A Practical Improvement of the Varian Carbon Rod Atomizer

Matrix effects in graphite furnace atomic absorption spectrometry (GFAAS) have been attributed to both condensed and gas phase phenomena. Gas phase interference effects are largely due to the reaction of gaseous metal atoms with co-volatilized matrix concomitants (e.g., chlorine) to form radicals or other molecular species. This mechanism of interference usually results in a negative bias if simple standards are used. In general, the most satisfactory solution to this problem is to increase the temperature of the gas phase within that portion of the atomizer optically sampled by the AA spectrometer. Raising that temperature promotes dissociation because the entropy term (–TΔS) in the overall free energy expression for the chemical reaction becomes predominant at higher temperatures.