Mass spectroscopy ionization

SIMS Secondary-ion mass spectroscopy [106, 166-168] (L-SIMS liquids) [169, 170] Ionized surface atoms are ejected by impact of -1 keV ions and analyzed by mass spectroscopy Surface composition... 

Historically, measurements have classified ambient hydrocarbons in two classes methane (CH4) and all other nonmethane volatile organic compounds (NMVOCs). Analyzing hydrocarbons in the atmosphere involves a three-step process collection, separation, and quantification. Collection involves obtaining an aliquot of air, e.g., with an evacuated canister. The principal separation process is gas chromatography (GC), and the principal quantification technique is wdth a calibrated flame ionization detector (FID). Mass spectroscopy (MS) is used along with GC to identify individual hydrocarbon compounds. 

Anbar, Determination of Subprogram Amounts of Chemical Agents in the Atmosphere , Edge-woodArs Contract Rept EC-CR-74028, SRI Proj 3122 (1974) ( A method of mass spectroscopy, employing a silicone membrane and field ionization, which involves other new techniques, is presented which is sensitive to picogram amts of chemical agents in the atm)... 

Various ionization methods were used to bombard phenol-formaldehyde oligomers in mass spectroscopic analysis. The molecular weights of resole resins were calculated using field desorption mass spectroscopy of acetyl-derivatized samples.74 Phenol acetylation was used to enable quantitative characterization of all molecular fractions by increasing the molecular weights in increments of 42. 

Mass spectroscopy is a useful technique for the characterization of dendrimers because it can be used to determine relative molar mass. Also, from the fragmentation pattern, the details of the monomer assembly in the branches can be confirmed. A variety of mass spectroscopic techniques have been used for this, including electron impact, fast atom bombardment and matrix-assisted laser desorption ionization (MALDI) mass spectroscopy. 

The anion 19 has been generated by high-energy collision of the p-pentazoylphenolate anion with an inert gas [109] and by laser desorption ionization time-of-flight mass spectroscopy of sohd p-dimethylaminophenylpentazole [110]. N AsP, NjSbF, and [Nj]jSnF have been used by Gordon, Christe et al. [Ill] in their attanpt to observe N F. 

Considering these situations, the observation of molecular weights, particularly by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF MASS), is essential [33]. The operation is simple and enables us to observe the molecular ion peaks of CPOs with molecular weights exceeding 10,000. The quahty of the measurement is strongly dependent on the choice of the matrix. Therefore, the search for the best matrix for each CPO should be pursued. 

Peaks are analyzed separately by their retention times, absorption, and fluorescence properties. RCCs show absorbance maxima near A.500 and 316 nm. For FCCs, UV-Vis specna show two prominent bands near 361 and 320 mn and a luminescence maximum at 436 mn and NCCs show UV-Vis spectra with absorbance maxima near 320 and 210 nm. Nevertheless, as none of these approaches is suitable for elucidating structures, it is necessary to apply additional MS and NMR analyses to fully characterize snuctural features. Electron spray ionization (ESI) and high-resolution EAB mass spectroscopy have been applied to elucidate the molecular formulae of colorless compounds. ... 

Knowledge on the plasma species can be obtained by the use of plasma diagnostics techniques, such as optical emission spectroscopy (OES) and mass spectroscopy (MS). Both techniques are able to probe atomic and molecular, neutral or ionized species present in plasmas. OES is based on measuring the light emission spectrum that arises from the relaxation of plasma species in excited energy states. MS, on the other hand, is generally based on the measurement of mass spectra of ground state species. 

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. 

Hau, J. and Roberts, M., Advantages of pressurization in capillary electrophoresis/electrospray ionization mass spectroscopy, Anal. Chem. 71, 3977,... 

Syage JA, Pollard JE, Cohen RB. 1988. Ultrasensitive detection of atmospheric constituents by supersonic molecular beam, multiphoton ionization mass spectroscopy. El Segundo, CA Aerospace Corp. NTIS No. AD-A202-299. 

Pyrolysis mass spectroscopy was conducted with a Hewlett-Packard model 5985B gas chromatograph/quadrupole mass spectrometer, operated at sslO- Torr and 70eV electron-impact ionization energy. Samples were introduced into the mass spectrometer via a glass lined direct insertion probe (DIP). The samples were decomposed in the DIP to a nominal temperature of 300°C at a heating rate of 30°C/min. 

The general principle of detection of free radicals is based on the spectroscopy (absorption and emission) and mass spectrometry (ionization) or combination of both. An early review has summarized various techniques to detect small free radicals, particularly diatomic and triatomic species.68 Essentially, the spectroscopy of free radicals provides basic knowledge for the detection of radicals, and the spectroscopy of numerous free radicals has been well characterized (see recent reviews2-4). Two experimental techniques are most popular for spectroscopy studies and thus for detection of radicals laser-induced fluorescence (LIF) and resonance-enhanced multiphoton ionization (REMPI). In the photochemistry studies of free radicals, the intense, tunable and narrow-bandwidth lasers are essential for both the detection (via spectroscopy and photoionization) and the photodissociation of free radicals. 

In mass spectroscopy, sample molecules are ionized and the different masses of the ions formed are selected by use of an electric or magnetic field. In its simplest form, a mass spectrometer is an instrument that measures the mass-to-electric charge ratios of ions formed when a sample is ionized. If some of the sample molecules are singly ionized and reach the ion detector without fragmenting, then the mass-to-electric charge ratio of the ions gives a direct measurement of the weight of the molecule (de Hoffmann and Stroobant 2001). 

Wang, Z. Russon, L. Li, L. Roser, D. C. Long, S. R. Investigation of spectral reproducibility in direct analysis of bacteria proteins by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy. Rapid Comm. Mass Spectrom. 1998,12,456-464. 

Acrylonitrile in both biological and environmental samples is most commonly determined by gas chromatography with a nitrogen-phosphorus detector (GC/NPD) (Page 1985), gas chromatography/flame ionization detection (GC/FID) (EPA 1982a), or gas chromatography/mass spectroscopy (GC/MS) (Anderson and Harland 1980). Infrared spectroscopy (Jacobs and Syrjala... 

Stintzing FC, Schieber A and Carle R. 2002. Identification of betalains from yellowbeet (beta vulgaris L.) and cactus pear (Opuntiaficus-indica L. Mill.) by high performance liquid chromatography-electrospray ionization mass spectroscopy. J Agric Food Chem 50 2302—2307. 

L. Zandee, R. B. Bernstein, and D. A. Lichtin. Vibronic/Mass Spectroscopy via Multiphoton Ionization of a Molecular Beam The I2 Molecule. J. Chem. Phys., 69(1978) 3427-3429. 

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. 

Electrospray ionization mass spectroscopy have been carried out on aqueous tungstate solutions and species such as [HWOJ, [HW207]3, [W4013r, [HW4013r, rw60192 ], [ WioOga]2-, or [HW5016r have been observed in the mass spectrum (155). 

After device construction, structural and functional analysis are critical. One might argue that only the second issue matters, but structural data often give insights into why devices perform suboptimally, and provide important clues about how to improve device function. We routinely use protein analytics (matrix-assisted laser desorption-ionization mass spectroscopy, amino acid composition analysis, gel electrophoresis, Western blotting, circular dichroism, vari-... 

Caldwell, G.W., Easlick, S.M., Gunnet, J., Masucci, J.A., and Demarest, K., In vitro permeability of eight beta-blockers through Caco-2 monolayers utilizing liquid chromatography/electrospray ionization mass spectroscopy, /. Mass Spectrom., 33, 607,1998. 

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