Ion bombardment glow-discharge furnaces for atomic emission spectroscopy

Miscellaneous · Mon Jan 01 00:00:00 EST 1990

OSTI ID:5943955

Tanguay, S L

Two glow discharge plasma devices for the atomic emission analysis of aqueous samples were investigated. The devices use thermal vaporization of samples from a graphite cathode coupled with glow-discharge excitation. Furnace heating of the cathode is accomplished by the positive ion bombardment of the cathode during plasma operation. The dc plasma operates in Ar at 0.5-5.0 torr, with currents up to 250 mA. A cw, axial magnetic field of up to 1.25 kG is applied to the cylindrical-post cathode system to reduce electron losses, thereby increasing plasma excitation and ionization efficiency. At higher currents, the cathodes heat to temperatures as high as 2,500{degree}C in the case of the cylindrical-post cathode. Hollow-cathode heating temperatures are lower under comparable conditions, due to the larger cathode surface area, greater cathode mass, and lower power dissipation. The peak furnace temperature using this configuration is approximately 2100{degree}C. The role of the emission of thermionic electrons from the hot cathodes in limiting the cathode heating and in regulating the cathode temperature are considered. Sample residues of up to 50 ng of the analyte are vaporized from the cylindrical-post cathode within a few seconds of the initiation of the discharge, resulting in a transient emission intensity profile. With the hollow-cathode furnace, vaporization may take several seconds. Although a lower rate of cathode heating and a lower sample vapor residence time results in limits of detection which are one to two orders of magnitude lower than those achieved using the cylindrical-post cathode system. For the hollow cathode, limits of detection are on the order of 10 pg to 1 ng.

• Research Organization: Michigan Univ., Ann Arbor, MI (United States)
• OSTI ID: 5943955
• Resource Relation: Other Information: Thesis (Ph.D)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
EMISSION SPECTROSCOPY
PLASMA FURNACES
PERFORMANCE TESTING
AQUEOUS SOLUTIONS
CATHODES
ELECTRIC CURRENTS
EVAPORATION
EXCITATION
GLOW DISCHARGES
GRAPHITE
IONIZATION
MAGNETIC FIELDS
OPERATION
SPECIFICATIONS
VERY HIGH TEMPERATURE
CARBON
CURRENTS
DISPERSIONS
ELECTRIC DISCHARGES
ELECTRODES
ELEMENTAL MINERALS
ELEMENTS
ENERGY-LEVEL TRANSITIONS
FURNACES
MINERALS
MIXTURES
NONMETALS
PHASE TRANSFORMATIONS
SOLUTIONS
SPECTROSCOPY
TESTING
400102* - Chemical & Spectral Procedures