Synergistic Ionization via Plasma-Droplet Coupling in an LTP-DESI Hybrid Source for Sensitive Analysis of Volatile Aroma Compounds

Rapid and sensitive detection of volatile compounds in complex matrices remains challenging due to limited ionization efficiency. Herein, we developed a novel hybrid ionization source by coaxially integrating low-temperature plasma with desorption electrospray ionization (LTP-DESI). The LTP-DESI hybrid source was equipped with a triple quadrupole mass spectrometer to analyze volatile aroma compounds. Under the LTP-DESI mode, volatile aroma compounds exhibited significant signal enhancements, with intensities increased by up to 2 orders of magnitude compared with DESI or LTP. This enhancement arises from a three-stage synergistic mechanism: (1) droplet and plasma-driven desorption, (2) primary ionization by both charged droplets and plasma species, and (3) synergistic ionization enhancement via plasma-droplet interaction. The spatial and temporal overlap of the charged droplet and plasma plume significantly promotes [M + H]⁺ generation through Penning ionization, proton transfer and charge exchange under atmospheric pressure. The quantitative and qualitative capability of the LTP-DESI-MS platform was validated through analyses of commercial perfumes and banana tissues, achieving recoveries of 75.3-108.5% with relative standard deviations of 2.7-17.1%. These results highlight the potential of the LTP-DESI system as a robust, practical technique for rapid ambient analysis of aromas in diverse complex samples.