Use of coupled ion mobility spectrometry-time of flight mass spectrometry to analyze saturated and unsaturated phenylpropanoic acids and chalcones

BACKGROUND: In metabolite profiling screens or analyses, where generic separation and analysis conditions are used in efforts to measure as many metabolites as possible, overlapping signals from very similar molecules often make it very difficult if not impossible to separate and identify specific molecules of specific classes. The aim of this study was to evaluate the utility of coupling ion mobility spectrometry to UPLC-TOFMS (UPLC-Q-IMS-TOFMS) as a means to separate and identify saturated and unsaturated phenylpropanoic acids and chalcones, phenylpropanoid-acetate pathway derived compounds that are common in plant extracts. RESULTS: This approach readily separated most of the unsaturated phenylpropanoid acids (t-cinnamate, p-coumarate, caffeate, ferulate) from the corresponding saturated (dihydro-) compounds, and analysis of two dimensional plots of mass/charge ratio values versus ion mobility drift time revealed that the other compounds can indeed be distinguished. However, this approach was less effective for the larger chalcones. CONCLUSIONS: UPLC-Q-IMS-TOFMS is a promising tool to enable the separation, identification and quantification of very similar molecules. Although it has its limitations, as was seen for the chalcones that were not well separated in this investigation, ion mobility spectrometry nevertheless adds an additional level of characterization to large-scale metabolomic screens, which increases the power of such screens without the demand for multiple analyses using very different column chemistries.