Wang, K; Liu, Z; Huang, Jan; Fu, D; Liu, F; Gong, Y; Wu, X
The potential of polyamide as adsorbent for separation of nine compounds - (+/-)-catechin (DL-C), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), (-)-epigallocatechin gallate (EGCg), theaflavin (TF1), theaflavin 3-gallate (TF2A), theaflavin 3'-gallate (TF2B), and theaflavin 3,3'-digallate (TF3) - was studied. Polyamide TLC plates dried with a hair dryer, application as bands, and development in a horizontal chamber gave the best results. Detection was performed using iron(III) chloride-ethanol reagent. Twofold development with chloroform-methanol 2:3 (v/v) as mobile phase resulted in the separation of TFI, MA, TF2B, and TF3 from all the other compounds. EGCg, ECg, and EGC were separated but EC and DL-C were not separated from each other. The best mobile phase for each of the compounds is reported. The best separation of the five main catechins (EC, DL-C, EGC, ECg, and EGCg) was achieved by use of n-butanol-acetone-acetic acid 5:5:3 (v/v). In addition, separation of the flavonols myricetin, quercetin, kaempferol, and rutin and the phenolic acids gallic acid, chlorogenic acid, and caffeic acid was achieved by twofold development with chloroform-methanol 2:3 (v/v). The applicability of the method was checked by screening of extracts of green, black, oolong, and pu-erh tea.