Dr. Alexandra C. Stenson, 
Associate Professor
Professional Preparation:
Florida State University, Chemistry & Environmental Chemistry, B.S., 1998
Florida State University, Analytical Chemistry, Ph.D., 2002
Contact Information:
Office location: CHEM 231
Phone: (251) 460-6181
Email: astenson@southalabama.edu
Courses:
CH 131 General Chemistry I, CH 265 Quantitative Analysis, CH 394/494 Directed Studies, CH 499 Senior Honors Chemistry
Undergraduate Research in the Stenson Lab
Research Summary:
Characterization of unknown compounds from extremely complex mixtures remains one of the major challenges in modern analytical chemistry. Complex mixtures in themselves are not necessarily crippling if enough is known about the components allowing for the design of highly specific separation techniques (this is generally taken advantage of for biological samples). True unknowns are somewhat more difficult, but can generally be structurally identified as long as enough information-rich data are compiled (e.g. NMR, IR, X-ray crystallography and mass spectra). The combination of complexity and true unknowns is, however, still a large stumbling block.
Mixtures too complex to be fractionated into individual components are relatively common in nature. Humic substances (the condensation and degradation products of dead and decaying plant and animal matter) are one such example. Humics are ubiquitous in nature and of great agricultural and environmental importance. More recently biomedical uses for these compounds (particularly as antiviral agents) have also been identified.
In this research group we are using chromatography and mass spectrometry to
characterize humic substances on the molecular level. Research goals involve the
development of pre-fractionation methods that reduce the overall complexity of humic mixtures; identification of structural components for individual humic molecules through tandem MS techniques; and mimicking of humic substances through synthetic standards.
Recent Publications & Collaborations:
O’Brien, R.A.; Mirjafari, A.; Jajam, V.; Capley, E. N.; Stenson, A.C.; West, K. N.; Davis, Jr, J. H. Functionalized ionic liquids with highly polar polyhydroxylated appendages and their rapid synthesis via thiol-ene click chemistry. Tetrahedron Letters (2011), 52(40), 5173-5175.
Capley, E. N.; Tipton, J. D.; Marshall, A. G.; Stenson, A. C.; Chromatographic
Reduction in Isobaric and Isomeric Complexity of Fulvic Acids Enables Multistage Tandem Mass Spectral Characterization. Analytical Chemistry (2010), 82, 8194-8202.
Stenson, A. C. Fourier Transform Ion Cyclotron Resonance Mass Spectral Characterization of Metal-Humic Binding. Rapid Communications in Mass Spectrometry (2009), 23(4), 465-476.
Figure A: Chromatographic Pre-fractionation
of Suwannee River
(Click image to enlarge)
Fulvic Acid: a) Isobaric complexity is reduced in
early and late eluting fractions, b & c) compositional differences between fractions are evident; as
expected, early eluting material is more polar (i.e.
more oxidized as indicated by higher O/C rations
and KMDs).
Figure B: Compositional Differences between
Suwannee River
(Click image to enlarge)
Fulvic Acid Fractions: Summarized are MS2
and H/D exchange data. Together, they indicate
that early eluting fractions have a high carboxylic
acid content while late eluting fractions have a higher
alcohol and ether (especially methyl ether) content.
Thus, late eluting fractions retain more of the
characteristics of recursor material such as lignin and tannins suggesting that this material is newer/
less oxidized whereas late-eluting material represent
the older/more oxidized material.
© 2012 University of South Alabama Mobile, AL 36688-0002
Phone: (251) 460-6181
Fax: (251) 460-7359
For questions or comments Contact
Us
Last Updated:
June 19, 2013 9:40 AM
http://www.southalabama.edu/chemistry/stenson/index.html