A sensitive TLC method to identify Echinaceae pallidae radix

In this work a fast, simple and sensitive qualitative TLC method was developed to identify Echinaceae pallidae radix and to distinguish this drug from similar ones. The TLC method is based on the lipophilic compounds of E. pallida. Three mobile phases provided good separation, e.g. toluene/ethylacetate 7 + 3 (v/v). A marker substance was found which shows a blue fluorescence at an excitation wavelength of 366 nm after detection with a spray agent containing 95 volume parts ethanol 96%, 5 parts trifluoroacetic acid 99% and zinc ions in 0.15 molar concentration. After spraying the chromatogram was heated at 110 degrees C for 7 min. This method is superior to HPLC methods to characterise mixtures of Echinacea extracts in terms of selectivity due to this post-chromatographic derivatisation and subsequent fluorescence detection.