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RECEIVED for review July 8,1985. Accepted August 26,1985. The financial assistance of Yarmouk University to Amin T. Haj-Hussein (on sabbatical leave) for this research is gratefully acknowledged.
Carbon-Oxygen Reactions in Graphite Furnace Atomic Absorption Spectrometry R. E. Sturgeon,* K. W. M. Siu, G. J. Gardner, and S. S. Berman Division of Chemistry, National Research Council of Canada,l Ottawa, Ontario, Canada K1A OR9
Heterogeneous reactions between oxygen and carbon have been lnvestlgated in the hlgh-temperaturegraphite furnace by interfacing a Massmann-type atomizer to a gas chromatograph. Methanation of CO, and CO permltted thelr quantitatlon with a flame ionization detector. The primary product of combustion is CO whose concentration increases exponentially with temperature up to approximately 2 X atm at 2700 K. Minor amounts of CO,, CH,, C,H,, C2H2,and C,H, ( atm) were also identlfled. Heterogeneous equiiibrla Including solid carbon are not attained at temperatures below 2600 K. The signlflcance of these results is discussed in connection with the partial pressure of oxygen in the furnace.
The partial pressure of oxygen (Po,) in the graphite furnace is of considerable interest to both analysts and those modeling physical processes within the furnace. Its magnitude has a direct influence on the sensitivity of determination of a number of elements ( I ) , appears to be a prime variable mediating the kinetics of atom formation of analyte oxides (2, 3),and has been associated with physicochemical interferences ( 4 , 5 ) and temporal shifting of absorption pulses ( 3 , 4 ,6, 7). Although several workers have experimentally estimated the Po, in nonisothermal semienclosed Massmann-type furnaces, no concensus has developed as to the most probable variation of Po, with temperature. Recent estimates are as divergent as 12 orders of magnitude a t 2500 K (cf. ref 3, 9, and 10). Direct measurement of PO,in the range expected in the heated furnace (
