 is used to study the dependence of reduced ion mobilities on the drift gas humidity and the effective ion temperature for the positive reactant ions H3O+(H2O)n, O2+(H2O)n, NO+(H2O)n, NO2+(H2O)n, and NH4+(H2O)n, as well as the negative reactant ions O2-(H2O)n, O3-(H2O)n, CO3-(H2O)n, HCO3-(H2O)n, and NO2-(H2O)n. By varying the reduced electric field strength in the drift region, cluster transitions are observed in the ion mobility spectra. This is demonstrated for the cluster systems H3O+(H2O)n and NO+(H2O)n.
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Negative Reactant Ion Formation in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Bennet Timke, Stefan ZimmermannAbstract:Due to the operation at background pressures between 10-40 mbar and High reduced electric field strengths of up to 120 Td, the ion-molecule reactions in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) differ from those in classical ambient pressure IMS. In the positive ion polarity mode, the reactant ions H+(H2O)n, O2+(H2O)n, and NO+(H2O)n are observed in the HiKE-IMS. The relative abundances of these reactant ion species significantly depend on the reduced electric field strength in the reaction region, the operating pressure, and the water concentration in the reaction region. In this work, the formation of negative reactant ions in HiKE-IMS is investigated in detail. On the basis of Kinetic and thermodynamic data from the literature, the processes resulting in the formation of negative reactant ions are Kinetically modeled. To verify the model, we present measurements of the negative reactant ion population in the HiKE-IMS and its dependence on the reduced electric field strength as well as the water and carbon dioxide concentrations in the reaction region. The ion species underlying individual peaks in the ion mobility spectrum are identified by coupling the HiKE-IMS to a time-of-flight mass spectrometer (TOF-MS) using a simple gated interface that enables the transfer of selected peaks of the ion mobility spectrum into the TOF-MS. Both the theoretical model as well as the experimental data suggest the predominant generation of the oxygen-based ions O-, OH-, O2-, and O3- in purified air containing 70 ppmv of water and 30 ppmv of carbon dioxide. Additionally, small amounts of NO2- and CO3- are observed. Their relative abundances Highly depend on the reduced electric field strength as well as the water and carbon dioxide concentration. An increase of the water concentration in the reaction region results in the generation of OH- ions, whereas increasing the carbon dioxide concentration favors the generation of CO3- ions, as expected.
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High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) at 40 mbar.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Florian Schlottmann, Maria Allers, Ansgar T. Kirk, Alexander Bohnhorst, Stefan ZimmermannAbstract:High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at an absolute pressure of 20 mbar reaching High reduced electric field strengths of up to 125 Td for controlled reaction Kinetics. This significantly increases the linear range and limits chemical cross sensitivities. Furthermore, HiKE-IMS enables the ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to new reaction pathways and the inhibition of clustering reactions. In addition, HiKE-IMS allows the observation of additional orthogonal parameters related to an increased ion temperature such as fragmentation and field-dependent ion mobility, which may help to separate compounds that have similar ion mobility under low field conditions. Aiming for a hand-held HiKE-IMS to carry its benefits into field applications, reducing size and power consumption of the vacuum system is necessary. In this work, we present a novel HiKE-IMS design entirely manufactured from standard printed circuit boards (PCB) and experimentally investigate the analytical performance in dependence of the operating pressure between 20 mbar and 40 mbar. Hereby, the limit of detection (LoD) for benzene in purified, dry air (1.4 ppmV water) improved from 7 ppbV at 20 mbar down to 1.8 ppbV at 40 mbar. Furthermore, adding 0.9 ppmV toluene, the signal of the benzene B+ peak decreased by only 2% at 40 mbar. Even in the presence of High relative humidity in the sample gas above 90% or toluene concentrations of up to 20 ppmV, the LoD for benzene just increased to 9 ppbV at 40 mbar.
Tim Kobelt - One of the best experts on this subject based on the ideXlab platform.
