Probing Chemical Bond Energy Using an Instructional Mass Spectrometer for Undergraduate Experiments

Herein, an undergraduate experiment design is reported to probe chemical bond energy using an instructional mass spectrometer. The experimental procedure involved measuring the dissociation energy of chemical bonds by precisely modulating the electron energy during ionization. This energy was determined by correcting the threshold appearance energy of the resulting fragment ions. Acetonitrile, nitrogen, and oxygen were used as standard substances and target samples to calibrate the electron energy within the ion source and validate the proposed method. This practical laboratory exercise, conducted for chemistry undergraduates, enabled students to master the entire workflow of electron ionization–mass spectrometry (EI-MS), including fundamental principles, instrument tuning, spectral interpretation, and the determination of chemical bond energy. Teaching evaluations indicated that the experiment significantly enhanced student interest, practical skills, and their understanding of the relation between chemical bond stability and instrumental parameters. This study offers a replicable model for integrating modern analytical techniques with basic chemical knowledge into undergraduate laboratory curricula.