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

2. Fiber as Evidence Trace evidence
Collected and 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

3. 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

4. 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

5. 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., p.1)
Cantrell collected and 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)

6. 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

7. Detector
100 scans of four different yellow fibers where taken and averaged over a spectrum range of 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 

8. UV-VIS using PCA vs. LDA

9. Excitation and Emission Spectra
Fluorescence excitation and emission spectra of LysoTracker Red DND-99
in pH 5.2 buffer
(Invitrogen)

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

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

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

13. 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

14. 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.)

15. References
Invitrogen. (2010). Product spectra. Retrieved from t-Technical-Resources/Product-Spectra.7528p52.html
Microspectrophotometry. The American Heritage® Medical Dictionary. (2007). Retrieved from dictionary.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 Retrieved from EuropeanFibresGroup_2004.pdf