Chiral differentiation of amino acids through binuclear copper bound tetramers by ion mobility mass spectrometry

In this study, travelling wave ion mobility mass spectrometry has been used to investigate chiral differentiation of common chiral amino acids, through separation of binuclear copper bound tetrameric ions formed with chiral selector tryptophan, proline, tyrosine, phenylalanine or histidine. Significant chiral recognition was observed for amino acids with aromatic rings or long and active side chains, with peak-to-peak resolutions up to 1.826. Tryptophan and histidine offered better enantioselectivity, compared to other chiral selectors. The results suggested that the mechanism for chiral recognition in ion mobility mass spectrometry might be significantly different from that in tandem mass spectrometry. Linear calibration curves were also established to allow determination of enantiomeric excess of the analytes by the approach. This study showed that higher assembly of chiral analyte and chiral selector might enable better chiral discrimination and ion mobility mass spectrometry could be a powerful technique for provide qualitative, quantitative and structural information of chiral analysis.