Types of Ions Produced

Mostly, positive-ion FAB yields protonated quasi-molecular ions [M -l- H], and the negative-ion mode yields [M - H]. In the presence of metal salts (e.g., KCl) that are sometimes added to improve efficiency in the LC column, ions of the type [M -t- XJ- are common, where X is the metal. Another type of ion that is observed is the so-called cluster, a complex of several molecules with one proton, [M + H]+ with n = 1, 2, 3,. .., etc. Few fragment ions are produced. 

By passing a continuous flow of solvent (admixed with a matrix material) from an LC column to a target area on the end of a probe tip and then bombarding the target with fast atoms or ions, secondary positive or negative ions are ejected from the surface of the liquid. These ions are then extracted into the analyzer of amass spectrometer for measurement of a mass spectrum. As mixture components emerge from the LC column, their mass spectra are obtained. 

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Ionization chambers combined with mass spectrometers permit determination of the types of ions produced at definite voltages138. Molecular ions produced by electron bombardment... 

With 0.0200 mol of acid and 0.0216 mol of particles (un-ionized acid molecules, hydronium ions, and anions), the increase in concentration corresponds to the number of each type of ion produced, since two ions are produced from each molecule. There is 0.0016 mol/L of HA ionized, as seen in the following table ... 

Table 12.1 provided an indication of the methods used in the analysis of each type of surfactant. Sections 12.6.3-12.6.9 describe the types of ion produced by typical members of each surfactant type in the appropriate... 

Because of its overwhelming importance in mass spectrometry, only El (and, to a lesser extent, PI) will be treated here. We will consider the ionization mechanism, the various types of ions produced and the kinetics and dynamics of the ionization process and subsequent fragmentation reactions. 

There are two common occasions when rapid measurement is preferable. The first is with ionization sources using laser desorption or radionuclides. A pulse of ions is produced in a very short interval of time, often of the order of a few nanoseconds. If the mass spectrometer takes 1 sec to attempt to scan the range of ions produced, then clearly there will be no ions left by the time the scan has completed more than a few nanoseconds (ion traps excluded). If a point ion detector were to be used for this type of pulsed ionization, then after the beginning of the scan no more ions would reach the collector because there would not be any left The array collector overcomes this difficulty by detecting the ions produced all at the same instant. 

Another type of ion gun produces positive ions from a liquid metal (almost always gallium) in the manner shown schematically in Fig. 3.2 [3.7]. A fine needle (f tip radius 5 pm) of refractory metal passes through a capillary tube (d) into a reservoir of liquid metal (e). The liquid is drawn up through the tube over the needle tip by capil-... 

New types of ion exchange resins have also been developed to meet the specific needs of high-performance liquid chromatography (HPLC) (Chapter 8). These include pellicular resins and microparticle packings (e.g. the Aminex-type resins produced by Bio-Rad). A review of the care, use and application of the various ion exchange packings available for HPLC is given in Ref. 19. 

When a salt dissolves in water, it produces cations and anions. Lead(II) nitrate and potassium iodide are soluble salts. Lead(II) nitrate dissolves in water to generate Pb cations and NO3 anions. Potassium iodide dissolves in water to generate K and I ions. Mixing the solutions combines all four types of ions. A precipitate forms if any of the new combinations of the ions forms a salt that is insoluble in water. The new combinations when these two solutions mix are K combining with NO3 or Pb combining with I ... 

The volatility of ammonia can be significantly affected by high concentrations of dissolved ions in the liquid phase. Unfortunately the effect varies depending on the types of ions in solution. Sodium acetate produces a... 

Smoke detector Senses invisible and/or visible products of combustion. The two principal types of smoke detector are photoelectric and ionization detectors. The major differences between these devices are described below Photoelectric smoke detectors react to visible particles of smoke. These detectors are more sensitive to the cooler smoke with large smoke particles that is typical of smoldering fires. Ionization smoke detectors are sensitive to the presence of ions produced by the chemical reactions that take place with few smoke particles, such as those typically produced by fast-burning/flaming fi res. 

FAB produces a variety of ions depending on the polarity and on the ionization energy of the analyte as well as on the presence or absence of impurities such as alkali metal ions. [138] However, with some knowledge of the types of ions formed, reasonable compositions can be assigned to the signals (Table 9.1). 

