Nano-liquid chromatography and conventional HPLC were used for the separation of diastereomers of (+)-catechin-ethyl-malvidin-3-glucoside. Those bridged anthocyanin dyes were obtained by reaction of (+)-catechin with malvidin-3-glucoside in the presence of acetaldehyde. Both diastereomers were isolated with semipreparative chromatography and their structures were confirmed by nuclear magnetic resonance and mass spectrometry. In-laboratory prepared capillary columns packed with fully porous particles Chromosphere C18, dp=3μm, core-shell particles Kinetex C18, dp=2.6μm (100μm i.d.) and monolithic column Chromolith CapRod (100μm i.d.) were used for the separation of (+)-catechin, malvidin-3-glucoside and both diastereomers. Chromosphere C18 stationary phase provided the best chromatographic performance. Mobile phase containing water:acetonitrile (80:20) acidified with trifluoroacetic acid (0.1%, v/v/v) was used in an isocratic elution mode with a flow rate of 360nLmin(-1). Separation of studied compounds was achieved in less than 7min under optimized conditions. The nano-liquid chromatographic method and a conventional HPLC one using the same fully porous particles (Chromosphere C18, 3μm, 100mm×4.6mm) were compared providing higher separation efficiency with the first analytical method and similar selectivity. A better peak symmetry and higher resolution of the studied diastereomers was achieved by conventional chromatography. Nevertheless, nano-liquid chromatography appeared to be useful for the separation of complex anthocyanin dyes and can be utilized for their analysis in plant and food micro-samples. The developed method was used for analysis of red wine grape pomace.

Centre of the Region Haná for Biotechnological and Agricultural Research Department of Chemical Biology and Genetics Faculty of Science Palacký University Šlechtitelů 27 78371 Olomouc Czech Republic

Institute of Chemical Methodologies Italian National Research Council Area della Ricerca di Roma 1 Via Salaria Km 29 300 Monterotondo 00015 Rome Italy

Regional Centre of Advanced Technologies and Materials Department of Analytical Chemistry Faculty of Science Palacký University 17 listopadu 12 779 00 Olomouc Czech Republic

Regional Centre of Advanced Technologies and Materials Department of Analytical Chemistry Faculty of Science Palacký University 17 listopadu 12 779 00 Olomouc Czech Republic; Institute of Chemical Methodologies Italian National Research Council Area della Ricerca di Roma 1 Via Salaria Km 29 300 Monterotondo 00015 Rome Italy

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