Mass spectrometers chemical ionization sources

As described above, the mobile phase carrying mixture components along a gas chromatographic column is a gas, usually nitrogen or helium. This gas flows at or near atmospheric pressure at a rate generally about 0,5 to 3.0 ml/min and evenmally flows out of the end of the capillary column into the ion source of the mass spectrometer. The ion sources in GC/MS systems normally operate at about 10 mbar for electron ionization to about 10 mbar for chemical ionization. This large pressure... 

S. Bajic, Electrospray and atmospheric pressnre chemical ionization mass spectrometer and ion source. Patent 5756994, May 26, 1998. 

Schwarz and coworkers have used the technique of neutralization-reionization mass spectrometry (NRMS) to structurally characterize numerous elusive silicon-containing molecules of interstellar interest342. The identification of HNSi was supported by ab initio calculations. The radical ion [HNSi] + was produced from N2 and SiH3I in the chemical ionization source of the mass spectrometer. 

API The atmospheric pressure ionization (API) source is the most common category of source for LC-MS analysis, in which ionization is performed outside of the high-vacuum region of the mass spectrometer. Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) sources are both examples of API sources. 

The chemical ionization mass spectrum of cimetidine and the major fragmentation ions are presented in Figure 8 and Table 4. The spectrum was obtained using a Finnigan lYbdel 3200 quadrupole mass spectrometer fitted with a chemical ionization source. The sample, applied to the probe from an acetone solution, was introduced via the direct inlet system. Methane was used as the reactant gas. 

The analytically important features of Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometry (1) have recently been reviewed (2-9) ultrahigh mass resolution (>1,000,000 at m/z. < 200) with accurate mass measurement even 1n gas chromatography/mass spectrometry experiments sensitive detection of low-volatility samples due to 1,000-fold lower source pressure than in other mass spectrometers versatile Ion sources (electron impact (El), self-chemical ionization (self-Cl), laser desorption (LD), secondary ionization (e.g., Cs+-bombardment), fast atom bombardment (FAB), and plasma desorption (e.g., 252cf fission) trapped-ion capability for study of ion-molecule reaction connectivities, kinetics, equilibria, and energetics and mass spectrometry/mass spectrometry (MS/MS) with a single mass analyzer and dual collision chamber. 

N-C Hj-morphine as internal standard. The internal standard was added to 10 ml urine, the urine buffered to pH 8.5 and extracted with chloroform isopropanol (4 1). The extraction residue was trimethylsilylated by adding 25 ul of N,0-bis(trimethylsilylJacetamide and heating at 60°C for about 1 h. About 2 ul was analyzed on a 3 % 0V-17 column at 230°C coupled direct to a Finnegan 1015 quadrupole mass spectrometer equipped with a chemical ionization source, which was operated at an ionizing energy of 100 eV, an ion repeller voltage of 0 V and a filament emission of 300 uA. The mass spectrometer was interfaced with a System Indus-... 

Figure 8.16. TG-MS with a chemical ionization source as described by Bamngarmer and Nachbaur (74). 1, thermobalance 2. furnace 3,3-way valve 4. reaction gas cylinder 5. rotary-pumps 6, coupling line 7. quadrupole mass spectrometer 8. Cl-ion source 9. metering valve 10, ionization gauge 11, analyzer diffusion pump 12. Cl diffusion pump.

When the device is operated as a mass spectrometer, ions produced by an electron-impact or chemical ionization source are admitted through a grid in the upper end cap. The ionization source is pulsed so as to create a burst of ions. The ions over a large mass range of interest are trapped simultaneously. The ion trap can store ions for relatively long times, up to l.o minutes for some stable ions. A technique called mns.s-.te/ct/ri C ejeaion is then used to sequentially eject the trapped ions in order of ma,ss by increasing the radio-frequency... 

All mass spectra were recorded using a Hewlett-Packard 5985B mass spectrometer equipped with a dual electron impact/chemical ionization source including negative ion capability. The source temperature was 125QC, filament emission current was 300 uA, and electron energy was 230 ev. The interface between the GC and MS was a glass-lined stainless steel transfer line. Methane was used both for carrier gas and as the chemical ionization reactant gas. A methane flow of 11.5 mL/min. resulted in an ion source pressure of 0.5 torr. 

The other chief comptment of a mass spectrometer, the ion source, determines the types of ions that can be examined when starting fi om a specific sample (Gross and Caprioli, 2007). Laser-based methods, variably dubbed ablation, ionization, and desorption/ionization supposedly depending on the involved laser power, have played an important role fi om initial studies of bare metal ions to the widespread sought-after production of cluster ions for these latter species, the development of the so-called cluster sources was key to progress (Duncan, 2012). In more recent years, electrospray ionization (ESI) has played a central role due to its capacity to transfer/produce ions from solutions under mild conditions. Besides yielding new types of ions for chemical probing, ESI became a method of choice for the identification of solution species (speciation) and for direct observation of reaction... 

Methane gas served as both the gas chromatographic carrier gas and the reagent gas in the chemical ionization source (at 1000 y pressure). The mass spectrometer was operated in the selected ion recording mode, and the quasimolecular ions of PF and Ara-Virazole were monitored at m/e 692 and m/e 517, respectively two fragment ions (loss of methyl group) were also monitored. A calibration curve was established using known amounts of PF added to pooled human serum. The observed areas of PF and the internal standard were used to calculate area ratios which, in turn, were used to determine the amount of PF in serum. Using this method minimum detectable quantity is 10 ng/ml serum lowest level at which quantification is still reliable is 100 ng/ml serum. 

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