A different direction in ion-selective electrode research is based on experiments with antibiotics that uncouple oxidative phosphorylation in mitochondria [59]. These substances act as ion carriers (ionophores) and produce ion-specific potentials at bilayer lipid membranes [72]. This function led Stefanac and Simon to obtain a new type of ion-selective electrode for alkali metal ions [92] and is also important in supporting the chemi-osmotic theory of oxidative phosphorylation [69]. The range of ionophores, in view of their selectivity for other ions, was broadened by new synthetic substances [1,61]. 

The photoelectron retains most of the energy of the incident photon and itself produces further ionizations. It produces many more H20 +, /e" pairs in losing its energy. The excess of energy possessed by the electrons so produced is used in such further ionizations until the electrons become thermalized, i.e. they have translational energies typical of the temperature of the bulk medium. Both types of ion become hydrated by interaction with the water solvent ... 

Two types of ion source produce high enough brightness (> 106 A/cm2.ster., 20 keV) for them to be considered for semiconductor fabrication applications the field ion source (56) and the liquid metal source (57,58). The field ion source produces relatively small energy spread (<3 eV) and when combined with a short focal length (< 1 cm) electrostatic focusing system should be able to produce beam sizes as small as 10 nm with adequate current (10-11 amp) for laboratory microfabrication experiments. As with field emission electron sources, the field ion source only produces a limited total current and the maximum beam current is limited to about 1 10 amp. 

These are not the only types of tandem mass spectrometers. There are numerous configurations of instruments that are based on the type of ion separation and many new terms associated with these instrument types. For example, there are instruments known as ion traps. The ion trap is a device that can measure mass, fragment a selected mass (as could be done in a collision cell) and then measure the mass of the fragment. The product ion produced by this all in one device is the same product ion that would be produced in a tandem quadrupole instrument. However, there is only one mass analyzer that functions as both the collision cell and mass measuring device. These types of instruments are sometimes referred to as tandem mass spectrometers, but are not abbreviated as MS/MS. The MS/MS analysis is done by separating the analysis in time (tandem in time) rather than two devices separated in space. A more generic term is best suited. This term is MS , where the n represents... 

Improvements in solid mass spectrometry after the Second World War focused on the development of several types of ion source and mass analyzers. For example, the fundamentals of secondary ion mass spectrometry had already been described by the observation of secondary ions by Thomson in 1910 5 T had the occasion.. . to investigate the secondary Canalstrahlen produced when primary Canalstrahlen strike against a metal plate. Significantly later in 1949, the first instrumental arrangement for secondary ion mass spectrometric measurements was reported by Herzog and Viehbock.43 The idea of applying secondary ions for surface analysis was developed in 1950 at the RCA Laboratories, Princeton, where Honig44 presented results of early SIMS studies. 

For a d1 ion in a tetrahedral environment, exactly the same procedure can be carried out. The free ion states will be the same as in the octahedral case. The type of states produced from a particular free-ion... 

Basically, the relative volatility of the components in sea water or saline waters is reversed by this type of ion exchange. Thus, the 3.5% of ordinarily nonvolatile salts present in sea water are made volatile by substituting for them a volatile salt such as one of the ammonium carbonates. This substitution puts distillation in an entirely different light The minor component is now to be distilled away from the major component, water, which should reduce the amount of distillation to be done per unit quantity of water produced by manyfold compared to distillation (or evaporation) processes in which all of the recovered water must be distilled. 

Mass spectrometric techniques are based on the measurement or counting of ions produced at high temperatures. An ion can be identified on the basis of its mass-to-charge ratio (m/z), characteristic of a certain isotope. In addition, quantification is based on the dependence between the number of ions and the concentration of a given isotope in the sample. Mass spectrometers consist of an ion source, a mass analyzer, and an ion detector. The ion source is typically the basis for the different types of mass spectrometric techniques. Plasmas are the most common ion sources for Mass spectrometric elemental determinations, and it is mass spectrometry (MS) using this ion source that will now be described. Complete details of this technique can be found in published monographs.29,30... 

Ion scattering spectrometry and secondary ion mass spectrometry are the best-known types of ion-beam-induced analyses applicable to catalysis. Other ion-beam techniques have not enjoyed wide use, probably because accelerators are required to produce sufficiently energetic ion beams. 

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