ABSTRACT
This chapter deals with multidimensional thin-layer chromatography conveniently defined as separations involving the sequential application of more than one separation mechanism to resolve the mixture. Thin-layer chromatography (TLC) has changed rapidly during the past decade in response to theoretical and practical optimization of all aspects of the chromatographic process. Excluded from the discussion is the use of thin-layer chromatography as a sample preparation procedure for gas or liquid chromatography. The spot capacity, therefore, becomes comparable to that achieved in column chromatography; only the available pressure drop and plate length limit the spot capacity. Instrumentation for two-dimensional TLC with forced-flow development, also known as two-dimensional column chromatography or bidirectional column chromatography, is at an early state of development. Interfacing gas or liquid chromatography to thin-layer chromatography is not particularly difficult but is not widely practiced. Gas chromatography/TLC enjoyed some popularity in the late 1960s when several working instruments were developed.
