Separation, Quantification and Structural Study of (+)-Catechin and (–)-Epicatechin by Ion Mobility Mass Spectrometry Combined with Theoretical Algorithms

Summary of main observation and conclusion Two catechin epimers and their non-covalent complexes with γ-cyclodextrin were studied by using ion mobility coupled with mass spectrometry (IM-MS). Rapid separation of complexes was achieved with the peak-to-peak resolution reaching 0.86 after optimization of IM condition. Collision cross section (CCS) was measured to explore the structural difference of complexes. A gap of 11.75 Å 2 between two complexes was found. Molecular modeling and theoretical CCS calculation were adopted to explain the measurement results. Two binding ways of both complexes were found and the calculated CCS corresponds accurately to the measured CCS. Quantification of catechins in mixtures was performed and the relative error was less than 15%, indicating the effectiveness of quantification by IM-MS.