Fibers forensic analysis

Other uses of an IR microscope in forensic analysis include the examination of fibers, drugs, and traces of explosives. For example, oxidation of hair can occur chemically or by sunlight oxidation of cystine to cysteic acid can be seen in hair fibers by FTIR microscopy (Robotham and Izzia). Excellent examples in full color of FTIR imaging microscopy can be found on the websites of companies like PerkinElmer and Thermo Fisher Scientific. Our limitations in use of gray scale make many of the examples unsuited for reproduction in the text. A novel IR microscope combined with atomic force microscopy, the nanoIR platform from Anasys Instruments (www.anasysinstruments.com), permits nanoscale IR spectroscopy, AFM topography, nanoscale thermal analysis, and mechanical testing. 

Causin, V. Marega, C. Schiavone, S. Della Guardia, V. Marigo, A. Forensic analysis of acrylic fibers by pyrolysis-gas chromatography/mass spectrometry. J. Anal. Appl. Pyrol. 2006, 75, 43 8. 

E2224-02 Standard Guide for Forensic Analysis of Fibers by Infrared Spectroscopy... 

Another vibrational technique, Raman spectroscopy is gamering attention for the forensic analysis of drugs and pharmaceuticals, paints, fibers, and inks. Raman techniques differ from traditional vibration IR in that scattered radiation, rather than absorbed radiation, is studied. Furthermore, Raman interactions are dependent, not on the existence of polar bonds, but instead on the existence of polarizable bonds as shown in Figure 5.36. 

Chapter 14 The Forensic Analysis of Paper, Fibers, and Polymers... 

Several characteristics of fibers are targeted by forensic analysis. As shown in Figure 14.8, the chemical composition of the fiber is just one of many important characteristics. The diameter and cross section are useful for determining how a fiber is used. For example, carpet fibers are relatively thick and often have hollowed-out cross sections compared with those of fibers used in clothing. Cotton fibers have a characteristic flat ribbon geometry. Fiber color and how it... 

Koons, R. D., et al. "Comparison of Individual Carpet Fibers Using Energy Dispersive X-Ray Fluorescence Forensic Analysis of Sin e Fibers by Raman Spectroscopy." Journal cf Forensic Sciences 41 (1996), 199-206. 

The only way to overcome all of these problems is to use a nondestructive in situ analytical technique. Given the small quantities of colorants present in trace samples, ultaviolet (UV)-visible microspectrophotometry is one of the few analytical techniques that can be used in situ. Unfortunately, the electronic spectra data obtained provide only a very limited amount of molecular information to compare samples and help in the identification of a dye. The technique is very poor where discrimination of dyes in the mixture is required and this can be a key piece of information, for example, if a fiber is to be related to a garment. Thus, Raman spectroscopy using near-infrared excitation and SERRS are techniques with very considerable potential in forensic analysis. 

The analysis of many classes of materials is undertaken with the purpose of discovering the chemical and physical history of the object. This is certainly the case in forensic analysis where substances collected from a crime scene can provide vital information that may incriminate suspected criminals. The exchange principle enunciated by Edmund Locard (Thornton, 1997) is also applicable to fibers in the sense that every stage in the synthesis or processing of the fibers or filaments, every thermal or mechanical treatment and every subsequent contact with chemicals leaves an indelible mark on the material. The challenge is to detect, characterize, and correctly interpret the information. Thermal analysis provides a set of tools that, effectively applied, can provide a wealth of information from minute samples. 

Flynn, K., R. O Leary, C. Roux, and B. J. Reedy, Forensic Analysis of Bicomponent fibers using infrared chemical imaging, J. Forensic Sci., 51, 586 (2006). 

Microscopists in every technical field use the microscope to characterize, compare, and identify a wide variety of substances, eg, protozoa, bacteria, vimses, and plant and animal tissue, as well as minerals, building materials, ceramics, metals, abrasives, pigments, foods, dmgs, explosives, fibers, hairs, and even single atoms. In addition, microscopists help to solve production and process problems, control quaUty, and handle trouble-shooting problems and customer complaints. Microscopists also do basic research in instmmentation, new techniques, specimen preparation, and appHcations of microscopy. The areas of appHcation include forensic trace evidence, contamination analysis, art conservation and authentication, and asbestos control, among others. 

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