Mass spectrometry thermionic

Plants (rice, potato, cabbage, lettuce, soybean, pear, cucumber, tomato, eggplant, ornamentals), soil and water Gas-chromatographic determination [with mass spectrometry (MS) or flame thermionic detection (FTD)] for plant materials, soil and water... 

Shinohara et al. [299] have described a procedure based on gas chromatography for the determination of traces of two, three, and five-ring azarenes in seawater. The procedure is based on the concentration of the compounds on Amberlite XAD-2 resin, separation by solvent partition [300], and determination by gas chromatography-mass spectrometry with a selective ion monitor. Detection limits by the flame thermionic detector were 0.5-3.0 ng and those by gas chromatography-mass spectrometry were in the range 0.02-0.5 ng. The preferred solvent for elution from the resin was dichloromethane and the recoveries were mainly in the range 89-94%. 

PDMS = polydimethylsiloxane. PA = polyacrylate. CW = Carbowax. DVB = divinylbenzene. FID = flame ionization detection. NPD = nitrogen-phosphorus detection. TSD = thermionic-specific detection. LOQ = limit of quantitation. LOD = limit of detection. TCA = trichloroacetic acid. PICI-MS = positive ion chemical mass spectrometry. SIM = selected ion monitoring. 

Jackson SE, Gunther D (2003) The nature and sources of laser induced isotopic fractionation in laser ablation-multicollector-inductively coupled plasma-mass spectrometry. J Anal At Spectrom 18 205-212 Jiang S-J, Houk RS, Stevens MA (1988) Alleviation of overlap interferences for determination of potassium isotope ratios by Inductively-Coupled Plasma Mass Spectrometry. Anal Chem 60 1217-1220 Lam JWH, Horlick G (1990) A comparison of argon and mixed gas plasmas for inductively coupled plasma-mass spectrometry. Spectrochim Acta Part B 45 1313-1325 Langmuir I, Kingdon KH(1925) Thermionic effects caused by vapours of alkali metals. Phil Trans R Soc A107 61-79... 

Cl = chemical ionization CI-NI = monitoring negative ions in the chemical ionization mode GC = gas chromatogmphy HPLC = high performance hquid chromatography MS = mass spectrometry pmol = picomole SPE = solid-phase extraction TSD = thermionic specific detection... 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

GC isotope ratio mass spectrometry [7] and GC using a caesium bromide thermionic detector [8] have been used to determine, respectively, carboxylic ethers in apples and tetraethyl pyrophosphate in chloroform-acetone extracts of crops in amounts down to 0.01 ppm. 

As in the sources used in optical atomic spectrometry a considerable ionization takes place, they are also of use as ion sources for mass spectrometry. Although an overall treatment of instrumentation for mass spectrometry is given in other textbooks [68], the most common types of mass spectrometers will be briefly outlined here. In particular, the new types of elemental mass spectrometry sources have to be considered, namely the glow discharges and the inductively and eventually the microwave plasmas. In contrast with classical high voltage spark mass spectrometry (for a review see Ref. [69]) or thermionic mass spectrometry (see e.g. Ref. [70]), the plasma sources mentioned are operated at a pressure which is considerably... 

GC can achieve the highest resolution of the essential oils, but there are some significant limitations with regards to preparative scale separations. Typically, as the sample capacity is increased, the resolution of the chromatographic separation is reduced. On a lab scale, equipment is available that permits 24-hour automated and unattended separations, however, the recovery yield and sample resolution are still problematic [57]. Capillary column GC has become so routine for essential oil analysis that one rarely finds a lab without that capability. A multitude of detectors exist for GC thermal conductivity (TCD), flame ionization (FID), flame photometric (FPD), thermionic specific (TSD), photoionization (PID), electron capture (ECD), atomic emission (AED), mass spectrometry (MS), and infrared spectroscopy (FTIR) [58,59]. The TCD is used primarily with preparative-GC (packed column) because it is... 

Mass spectrometry with flash- or thermionic-excitation also achieves very low detection limits. Isotope dilution mass spectrometry (IDMS) is a very precise reference method, with high reliability. 

Mass spectrometry, which is the only technique that can be used to characterize met-cars and related metal-carbide clusters, implies that the detected clusters are ionized. This requirement opens a route to a variety of experimental procedures enabling insight to be gained into physical properties such as ionization energies, electron affinities, structure, and collective electronic properties such as thermionic electron emission and delayed atomic ion emission. 

Bombiok D, Pinkston JD, Allison J. Potassium ion chemical ionization and other uses of an alkali thermionic emitter in mass spectrometry. Anal Chem. 1984 56 396-402. Schmelzeisen-Redeker G, Giessmam U, Rollgen FW. In-beam ionization by alkali ion attachment applying a two-filament ion source. Org Mass Spectrom. 1985 20 305-309. Anderson WR Jr, Frick W, Daves CD Jr A direct technique for obtaining electron-impact mass spectra of polar, involatile compounds. Application to underivatized disacchaiides. J Am Chem Soc. 1978 100 1974-75. 

Bombick D, Pinkston JD, Allison J. Potassium ion chemical ionization and other uses of an alkali thermionic emitter in mass spectrometry. Anal Chem. 1984 56 396 02. 

Since then, new developments related to the chemistry of organic compounds have followed. Davis [12] has constructed a magnetic sector mass spectrometer with a direct air sample inlet system and thermionic rhenium emitter. He demonstrated that many organic compounds in normal laboratory air were efficiently ionized on an oxidized rhenium surface. Along with these results, it was suggested that the SI phenomenon could be exploited in gas chromatography (GC) and mass spectrometry (MS). 

Surface-ionization mass spectrometry (SI-MS) studies of organic compounds show that in most cases the compounds decompose into radicals, which have a lower ionization energy IE) than the corresponding molecules, and are ionized more efficiently. For a given type of secondary species, s, formed on the surface, the resulting positive thermionic emission currents (/) and their dependence on surface temperature (7) are described by the ionization efficiency, Ps(7), and by YXT), the yield of chemical reactions on the surface, such that... 

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