Twisted Dipole\nIon Guide (TDIG) for Flexible Ion Transfer\nin Atmospheric Pressure Ionization Mass Spectrometry

In ambient mass spectrometry, the performance in direct\nin situ\nanalysis applications has been hindered by the lack of efficient ion-transferring\ntechnique between the atmosphere pressure ionization source and the\nmass analyzer. Building upon the hybrid concept of a stack ring ion\nguide and multipole ion guide, this study proposes the concept of\na reconfigurable twisted dipole ion guide (TDIG) that enables flexible\nion transfer between atmosphere and vacuum. Initially, theoretical\nand numerical studies were conducted to understand the basic ion confining\nprinciple of the twisted dipole ion guide, revealing its unique merits\nin long-distance flexible ion transmission. The gas dynamics and ion\ntransport performance of the TDIG are then evaluated by using computational\nfluid dynamics and ion trajectory simulation. To actualize the concept,\nspecialized insulation brackets were designed based on the universal\njoint mechanism, and a practical twisted dipole ion guide prototype\nwas built. The prototype was tested on a homemade nano electrospray\nionization-time-of-flight-mass spectrometry (ESI-TOF-MS) platform.\nThe results suggest that it is competent in flexible ion transfer\nand may serve as a versatile tool in ambient mass spectrometry. This\ninnovation can potentially advance the development of in situ analytical\nmass spectrometry techniques.