Reversed Phase High Performance Thin Layer Chromatography of Aqueous Samples in Student Laboratories Using the Example of Anthocyanin Patterns from Flower Petals

When student projects require an analytical step that is robust and sufficiently selective, high performance thin layer chromatography (HPTLC) is a method to be considered. However, for student laboratories not equipped for HPTLC, sample application as a sharp narrow band is a hurdle. The low eluting power of water on reversed phase plates can be utilized for the application of aqueous samples to overcome this hurdle. We demonstrate the performance of this approach using the example of anthocyanin patterns from small pieces of petals or fruits. Additionally, the pH behavior and complexation with metal ions of individual components of the anthocyanin pattern can be studied directly on the plate after chromatographic separation. Furthermore, rapid prechromatographic glycoside cleavage can release the underlying basic structures of the nonglycosylated anthocyanidins, which can be analyzed without further treatment or purification. The separation is performed on small RP18W-plates after a manual autofocusing application. The chromatographic method can be adapted to a broad spectrum of polar compounds in aqueous solution and may provide tips and tricks and serve as a tool for students to support their research work.