Indiana University-Purdue University Indianapolis (IUPUI) / Ion Mobility Spectrometry (IMS) is an analytical technique for separation of charged particles in the gas phase. The history of IMS is not very old, and in this century, the IMS technique has grown rapidly in the advent of modern instruments. Among currently available ion mobility spectrometers, the DTIMS, FAIMS, TWIMS, DMA are notable. Though all the IMS systems have some uniqueness in case of particle separation and detection, however, all instruments have common shortcomings. They lack in resolution, which is independent of mobility of different charged particles and they are not able to separate bigger particles (20 120 nm) with good accuracy. The work presented here demonstrates a new concept of IMS technique at atmospheric pressure which has a resolution much higher than that of the currently available DTIMS (Drift Tube Ion Mobility Spectrometry) instruments. The unique feature of this instrument is the diffusion auto-correction. Being tunable, It can separate the wide range of particles of different diameters. The working principle of this new IMS technique is different from the typical DTIMS and to simply put, it can be considered as an inversion of commonly used technique, so termed as Inverted Drift Tube (IDT).The whole work performed here can be divided into three major phases. In the first phase, the analytical solution was derived for two new separation techniques: IPF (Intermittent push flow) and NSP (Nearly stopping potential) separations. In the next phase, simulations were done to show the accuracy of the analytical solution. An ion optics simulator software called SIMION 8.1 was used for conducting the simulation works. These simulations adopted the statistical diffusion (SDS) collision algorithm to emulate the real scenario in gas phase more precisely. In the last phase, a prototype of experimental setup was built. The experimental results were then validated by simulated results.

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<p>Advancements in 3D printing technology have provided (1) easy access to low-cost, open- source robotics, and (2) a fast fabrication technique for analytical devices among others. Using the robotics of a 3D printer, a mass spectrometry-based reaction screening device was built as a low- cost, modest throughput alternative to expensive, very fast systems. Using the 3D printer for fabrication, ion mobility devices were fabricated. Fundamental studies of the motion of ions in these devices were performed in addition to applications of ion mobility-mass spectrometry using a 3D printed drift tube ion mobility spectrometer.</p><p><br></p><p>With only simple modification, 3D printer kits provide nearly all the necessary parts for a functional reaction screening device. Replacing the hotend assembly with custom parts to hold a syringe, precise volumes of reaction mixtures can be dispensed, and high voltage applied to the needle for direct analysis of solutions by mass spectrometry. Direct analysis of reaction mixtures in a 96-well microtiter plates was completed in approximately 105 minutes (~65 seconds per reaction mixture, including washing of syringe). Following analysis, product distributions derived from the electrospray mass spectra were represented as heatmaps and optimum reaction conditions were determined. Using low-cost, open-source hardware, a modest throughput for reaction screening could be achieved using electrospray ionization mass spectrometry.</p><p><br></p><p>The manipulation of ions at reduced pressures is very well understood, whereas the efficient manipulation of ions at atmospheric pressure is far less understood. Using 3D printing, multiple iterations of atmospheric pressure drift tube ion mobility spectrometers were fabricated with one and two turns in the drift path. Optimum electrode geometries for ion transmission and resolution were determined by both simulation and experiment. Racetrack effects, where ions on the inside of turns have a shorter path than ions on the outside, were determined to be highly detrimental to resolving power. Drift tubes with two turns in opposite directions (a chicane) corrected for racetrack effects and had only marginally poorer resolving power than a straight drift tube. Additionally, ion intensities were nearly identical between optimized straight and turned ion paths, showing that these manipulations can be done with high efficiency. The focusing of ions at reduced pressure using RF ion funnels at reduced pressure can have nearly 100 percent transmission. At atmospheric pressure, RF fields are not nearly as efficient at focusing ions. By using non-uniform DC fields at atmospheric pressure, ions can be focused, but not nearly to the extent as at reduced pressure.</p><p><br></p><div><div><div><p>The coupling of atmospheric pressure drift tube ion mobility with ion trap mass spectrometry is inefficient due to the mismatch in duty cycle between the two instruments. For this reason, increasing the amount of data collected from a single experiment is of high importance. Fourier transform ion mobility increases the duty cycle from less than 1% to 25%. When ions are fragmented in the mass spectrometer, they maintain the frequency characteristic of the precursor. Therefore, ions can be fragmented without isolation in the ion trap (reducing duty cycle further) and related precursors and product ions identified through their drift time. Two-dimensional tandem mass spectrometry is a method to collect all tandem mass spectrometry information in a single scan. When coupled with ion mobility, this data can be used to generate functional group- specific ion mobility spectra where ion intensity is measured along a precursor or neutral loss scan line. This was demonstrated for a lipid sample in which head-group specific ion mobility spectra were obtained using head-group specific precursor and neutral loss scan lines.</p></div></div></div>

