Comparison of coherent forward scattering and atomic absorption profiles of O I 844.6-nm and Ar I 842.5-nm lines in the pulsed and continuous radio-frequency glow-discharge plasmas

Studies are performed to evaluate the roles of discharge power and pressure as well as limiting orifice diameter on the production of free, gas-phase atoms with a radio-frequency glow discharge-atomic absorption spectrophotometry (rf-GD-AAS) atomizer. Results indicate that nominal pressures of ∼4 Torr Ar are optimal for conductive samples, whereas a pressure of ∼1 Torr is desired for nonconductive sample types. As might be expected, absorbance signals increase with increases in discharge power to a level of ∼30 W, though trade-offs between ablation rates and source stability exist at higher levels. Completely opposite to the bulk atomization characteristics, large limiting orifice diameters yield higher absorbances. Plasma stabilization times are seen to be on the order of 20 s after initiation of the plasma for conductive and nonconductive sample types. Despite limitations imposed by the current optical instrumentation, it is believed that rf powering in GD-AAS is a viable alternative to conventional dc-powered sources, with the advantage of direct analysis of nonconductive sample types.

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Effect of Anode Dimensions and Location of the Discharge Gas Inlet Port on the Spatial Distribution of Copper Atoms in a Radio Frequency Glow Discharge Atomizer for Atomic Absorption Spectrometry

Analytical Chemistry ◽

10.1021/ac971075x ◽

1998 ◽

Vol 70 (16) ◽

pp. 3434-3443 ◽

Cited By ~ 2

Author(s):

G. Absalan ◽

C. L. Chakrabarti ◽

K. L. Headrick ◽

M. Parker ◽

R. K. Marcus

Keyword(s):

Spatial Distribution ◽

Glow Discharge ◽

Radio Frequency ◽

Atomic Absorption Spectrometry ◽

Atomic Absorption ◽

Absorption Spectrometry ◽

Radio Frequency Glow Discharge ◽

Inlet Port ◽

Discharge Gas

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Ion Kinetic Energy Determinations in Radio-Frequency Glow Discharge Mass Spectrometry

Applied Spectroscopy ◽

10.1366/0003702953964859 ◽

1995 ◽

Vol 49 (7) ◽

pp. 917-926 ◽

Cited By ~ 5

Author(s):

Paula R. Cable ◽

R. Kenneth Marcus

Keyword(s):

Kinetic Energy ◽

Glow Discharge ◽

Radio Frequency ◽

Source Region ◽

Potential Method ◽

Operating Conditions ◽

Atmospheric Plasma ◽

Radio Frequency Glow Discharge ◽

Ion Trajectory ◽

Ion Kinetic Energy

Radio-frequency glow discharge (rf-GD) sources produce an abundance of both atoms and ions. For the mass spectrometric application of the glow discharge technique, knowledge of the ion kinetic energies is required to optimize extraction and focusing of ions from the source region into the analyzer. This paper details kinetic energies experimentally determined with the use of the “retarding potential” method. For this study, the analyzer quadrupole of a double-quadrupole mass spectrometer was positively biased to act as a repeller. Ion kinetic energies (IKEs) determined for a variety of discharge and analyzer operating conditions ranged from 12.5 eV to 25.0 eV for 63Cu+. Kinetic energy measurements were confirmed from ion trajectory simulations and follow closely the experimental values for identical analyzer conditions and initial IKEs. Results of this study indicate that the conditions under which ions are formed (plasma conditions) affect IKEs and energy spreads to a greater extent than analyzer parameter variations. Different from atmospheric plasma sources, IKEs for rf-GD species do not vary as a function of ion mass/identity. Evidence is also given in support of a slight mass biasing owing to the transmission properties of double-quadrupole analyzers. The findings detailed herein demonstrate the effects of rf modulation on both ion kinetic energy values and distributions.

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