Three-Layer Electrospray Constructing Charged Microdroplets for Online Derivatization and Position Identification of Lipid C═C Bonds

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Numerous studies have demonstrated that charged microdroplets can significantly accelerate chemical reactions. In this work, we developed a novel three-layer electrospray ionization source (TL-ESI). This source generated charged microdroplets capable of facilitating the rapid epoxidation of unsaturated lipid C═C bonds with the derivatization reagent 3-chloroperbenzoic acid ( m -CPBA) in an online process, achieving a conversion rate of up to 92.8%─a performance not achievable with conventional electrospray ionization source (ESI). Compared to conventional ESI, the TL-ESI effectively compartmentalized reactants, enabled precise control over the reaction process, and supported rapid online derivatization of lipid C═C bonds with m -CPBA. When integrated with tandem mass spectrometry (MS/MS), this source further enabled the localization of lipid C═C bond positions. The TL-ESI is characterized by its simplicity in design, ease of operation, and seamless integration with mass spectrometry (MS). These advantages make it an efficient and practical tool for locating C═C bond positions in unsaturated lipids, even within complex sample matrices. Additionally, this work highlights the potential of the TL-ESI as an innovative platform for accelerating chemical reactions via charged microdroplets, offering a valuable addition to the toolbox of modern analytical chemistry.