Modifying an Orbitrap Mass Spectrometer for Analysis of Gas-Phase Molecules
Michael Duncan ’23
Douglas Collins, Chemistry
Presidential Fellows Program
The most common method of analysis for trace gases in air employs chemical ionization-time of flight mass spectrometry (CI-TOF-MS). Transportable CI-TOF-MS instruments have relatively low mass resolving power (m/Δm 50,000, allowing for the exact monoisotopic mass to be determined. However, Orbitrap instruments are most commonly designed to analyze sprayed liquid samples. Atmospheric chemists commonly need to analyze the molecular composition of gases that include a variety of large organic molecules that have a similar mass to charge ratios as one another, making it difficult to accurately identify them using a CI-TOF-MS. This project set out to design a chemical ionization apparatus for Orbitrap mass spectrometry and allow for the analysis of gaseous samples. The design has been focused on low costs, modularity, and adaptability, all in order to keep the horizon of users and use cases as broad as possible. Analyte ions will be formed by ion-molecule reactions within a cone-shaped flow reactor. Reagent ions will be supplied to the ion-molecule reactor using a continuous soft x-ray photoionization process. Computer-aided design in Solidworks along with rapid prototyping with 3D printing has allowed for conceptualization, realization, and testing of key components before fabrication. The first machined prototype is the next major step that will provide the opportunity to test the concept.