The chromatographic processes in the S-chamber with the counter plate

► The mechanism of separation in the TLC variant with the counter-plate was discovered. ► Using the counter-plate allows additional consumption of the mobile phase. ► Using the counter-plate in the S-chamber allows improving the separation. ► Increase in the counter-plate layer thickness allows improving the separation. For the first time the chromatographic processes in the new variant of a S min-chamber with a counter plate (a S min(CP)-chamber) positioned at a small distance above a separating plate have been studied, given the adsorption layers of the both plates (the separating plate and the counter plate) are turned to each other. It should be noted that the features of this method have not been completely studied, only two publications were devoted to the practical using of the S(CP)-chamber. Using of a dry counter plate in the S min-chamber having been proposed by us recently leads to the marked increase in the volume of the mobile phase that continuously migrates through the separating plate. Using of the S min-chamber with the dry counter plate for separation allows, first, substantially (up to 50%) increasing the value of R f (especially, in the range of the small meanings of R f (0–0.3)), second, increasing the efficiency of separation by 2.0–2.5 times, and, third, increasing the peak resolution of the method by ∼25%. It should be noted that although when separating a mixture in the S min(CP)-chamber a slight increase in the experiment duration also occurs (by 20–50% depending on the sizes of the used plate), in all the cases chromatographic characteristics markedly improve (in comparison with separation in the same conditions, but without using of the counter plate).