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A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources
Journal of The American Society for Mass Spectrometry, 2018Co-Authors: Ansgar Thomas Kirk, Tim Kobelt, Hauke Spehlbrink, Stefan ZimmermannAbstract:Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with High ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region. Graphical Abstract ᅟ
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A Simple Analytical Model for Predicting the Detectable Ion Current in Ion Mobility Spectrometry Using Corona Discharge Ionization Sources
Journal of The American Society for Mass Spectrometry, 2018Co-Authors: Ansgar T. Kirk, Tim Kobelt, Hauke Spehlbrink, Stefan ZimmermannAbstract:Corona discharge ionization sources are often used in ion mobility spectrometers (IMS) when a non-radioactive ion source with High ion currents is required. Typically, the corona discharge is followed by a reaction region where analyte ions are formed from the reactant ions. In this work, we present a simple yet sufficiently accurate model for predicting the ion current available at the end of this reaction region when operating at reduced pressure as in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) or most IMS-MS instruments. It yields excellent qualitative agreement with measurement results and is even able to calculate the ion current within an error of 15%. Additional interesting findings of this model are the ion current at the end of the reaction region being independent from the ion current generated by the corona discharge and the ion current in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) growing quadratically when scaling down the length of the reaction region.
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High-Resolution High Kinetic Energy Ion Mobility Spectrometer Based on a Low-Discrimination Tristate Ion Shutter
Analytical Chemistry, 2018Co-Authors: Ansgar T. Kirk, Denise Grube, Tim Kobelt, Cornelius Wendt, Stefan ZimmermannAbstract:High Kinetic Energy ion mobility spectrometry (HiKE-IMS) allows for sensitive trace gas analysis within seconds, mitigating many disadvantages of standard ion mobility spectrometers through operation at reduced pressure and High electric field strengths. However, these advantages usually come at the cost of reduced resolving power, ranging from a maximum of 75 down to 50 at a reduced field strength of 120 Td for the original device. In this work, we present an extended theory for HiKE-IMS resolving power and a novel tristate ion shutter principle able to achieve initial ion packet widths of 1 μs without significant mobility discrimination. Such an ultrashort injection time allows for improving the resolving power of the HiKE-IMS to 140 for a wide range of reduced electric field strengths. With this resolving power, separating all ion species generated from a mixture of benzene, toluene, and xylene is possible. Furthermore, a resolving power of 140 is sufficient to partially separate isotopologues under hi...
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High resolution High Kinetic Energy ion mobility spectrometer based on a low discrimination tristate ion shutter
Analytical Chemistry, 2018Co-Authors: Ansgar T. Kirk, Denise Grube, Tim Kobelt, Cornelius Wendt, Stefan ZimmermannAbstract:High Kinetic Energy ion mobility spectrometry (HiKE-IMS) allows for sensitive trace gas analysis within seconds, mitigating many disadvantages of standard ion mobility spectrometers through operation at reduced pressure and High electric field strengths. However, these advantages usually come at the cost of reduced resolving power, ranging from a maximum of 75 down to 50 at a reduced field strength of 120 Td for the original device. In this work, we present an extended theory for HiKE-IMS resolving power and a novel tristate ion shutter principle able to achieve initial ion packet widths of 1 μs without significant mobility discrimination. Such an ultrashort injection time allows for improving the resolving power of the HiKE-IMS to 140 for a wide range of reduced electric field strengths. With this resolving power, separating all ion species generated from a mixture of benzene, toluene, and xylene is possible. Furthermore, a resolving power of 140 is sufficient to partially separate isotopologues under High electric field strengths.
Maria Allers - One of the best experts on this subject based on the ideXlab platform.
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Formation of positive product ions from substances with low proton affinity in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Rapid Communications in Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Florian Schlottmann, Stefan ZimmermannAbstract:RATIONALE Ion mobility spectrometer are typically equipped with atmospheric pressure chemical ionization (APCI) sources operated at ambient pressure. However, classical APCI ion mobility spectrometers suffer from a limited ionization yield for nonpolar substances with low proton affinity. This is mainly due to ion clustering processes, especially those that involve water molecules, inhibiting the ionization of these substances. METHODS High Kinetic Energy (Hike) Ion Mobility Spectrometers are operated at decreased pressures and High reduced electric field strengths. As most clustering reactions are inhibited under these conditions, the ionization yield for nonpolar substances with low proton affinity in HiKE-ion mobility spectrometry (IMS) should differ from that in classical APCI-IMS. In order to gain first insights into the ionization capabilities and limitation of HiKE-IMS, we investigated the ionization of four model substances with low proton affinity in HiKE-IMS by HiKE-IMS-MS as a function of the reduced electric field strength. RESULTS The four model substances all have proton affinities between those of H2 O and (H2 O)2 but exhibit different ionization energies, dipole moments and polarizabilities. As expected, the results show that the ionization yield for these substances differs considerably at low reduced electric field strengths due to ion cluster formation. In contrast, at High reduced electric field strengths, all substances can be ionized via charge and/or proton transfer in HiKE-IMS. CONCLUSIONS Considering the detection of polar substances with High proton affinity, classical ambient pressure IMS should reach better detection limits than HiKE-IMS. However, considering the detection of nonpolar substances with low proton affinity that are not detected, or only difficult to detect, at ambient pressure, HiKE-IMS would be beneficial.
