Dr. Gabriella Weiss
NASA/GSFC – UMBC
Friday, September 12, 2025
12:00 Noon
Room 120 – Meyerhoff Chemistry Building
Host: Dr. Brian Cullum
“Mapping intramolecular carbon isotope patterns in small molecules with Fourier transform mass spectrometry”
Molecules form via the addition of single atoms or subunits of atoms and measuring the isotopic composition of different parts of a molecule can provide information about synthesis as well as alteration by biological and/or abiotic processes. Molecule fragmentation using mass spectrometry is a common form of compound identification and recently, this has been leveraged to investigate the isotopic composition of specific compound moieties. Historically, intramolecular isotope measurements (i.e., position-specific isotope analysis, PSIA) were laborious, requiring large amounts of analyte and specialized instrumentation. Here, we discuss the use of Fourier transform mass spectrometry (FT-MS) for making molecular average and position-specific isotope measurements. FT-MS (i.e., Orbitrap mass spectrometry) permits the measurement of isotope ratios of intact molecules and their fragments without requiring conversion to simple gases like CO2. Two case studies will be discussed: one using direct infusion and electrospray ionization to analyze the amino acid alanine and the other using gas chromatography and electron impact ionization to measure toluene.