Studies and comparisons of reductive pyrolysis: Sample introduction and far ultraviolet spectrometry with helium microwave-induced plasmas

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1993

OSTI ID:7164574

Alvarado, J

The helium microwave-induced plasma (He-MIP) has been shown to be an excellent source for nonmetal determination. A description of the analytical characteristics of He-MIPs in different spectral regions using moderate and high power discharges for the determination of nonmetals is presented. Initial investigations using electrothermal vaporization (ETV) for sample introduction showed detection limits in the part-per-billion range for arsenic, selenium and antimony. Samples sizes were 15 [mu]L. A tantalum-coated carbon cup was used to minimize interferences. The determination of metals, nonmetals and metalloids in the vacuum ultraviolet (VUV) was accomplished. To observed atomic emission at wavelengths in the VUV region, a system which contained no N[sub 2] and O[sub 2] in the optical path was designed and implemented. This arrangement was produced by using an optical sampler to couple the plasma discharge with a helium purged monochromator. Sample introduction was accomplished with ultrasonic nebulization. Limits of detection, linear ranges, and matrix effects using groups IA and IIA elements were studied. A study involving sulfur-containing compounds in the near infrared region demonstrated the feasibility of the determination of inorganic and organic sulfur using differential electrothermal vaporization sample introduction. Sulfur detection limits were improved when a reductive pyrolysis of the sample was performed. The analyte was passed through a high temperature region in the presence of hydrogen gas to form H[sub 2]S. The resultant H[sub 2]S was condensed in a liquid nitrogen trap. Following preconcentration, flash vaporization into the stream of flowing helium routed the H[sub 2]S to the plasma for atomic emission detection. Results showed linear response and detection limits of 30 parts-per-million when the 921.3 nm sulfur emission line was monitored, and 400 parts-per-trillion when the resonant sulfur line at 180.73 nm was observed.

• Research Organization: Northern Illinois Univ., De Kalb, IL (United States)
• OSTI ID: 7164574
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
DECOMPOSITION
ELECTRIC DISCHARGES
ELEMENTS
HIGH-FREQUENCY DISCHARGES
NONMETALS
PYROLYSIS
QUANTITATIVE CHEMICAL ANALYSIS
SEMIMETALS
SENSITIVITY
SPECTRA
THERMOCHEMICAL PROCESSES
ULTRAVIOLET SPECTRA