Thin-layer chromatography with eutectic mobile phases—preliminary results

Abstract

The presented paper is the first to show thin layer chromatography (TLC) analysis based on eutectic mobile phases (Deep Eutectic Solvents – DES). During the experiment 25 eutectic mixtures were investigated for their chromatographic properties. Most of them belong to the natural deep eutectic solvents (NADES) group. Also, new eutectic liquids based on phenolics and terpenes, not previously employed in analytical practice, were tested. The eutectic liquids were investigated as pure or diluted with solvents used in chromatographic routine: methanol, water, acetone, chloroform or diethyl ether. The analyses were carried out using classic and high performance silica gel plates. The working solution was a mixture of five alkaloids found in genus Chelidonium, namely sanguinarine, coptisine, chelerythrine, chelidonine, and berberine, with UV light detection of 366 nm. This report proves that eutectic TLC is possible and that the eutectic interactions play a crucial role in the separation process. In most of the tested modifications at least partial separation was achieved. The most successful mobile phase, which enabled separation of all the tested alkaloids, was the equimolar mixture of menthol and phenol with a 35% addition of methanol. The system was also effective in separating alkaloids in the real Chelidonium maius extract sample.