The Surface Structure of “Monomeric” and “Polymeric” Reversed Stationary Phases and Mechanisms of Carotenoid Separation

The patterns of retention of carotenoids under reversed-phase chromatography conditions on “monomeric” and “polymeric” stationary phases are compared. It is shown which chromatographic properties are characteristic of “monomeric” reversed phases as a consequence of the specific structure of the surface of the sorbents. The main properties include the distribution mechanism of sorption, and the penetration of carotenoids into the phase is easily implemented due to the large space between the grafted alkyl substituents. “Polymeric” reversed phases are characterized by self-association of alkyl radicals like alkanes in the solid phase, which provides an adsorption mechanism that is most preferable for molecules with linear structural fragments. This type of retention does not correlate with the lipophilicity parameter, but is convenient for the separation of xanthophyll esters due to higher specific selectivity compared to “monomeric” reversed phases.