Distinguished Lecture Series: Dr. Stephen Stein

Date: April 19, 2012 (All day)

Location: 106 Woodward Hall

Lecture Title: Mass Spectral Reference Libraries: An Ever-Expanding Resource for Chemical Identification

Speaker: Dr. Stephen Stein

Abstract: Determining the identity of a compound is a central task in chemical analysis. For volatile compounds, a GC/MS analysis, following by library searching, has long been an accepted way of making this identification. For any acquired spectrum, this method locates the most similar spectra in a reference library and presents them in a ‘hit list’ sorted by their match factors’. In this talk, we first examine the fundamentals of chemical identification by library searching using an intuitive ‘Bayesian’ statistical model. This divides the confidence of identification into three factors - prior probability, false negative potential and false positive potential. We then examine various aspects of library search identification according to these factors. Then we review spectrum similarity measures in current use and how they can be used to indicate if the search spectrum is in the library. Next we examine basic features of electron ionization and collision induced fragmentation of ions and their implications for library building and use. Then ideas underlying library quality and the role of high resolution are presented. We then describe ‘recurrent spectra’ libraries, a new class of libraries that contain good quality spectra of unidentified spectra in common materials. We then briefly discuss the merit of linking structures and peaks in spectra and conclude with an overview of the process of chemical identification by MS library searching.

Bio: :Stephen E. Stein is a NIST Fellow, Group Leader and Director of the NIST Mass Spectrometry Data Center in the Chemical and Biochemical Reference Data Division, Chemical Science and Technology Laboratory, National Institute of Standards and Technology. He received his PhD degree from the University of Washington and held positions at SRI International and West Virginia University before joining NIST. He has received numerous awards, including the Presidential Rank Award in 2011

Timings: 3:00  PM to 4:00  PM

For more information: This presentation is part of the 2011-2012 Distinguished Lecture Series sponsored by the UNC Charlotte College of Computing and Informatics.