Ion mobility/mass spectroscopy

Scarff, C.A. Thalassinos, K. Hilton, G.R. Scrivens, J.H., Travelling wave ion mobility mass spectrometry studies of protein structure biological significance and comparison with X-ray crystallography and nuclear magnetic resonance spectroscopy measurements, Rapid Commun. Mass Spectmm. 2008, 22, 3297-3304. 

Most ion-molecule techniques study reactivity at pressures below 1000 Pa however, several techniques now exist for studying reactions above this pressure range. These include time-resolved, atmospheric-pressure, mass spectrometry optical spectroscopy in a pulsed discharge ion-mobility spectrometry [108] and the turbulent flow reactor [109]. 

A detailed description of sources used in atmospheric pressure ionization by electrospray or chemical ionization has been compiled.2 Atmospheric pressure has been used in a wide array of applications with electron impact, chemical ionization, pressure spray ionization (ionization when the electrode is below the threshold for corona discharge), electrospray ionization, and sonic spray ionization.3 Interferences potentially include overlap of ions of about the same mass-charge ratio, mobile-phase components, formation of adducts such as alkali metal ions, and suppression of ionization by substances more easily ionized than the analyte.4 A number of applications of mass spectroscopy are given in subsequent chapters. However, this section will serve as a brief synopsis, focusing on key techniques. 

Figure 7.31 Negative-ion thermospray mass spectrum of the disulfonated azo dye Direct Red 81 (mobile phase contains 10mmolL ammonium acetate). After Niessen [568]. Reprinted from W. Niessen, in Encyclopedia of Spectroscopy and Spectrometry (J.C. Lindon, ed.), Academic Press, pp. 2353-2360, Copyright (2000), with permission from Elsevier...

L.M. Matz and H.H. Hill Jr., Separation of benzodiazepines by electrospray ionization ion mobility spectrometry-mass spectroscopy, Anal. Chim. Acta, 457 (2002) 235-245. 

S.D. Huang, L. Kolaitis and D.M. Lubman, Detection of explosives using laser desorption in ion mobility spectrometry/mass spectrometry, AppUed Spectroscopy 41(8) (1987) 1371—1376... 

Hall effect measurements were used to investigate the electrical properties of the poly-Si films formed by the ALILE process. Due to the incorporated Al, the poly-Si films are always p-type. At room temperature, a hole concentration of 2.6 x 1018 run 3 and a hole mobility of 56.3 cm2 V 1 s 1 were determined [16]. Temperature dependent Hall measurements revealed both valence band conduction and defect band conduction (two-band conduction). For such highly doped material, the presence of a defect band conduction is expected. The Al concentration in the poly-Si films was measured by secondary ion mass spectroscopy (SIMS). An Al concentration of about 3 x 1019 cm 3 was found, which is about a factor of 10 larger than the... 

Four of the most powerful methods presently applied to elucidate metal cluster geometric structure will be presented in the following. These are mass-selected negative ion photoelectron spectroscopy, infrared vibrational spectroscopy made possible by very recent advances in free electron laser (FEL) technology, gas-phase ion chromatography (ion mobility measurements), and rf-ion trap electron diffraction of stored mass-selected cluster ions. All methods include mass-selection techniques as discussed in the previous section and efficient ion detection schemes which are customary in current gas-phase ion chemistry and physics [71]. 

Those are, for instance, known as active chemical ionization mass spectrometry (ACIMS) for atmospheric trace-gas measurements in the chemosphere, proton transfer reaction mass spectrometry (PRT-MS), selected ion flow tube mass spectrometry (SIFT-MS), ion-molectrle reaction mass spectrometry (IMR-MS), ion attachment mass spectrometry (lAMS), and ion mobility spectroscopy (IMS). Those have now become part of the exterrsive resources of experimental techniques dedicated to all the scientific fields, especially such as fundamentals of gas-phase ion kinetics and thermochentistry, physical organic chemistry, atmospheric chemistry, interstellar chemistry, plasma, and combustion chemistry, radiation chemistry, analytical chemistry, and irltimately even medicine and biology. 

Chapter 6 describes the concept of hybrid mass spectrometric system with ion attachment technique as ionization method. A combined (hypemated) MS represents time-of-flight (TOP), ion trap quadmpole, ion mobility spectroscopy, ion cyclotron resonance (ICR) or aerosol MS, while descriptions of specially designed inlet system include chromatographic introduction (inlets), and various pyrolysis probes for evolved gas analysis. Some applications of each technology are presented, together with representative and/or illustrative examples. In addition, development of portable lAMS is provided along with explanations and spectral applications. 

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