Desmond Allen Kaplan Improvements to the Analytical Performance of Ion Trap Mass Spectrometry (Un... more Desmond Allen Kaplan Improvements to the Analytical Performance of Ion Trap Mass Spectrometry (Under the direction of Professor Gary L. Glish) Mass spectrometry is a powerful analytical technique that is capable of a wide range of chemical and biological analyses. The quadrupole ion trap mass spectrometer (QITMS) is known for its ruggedness, sensitivity, and high efficiency for tandem mass spectrometry (MS/MS) experiments. Non-idealities in electrode geometry result in small contributions of higher order fields (HOFs) to the primary quadrupolar electric field of the ion trap. These HOFs have been useful in enhancing the resolution, MS/MS efficiency, and sensitivity in the QITMS. A portion of the work presented in this dissertation is intended to serve as a basis for improved ion trap performance through the judicious use of HOFs. Development of rf circuitry and characterization of a compensated cylindrical ion trap (CCIT) mass spectrometer, designed for studying the effects of HOFs,...
The Bruker maXisTM is equipped with a nCI-source and a hexapolar ETD reaction cell. ETD Reagent a... more The Bruker maXisTM is equipped with a nCI-source and a hexapolar ETD reaction cell. ETD Reagent anion and analyte ions were mass selectively transmitted through a mass resolving quadrupole. ETD reactions are performed in the reaction cell following the quadrupole, where the ions of different polarity are mutually stored. The ETD experiment (performed in trapping mode) consists of four steps: cation accumulation, anion accumulation, extension of the ETD reaction and finally the detection of the product ions in the orthogonal TOF. While ions are extracted, the next ETD experiment is performed in the reaction cell thus maximizing duty cycle.
The highly compact Linear Ion Trap Mass Spectrometer (LITMS) combines pyrolysis gas-chromatograph... more The highly compact Linear Ion Trap Mass Spectrometer (LITMS) combines pyrolysis gas-chromatography/mass spectrometry (GCMS) and Mars-ambient laser desorption mass spectrometry (LDMS) through a single, miniaturized yet highly-capable linear ion trap mass analyzer. The LITMS instrument is based substantially on the Mars Organic Molecule Analyzer - Mass Spectrometer (MOMA-MS) for the 2020 ExoMars mission but features further analytical enhancements. In addition to the core MOMA capabilities, LITMS enhances the instrument performance by including negative ion detection, a dual frequency RF power supply to increase mass range, precision subsampling of drill cores at fine (≤ 1 mm) spatial scales, and pyrolysis of powdered sample for evolved gas analysis (EGA) of organic content and mineral assemblages. LITMS enables in situ characterization of inorganics and organics in individual rock core layers and features. This level of integrated analytical capability is critical to achieve advanced astrobiology objectives on Mars and other planets.
Comprehensive characterization of post-translationally modified histone proteoforms is challengin... more Comprehensive characterization of post-translationally modified histone proteoforms is challenging due to their high isobaric and isomeric content. Trapped ion mobility spectrometry (TIMS), implemented on a quadrupole/time-of-flight (Q-ToF) mass spectrometer, has shown great promise in discriminating isomeric complete histone tails. The absence of electron activated dissociation (ExD) in the current platform prevents the comprehensive characterization of unknown histone proteoforms. In the present work, we report for the first time the use of an electromagnetostatic (EMS) cell devised for nonergodic dissociation based on electron capture dissociation (ECD), implemented within a nESI-TIMS-Q-ToF mass spectrometer for the characterization of acetylated (AcK18 and AcK27) and trimethylated (TriMetK4, TriMetK9 and TriMetK27) complete histone tails. The integration of the EMS cell in a TIMS-q-TOF MS permitted fast mobility-selected top-down ECD fragmentation with near 10% efficiency overall. The potential of this coupling was illustrated using isobaric (AcK18/TriMetK4) and isomeric (AcK18/AcK27 and TriMetK4/TriMetK9) binary H3 histone tail mixtures, and the H3.1 TriMetK27 histone tail structural diversity (e.g., three IMS bands at z = 7+). The binary isobaric and isomeric mixtures can be separated in the mobility domain with RIMS > 100 and the nonergodic ECD fragmentation permitted the PTM localization (sequence coverage of ∼86%). Differences in the ECD patterns per mobility band of the z = 7+ H3 TriMetK27 molecular ions suggested that the charge location is responsible for the structural differences observed in the mobility domain. This coupling further enhances the structural toolbox with fast, high resolution mobility separations in tandem with nonergodic fragmentation for effective proteoform differentiation.
