Atomization from solutions and slurries in electrothermal atomic absorption spectrometry

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7178510

Qiao, H

The effects of palladium and mixtures containing palladium on the absorbance characteristics of lead, thallium, cadmium, selenium, manganese and cobalt in a graphite furnace electrothermal atomizer are described. These data, together with results of scanning electron microscopy showing the distribution of palladium on the graphite surface, indicate that palladium stabilizes analytes during electrothermal atomic absorption spectrometry through a physical mechanism. During graphite furnace heating, the analyte dissolves in molten palladium and may combine with it chemically. However, the rate limiting step leading to atomization appears to be diffusion of the analyte from palladium. The addition of magnesium, molybdenum, or powdered carbon increases the speed of diffusion by causing palladium to form smaller droplets, and hence produces sharper absorbance peaks. Palladium becomes less effective as the atomization temperature increases, because the rate of diffusion is higher. This accounts for palladium has no significant effect on its modifying properties in a dilute nitric acid matrix. This physical effect theory is also supported by results of palladium used as a modifier to stabilize thallium in the presence of a large amount of sodium chloride. Results of kinetic studies obtained for nickel, copper, cobalt and magnesium as modifiers in stabilizing selenium are consistent with analyte diffusion out of the modifier as the rate-limiting step leading to atomization. The atomization of lead from a sediment slurry is studied. Absorbance characteristics with and without addition of a palladium/magnesium modifier mixture are compared, and scanning electron micrographs are presented to show the distribution of palladium and slurry particles in the graphite furnace during the heating cycle. The results are consistent with a physical mechanism of modification by palladium. The rate-limiting step leading to atomization is then diffusion of lead through the palladium layer.

• Research Organization: State Univ. of New York, Albany, NY (United States)
• OSTI ID: 7178510
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400102 -- Chemical & Spectral Procedures
400201* -- Chemical & Physicochemical Properties
ABSORPTION SPECTROSCOPY
ATOMIZATION
CHEMICAL PROPERTIES
DISPERSIONS
ELEMENTS
METALS
MIXTURES
PALLADIUM
PLATINUM METALS
SLURRIES
SOLUTIONS
SPECTROSCOPY
SUSPENSIONS
TEMPERATURE DEPENDENCE
TRANSITION ELEMENTS