The reasons for the elimination of interferences in a filter furnace used as an atomizer in electrothermal atomic absorption spectroscopy, were examined theoretically and experimentally. The results of observations of stepped or multi-peak background absorption signals for NaCl, NaI, KCl, KBr, KI, CaCl2 and MgSO4, which were characteristic for each matrix and different types of graphite used, leads to hypotheses about the formation of molecule-graphite intercalation composites. These were treated as stable compounds of different stoichiometry having substantial specific enthalpy of formation. The validity of the idea was confirmed with the measurements of the rate of NaCl vapor release through a graphite filter as a function of temperature, and comparison with the literature data for similar compounds of alkali metals. The effect of implantation of molecular particles into a crystalline lattice leads to reduction of their diffusion rate through graphite, which in turn provides time-resolved background and atomic absorption signals.

Diffusion of Molecular Vapors through Heated Graphite. Katskov, D.A., Schwarzer, R., Marais, P.J.J., McCrindle, R.I.: Spectrochimica Acta B, 1995, 50[8], 763-80