A cryogenic (325-80 K) ion mobility-mass spectrometer was designed and constructed in order to improve the analytical figures-of-merit for the chemical analysis of small mass analytes using ion mobility-mass spectrometry. The instrument incorporates an electron ionization source, a quadrupole mass spectrometer, a uniform field drift cell spectrometer encased in a cryogenic envelope, and an orthogonal geometry time-of-flight mass spectrometer. The analytical benefits of low temperature ion mobility are discussed in terms of enhanced separation ability, ion selectivity and sensitivity. The distinction between resolving power and resolution for ion mobility is also discussed. Detailed experimental designs and rationales are provided for each instrument component. Tuning and calibration data and methods are also provided for the technique. Proof-of-concept experiments for an array of analytes including rare gases (argon, krypton, xenon), hydrocarbons (acetone, ethylene glycol, methanol), and halides (carbon tetrachloride) are provided in order to demonstrate the advantages and limitations of the instrument for obtaining analytically useful information. Trendline partitioning of small analyte ions based on chemical composition is demonstrated as a novel chemical analysis method. The utility of mobility-mass analysis for mass selected ions is also demonstrated, particularly for probing the ion chemistry which occurs in the drift tube for small mass ions. As a final demonstration of the separation abilities of the instrument, the electronic states of chromium and titanium (ground and excited) are separated with low temperature. The transition metal electronic state separations demonstrated here are at the highest resolution ever obtained for ion mobility methods. The electronic conformational mass isomers of methanol (conventional and distonic) are also partially separated at low temperature. Various drift gases (helium, neon, and argon) are explored for the methanol system in order to probe stronger ion-neutral interaction potentials and effectuate higher resolution separations of the two isomeric ions. Finally, two versatile ion source designs and a method for axially focusing ions at low pressure (1-10 torr) using electrostatic fields is presented along with some preliminary work on the ion sources.

This thesis describes development of the new selected ion flow-drift tube mass spectrometry technique, SIFDT-MS, for online quantification of volatile organic compounds, VOCs, based on gas phase ion-molecule reactions. SIFDT-MS represents a new generation of the successfully used selected ion flow tube, SIFT- MS, analytical method. The essential extension of SIFDT-MS is the uniform electric field E applied across the flow tube reactor, thus converting it to the flow-drift tube where the ion processes can be governed by strength of field E. Newly introduces Hadamard modulation of the gate lens before the flow-drift tube enables direct ion residence, and correspondently ion-molecule reaction, time measurement that is necessary for the precise concentration calculations under variable conditions. The detailed experimental study of these processes results was carried out to form a basis of the analytical method. In order to overcome a well-known issue of SIFT-MS, when mass spectral peaks of isobaric ions overlap, the pseudoinverse matrix multiplication for isobaric mixtures was demonstrated. Finally two data mining approaches were successfully tested on the data of the fragmentation signals of seven monoterpene isomers obtained in SIFT-MS.

<p dir="ltr">The field of nanoclusters includes a broad range of sizes and structures that influence both their physical and chemical properties. Scientists use several techniques, such as atom-by-atom substitution, to synthesize atomically precise nanoclusters, and ligand shell mixing to protect nanoclusters from unwanted side reactions, while controlling their reactivity and solubility. These combined techniques can provide stable products, but isomers and structural analogs often remain in the product mixture, complicating the structural characterization of individual nanoclusters. Leading structural characterization techniques in nanocluster research are often limited in their ability to examine both the structure of the metal core and ligand shell in sufficient detail. The primary aim of this research is to systematically characterize the structures and chemical properties of several types of transition metal oxide nanoclusters of interest to applications in energy production, catalysis, and magnetic resonance imaging, without requiring purification. Specifically, this work focuses on 1) Polyoxovanadates (POV) with a mixture of methoxy, ethoxy, and ether ligands, 2) Fe- and W-substituted POV alkoxides, and 3) Octanuclear iron oxide clusters substituted with In atoms. Mass spectrometry techniques enable the structural characterization of individual clusters from multicomponent mixtures without interference. Specifically, we use ion mobility spectrometry to explore how surface ligands affect the metal core in mixed-ligand POV alkoxide species. We examine structure-specific fragments to identify the positions of ligands and heteroatoms within the metal core of mixed-ligand species and W and Fe-substituted POV methoxides. Additionally, we use ion soft-landing to purify W-substituted POV methoxide anions on surfaces for characterization using cyclic voltammetry and infrared spectroscopy. We discovered unique characteristics of each nanocluster including the position of heteroatoms, ligands shell mobilities, structures and collisional cross sections, and provided first insights into the redox properties of W-substituted POV alkoxide. These results highlight the growing influence of mass spectrometry in the field of nanocluster characterization and design.</p>

