Arrhenius plots for activation energy of atomization in graphite-furnace atomic-absorption spectrometry.
Activation energy plots drawn by use of various Arrhenius-type equations for atomization reactions in graphite-furnace atomic-absorption spectrometry (GFAAS) do not give reliable kinetic information about the atomization mechanism of the analyte element beyond a few data-points located near the very beginning of the absorbance signal profile. These plots are non-linear if they are drawn with data points near the maximum of the absorbance signal profile. This paper presents two Arrhenius-type equations which give linear plots over a long range of data-points, and hence reliable values for the activation energy. Also, a simple method is proposed for calculating the activation energy from the data-points anywhere from the initial appearance of the absorbance signal to its maximum. Activation energy values given by these two equations and by the method of calculation are compared with each other and with those given by the commonly used methods. The calculated activation energy values obtained can be used to verify those obtained experimentally. The three proposed methods also provide reliable kinetic information on atom-formation reactions in GFAAS. A mechanism for the atomization of copper, based on the experimentally determined activation energy and reaction order is proposed.
Chakrabarti
C L
CL
Centre for Analytical and Environmental Chemistry, Chemistry Department, Carleton University, Ottawa, Ontario, Canada K1S 5B6.
Cathum
S J
SJ