Forensic Application of Fluorescence Fiber By Team Yellow

Forensic Application of Fluorescence Fiber By: Team Yellow September 15, 2010

Fiber as Evidence Trace evidence Collected analyzed when there has been a personal contact - homicide, assault, sexual offenses - hit-and-run, other vehicle accidents - burglaries Advantage - can remain intact for years - easily transferred Disadvantage - class characteristics only - adhering problems due to type of fiber or type of receiving material

Uses in forensic science labs Examine transferred fibers and compare them to a known or reference fiber to find its origin Fluorescence of the dyes are added to fibers Identification/Comparison: 1) Type e. g. synthetic polymer and 2) Subtype e. g. nylon Main classification scheme: method of dye application Ex) acid (wool or silk), basic (polyester), direct (cotton or rayon), disperse (polyester or acetate) dyes Cannot identify a particular dye or mixture of dyes

Analytical Methods Polarized light microscopy (PLM) Energy dispersive X-ray analysis Thin layer chromatography (TLC) High performance liquid chromatography (HPLC) Pyrolysis gas chromatography (PGC) Fourier transform infrared spectroscopy Raman spectroscopy UV-VIS & Fluorescence MSP: nondestructive, prevent contamination, decrease overall analysis, are direct, and inexpensive

Microspectrophotometry “The technique of measuring the light absorbed, reflected, or emitted by a microscopic specimen at different wavelengths. ” (The Free Dictionary) “VIS, UV/VIS, and fluorescence microspectrophotometry offer direct, relatively inexpensive, and informative means of characterizing dyed fibers. ” (Morgan, et al. , 2004. p. 1) Cantrell collected analyzed over 3, 000 types of fibers from movie theater seats and concluded that; - Even though fibers are mass-produced, most fibers exhibit high variability. - Fluorescence, in particular, was found to add considerable discrimination even within common fiber class/color combinations. (Morgan, et al. , 2004)

Instrument Light Source: UV-VIS uses Xenon, Fluorescence MSP uses Mercury lamp Detector: QDI 1000 Microspectrophotometer (MSP) using GRAMS/AI 7. 00 software for data acquisition

Detector 100 scans of four different yellow fibers where taken and averaged over a spectrum range of 200 -850 nm Two multivarient data analysis to record and obtain numerous spectra with more than one feature 1. Principle Component Analysis (PCA) --Unsupervised technique --Determines linear combinations between original variations and maximum variations of data set 2. Linear Discrimination Analysis (LDA) --Supervised technique --Determine linear combinations of features that best separate the data into two or more predefined groups

UV-VIS using PCA vs. LDA

Excitation and Emission Spectra Fluorescence excitation and emission spectra of Lyso. Tracker Red DND 99 in p. H 5. 2 buffer (Invitrogen)

Emission Spectra Emission spectra of dyed fibers (Morgan, et al. , 2004)

Emission Spectra Emission spectra of red acrylic fiber using different excitation wavelengths (Morgan, et al. , 2004)

Absorption vs. Fluorescence spectrum of 3 red polyester fibers (at excitation 546 nm)

Potential problems, Interferences When dealing with fibers you must know a head of time the general chemical nature, i. e. : Acidic, basic, or neutral Two other types of interference are: extraction solvents & possible degradations e. g. organic solvents used in the extraction of the fiber dye can either negatively impact the separation or present interferences to a UV–visible detector Solution: Antioxidants, prompt analysis, and low extraction temperatures are used to combat against dyes that have been degraded

Conclusion 1. The groups of fluorescence spectra can be visually distinguished from one another, which cannot be done with the UV-VIS spectra 2. At least for certain fiber/dye combinations, fluorescence spectra appear to exhibit higher discrimination power than UV-VIS absorbance spectra Fluorescing textile fiber with 365 nm excitation. (Photo and spectra courtesy Dr. Paul Martin, CRAIC Technologies Corp. )

References Invitrogen. (2010). Product spectra. Retrieved from http: //www. invitrogen. com/site/us/en/home/support/Produc t-Technical-Resources/Product-Spectra. 7528 p 52. html Microspectrophotometry. The American Heritage® Medical Dictionary. (2007). Retrieved from http: //medicaldictionary. thefreedictionary. com/microspectrophotometry Morgan, S. L. , Nieuwland, A. A. , Mubarak, C. R. , Hendrix, J. E. , Enlow, E. M. , & Vasser, B. J. (2004). Forensic discrimination of dyed textile fibers using UV-VIS and fluorescence microspectrophotometry. Proceedings of the European Fibres Group, 25 May 2004. Retrieved from http: //www. chem. sc. edu/faculty/morgan/pubs/Bartick_et_al _European. Fibres. Group_2004. pdf