Date of Award

2016

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

College of Arts and Sciences

First Advisor

Stephen L. Morgan

Abstract

Textile fibers found in an investigation are trace evidence that can connect a suspect to a victim or crime scene. Examination involves comparison of the color and morphology of a questioned fiber to a known fiber with optical spectroscopy. Fibers are considered class evidence, so evaluating more characteristics increases their significance as evidence if a match cannot be excluded. Acrylic, nylon, and polyester are textile polymers that require different extraction solvents based on the polymer chemistry. Methods have been developed for UPLC analysis of basic dyes on acrylic, acid on nylon, and disperse dyes on polyester. After microextraction from single fibers, a two minute run enables separation and identification of dyes by UV/visible detection with retention time matching and spectral comparison.

However, fibers are rarely found in pristine condition. Over the normal course of the lifetime of a garment, the pattern of dye weathering or photodegradation may even individualize an item of evidence. On the other hand, fibers from a clothed body left in extreme desert conditions might lose dye to photodegradation, lowering their viability as trace evidence. We demonstrate trace analysis of dyestuff residues from single 10 mm fibers of acrylic, nylon, and polyester samples after exposure to varying humidity and temperature at ASTM testing sites in Phoenix, AZ, and Miami, FL. Despite the loss of dye amounts with increasing environmental exposure, all dyes were detected even in the most weathered fabrics subjected to a year of outdoor exposure. To evaluate the changes in fabrics and dyes after laundering conditions, three brands of detergent (Tide®, Gain®, and Wisk®) were used alone, with bleach, or with Clorox 2® (stain remover and color booster) to wash polyester, acrylic and nylon up to 50 times. Separation and spectral characterization are used to compare spectral differences of dyes extracted from laundered nylon, which are valuable in understanding the forensic relevance of trace fiber evidence.

Rights

© 2016, Molly Rebecca Burnip

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