Abstract: In response to the current situation in chemistry education, where experiments predominantly focus on verification and students’ ability for independent innovation is limited, a novel experiment titled “Self-developed Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry for Detection of Unsaturated Fatty Acids” has been designed. By guiding students to build their own atmospheric corona discharge ionization device, the experiment offers a deep understanding of the principles of ionization and epoxidation, encouraging experimental initiative. The homemade device is simple, efficient, and significantly reduces teaching costs, while also avoiding the use of organic reagents, reflecting an environmentally friendly approach. In this experiment, students investigate the epoxidation of the C＝C bond of oleic acid with the water radical cation (H₂O)₂^+·, a novel active species, for the rapid quantitative analysis of oleic acid in vegetable oils. The experiment emphasizes essential analytical chemistry techniques and organic mass spectrometry skills, with the goal of cultivating students’ hands-on abilities and fostering scientific innovation. This experiment is particularly suitable for undergraduate chemistry laboratory courses.

Key words: Oleic acid, Direct mass spectrometry, Quantitative analysis, Teaching reform experiment, No sample pretreatment