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Chemistry and Biochemistry Faculty Seminar: Dr. Stephen Morgan

Friday, January 18, 2013 - 4:00 pm to 5:00 pm

Dr. Stephen Morgan
Professor of Chemistry and Biochemistry
University of South Carolina

“Analytical Chemistry Research for Forensic and Cultural Heritage Decision-Making”

Jones Physical Science Center Room 006 (Map)

Current research in our laboratories includes improving discrimination of trace evidence
fibers, diagnosis of audio tape degradation for cultural heritage institutions, and remote
imaging of blood at crime scenes.
Fiber evidence is class evidence: discovery of a fiber at a crime scene and its identification
as a particular fiber type (e.g., acrylic, cotton, nylon, polyester) may not provide much
support for a forensic investigation. The probative value of a fiber depends on its uniqueness
relative to the background of normal fibers encountered. We have employed direct UV/visible
microspectrophotometry (MSP) coupled with pattern recognition, as well as microextraction
followed by liquid chromatographic separation and detection of individual dye components
by mass spectrometry. Qualitative and semi-quantitative fiber dye ‘fingerprints” can define the
number and relative amounts of dyes present; characterizing fiber dyes at the molecular level
offers information not available from microscopy or spectroscopy alone.
Another project concerns the need for a rapid method to identify degraded audio tape to
facilitate treatment priority before copying and/or digitizing at cultural heritage institutions
and archives. Tapes produced during the 1970-1990’s often contain polyester-urethane (PEU)
binders that hold magnetic particles onto polyethylene terephthalate substrates. PEU binders
are known to degrade via hydrolysis, which causes squealing and/or shedding of magnetic
material onto playback device heads (‘sticky shed syndrome’). No reliable non-destructive
methods for rapidly identifying degraded tapes existed before this work. We have found
IR spectroscopy combined with multivariate statistics can correctly predict tape condition
better than 98% of the time. This approach for rapid, on-site analysis of collection material
will be validated in collaboration with the Library of Congress, the Moving Images Research
Collection at USC, the Museum of Modern Art, and National Public Radio.
Current ways to visualize blood at crime scenes are not specific, require dark conditions,
potentially contaminate evidence, and expose investigators to chemicals. The Morgan and
Myrick groups at USC have developed an instrument based on mid-infrared (IR) diffuse
reflectance for visualization of latent blood stains. A modulated infrared source illuminates
the target, and reflected light is filtered and collected by an imaging chip. Each pixel is
processed by a lock-in amplifier approach to produce an output that is proportional to
contrast between stain/no-stain regions. Response is further sensitized to spectral regions
of blood components (e.g., proteins) by chemical filters. The resulting image shows regions
indicative of the target analyte (latent blood) contrasted from background. Blood below
several hundred to several thousand times diluted can be detected, and discrimination is
possible against substances yielding false-positive responses with other techniques. Further
design and validation is in progress to realize our ultimate forensic goals and to place a system
into use at the State Law Enforcement Division Forensic Laboratory.
References:
Myrick, M.L.; Morgan, S. L.. “Infrared specular reflection calculated for polymer films on polymer substrates: Models for the
spectra of coated plastics,” Spectroscopy, August 2012, 40-56.
Brooke, H.; Baranowski, M. R.; McCutcheon, J. N.; Morgan, S. L.; Myrick, M. L. “Multi-mode Imaging in the Thermal
Infrared for Chemical Contrast Enhancement Part 3: Visualizing Blood on Fabrics,” Analytical Chemistry, 2010, 82, 8427-
8431.
Stefan, A. R., Dockery, C. R., Baguley, B.M., Vann, B. C., Nieuwland, A. A., Hendrix, J. E., Morgan, S. L. “Microextraction,
capillary electrophoresis, and mass spectrometry for forensic analysis of azo and methine basic dyes from acrylic fibers,” Anal.
Bioanal. Chem. 2009, 394, 2087-2094.

Refreshments served at 3:45PM

www.chem.sc.edu


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