Mass Spectrometric Behaviors Of Ionic Liquids And Their Applications In Pharmaceutical Analysis

Owing to their many special and extraordinary properties,ionic liquids(ILs) have great potential for industrial applications.Therefore,study of ILs is of great significance in terms of both science and application.Here we first give a brief introduction of the physical and chemical properties of ILs and scientific instruments used in this area,e.g.,various mass spectrometries and chromatographies,as well as the current status of the research in this field.Then we will focus on our mass spectrometric study of ILs and fragmentation mechanisms of ILs,as well as applications of ILs.(1) We have systematically studied the characteristic behaviors of the electrospray ionization mass spectra of various types of ILs,including imidazolium, pyridine,and quaternary ammonium ILs.We have proposed schemes of their fragmentation pathways and mechanisms.(2) We have studied the effects of the length of the side alkyl chain of the ILs,and found that it has dramatic effects on their fragmentation.The longer the chain, the higher the collision voltage required to dissociate the ILs.This suggests that a longer chain leads to a more stable chemical structure.At the same time, our results demonstrate that the presence of sulfonic groups in the cations of the ILs have a great impact of their fragmentation.Such sulfonic groups also cause the appearance of peaks of[M-H+Na]~+ and[M-2H+2Na]~+ in the mass spectra.This is likely because that sulfonic groups have a high electron affinity and thus a strong effect in the distribution of the election cloud.In this way,they strongly influence the fragmentation pathways.(3) We have systematically studied the solvation of fragment ions of various types of ILs which contain alkyl chains terminated with a sulfonic group.Under normal operation conditions of ESI-MS,we have observed unusual solvation phenomena via mass spectral analysis.Such solvation seriously complicates the interpretation of the mass spectra and needs necessarily to be understood in order to avoid erroneous interpretation of the mass spectral data.(4) We have developed a green and effective method based on the IL-based ultrasonic assisted extraction,and applied it in the extraction of piperine from white pepper and of leonurine from motherwort.Compared with conventional HRE and regular UAE extraction,the proposed approach provides higher extraction efficiency,and obviously reduced extraction time,and therefore has a great potential for applications.