Abstract NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan to in... more Abstract NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan to investigate the prebiotic chemistry, habitability, and potential presence of chemical biosignatures on Saturn’s largest moon. One of the key analytical instruments onboard is the Dragonfly Mass Spectrometer (DraMS) that will perform detailed chemical analyses of the Titan surface and atmosphere. The DraMS instrument is capable of multiple analytical modalities, including Laser Desorption Mass Spectrometry (LDMS), in which DraMS primarily seeks to characterize the low volatility/refractory organic content in acquired Titan surface samples. Several key design adaptations will be needed for DraMS to meet its LDMS measurement objectives at Titan as compared to previous development efforts for similar analysis at Mars. These adaptations include an altered sample collection and delivery approach, modifications to the LDMS ion source, and performance optimization for operations with Titan atmospheric gas.
A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for ma... more A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for mass scanning is that, in order to detect a subset of an ion population, the rest of the ion population must also be interrogated. That is, ions cannot be detected out of order; they must be detected in order of either increasing or decreasing mass-to-charge (m/z). However, an ion trap operated in the ac frequency scan mode, where the rf amplitude is kept constant and instead the ac frequency is used for mass-selective operations, has no such limitation because any variation in the ac frequency affects only the subset of ions whose secular frequencies match the perturbation frequency. Hence, an ion trap operated in the ac frequency scan mode can perform any arbitrary mass scan, as well as a sequence of scans, using a single ion injection; we demonstrate both capabilities here. Combining these two capabilities, we demonstrate the acquisition of a full mass spectrum, a product ion spectrum, ...
ABSTRACT Over the last decade, a variety of new types of Ion Mobility Spectrometry (IMS) analyzer... more ABSTRACT Over the last decade, a variety of new types of Ion Mobility Spectrometry (IMS) analyzers have been developed (e.g., periodic focusing DC ion guide, segmented quadrupole drift cell, multistage IMS, field asymmetric IMS and transient wave ion guide). High resolution IMS (R>50) has been mainly restricted to long IMS cells (1-2 m), where ions are separated based on size-to-charge ratio as they are pushed by an electric field through a stationary bath gas. In the present work we describe a Trapped Ion Mobility Spectrometer (TIMS) and its applications. In as much as TIMS uses an electric field to hold ions stationary in a moving bath gas, it represents a paradigm shift in mobility analysis. This results in an analyzer capable of high resolution mobility separations (R>80) in a compact (< 10 cm), low voltage (< 300 V) design. Hybridization with a mass analyser (TIMS-MS) provides versatility for the analysis, separation and structural characterization of a variety of chemical compounds with increasing complexity. In particular, examples of TIMS -- MS separation for complex biological and heteroatom hydrocarbons will be shown.
Desmond Allen Kaplan Improvements to the Analytical Performance of Ion Trap Mass Spectrometry (Un... more Desmond Allen Kaplan Improvements to the Analytical Performance of Ion Trap Mass Spectrometry (Under the direction of Professor Gary L. Glish) Mass spectrometry is a powerful analytical technique that is capable of a wide range of chemical and biological analyses. The quadrupole ion trap mass spectrometer (QITMS) is known for its ruggedness, sensitivity, and high efficiency for tandem mass spectrometry (MS/MS) experiments. Non-idealities in electrode geometry result in small contributions of higher order fields (HOFs) to the primary quadrupolar electric field of the ion trap. These HOFs have been useful in enhancing the resolution, MS/MS efficiency, and sensitivity in the QITMS. A portion of the work presented in this dissertation is intended to serve as a basis for improved ion trap performance through the judicious use of HOFs. Development of rf circuitry and characterization of a compensated cylindrical ion trap (CCIT) mass spectrometer, designed for studying the effects of HOFs,...
The Bruker maXisTM is equipped with a nCI-source and a hexapolar ETD reaction cell. ETD Reagent a... more The Bruker maXisTM is equipped with a nCI-source and a hexapolar ETD reaction cell. ETD Reagent anion and analyte ions were mass selectively transmitted through a mass resolving quadrupole. ETD reactions are performed in the reaction cell following the quadrupole, where the ions of different polarity are mutually stored. The ETD experiment (performed in trapping mode) consists of four steps: cation accumulation, anion accumulation, extension of the ETD reaction and finally the detection of the product ions in the orthogonal TOF. While ions are extracted, the next ETD experiment is performed in the reaction cell thus maximizing duty cycle.
The highly compact Linear Ion Trap Mass Spectrometer (LITMS) combines pyrolysis gas-chromatograph... more The highly compact Linear Ion Trap Mass Spectrometer (LITMS) combines pyrolysis gas-chromatography/mass spectrometry (GCMS) and Mars-ambient laser desorption mass spectrometry (LDMS) through a single, miniaturized yet highly-capable linear ion trap mass analyzer. The LITMS instrument is based substantially on the Mars Organic Molecule Analyzer - Mass Spectrometer (MOMA-MS) for the 2020 ExoMars mission but features further analytical enhancements. In addition to the core MOMA capabilities, LITMS enhances the instrument performance by including negative ion detection, a dual frequency RF power supply to increase mass range, precision subsampling of drill cores at fine (≤ 1 mm) spatial scales, and pyrolysis of powdered sample for evolved gas analysis (EGA) of organic content and mineral assemblages. LITMS enables in situ characterization of inorganics and organics in individual rock core layers and features. This level of integrated analytical capability is critical to achieve advanced astrobiology objectives on Mars and other planets.
