Detection of characterising compounds on TLC by DART-MS

Abstract

The new ion source technique, direct analysis in real time (DART) atmospheric pressure ionization allows high resolution mass measurements of gas, liquid and solid samples. Ionization is proceed through a combination of processes including direct energy transfer from the metastable species and proton transfer after ionization of atmospheric water by the metastables. In positive ionization mode, analytes vaporized from the sample react with charged water clusters, forming protonated adduct ions. Since protonated molecular ions are observed by DART-TOF-MS for most compounds, it produces relatively simple and clear mass spectra for multi-component samples. In order to take advantage of quick and simple detection capacity of DART-mass for the analysis of characterising compounds of crude herbal drugs directly, separation on TLC plate was performed for some medicinal plants. Four medicinal plants were selected for this study. They have been reported to contain various bioactive constituents such as atractylon from Atractylodis Rhizoma Alba, paeonol from Moutan Cortex Radicis, berberine from Phellodendri Cortex, and anethol from Foeniculi Fructus. The developed plate was placed between the DART gas beam and the orifice for the real time analysis of each band directly. The bands expected to contain characterising compounds produced exact molecular ion peaks of four compounds within a few seconds of measurement. These results show that the real time analysis of characterising compounds on TLC by DART-TOF-MS could be an efficient tool for natural products analysis.