Les polyoxométallates (POM) sont des composés anioniques constitués par l’assemblage de polyèdres d’oxydes métalliques {MOy}, (avec M, MoVI ou WVI) reliés entre eux par des atomes d'oxygène. Les POM forment ainsi une classe remarquable de clusters d’oxydes métalliques inorganiques nanométriques, avec une grande variété de charges et de structures. Il est possible de former des systèmes hybrides incluant la partie inorganique du POM et une partie organique greffée, permettant d’apporter de nouvelles fonctionnalités aux POM, tel que l’auto-assemblage. Nous avons consacré ces travaux de thèse à la caractérisation de systèmes classiques, hybrides et auto-assemblés de POM par spectrométrie de masse couplée à la spectrométrie à la mobilité ionique (IMS-MS). Une première approche expérimentale par spectrométrie de mobilité ionique en tube de dérive (DTIMS) nous a permis de déterminer les sections efficaces de collisions (CCS) de POM étalons dans l’hélium et dans l’azote. Les CCS des étalons POM nous ont ensuite permis d’étalonner une cellule IMS de type Travelling Wave (TWIMS). L’analyse par IMS-MS de POM hybrides organiques-inorganiques seuls ou en présence de PdCl2 a mis en évidence la présence de systèmes auto-assemblés triangulaires [POM3·cation3], carrés [POM4·cation4] ou pentagonaux [POM5·cation5] avec différents états de charges. Des valeurs de CCS de ces auto-assemblages ont également pu être estimées à partir de l’étalonnage de la cellule TWIMS. Par une approche théorique, nous avons modélisé plusieurs structures de POM standards avec et sans contre-ion tetrabutylammonium (TBA+) par la théorie de la fonctionnelle de la densité (DFT). Les structures optimisées ont été utilisées afin de déterminer des CCS théoriques grâce au logiciel MOBCAL, auquel nous avons incorporé les atomes de molybdène et de tungstène pour lesquels nous avons optimisé de nouveaux paramètres de potentiel de Lennard Jones. La correspondance des CCS expérimentales et théoriques des structures de POM standards offre de nouvelles possibilités pour une attribution structurale pour les POM hybrides auto-assemblés par coordination en présence de cations métalliques. / Polyoxometalates (POM) are anionic compounds formed by the assembly of metal oxide polyhedra {MOy}, (with M, MoVI or WVI) linked together by oxygen atoms. POM thus form a remarkable class of nanometric inorganic metal oxide clusters, with a wide variety of charges and structures. It is possible to form hybrid systems including the inorganic part of the POM and a grafted organic part, allowing new functionalities to be added to the POM, such as selfassembly. We have dedicated this thesis work to the characterization of standards, hybrid and self-assembled POM systems by mass spectrometry coupled to ion mobility spectrometry (IMS-MS). A first experimental approach using drift tube ion mobility spectrometry (DTIMS) allowed us to determine the collision cross sections (CCS) of standard POM in helium and nitrogen. The CCS of the POM standards then allowed us to calibrate an IMS cell of a Travelling Wave ion mobility instrument (TWIMS). The analysis by IMS-MS of organic-inorganic hybrid POMs alone or in the presence of transition metal cations revealed the presence of self-assembled triangular [POM3·cation3], square [POM4·cation4] or pentagonal [POM5·cation5] systems with different charge states. CCS values of these self-assemblies was estimated from the calibration of the TWIMS cell. Using a theoretical approach, we modelled several standard POM structures with and without tetrabutylammonium counterion (TBA+) using density functional theory (DFT). The optimized structures were used to determine theoretical CCS using the trajectory method of the MOBCAL software, in which we incorporated molybdenum and tungsten atoms for which we optimized new Lennard Jones potential parameters. The correspondence of experimental and theoretical CCS of standard POM structures offers new possibilities for structural attribution of self-assembled hybrid POM by coordination in the presence of metal cations.