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Ionization Chamber (ionization + chamber)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Development of ambient sampling chemi/chemical ion source with dielectric barrier discharge

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 8 2010
Lee Chuin Chen
Abstract The development of a new configuration of chemical ionization (CI)-based ion source is presented. The ambient air containing the gaseous sample is sniffed into an enclosed ionization chamber which is of sub-ambient pressure, and is subsequently mixed with metastable species in front of the ion inlet of the mass spectrometer. Metastable helium atoms (He*) are used in this study as the primary ionizing agents and are generated from a dielectric barrier discharge (DBD) source. The DBD is powered by an AC high-voltage supply and the configuration of the electrodes is in such a way that the generated plasma is confined within the discharge tube and is not extended into the ionization chamber. The construction of the ion source is simple, and volatile compounds released from the bulky sample can also be analyzed directly by approaching the sample to the sampling nozzle. When combined with heated nitrogen or other desorption methods, its application can also be extended to non-volatile compounds, and the consumption for helium can be kept minimum solely for maintaining the stable discharge and gas phase ionization. Applications to non-proximate sample analysis, direct determination of active ingredients in drug tablets and the detection of trace explosive such as hexamethylene triperoxide diamine are demonstrated. Copyright © 2010 John Wiley & Sons, Ltd. [source]

A position-sensitive ionization chamber for XAFS studies at synchrotron sources

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001
Kazumichi Sato
A position-sensitive ionization chamber has been developed with backgammon-type-segmented electrodes. This novel detector possesses a linear range of 8 mm for determining the incident position of the X-ray beam incoming. The position resolution was found to be less than 10 µm, probably close the sub-micrometer region. Owing to its high spatial resolution, the position-sensitive ionization chamber was able to commit that the gradual decrease observed in the X-ray beam intensity at a SPring-8 beamline was mainly due to the spatial variation of the X-ray beam in time. The present work also confirmed the applicability of the novel detector to the accurate monochromator adjustment for experiments using diamond anvil cells. [source]

New isotope ratio mass spectrometric method of precise ,37Cl determinations

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 7 2009
Stanislaw Halas
The most precise method of chlorine isotope analysis described to date is based on the isotope ratio mass spectrometry (IRMS) of chlorine quantitatively converted into chloromethane, CH3Cl. This gas can be produced from several chlorine-containing compounds and analyzed by IRMS. However, the mass spectrum of chloromethane is rather complicated and the ratio of the most abundant ions (mass-52/mass-50) differs from the 37Cl/35Cl isotope ratio. This difference becomes significant when the , exceeds 10,. Moreover, the electron ionization source yields approximately 80% of all the ionic species at the useful masses 50 and 52. To overcome these drawbacks, we have devised a negative ion mass spectrometer which retains all the best features of IRMS, including a dual-inlet system with changeover valve, dual collector assembly and CH3Cl gas as analyte. In the modified ion source we have replaced the ionization chamber with an electron beam by a metal tube with a hot metal filament inside it. Within this tube the 35Cl, and 37Cl, ions are produced with an efficiency dependent on the filament material and its temperature. No other ionic species were found in the mass spectrum except of traces at masses 26 and 28 at ppm levels, probably due to the formation of CN, and CO,. The minimal amount of Cl used in our method is of the order of 5,µmol (3,mg AgCl) and the precision is better than 0.005, (1,). Copyright © 2009 John Wiley & Sons, Ltd. [source]