Semi-open bidirectional low-temperature plasma source coupled with IMS for in situ detection of multiphase samples

This study proposes a semi-open low-temperature plasma ambient ionization source coupled with ion mobility spectrometry for in situ analysis of multiphase samples. For the first time, a bidirectional plasma jet configuration is introduced into the IMS system, enabling the dielectric barrier discharge device to simultaneously generate an ionization jet and a transport jet. The ionization jet efficiently ionizes external samples, while the transport jet stably delivers the ionized products into the reaction region of the ion mobility spectrometer. The coordinated action of the two jets creates a plasma-rich ionization and transfer environment between the sample surface and the IMS inlet, effectively suppressing ion neutralization and ion loss, thereby enhancing signal intensity and detection sensitivity. To further optimize ion transmission, the semi-open ionization source is vertically coupled to the reaction region of the ion mobility spectrometer, which helps reduce direct intrusion of neutral gas into the drift region and improves signal stability. The system enables in situ detection without complex pretreatment, reducing background interference and improving the signal-to-noise ratio. Experiments demonstrate rapid detection of analytes including triethylamine, dimethylformamide, acetaminophen, caffeine, acetone, and ethanol, with clear separation between the reactant ion peaks and the analyte peaks. These results confirm the feasibility and application potential of the semi-open bidirectional low-temperature plasma dielectric barrier discharge ion mobility spectrometry system for rapid in situ detection of multiphase samples, providing a promising approach for environmental monitoring, public safety, food safety, and pharmaceutical analysis.