Armentrout received his B.S. degree from Case Western Reserve University in 1975 and earned his Ph.D. from the California Institute of Technology in 1980. During these studies he determined that much of the published information on thermodynamic states was not reliable, or was presented in differing formats. When he became a research professor he used this frustration as motivation to invent and construct the guided ion-beam tandem mass spectrometer, which provided highly accurate thermodynamic measurements. With this instrument in hand, he went on to invent or improve tools to analyze those measurements, including advanced computer algorithms. He has published much data on the properties of transition metals, and has worked most recently on the thermodynamic properties of biological systems.
^Bierbaum, Veronica M. (2002). "Focus on ion thermochemistry in honor of Peter B. Armentrout, recipient of the 2001 Biemann Medal". Journal of the American Society for Mass Spectrometry. 13 (5): 417–418. doi:10.1016/S1044-0305(02)00377-X.