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Ion Mobility Shift of Isotopologues in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at Elevated Effective Temperatures.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Christoph Schaefer, Maria Allers, Ansgar T. Kirk, Stefan ZimmermannAbstract:Ion mobility spectrometers (IMS) separate ions mainly by ion-neutral collision cross section and to a lesser extent by ion mass and effective temperature. When investigating isotopologues, the diff...
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Field-Dependent Reduced Ion Mobilities of Positive and Negative Ions in Air and Nitrogen in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Christoph Schaefer, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Stefan ZimmermannAbstract:In High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS), ions are formed in a reaction region and separated in a drift region, which is similar to classical drift tube ion mobility spectrometers (IMS) operated at ambient pressure. However, in contrast to the latter, the HiKE-IMS is operated at a decreased background pressure of 10-40 mbar and achieves High reduced electric field strengths of up to 120 Td in both the reaction and the drift region. Thus, the HiKE-IMS allows insights into the chemical Kinetics of ion-bound water cluster systems at effective ion temperatures exceeding 1000 K, although it is operated at the low absolute temperature of 45 °C. In this work, a HiKE-IMS with a High resolving power of RP = 140 is used to study the dependence of reduced ion mobilities on the drift gas humidity and the effective ion temperature for the positive reactant ions H3O+(H2O)n, O2+(H2O)n, NO+(H2O)n, NO2+(H2O)n, and NH4+(H2O)n, as well as the negative reactant ions O2-(H2O)n, O3-(H2O)n, CO3-(H2O)n, HCO3-(H2O)n, and NO2-(H2O)n. By varying the reduced electric field strength in the drift region, cluster transitions are observed in the ion mobility spectra. This is demonstrated for the cluster systems H3O+(H2O)n and NO+(H2O)n.
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Negative Reactant Ion Formation in High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS).
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Maria Allers, Ansgar T. Kirk, Duygu Erdogdu, Walter Wissdorf, Thorsten Benter, Bennet Timke, Stefan ZimmermannAbstract:Due to the operation at background pressures between 10-40 mbar and High reduced electric field strengths of up to 120 Td, the ion-molecule reactions in High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) differ from those in classical ambient pressure IMS. In the positive ion polarity mode, the reactant ions H+(H2O)n, O2+(H2O)n, and NO+(H2O)n are observed in the HiKE-IMS. The relative abundances of these reactant ion species significantly depend on the reduced electric field strength in the reaction region, the operating pressure, and the water concentration in the reaction region. In this work, the formation of negative reactant ions in HiKE-IMS is investigated in detail. On the basis of Kinetic and thermodynamic data from the literature, the processes resulting in the formation of negative reactant ions are Kinetically modeled. To verify the model, we present measurements of the negative reactant ion population in the HiKE-IMS and its dependence on the reduced electric field strength as well as the water and carbon dioxide concentrations in the reaction region. The ion species underlying individual peaks in the ion mobility spectrum are identified by coupling the HiKE-IMS to a time-of-flight mass spectrometer (TOF-MS) using a simple gated interface that enables the transfer of selected peaks of the ion mobility spectrum into the TOF-MS. Both the theoretical model as well as the experimental data suggest the predominant generation of the oxygen-based ions O-, OH-, O2-, and O3- in purified air containing 70 ppmv of water and 30 ppmv of carbon dioxide. Additionally, small amounts of NO2- and CO3- are observed. Their relative abundances Highly depend on the reduced electric field strength as well as the water and carbon dioxide concentration. An increase of the water concentration in the reaction region results in the generation of OH- ions, whereas increasing the carbon dioxide concentration favors the generation of CO3- ions, as expected.
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High Kinetic Energy Ion Mobility Spectrometry (HiKE-IMS) at 40 mbar.
