Rapid Profiling and Real-Time Monitoring of Volatile Compounds Using a Low-Pressure Photoionization Source Combined with an Orbitrap Mass Spectrometer

This study employed a low-pressure photoionization source combined with an orbitrap mass spectrometer (LPPI-MS) for rapid and comprehensive profiling of volatile organic compounds (VOCs) across chemically diverse biological samples. Garlic was first selected to evaluate the performance of LPPI, where strong aroma and high abundance of sulfur-containing volatiles like alk(en)yl sulfides, thiophenes, and dithiin derivatives derived from alliin-related transformations were detected. Toluene was introduced as a dopant to enhance the photoionization efficiency during the analysis of garlic and fresh-cut apple samples. The method was subsequently applied to four commercially available Chinese liquors, representing complex fermented matrices, where alcohols, esters, and other fermentation-derived VOCs were identified and used to differentiate product profiles. Finally, fresh-cut apple, characterized by a more subtle aroma, was analyzed under dopant-assisted conditions, revealing aldehydes, alcohols, esters, and aromatic compounds associated with related biosynthetic pathways triggered by tissue disruption. This sequential progression from easily detectable to more challenging VOC profiles demonstrated the robustness, sensitivity, and broad applicability of LPPI-MS for real-time aroma analysis in food quality control and metabolic studies.