Sorbents and Precoated Layers for the Analysis and Isolation of Primary and Secondary Metabolites

This chapter will cover mainly commercial precoated layers for thin layer chromatography (TLC) and high performance TLC (HPTLC) that have been used for phytochemical separations and analyses. Bulk sorbents are available commercially for those who want to prepare handmade plates, but the variety is much less than those for precoated plates and the resultant plates are not as reproducible when compared with precoated plates. As an example of availability, the EMD Chemicals, Inc. (an affiliate of Merck KGaA, Darmstadt Germany) catalog lists only the following bulk sorbents for analytical and preparative TLC: silica gel 60, aluminum oxide 60, kieselguhr G, and silica gel 60 RP-18.