Non-trivial Mechanisms in Gas-Solid Chromatography

The problems met in evaluating the gas-solid chromatography data get more complicated when the underlying mechanisms are other than the reversible physisorption. It may be necessary to admit participation of novel compounds of known elements 

In the case of the simplest mechanism of repeated adsorption-desorption events of the unaltered molecules, the retention time and the peak shape are insensitive to the composition of the carrier gas — now we would add provided that it constantly modifies the column surface. Some of the more complex mechanisms of migration are indistinguishable from the outside because they are analogously insensitive. It is, for instance, simple chemisorption, when the initial electronic structure of the adsorptive substantially changes upon adsorption, but is restored at the desorption stage. Such is also the microscopic history of metallic adatoms in metal columns. Another case is the chromatography of molecular halides in columns loaded with alkali halides the adsorbed state is a surface complex between the two halides see Sect. 1.5.1. In both examples the structure of the original adsorption sites is not necessarily restored. It is, of course, unimportant in the experiments with tracers. 

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