Mechanism of atomization at constant temperature in capacitive discharge graphite furnace atomic absorption spectrometry

At constant temperature (isothermal) maintained throughout in the capacitive discharge technique, the measured absorbance at any time t due to concentration of analyte atoms can be given by: absorbance = p[A]₀{k₁/(k₁?k₂)}[exp(?k₂t)-exp(?k₁t)], where p is a function of the oscillator strength (a constant) and the efficiency with which the analyte atoms are produced, [A]₀ is the initial concentration of the analyte atoms, k₁ and k₂ are first-order rate constants for formation and decay of analyte atoms, respectively. This technique yields k₁?k₂ and k₁t?k₂t; and so the above equation reduces to: absorbance ?p[A]₀, resulting in large enhancement in sensitivity. In the case of lead, the immediate precursor of the gaseous lead monomer is the gaseous lead dimer, which is partly lost by diffusion of the lead dimer with a first-order rate constant, k₃. The kinetic parameters k₁, k₂ and k₃ have been evaluated, and the values of k₁ at different temperatures used to draw the Arrhenius plots, from which activation energies of the rate-determining steps have been determined. The activation energies have been used to elucidate atomization mechanisms by extensive correlation of the experimental energy values with the literature values.