Characterization of noises and interferences in analytical flames and plasmas

Miscellaneous · Fri Jan 01 00:00:00 EST 1988

OSTI ID:6859167

Weeks, III, N J

The presence and adverse effects of noises and interferences which limit the capabilities of spectrometric techniques have studied by means of two-dimensional profiles of signal and signal-to-noise ratio (SNR) for a 3-electrode direct current plasma (DCP) excitation source and for a flame atom reservoir. These studies have led to suggestions for the improvement of these analysis systems. Simple measurement of DCP emission intensity belies an enhanced sensitivity for most elements when a high injection velocity of small aerosol delivery tube (ADT) is utilized. Spatial profiles of the DCP have shown that for the larger, 7 mm ADT, the region of greatest analyte emission did not coincide with that of greatest SNR and that this effect was eased when a 2 mm aerosol delivery tube was used. Noise analysis via a fast Fourier transform (FFT) in the intensity-rich, SNR-poor region has shown a form of low frequency flicker noise to be responsible for SNR attenuation here. Later experiments have shown that the DCP is useful for the analysis of coal slurries, except that poor sensitivity was displayed for some elements. In an effort to explain this, a Fraunhofer diffraction particle size measurement apparatus was constructed in order to determine the fate of coal particles in the plasma. Lastly, spatial profiling of absorbance and SNR in absorbance, along with FFT noise analyses, have been performed in order to identify the noises responsible for limiting sensitivity in flame atomic absorption measurements. It has been shown that some form of frequency-dependent noise was responsible for degrading SNR in the high-noise regions of the flame, and further that this effect is enhanced at high concentrations.

• Research Organization: Alabama Univ., Huntsville, AL (USA)
• OSTI ID: 6859167
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
FUEL SLURRIES
COMBUSTION KINETICS
SPECTROSCOPY
PERFORMANCE TESTING
ABSORPTION SPECTROSCOPY
COAL
EMISSION SPECTROSCOPY
FLAMES
FOURIER TRANSFORMATION
FREQUENCY DEPENDENCE
NOISE
PARTICLE SIZE
PLASMA FURNACES
SIGNAL-TO-NOISE RATIO
WATER
X-RAY DIFFRACTION
CARBONACEOUS MATERIALS
CHEMICAL REACTION KINETICS
COHERENT SCATTERING
DIFFRACTION
DISPERSIONS
ENERGY SOURCES
FOSSIL FUELS
FUELS
FURNACES
HYDROGEN COMPOUNDS
INTEGRAL TRANSFORMATIONS
KINETICS
MATERIALS
MIXTURES
OXYGEN COMPOUNDS
REACTION KINETICS
SCATTERING
SIZE
SLURRIES
SUSPENSIONS
TESTING
TRANSFORMATIONS
010600* - Coal
Lignite
& Peat- Properties & Composition
400102 - Chemical & Spectral Procedures