Comprehensive characterization of post-translationally modified histone proteoforms is challengin... more Comprehensive characterization of post-translationally modified histone proteoforms is challenging due to their high isobaric and isomeric content. Trapped ion mobility spectrometry (TIMS), implemented on a quadrupole/time-of-flight (Q-ToF) mass spectrometer, has shown great promise in discriminating isomeric complete histone tails. The absence of electron activated dissociation (ExD) in the current platform prevents the comprehensive characterization of unknown histone proteoforms. In the present work, we report for the first time the use of an electromagnetostatic (EMS) cell devised for nonergodic dissociation based on electron capture dissociation (ECD), implemented within a nESI-TIMS-Q-ToF mass spectrometer for the characterization of acetylated (AcK18 and AcK27) and trimethylated (TriMetK4, TriMetK9 and TriMetK27) complete histone tails. The integration of the EMS cell in a TIMS-q-TOF MS permitted fast mobility-selected top-down ECD fragmentation with near 10% efficiency overall. The potential of this coupling was illustrated using isobaric (AcK18/TriMetK4) and isomeric (AcK18/AcK27 and TriMetK4/TriMetK9) binary H3 histone tail mixtures, and the H3.1 TriMetK27 histone tail structural diversity (e.g., three IMS bands at z = 7+). The binary isobaric and isomeric mixtures can be separated in the mobility domain with RIMS > 100 and the nonergodic ECD fragmentation permitted the PTM localization (sequence coverage of ∼86%). Differences in the ECD patterns per mobility band of the z = 7+ H3 TriMetK27 molecular ions suggested that the charge location is responsible for the structural differences observed in the mobility domain. This coupling further enhances the structural toolbox with fast, high resolution mobility separations in tandem with nonergodic fragmentation for effective proteoform differentiation.
Abstract NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan to in... more Abstract NASA's Dragonfly mission will send a rotorcraft lander to the surface of Titan to investigate the prebiotic chemistry, habitability, and potential presence of chemical biosignatures on Saturn’s largest moon. One of the key analytical instruments onboard is the Dragonfly Mass Spectrometer (DraMS) that will perform detailed chemical analyses of the Titan surface and atmosphere. The DraMS instrument is capable of multiple analytical modalities, including Laser Desorption Mass Spectrometry (LDMS), in which DraMS primarily seeks to characterize the low volatility/refractory organic content in acquired Titan surface samples. Several key design adaptations will be needed for DraMS to meet its LDMS measurement objectives at Titan as compared to previous development efforts for similar analysis at Mars. These adaptations include an altered sample collection and delivery approach, modifications to the LDMS ion source, and performance optimization for operations with Titan atmospheric gas.
A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for ma... more A limitation of conventional quadrupole ion trap scan modes which use rf amplitude control for mass scanning is that, in order to detect a subset of an ion population, the rest of the ion population must also be interrogated. That is, ions cannot be detected out of order; they must be detected in order of either increasing or decreasing mass-to-charge (m/z). However, an ion trap operated in the ac frequency scan mode, where the rf amplitude is kept constant and instead the ac frequency is used for mass-selective operations, has no such limitation because any variation in the ac frequency affects only the subset of ions whose secular frequencies match the perturbation frequency. Hence, an ion trap operated in the ac frequency scan mode can perform any arbitrary mass scan, as well as a sequence of scans, using a single ion injection; we demonstrate both capabilities here. Combining these two capabilities, we demonstrate the acquisition of a full mass spectrum, a product ion spectrum, ...
ABSTRACT Over the last decade, a variety of new types of Ion Mobility Spectrometry (IMS) analyzer... more ABSTRACT Over the last decade, a variety of new types of Ion Mobility Spectrometry (IMS) analyzers have been developed (e.g., periodic focusing DC ion guide, segmented quadrupole drift cell, multistage IMS, field asymmetric IMS and transient wave ion guide). High resolution IMS (R>50) has been mainly restricted to long IMS cells (1-2 m), where ions are separated based on size-to-charge ratio as they are pushed by an electric field through a stationary bath gas. In the present work we describe a Trapped Ion Mobility Spectrometer (TIMS) and its applications. In as much as TIMS uses an electric field to hold ions stationary in a moving bath gas, it represents a paradigm shift in mobility analysis. This results in an analyzer capable of high resolution mobility separations (R>80) in a compact (< 10 cm), low voltage (< 300 V) design. Hybridization with a mass analyser (TIMS-MS) provides versatility for the analysis, separation and structural characterization of a variety of chemical compounds with increasing complexity. In particular, examples of TIMS -- MS separation for complex biological and heteroatom hydrocarbons will be shown.
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Papers by Desmond Kaplan