Plasma-assisted electrospray ionization mass spectrometry.

Microlightning between oppositely charged microdroplets within neutral water droplets imparts unique chemical reactivity. Nevertheless, this phenomenon occurs with limited intensity under common spray conditions, necessitating amplification for practical application. This study presents an innovative plasma-assisted electrospray ionization mass spectrometry (PAESI-MS) platform distinguished by its simple design, low cost, and efficient integration of plasma with ESI in situ. By incorporating a grounded metal mesh at the front end of a commercial ESI source, plasma generated from the nebulizing gas (NG) couples with the electrospray plume within the same spatial domain. The resulting activated species are transferred into charged microdroplets, triggering synergistic interactions. This platform substantially enhances detection sensitivity for highly polar compounds and enables efficient analysis of low-polarity analytes. Compound detection across a broad polarity range was experimentally validated following systematic optimization of key parameters, including applied voltage, NG flow rate, and sample infusion rate. The results demonstrate the strong potential of PAESI-MS for real-sample analysis, establishing a cost-effective and versatile MS strategy. Furthermore, plasma activation effectively overcomes the excitation energy barrier of the carrier gas, macroscopically amplifying microdischarges between microdroplets of varying sizes. This unique characteristic underscores the potential of PAESI-MS as a powerful platform for advancing microdroplet chemistry research.