Application of mobile phases containing ionic liquid for the separation of a mixture of ten selected isoquinoline alkaloids by 2D-TLC and identification of analytes in Rhizoma Coptidis (Huang Lian) Extract by TLC and HPLC—DAD

Abstract

A simple and inexpensive two-dimensional thin-layer chromatography (2D-TLC) method was applied with mobile phase containing ionic liquid (IL) for the separation of ten components of a mixture of isoquinoline alkaloids such as allocryptopine (A), berberine (Be), boldine (Bo), chelidonine (Ch), papaverine (Pa), emetine (E), columbamine (Col), magnoflorine (M), palmatine (Pal), and coptisine (Cop). Separation of the alkaloid mixture was achieved by 2D-TLC using an aqueous mobile phase (RP) in the first dimension (80% methanol—water—0.05 M L−1 diethylamine) and a normal phase (NP) in the second dimension (75% methanol [MeOH], 24.75% ethyl methyl ketone—0.25% IL (1-butyl-3-methylimidazolium tetrafluoroborate) (v/v) on bilayer Multi-K CS5 plates. The procedure was evaluated in terms of natural samples analysis. Coptisine, palmatine, and berberine were identified in Rhizoma Coptidis (Huang Lian) extract. Additionally, the alkaloids in the extract sample were confirmed by high-performance liquid chromatography—diode-array detection (HPLC—DAD) method with application of a Synergi Polar RP column and a mobile phase consisting of a mixture of 25% acetonitrile (MeCN), 0.25% IL (1-butyl-3-methylimidazolium tetrafluoroborate), and 74.75% water (v/v). The composition of the mobile phases was optimized in terms of retention, separation selectivity, spots symmetry, and system efficiency. Limits of detection (LODs) were from 0.10 and 0.13 μg mL−1 and limits of quantification ( LOQs) between 0.31 and 0.41 μg mL−1.