The thermochromatography method (TC) in combination with a simulation program, allows to evaluate the standard adsorption enthalpies at zero surface coverage of chemical species on specific materials. In particular, in TC trace amounts of the investigated species, in its elemental state or as chemical compound, are desorbed from a starting phase and carried by a gas through the stationary phase with a negative temperature gradient in the direction of the carrier gas flow. Inert or reactive gases can be used as carrier to transport the investigated species through the stationary phase. The use of inert gas, e.g. helium, tends to preserve the chemical state of the species during the experiment. On the other hand, the use of reactive gas, e.g. oxygen or hydrogen, can induce chemical reactions, in both gas and adsorbed phase, with the formation of one or several new compounds. Reactive gas can also change the chemical characteristics of the stationary phase. If different chemical species are formed in the gas phase, they will show different retention and each species will be concentrated in a specific region of the stationary phase characterized by a defined temperature range. Thus, in thermochromatography, differently than other conventional chromatography methods, the investigated species are typically not eluted but they remain adsorbed on the stationary phase. The TC experiments result in a thermochromatogram that is a pattern expressing the concentration of the investigated species and its distribution in function of either its position in the column or its deposition temperature, i.e., c = f(x) or c = f(T), which can be simulated by a Monte Carlo code for gas chromatography [1]. From the simulation, it is possible to extract the value of the standard adsorption enthalpy, which is characteristic to the adsorbed species.

[1] I. Zvara, Simulation of thermochromatographic processes by the Monte Carlo method, Radiochim. Acta, 38 (1985) 95.
[2] I. Zvara, The Inorganic radiochemistry of heavy elements, Springer, Netherlands, 2010.