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Florian Schlottmann, Maria Allers, Ansgar T. Kirk, Alexander Bohnhorst, Stefan ZimmermannAbstract:High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at an absolute pressure of 20 mbar reaching High reduced electric field strengths of up to 125 Td for controlled reaction Kinetics. This significantly increases the linear range and limits chemical cross sensitivities. Furthermore, HiKE-IMS enables the ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to new reaction pathways and the inhibition of clustering reactions. In addition, HiKE-IMS allows the observation of additional orthogonal parameters related to an increased ion temperature such as fragmentation and field-dependent ion mobility, which may help to separate compounds that have similar ion mobility under low field conditions. Aiming for a hand-held HiKE-IMS to carry its benefits into field applications, reducing size and power consumption of the vacuum system is necessary. In this work, we present a novel HiKE-IMS design entirely manufactured from standard printed circuit boards (PCB) and experimentally investigate the analytical performance in dependence of the operating pressure between 20 mbar and 40 mbar. Hereby, the limit of detection (LoD) for benzene in purified, dry air (1.4 ppmV water) improved from 7 ppbV at 20 mbar down to 1.8 ppbV at 40 mbar. Furthermore, adding 0.9 ppmV toluene, the signal of the benzene B+ peak decreased by only 2% at 40 mbar. Even in the presence of High relative humidity in the sample gas above 90% or toluene concentrations of up to 20 ppmV, the LoD for benzene just increased to 9 ppbV at 40 mbar.
Mihaela Gorgoi - One of the best experts on this subject based on the ideXlab platform.
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Relative sub-shell photoionization cross-sections of nickel metal determined by hard X-ray High Kinetic Energy photoemission
Journal of Electron Spectroscopy and Related Phenomena, 2013Co-Authors: Mihaela Gorgoi, Sören Svensson, Franz Schäfers, Nils MårtenssonAbstract:Recently, hard X-ray High Kinetic Energy photoelectron spectroscopy has lead to a break-through due to its non destructive way of investigating the bulk electronic properties of materials. However, ...
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Quantifying the Metal Nickel Enrichment on Stainless Steel
Electrochemical and Solid-State Letters, 2011Co-Authors: C. Oa. Olsson, Mihaela Gorgoi, Sara Malmgren, Kristina EdströmAbstract:Enrichment in metallic nickel below the passive film on a stainless steel was quantified using the novel High Kinetic Energy Photo-Electron Spectroscopy technique. Two surfaces were tested: one pas ...
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Understanding interface properties from High Kinetic Energy photoelectron spectroscopy and first principles theory
Journal of Electron Spectroscopy and Related Phenomena, 2010Co-Authors: Sari Granroth, Weine Olovsson, Erik Holmström, Ronny Knut, Mihaela Gorgoi, Svante Svensson, Olof KarisAbstract:Advances in instrumentation regarding 3rd generation synchrotron light sources and electron spectrometers has enabled the field of High Kinetic Energy photoelectron spectroscopy (HIKE) (also often ...
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Investigation of interface properties of Ni/Cu multilayers by High Kinetic Energy photoelectron spectroscopy
Physical Review B, 2009Co-Authors: Sari Granroth, Ronny Knut, Mihaela Gorgoi, Svante Svensson, Olof Karis, Franz Schäfers, W. Braun, Moreno Marcellini, Gabriella Andersson, Wolfgang EberhardtAbstract:High Kinetic-Energy photoelectron spectroscopy (HIKE) or hard x-ray photoelectron spectroscopy has been used to investigate the alloying of Ni/Cu (100) multilayers. Relative intensities of the corelevels and their chemical shifts derived from binding Energy changes are shown to give precise information on physicochemical properties and quality of the buried layers. Interface roughening, including Kinetic properties such as the rate of alloying, and temperature effects on the processes can be analyzed quantitatively. Using HIKE, we have been able to precisely follow the deterioration of the multilayer structure at the atomic scale and observe the diffusion of the capping layer into the multilayer structure which in turn is found to lead to a segregation in the ternary system. This is of great importance for future research on multilayered systems of this kind. Our experimental data are supplemented by first-principles theoretical calculations of the core-level shifts for a ternary alloy to allow for modeling of the influence of capping materials on the chemical shifts. (Less)
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Hard X-ray High Kinetic Energy photoelectron spectroscopy at the KMC-1 beamline at BESSY
The European Physical Journal Special Topics, 2009Co-Authors: Mihaela Gorgoi, Sören Svensson, Franz Schäfers, W. Braun, Wolfgang EberhardtAbstract:Photoelectron spectroscopy at High Kinetic Energy is a research field that receives an increasing interest due to the possibility of studying bulk properties of materials and deeply buried interfaces. Recently, the hard x-ray High Kinetic Energy electron spectroscopy facility (HIKE) at BESSY in Berlin has become operative at the bending magnet beamline KMC-1. First results show excellent performance. Electron spectra have been recorded using x-ray energies continuously tunable between 2 keV and 12 keV. Using back-scattering conditions in the crystal monochromator very High resolution has been achieved for photon energies around 2 keV, 6 keV and 8 keV.