The fundamentals of vacuum thermochromatography

Abstract

Species of dissimilar volatility (adsorbability) can be separated by a technique, which resembles the common gas–solid thermochromatography but is performed in evacuated columns. The negative longitudinal temperature gradient gives rise to an effective convectionless molecular flow and the gradually slower migration of the analyte results in a deposit within individual temperature range. The technique can serve some specific needs of separation of very small amounts of radiolabeled molecular entities (even single atoms). It also allows evaluation of desorption energies of such molecules from surfaces on the basis of a proper theory of the separation processes. The paper provides correct prescriptions for the Monte Carlo simulations of the migration of molecules in columns and of the deposit profiles, which are yet lacking. Numerous performed simulations give better understanding of influence of various experimental parameters on the data. Possibility, as well as limitation, of using the diffusion ansatz of the random flights for evaluation of desorption energies is discussed.