The Department of Chemistry invites you to its departmental seminar today at 4:10 p.m. in Fulmer Hall, room 201.
Dr. Nicolas C. Polfer from the University of Florida will present, Toward laser spectroscopy – mass spectrometry as a bioanalytical tool for the identification of unknowns
Abstract: Laser spectroscopy of gas-phase ions combines the structural information from spectroscopy (e.g. vibrational, electronic spectroscopy) with the analytical sensitivity and powerful separation capabilities of mass spectrometry. Routine operation of benchtop light sources have laid the path to making the techniques analytically more robust. This talk will mainly focus on infrared (IR) ion spectroscopy as a tool to confirm the chemical structures of ions based on diagnostic vibrations. For the example of the metabolite para-aminobenzoic acid (see figure), protonation at the carboxylic acid (top) results a very different IR spectrum than protonation on the amino group (bottom). A comparison to a theoretical IR spectrum via for instance density-functional theory (DFT) can serve as a powerful identifier of the structure. Similarly, chemical isoforms of aminobenzoic acid, such as the ortho- and meta-substituted forms, are also shown to have distinct IR spectral features, allowing their differentiation. While these approaches can answer some chemical questions, the limited spectral resolution of room-temperature IR ion spectroscopy often constrains its analytical use as a differentiation tool. For a more general identification of unknowns, IR ion spectroscopy performed at cryogenic temperatures (i.e., <30K) offers significantly enhanced resolution, but also introduces new challenges with respect to developing cryogenic instrumentation and methodologies.
